It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Monday, June 10, 2024
SPACE
Fighting fires from space in record time: how AI could prevent devastating wildfires
UNIVERSITY OF SOUTH AUSTRALIA
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THE CUBE SATELLITE WHICH WILL PROCESS COMPLEX IMAGERY ON BOARD, ENABLING MUCH FASTER DETECTION OF FIRES FROM SPACE.
Australian scientists are getting closer to detecting bushfires in record time, thanks to cube satellites with onboard AI now able to detect fires from space 500 times faster than traditional on-ground processing of imagery.
Remote sensing and computer science researchers have overcome the limitations of processing and compressing large amounts of hyperspectral imagery on board the smaller, more cost-effective cube satellites before sending it to the ground for analysis, saving precious time and energy.
The breakthrough, using artificial intelligence, means that bushfires will be detected earlier from space, even before they take hold and generate large amounts of heat, allowing on ground crews to respond more quickly and prevent loss of life and property.
A project funded by the SmartSat CRC and led by the University of South Australia (UniSA) has used cutting-edge onboard AI technology to develop an energy-efficient early fire smoke detection system for South Australia’s first cube satellite, Kanyini.
The Kanyini mission is a collaboration between the SA Government, SmartSat CRC and industry partners to launch a 6 U CubeSat satellite into low Earth orbit to detect bushfires as well as monitor inland and coastal water quality.
Equipped with a hyperspectral imager, the satellite sensor captures reflected light from Earth in different wavelengths to generate detailed surface maps for various applications, including bushfire monitoring, water quality assessment and land management.
Lead researcher UniSA geospatial scientist Dr Stefan Peters says that, traditionally, Earth observation satellites have not had the onboard processing capabilities to analyse complex images of Earth captured from space in real-time.
His team, which includes scientists from UniSA, Swinburne University of Technology and Geoscience Australia, has overcome this by building a lightweight AI model that can detect smoke within the available onboard processing, power consumption and data storage constraints of cube satellites.
Compared to the on-ground based processing of hyperspectral satellite imagery to detect fires, the AI onboard model reduced the volume of data downlinked to 16% of its original size, while consuming 69% less energy.
The AI onboard model also detected fire smoke 500 times faster than traditional on-ground processing.
“Smoke is usually the first thing you can see from space before the fire gets hot and big enough for sensors to identify it, so early detection is crucial,” Dr Peters says.
To demonstrate the AI model, they used simulated satellite imagery of recent Australian bushfires, using machine learning to train the model to detect smoke in an image.
“For most sensor systems, only a fraction of the data collected contains critical information related to the purpose of a mission. Because the data can’t be processed on board large satellites, all of it is downlinked to the ground where it is analysed, taking up a lot of space and energy. We have overcome this by training the model to differentiate smoke from cloud, which makes it much faster and more efficient.”
Using a past fire event in the Coorong as a case study, the simulated Kanyini AI onboard approach took less than 14 minutes to detect the smoke and send the data to the South Pole ground station.
“This research shows there are significant benefits of onboard AI compared to traditional on ground processing,” Dr Peters says. “This will not only prove invaluable in the event of bushfires but also serve as an early warning system for other natural disasters.”
The research team hopes to demonstrate the onboard AI fire detection system in orbit in 2025 when the Kanyini mission is operational.
“Once we have ironed out any issues, we hope to commercialise the technology and employ it on a CubeSat constellation, aiming to contribute to early fire detection within an hour.”
The researchers have published details of their experiment in the latest issue of IEEE Journal of Selected Topics in Applied Earth and Remote Sensing.
Onboard AI for Fire Smoke Detection using Hyperspectral Imagery: an Emulation for the Upcoming Kanyini Hyperscout-2 Mission
NASA’s Webb opens new window on supernova science
NASA/GODDARD SPACE FLIGHT CENTER
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THE JADES DEEP FIELD USES OBSERVATIONS TAKEN BY NASA’S JAMES WEBB SPACE TELESCOPE (JWST) AS PART OF THE JADES (JWST ADVANCED DEEP EXTRAGALACTIC SURVEY) PROGRAM. A TEAM OF ASTRONOMERS STUDYING JADES DATA IDENTIFIED ABOUT 80 OBJECTS (CIRCLED IN GREEN) THAT CHANGED IN BRIGHTNESS OVER TIME. MOST OF THESE OBJECTS, KNOWN AS TRANSIENTS, ARE THE RESULT OF EXPLODING STARS OR SUPERNOVAE. PRIOR TO THIS SURVEY, ONLY A HANDFUL OF SUPERNOVAE HAD BEEN FOUND ABOVE A REDSHIFT OF 2, WHICH CORRESPONDS TO WHEN THE UNIVERSE WAS ONLY 3.3 BILLION YEARS OLD — JUST 25% OF ITS CURRENT AGE. THE JADES SAMPLE CONTAINS MANY SUPERNOVAE THAT EXPLODED EVEN FURTHER IN THE PAST, WHEN THE UNIVERSE WAS LESS THAN 2 BILLION YEARS OLD. IT INCLUDES THE FARTHEST ONE EVER SPECTROSCOPICALLY CONFIRMED, AT A REDSHIFT OF 3.6. ITS PROGENITOR STAR EXPLODED WHEN THE UNIVERSE WAS ONLY 1.8 BILLION YEARS OLD.
CREDIT: NASA, ESA, CSA, STSCI, JADES COLLABORATION
Peering deeply into the cosmos, NASA’s James Webb Space Telescope is giving scientists their first detailed glimpse of supernovae from a time when our universe was just a small fraction of its current age. A team using Webb data has identified 10 times more supernovae in the early universe than were previously known. A few of the newfound exploding stars are the most distant examples of their type, including those used to measure the universe's expansion rate.
"Webb is a supernova discovery machine," said Christa DeCoursey, a third-year graduate student at the Steward Observatory and the University of Arizona in Tucson. “The sheer number of detections plus the great distances to these supernovae are the two most exciting outcomes from our survey.”
To make these discoveries, the team analyzed imaging data obtained as part of the JWST Advanced Deep Extragalactic Survey (JADES) program. Webb is ideal for finding extremely distant supernovae because their light isstretched into longer wavelengths — a phenomenon known as cosmological redshift.
Prior to Webb’s launch, only a handful of supernovae had been found above a redshift of 2, which corresponds to when the universe was only 3.3 billion years old — just 25% of its current age. The JADES sample contains many supernovae that exploded even further in the past, when the universe was less than 2 billion years old.
Previously, researchers used NASA’s Hubble Space Telescope to view supernovae from when the universe was in the "young adult" stage. With JADES, scientists are seeing supernovae when the universe was in its “teens” or “pre-teens.” In the future, they hope to look back to the “toddler” or “infant” phase of the universe.
To discover the supernovae, the team compared multiple images taken up to one year apart and looked for sources that disappeared or appeared in those images. These objects that vary in observed brightness over time are called transients, and supernovae are a type of transient. In all, the JADES Transient Survey Sample team uncovered about 80 supernovae in a patch of sky only about the thickness of a grain of rice held at arm’s length.
“This is really our first sample of what the high-redshift universe looks like for transient science,” said teammate Justin Pierel, a NASA Einstein Fellow at the Space Telescope Science Institute (STScI) in Baltimore, Maryland. “We are trying to identify whether distant supernovae are fundamentally different from or very much like what we see in the nearby universe.”
Pierel and other STScI researchers provided expert analysis to determine which transients were actually supernovae and which were not, because often they looked very similar.
The team identified a number of high-redshift supernovae, including the farthest one ever spectroscopically confirmed, at a redshift of 3.6. Its progenitor star exploded when the universe was only 1.8 billion years old. It is a so-called core-collapse supernova, an explosion of a massive star.
Uncovering Distant Type Ia Supernovae
Of particular interest to astrophysicists areType Ia supernovae. These exploding stars are so predictably bright that they are used to measure far-off cosmic distances and help scientists to calculate the universe's expansion rate. The team identified at least one Type Ia supernova at a redshift of 2.9. The light from this explosion began traveling to us 11.5 billion years ago when the universe was just 2.3 billion years old. The previous distance record for a spectroscopically confirmed Type Ia supernova was a redshift of 1.95, when the universe was 3.4 billion years old.
Scientists are eager to analyze Type Ia supernovae at high redshifts to see if they all have the same intrinsic brightness, regardless of distance. This is critically important, because if their brightness varies with redshift, they would not be reliable markers for measuring the expansion rate of the universe.
Pierel analyzed this Type Ia supernova found at redshift 2.9 to determine if its intrinsic brightness was different than expected. While this is just the first such object, the results indicate no evidence that Type Ia brightness changes with redshift. More data is needed, but for now, Type Ia supernova-based theories about the universe’s expansion rate and its ultimate fate remain intact. Pierel also presented his findings at the 244th meeting of the American Astronomical Society.
Jades Deep Field Transients (NIRCam)
This mosaic displays three of about 80 transients, or objects of changing brightness, identified in data from the JADES (JWST Advanced Deep Extragalactic Survey) program. Most of the transients are the result of exploding stars or supernovae. By comparing images taken in 2022 and 2023, astronomers could locate supernovae that recently exploded (like the examples shown in the first two columns), or supernovae that had already exploded and whose light was fading away (third column). The age of each supernova can be determined from its redshift (designated by ‘z’). The light of the most distant supernova, at a redshift of 3.8, originated when the universe was only 1.7 billion years old. A redshift of 2.845 corresponds to a time 2.3 billion years after the big bang. The closest example, at a redshift of 0.655, shows light that left its galaxy about 6 billion years ago, when the universe was just over half its current age.
CREDIT
NASA, ESA, CSA, STScI, C. DeCoursey (University of Arizona), JADES Collaboration
Looking Toward the Future
The early universe was a very different place with extreme environments. Scientists expect to see ancient supernovae that come from stars that contain far fewer heavy chemical elements than stars like our Sun. Comparing these supernovae with those in the local universe will help astrophysicists understand star formation and supernova explosion mechanisms at these early times.
“We’re essentially opening a new window on the transient universe,” said STScI Fellow Matthew Siebert, who is leading the spectroscopic analysis of the JADES supernovae. “Historically, whenever we've done that, we've found extremely exciting things — things that we didn't expect.”
“Because Webb is so sensitive, it's finding supernovae and other transients almost everywhere it’s pointed,” said JADES team member Eiichi Egami, a research professor at the University of Arizona in Tucson. “This is the first significant step toward more extensive surveys of supernovae with Webb.”
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
Hubble finds surprises around a star that erupted 40 years ago
NASA/GODDARD SPACE FLIGHT CENTER
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THIS ARTIST’S CONCEPT SHOWS THE NOVA SYSTEM HM SAGITTAE (HM SGE), WHERE A WHITE DWARF STAR IS PULLING MATERIAL FROM ITS RED GIANT COMPANION. THIS FORMS A BLAZING HOT DISK AROUND THE DWARF, WHICH CAN UNPREDICTABLY UNDERGO A SPONTANEOUS THERMONUCLEAR EXPLOSION AS THE INFALL OF HYDROGEN FROM THE RED GIANT GROWS DENSER AND REACHES A TIPPING POINT. THESE FIREWORKS BETWEEN COMPANION STARS ARE FASCINATING TO ASTRONOMERS BY YIELDING INSIGHTS INTO THE PHYSICS AND DYNAMICS OF STELLAR EVOLUTION IN BINARY SYSTEMS.
Astronomers have used new data from NASA's Hubble Space Telescope and the retired SOFIA (Stratospheric Observatory for Infrared Astronomy) as well as archival data from other missions to revisit one of the strangest binary star systems in our galaxy – 40 years after it burst onto the scene as a bright and long-lived nova. A nova is a star that suddenly increases its brightness tremendously and then fades away to its former obscurity, usually in a few months or years.
Between April and September 1975, the binary system HM Sagittae (HM Sge) grew 250 times brighter. Even more unusual, it did not rapidly fade away as novae commonly do, but has maintained its luminosity for decades. Recently, observations show that the system has gotten hotter, but paradoxically faded a little.
HM Sge is a particular kind of symbiotic star where a white dwarf and a bloated, dust-producing giant companion star are in an eccentric orbit around each other, and the white dwarf ingests gas flowing from the giant star. That gas forms a blazing hot disk around the white dwarf, which can unpredictably undergo a spontaneous thermonuclear explosion as the infall of hydrogen from the giant grows denser on the surface until it reaches a tipping point. These fireworks between companion stars fascinate astronomers by yielding insights into the physics and dynamics of stellar evolution in binary systems.
"In 1975 HM Sge went from being a nondescript star to something all astronomers in the field were looking at, and at some point that flurry of activity slowed down," said Ravi Sankrit of the Space Telescope Science Institute (STScI) in Baltimore. In 2021, Steven Goldman of STScI, Sankrit and collaborators used instruments on Hubble and SOFIA to see what had changed with HM Sge in the last 30 years at wavelengths of light from the infrared to the ultraviolet (UV).
The 2021 ultraviolet data from Hubble showed a strong emission line of highly ionized magnesium that was not present in earlier published spectra from 1990. Its presence shows that the estimated temperature of the white dwarf and accretion disk increased from less than 400,000 degrees Fahrenheit in 1989 to greater than 450,000 degrees Fahrenheit now. The highly ionized magnesium line is one of many seen in the UV spectrum, which analyzed together will reveal the energetics of the system, and how it has changed in the last three decades.
"When I first saw the new data," Sankrit said, "I went – 'wow this is what Hubble UV spectroscopy can do!' – I mean it's spectacular, really spectacular."
With data from NASA's flying telescope SOFIA, which retired in 2022, the team was able to detect the water, gas, and dust flowing in and around the system. Infrared spectral data shows that the giant star, which produces copious amounts of dust, returned to its normal behavior within only a couple years of the explosion, but also that it has dimmed in recent years, which is another puzzle to be explained.
With SOFIA astronomers were able to see water moving at around 18 miles per second, which they suspect is the speed of the sizzling accretion disk around the white dwarf. The bridge of gas connecting the giant star to the white dwarf must presently span about 2 billion miles.
The team has also been working with the AAVSO (American Association of Variable Star Observers), to collaborate with amateur astronomers from around the world who help keep telescopic eyes on HM Sge; their continued monitoring reveals changes that haven't been seen since its outburst 40 years ago.
"Symbiotic stars like HM Sge are rare in our galaxy, and witnessing a nova-like explosion is even rarer. This unique event is a treasure for astrophysicists spanning decades," said Goldman.
The initial results from the team's research were published in the Astrophysical Journal, and Sankrit is presenting research focused on the UV spectroscopy at the 244th meeting of the American Astronomical Society in Madison, Wisconsin.
The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, Colorado, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, Maryland, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
Hubble Image of Symbiotic Star Mira HM Sge
A Hubble Space Telescope image of the symbiotic star Mira HM Sge. Located 3,400 light-years away in the constellation Sagitta, it consists of a red giant and a white dwarf companion. The stars are too close together to be resolved by Hubble. Material bleeds off the red giant and falls onto the dwarf, making it extremely bright. This system first flared up as a nova in 1975. The red nebulosity is evidence of the stellar wind. The nebula is about one-quarter light-year across.
CREDIT
NASA, ESA, Ravi Sankrit (STScI), Steven Goldman (STScI); Image Processing: Joseph DePasquale (STScI)
New research led by Lia Siegelman, a physical oceanographer at UC San Diego’s Scripps Institution of Oceanography, shows that the roiling storms at the planet Jupiter’s polar regions are powered by processes known to physicists studying Earth’s oceans and atmosphere. The geophysical commonalities spanning the 452 million miles between the two planets could even help facilitate an improved understanding of those processes on Earth.
Siegelman first made the connection between our planet and the gas giant in 2018 when she noticed a striking similarity between images of Jupiter’s huge cyclones and the ocean turbulence she was studying. To a physicist, air and water are both considered fluids so applying ocean physics to Jupiter isn’t as far-fetched as it sounds, said Siegelman. “Jupiter is basically an ocean of gas.”
This initial observation led Siegelman to co-author a 2022 study published in Nature Physics that analyzed high-resolution infrared images of Jupiter’s cyclones taken by NASA’s Juno spacecraft. The analysis revealed that a type of convection similar to what is seen on Earth helps maintain Jupiter’s storms, which can be thousands of miles wide and last for years.
The 2022 study focused directly on Jupiter’s cyclones, but Siegelman also saw wispy tendrils, known to researchers as filaments, in the spaces between the gassy vortices. These filaments also had earthly analogs, and Siegelman used Juno’s detailed imagery to study whether this similarity to our planet’s oceanic and atmospheric processes was merely skin deep.
Published on June 6 in Nature Physics (LINK TK) and funded by Scripps and the National Science Foundation, Siegelman’s follow-up study finds additional similarities between the processes fueling Jupiter’s cyclones and those acting on Earth. The study shows that the filaments between Jupiter’s cyclones act in concert with convection to promote and sustain the planet’s giant storms. Specifically, Jupiter’s filaments act in ways that resemble what oceanographers and meteorologists call fronts on Earth.
Fronts are often discussed in weather forecasts – cold fronts or storm fronts, for example – but they apply to both gases and liquids. A front is the boundary between gas or liquid masses with different densities due to differences in properties like temperature. In the ocean, fronts can also be due to differences in salinity, which influences the density of seawater along with temperature. A key feature of fronts is that their leading edges feature strong vertical velocities that can create winds or currents.
To try to understand the role of the filaments she could clearly see in between the cyclones on Jupiter in Juno’s images, Siegelman looked at a series of infrared images from Juno. The batch of images were of Jupiter’s north polar region and were taken in 30-second increments.
The fact that the images were in infrared allowed Siegelman and her co-author Patrice Klein of NASA’s Jet Propulsion Laboratory, California Institute of Technology, and the Ecole Normale Superieure to calculate temperature – bright areas were warmer and dark areas were cooler. On Jupiter, the hotter parts of the atmosphere correspond to thin clouds and the colder parts represent thick cloud cover, blocking more of the heat emanating from Jupiter’s super-heated core. The researchers then tracked the movement of clouds and filaments across the 30 second intervals separating the photographs to calculate horizontal wind speeds.
These two pieces of information allowed Siegelman and Klein to apply methods from ocean and atmospheric science to Jupiter, allowing them to calculate the vertical wind speeds that would correspond to the temperatures and horizontal wind speeds the researchers derived from the images. Once the team calculated the vertical wind speeds, they were able to see that Jupiter’s filaments were indeed behaving like fronts on Earth.
Those vertical wind speeds at the edges of fronts on Jupiter also meant that the fronts were involved in transporting energy in the form of heat from the planet’s hot interior to its upper atmosphere – fueling the giant cyclones. Though convection is the main driver, the fronts account for a quarter of the total kinetic energy powering Jupiter’s cyclones and forty percent of the vertical heat transport.
“These cyclones on Jupiter’s poles have persisted since they were first observed in 2016,” said Siegelman. “These filaments in between the large vortices are relatively small but they are an important mechanism for sustaining the cyclones. It’s fascinating that fronts and convection are present and influential on Earth and Jupiter – it suggests that these processes may also be present on other turbulent fluid bodies in the universe.”
Siegelman also said that Jupiter’s massive scale and Juno’s high-resolution imagery can allow for a clearer visualization of the ways in which smaller-scale phenomena like fronts connect to larger ones like cyclones and the atmosphere at large – connections that are often hard to observe on Earth where they are much smaller and more ephemeral. However, she added, a long-awaited new satellite known to researchers as SWOT, is poised to make these kinds of ocean phenomena vastly easier to observe.
“There is some cosmic beauty in finding out that these physical mechanisms on Earth exist on other far-away planets,” said Siegelman.
Astronauts driving a vehicle around the landscape of the Moon must not only face dangers related to zero gravity and falling into craters, but also the problem of extreme fluctuations in temperature. The lunar environment oscillates between blistering highs of 127°C (260°F) and frigid lows of -173°C (-280°F). Future missions to explore the Moon will need reliable machines that can function under these harsh conditions. This led a team from Nagoya University in Japan to invent a heat-switch device that promises to extend the operational lifespan of lunar-roving vehicles. Their study, conducted in collaboration with the Japan Aerospace Exploration Agency, was published in the journal Applied Thermal Engineering.
“Heat-switch technology that can switch between daytime heat dissipation and nighttime insulation is essential for long-term lunar exploration,” said lead researcher Masahito Nishikawara. “During the day, the lunar rover is active, and the electronic equipment generates heat. Since there is no air in space, the heat generated by the electronics must be actively cooled and dissipated. On the other hand, during extremely cold nights, electronics must be insulated from the outside environment so that they don’t get too cold.”
Current devices tend to rely on heaters or passive valves attached to loop heat pipes for nighttime insulation. However, heaters are costly, and passive valves can increase the velocity of fluid flow, leading to a drop in pressure that can affect the efficiency of heat transfer. The technology developed by Nishikawara’s team offers a middle ground. With a lower pressure drop than passive valves and lower power consumption than heaters, it retains heat at night without compromising daytime cooling performance.
The thermal control device developed by the team combines a loop heat pipe (LHP) with an electrohydrodynamic (EHD) pump. During the day, the EHD pump is inactive, allowing the LHP to operate as usual. In lunar rovers, the LHP uses a refrigerant that cycles between vapor and liquid states. When the device heats up, the liquid refrigerant in the evaporator vaporizes, releasing heat through the rover’s radiator. The vapor then condenses back into liquid, which returns to the evaporator to absorb heat again. This cycle is driven by capillary forces in the evaporator, making it energy efficient.
At night, the EHD pump applies pressure opposite to the LHP flow, stopping the movement of the refrigerant. Electronics are completely insulated from the cold night environment with minimal electricity use. The team's research included selection of the EHD pump’s electrode shape, device design, performance evaluation, and a demonstration test to stop LHP operation with the EHD pump. The results showed that the power consumption at night was almost zero.
“This groundbreaking approach not only ensures the rover's survival in extreme temperatures but also minimizes energy expenditure, a critical consideration in the resource-constrained lunar environment,” Nishikawara said. “It lays the foundation for potential integration into future lunar missions, contributing to the realization of sustained lunar exploration efforts.”
The implications of this technology extend beyond lunar rovers to broader applications in spacecraft thermal management. Integrating EHD technology into thermal fluid control systems could improve heat transfer efficiency and mitigate operational challenges. In the future, this could play an important role in space exploration.
The development of this heat-switch device marks an important milestone in developing technology for long-term lunar missions and other space exploration endeavors. All of which means that, in the future, lunar rovers and other spacecraft should be better equipped to operate in the extreme environments of space.
HKUST researchers boost cosmological explorations with novel method of detecting high-frequency gravitational waves in planetary magnetospheres
HONG KONG UNIVERSITY OF SCIENCE AND TECHNOLOGY
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THE GROUNDBREAKING CONCEPT PROPOSED BY HKUST DEPARTMENT OF PHYSICS PROF. LIU’S TEAM ALLOWS A SINGLE ASTRONOMICAL TELESCOPE IN THE EARTH’S MAGNETOSPHERE TO FUNCTION AS A DETECTOR FOR GW SIGNALS.
A groundbreaking method of detecting high-frequency gravitational waves (HFGWs) has been proposed by a research team led by Prof. Tao LIU, Associate Professor from the Department of Physics at the Hong Kong University of Science and Technology (HKUST). The team's innovative approach may enable the successful detection of HFGWs by utilizing existing and technologically feasible astronomical telescopes in planetary magnetosphere, opening up new possibilities for studying the early universe and violent cosmic events in an effective and technically viable way.
Gravitational waves (GWs) are produced by various astronomical phenomena, such as phase transitions in the early universe and collisions of primordial black holes. However, their effects are extremely weak and have been discovered only in relatively low frequency band using the method of interferometry. Observing the universe using GWs thus presents significant technological challenges, particularly in probing the high-frequency band above one kilohertz, where the usage of interferometry becomes strongly restricted.
To address this difficulty, Prof. Tao LIU and his postdoctoral fellow Dr. Chen ZHANG have collaborated with Prof. Jing REN from the Institute of High Energy Physics at the Chinese Academy of Sciences, and achieved a significant breakthrough in their recent study. The research capitalizes on the intriguing physical effect that GWs residing within a magnetic field can be converted to potentially detectable electromagnetic waves. By leveraging the extended paths within planetary magnetosphere, the conversion efficiency is increased, yielding more signals of electromagnetic waves. The detection capability can be further enhanced for telescopes with a wide field of view because of the expansive angular distribution of signal flux within such a planet laboratory.
This innovative method allows a single astronomical telescope to function as a detector for GW signals. By combining multiple telescopes, a wide coverage of HFGW frequencies, ranging from megahertz to 10^28 hertz, can be achieved. This frequency range is equivalent to the electromagnetic spectrum used in astronomical observations and includes a large portion that has never been explored in the detection of GWs before. The study provides an initial assessment of sensitivity for satellite-based detectors in low Earth orbit and ongoing missions within Jupiter's magnetosphere.
The research was published in Physical Review Letters in March and was subsequently highlighted by Nature Astronomy in an article titled “Planet-sized laboratories offer cosmological insights” in May. This emphasizes the significance of the research in paving the way for future studies into novel GW detection technologies.
Limits on High-Frequency Gravitational Waves in Planetary Magnetospheres
Small, cool and sulfurous exoplanet may help write recipe for planetary formation
UW–Madison astronomers and their collaborators hope the discovery of one exoplanet's sulfurous atmosphere will advance our understanding of how planets forms.
UNIVERSITY OF WISCONSIN-MADISON
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THE SULFUR-LADEN ATMOSPHERE DISCOVERED ON GASEOUS EXOPLANET GJ 3470 B, SHOW HERE IN AN ILLUSTRATION ORBITING ITS STAR IN THE CONSTELLATION CANCER, COULD HELP RESEARCHERS FIGURE OUT HOW IT (AND SIMILAR PLANETS) WERE FORMED.
A surprising yellow haze of sulfur dioxide in the atmosphere of a gas “dwarf” exoplanet about 96 light years away from our own solar system makes the planet a prime target for scientists trying to understand how worlds are formed.
Astronomers discovered the planet, GJ 3470 b, in 2012 when the planet’s shadow crossed the star it orbits. GJ 3470 b is located in the constellation Cancer and is about half the size of Neptune, with a mass 10 times that of Earth. In the intervening years, researchers have compiled data on the planet using the Hubble and Spitzer space telescopes, culminating in a pair of recent observations with the James Webb Space Telescope.
Planets outside our solar system — called exoplanets — like GJ 3470 b are interesting subjects for researchers wondering how planets are created. Ideally, astronomers capture light from a star that shines through the edge of the planet’s atmosphere. This allows them to assemble a measure of the component light, or its spectrum, a readout marked by spikes and dips characteristic of the interesting molecules found in that atmosphere.
They saw evidence of water, carbon dioxide, methane and sulfur dioxide, findings Beatty presented in Madison today at the 244th meeting of the American Astronomical Society and that he will soon publish in Astrophysical Journal Letters with co-authors from Arizona State University, the University of Arizona, NASA’s Ames Research Center and other organizations.
GJ 3470 b is the lightest and coldest (averaging a mere 325 degrees Celsius, or more than 600 Fahrenheit) exoplanet to harbor sulfur dioxide. The compound is likely a sign of the churn of active chemical reactions in the planet’s atmosphere, created when radiation from its nearby star blasts apart the components of hydrogen sulfide, which then go looking for new molecular partners.
“We didn’t think we’d see sulfur dioxide on planets this small, and it’s exciting to see this new molecule in a place we didn’t expect, since it gives us a new way to figure out how these planets formed,” says Beatty, who worked as an instrument scientist on the James Webb Space Telescope before joining the UW–Madison faculty. “And small planets are especially interesting, because their compositions are really dependent on how the planet-formation process happened.”
Divining that process is one focus of Beatty’s research. It’s a little like spying on a baker only at the beginning of their work and then again when it’s nearly time for dessert.
“Laid out on our table, we have all the ingredients that go into a cake, and we have a finished cake,” he says. “Now, can we figure out the recipe — the steps that turned the raw materials into the end product — by measuring what’s in the cake?”
Astronomers like Beatty hope they will be able to do just that: figure out the recipe for planet formation by looking at what’s in exoplanets.
“Discovering sulfur dioxide in a planet as small as GJ 3470 b gives us one more important item on the planet formation ingredient list,” says Beatty.
In the case of GJ 3470 b, there are also other interesting features that might help fill out that recipe. The planet’s orbit around its star takes it nearly over the star’s poles, which is to say that it’s circling at a 90-degree angle to the expected path of planets in the system. It’s also surprisingly close to the star, close enough that the light from its star is blowing copious amounts of GJ 3470 b’s atmosphere away into space. The planet has probably lost about 40 percent of its mass since it was formed.
The close-in, off-kilter orbit is a sign that GJ 3470 b used to be somewhere else in its system, and at some point, the planet became entangled with the gravity of another and was pulled into a new path that eventually settled it in a different neighborhood.
“That migration history that led to this polar orbit and the loss of all this mass — those are things we don’t typically know about other exoplanet targets we’re looking at,” Beatty says. “Those are important steps in the recipe that created this particular planet and can help us understand how planets like it are made.”
With further analysis of the ingredients that remain in the planet’s atmosphere and the help of colleagues like those in UW–Madison’s Wisconsin Center for Origins Research who specialize in proto-planetary disks and migration dynamics, GJ 3470 b may help Beatty and others understand how planets like it got to be so appetizing — at least from the astronomers’ perspective.
This research was supported by grants from NASA.
Space race heats up: advanced electronics cooling systems for spacecraft
KEAI COMMUNICATIONS CO., LTD.
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SCHEMATIC OF THE THERMAL ENVIRONMENT FOR ELECTRONICS IN SPACECRAFT
A recent review focuses on the development and optimization of thermal management technologies (TMTs) for spacecraft electronics. These technologies address the challenges of heat acquisition, transport, and rejection in the harsh space environment. The review aims to guide future spacecraft thermal management systems, ensuring the reliability and performance of space missions.
Spacecraft electronics operate under extreme conditions, facing issues like microgravity, thermal cycling, and space radiation. These factors necessitate robust thermal management solutions to maintain the functionality and longevity of onboard equipment. Traditional thermal control methods often fall short in addressing these challenges. Based on these challenges, there is a need to conduct in-depth research on advanced thermal management technologies to ensure the stability and efficiency of space missions.
A comprehensive review (DOI: 10.1016/j.enss.2024.03.001) by researchers from Xi’an Jiaotong University and the Xi’an Institute of Space Radio Technology, published in Energy Storage and Saving on March 28, 2024, delves into advanced thermal management technologies for spacecraft electronics. The study categorizes these technologies based on heat transfer processes, including heat acquisition, transport, and rejection.
The review evaluates thermal management technologies (TMTs) for spacecraft electronics, focusing on heat acquisition, transport, and rejection. It explores high thermal conductance materials like carbon-based composites and annealed pyrolytic graphite (APG) and discusses novel packaging structures using micro-/nano-electromechanical system (MEMS/NEMS) technologies. Heat transport solutions, including various heat pipes and mechanically pumped fluid loops (MPFLs), are examined, with heat pipes categorized into unseparated and separated types. Advanced microfluidic cooling techniques for efficient heat removal are also highlighted. For heat rejection, the review focuses on deployable radiators, variable emissivity radiators, and phase change materials (PCMs), addressing the fluctuating thermal environment in space to ensure effective heat dissipation.
Dr. Wen-Xiao Chu, the corresponding author of the study, states, "Our review highlights the critical advancements in thermal management technologies that are essential for the success of future space missions. By addressing the unique thermal challenges in the spacecraft environment, these technologies ensure the reliability and performance of onboard electronics, paving the way for more ambitious space exploration and satellite missions."
Advancements in thermal management technologies have significant implications for the space industry. By ensuring efficient heat control, these technologies enhance the reliability and lifespan of spacecraft electronics, crucial for long missions. Lightweight and high-performance TMTs improve overall efficiency and cost-effectiveness. As demand for high-power and miniaturized space systems grows, implementing these advanced thermal solutions is vital for the future of space exploration and satellite technology.
Review on Thermal Management Technologies for Electronics in Spacecraft Environment
In a significant first, researchers detect water frost on solar system’s tallest volcanoes
A research team unveiled that Mars’ Tharsis volcanoes have on and off patches of water frost, challenging previous assumptions about the Martian climate and helping shed light on how water behaves on the planet.
BROWN UNIVERSITY
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THIS SIMULATED PERSPECTIVE OBLIQUE VIEW SHOWS OLYMPUS MONS, THE TALLEST VOLCANO NOT ONLY ON MARS BUT IN THE ENTIRE SOLAR SYSTEM. THE VOLCANO MEASURES SOME 600 KM ACROSS.
PROVIDENCE, R.I. [Brown University] — An international team of planetary scientists has detected patches of water frost sitting atop the Tharsis volcanoes on Mars, which are not only the tallest volcanic mountains on the Red Planet but in the entire solar system.
The discovery marks the first time frost has been spotted near the planet’s equator, challenging existing perceptions of the planet’s climate dynamics, according to the team’s new study in Nature Geoscience.
“We thought it was improbable for frost to form around Mars’ equator, as the mix of sunshine and thin atmosphere keeps temperatures during the day relatively high at both the surface and mountaintop — unlike what we see on Earth, where you might expect to see frosty peaks,” said Adomas Valantinas, a postdoctoral fellow at Brown University who led the work as a Ph.D. student at the University of Bern. “What we're seeing may be a remnant of an ancient climate cycle on modern Mars, where you had precipitation and maybe even snowfall on these volcanoes in the past.”
According to the study, the frost is present for only a few hours after sunrise before it evaporates in sunlight. The frost is also incredibly thin — likely only one-hundredth of a millimeter thick or about the width of a human hair. Still, it’s quite vast. The researchers calculate the frost constitutes at least 150,000 tons of water that swaps between the surface and atmosphere each day during the cold seasons. That’s the equivalent of roughly 60 Olympic-size swimming pools.
Tharsis, the region of Mars where the frost was found, hosts numerous volcanoes. They tower above the surrounding plains at heights ranging from one to two times that of Earth’s Mount Everest. Olympus Mons, for instance, is as wide as France.
The frost sits in the calderas of the volcanoes, which are large hollows at their summits created during past eruptions. The researchers propose that the way the air circulates above these mountains creates a unique microclimate that allows the thin patches of frost to form.
The researchers believe modelling how the frosts form could allow scientists to reveal more of Mars’ remaining secrets, including understanding where water exists and how it moves, as well as understanding the planet’s complex atmospheric dynamics, which is essential for future exploration and the search for possible signs of life.
The researchers detected the frost using high-resolution color images from the Colour and Stereo Surface Imaging System (CaSSIS) onboard the European Space Agency’s Trace Gas Orbiter. The findings were then validated using independent observations from the High Resolution Stereo Camera onboard the ESA’s Mars Express orbiter and by the Nadir and Occultation for Mars Discovery spectrometer onboard the Trace Gas Orbiter.
The effort involved analyzing over 30,000 images to both initially find the frost and then confirm its existence. Valantinas filtered the images based on where they were acquired as well as when they were acquired, like the time of day and the season. The meticulous approach helped isolate spectral signatures indicative of water frost and where it formed on the Martian surface.
Valantinas started analyzing the images in 2018. The majority of work was completed while earning his Ph.D. abroad but a portion of the reanalysis was completed while at Brown.
Transitioning to his role at Brown, Valantinas now plans to continue his exploration of Martian mysteries while pivoting to astrobiology. Working in the lab of Brown planetary scientist Jack Mustard, he’ll work toward characterizing ancient hydrothermal environments that could have supported microbial life. Samples from these environments may one day be brought back to Earth by the NASA-lead Mars Sample Return mission.
“This notion of a second genesis, of life beyond Earth, has always fascinated me,” Valantinas said.
Evidence for transient morning water frost deposits on the Tharsis volcanoes of Mars
ARTICLE PUBLICATION DATE
10-Jun-2024
Webb telescope reveals asteroid collision in neighboring star system
JOHNS HOPKINS UNIVERSITY
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TWO DIFFERENT SPACE TELESCOPES TOOK SNAPSHOTS 20 YEARS APART OF THE SAME AREA AROUND THE STAR CALLED BETA PICTORIS. SCIENTISTS THEORIZE THAT THE MASSIVE AMOUNT OF DUST SEEN IN THE 2004–05 IMAGE FROM THE SPITZER SPACE TELESCOPE INDICATES A COLLISION OF ASTEROIDS THAT HAD LARGELY CLEARED BY THE TIME THE JAMES WEBB SPACE TELESCOPE CAPTURED ITS IMAGES IN 2023.
CREDIT: ROBERTO MOLAR CANDANOSA/JOHNS HOPKINS UNIVERSITY, WITH BETA PICTORIS CONCEPT ART BY LYNETTE COOK/NASA.
Astronomers have captured what appears to be a snapshot of a massive collision of giant asteroids in Beta Pictoris, a neighboring star system known for its early age and tumultuous planet-forming activity.
The observations spotlight the volatile processes that shape star systems like our own, offering a unique glimpse into the primordial stages of planetary formation.
“Beta Pictoris is at an age when planet formation in the terrestrial planet zone is still ongoing through giant asteroid collisions, so what we could be seeing here is basically how rocky planets and other bodies are forming in real time,” said Christine Chen, a Johns Hopkins University astronomer who led the research.
The insights will be presented today at the 244th Meeting of the American Astronomical Society in Madison, Wisconsin.
Chen’s team spotted significant changes in the energy signatures emitted by dust grains around Beta Pictoris by comparing new data from the James Webb Space Telescope with observations by the Spitzer Space Telescope from 2004 and 2005. With Webb’s detailed measurements, the team tracked the dust particles’ composition and size in the exact area previously analyzed by Spitzer.
Focusing on heat emitted by crystalline silicates—minerals commonly found around young stars as well as on Earth and other celestial bodies—the scientists found no traces of the particles previously seen in 2004–05. This suggests a cataclysmic collision occurred among asteroids and other objects about 20 years ago, pulverizing the bodies into fine dust particles smaller than pollen or powdered sugar, Chen said.
“We think all that dust is what we saw initially in the Spitzer data from 2004 and 2005,” said Chen, who is also an astronomer at the Space Telescope Science Institute. “With Webb’s new data, the best explanation we have is that, in fact, we witnessed the aftermath of an infrequent, cataclysmic event between large asteroid-size bodies, marking a complete change in our understanding of this star system.”
The new data suggests dust that was dispersed outward by radiation from the system’s central star is no longer detectable, Chen said. Initially, dust near the star heated up and emitted thermal radiation that Spitzer’s instruments identified. Now, dust that cooled off as it moved far away from the star no longer emits those thermal features.
When Spitzer collected the earlier data, scientists assumed something like small bodies grinding down would stir and replenish the dust steadily over time. But Webb’s new observations show the dust disappeared and was not replaced. The amount of dust kicked up is about 100,000 times the size of the asteroid that killed the dinosaurs, Chen said.
Beta Pictoris, located about 63 light years from Earth, has long been a focal point for astronomers because of its proximity and random processes where collisions, space weathering, and other planet-making factors will dictate the system’s fate.
At only 20 million years—compared to our 4.5-billion-year-old solar system—Beta Pictoris is at a key age where giant planets have formed but terrestrial planets might still be developing. It has at least two known gas giants, Beta Pic b and c, which also influence the surrounding dust and debris.
“The question we are trying to contextualize is whether this whole process of terrestrial and giant planet formation is common or rare, and the even more basic question: Are planetary systems like the solar system that rare?” said co-author Kadin Worthen, a doctoral student in astrophysics at Johns Hopkins. “We’re basically trying to understand how weird or average we are.”
The new insights also underscore the unmatched capability of the Webb telescope to unveil the intricacies of exoplanets and star systems, the team reports. They offer key clues into how the architectures of other solar systems resemble ours and will likely deepen scientists’ understanding of how early turmoil influences planets’ atmospheres, water content, and other key aspects of habitability.
“Most discoveries by JWST come from things the telescope has detected directly,” said co-author Cicero Lu, a former Johns Hopkins doctoral student in astrophysics. “In this case, the story is a little different because our results come from what JWST did not see.”
Other authors are Yiwei Chai and Alexis Li of Johns Hopkins; David R. Law, B.A. Sargent, G.C. Sloan, Julien H. Girard, Dean C. Hines, Marshall Perrin and Laurent Pueyo of the Space Telescope Science Institute; Carey M. Lisse of the Johns Hopkins University Applied Physics Laboratory; Dan M. Watson of the University of Rochester; Jens Kammerer of the European Southern Observatory; Isabel Rebollido of the European Space Agency; and Christopher Stark of NASA Goddard Space Flight Center.
The research was supported by the National Aeronautics and Space Administration under Grant No. 80NSSC22K1752.
Journalists registered for the meeting can attend the presentation in person or virtually on Monday, June 10 at 10:15 a.m. Central Standard Time. Nonregistrants may watch the press conference on the AAS Press Office YouTube channel but will be unable to ask questions.
METHOD OF RESEARCH
Observational study
Galactic bloodlines: Many nearby star clusters originate from only three "families"
Supernova explosions from the formation history of these families also left traces on Earth
UNIVERSITY OF VIENNA
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THE ALPHA PERSEI STAR CLUSTER: AN OPTICAL IMAGE OF THE ALPHA PERSEI STAR CLUSTER FROM THE SECOND DIGITIZED SKY SURVEY (DSS-II). THIS CLUSTER IS ONE OF THE EARLIEST FORMED IN THE ALPHA PERSEI FAMILY AND IS THE NAMESAKE OF THE FAMILY.
An international team of astronomers led by the University of Vienna has deciphered the formation history of young star clusters, some of which we can see with the naked eye at night. The team, led by Cameren Swiggum and João Alves from the University of Vienna and Robert Benjamin from the University of Wisconsin-Whitewater, reports that most nearby young star clusters belong to only three families, which originate from very massive star-forming regions. This research also provides new insights into the effects of supernovae (violent explosions at the end of the life of very massive stars) on the formation of giant gas structures in galaxies like our Milky Way. The results were published in the renowned journal Nature.
"Young star clusters are excellent for exploring the history and structure of the Milky Way. By studying their movements in the past and thus their origin, we also gain important insights into the formation and evolution of our galaxy," says João Alves from the University of Vienna, co-author of the study. Using precise data from the European Space Agency's (ESA) Gaia mission and spectroscopic observations, the team traced the origins of 155 young star clusters within a radius of about 3,500 light-years around the Sun. Their analysis shows that these star clusters can be divided into three families with common origins and formation conditions. "This indicates that the young star clusters originate from only three very active and massive star-forming regions," says Alves. These three star families are named after their most prominent star clusters: Collinder 135 (Cr135), Messier 6 (M6), and Alpha Persei (αPer).
"These findings offer a clearer understanding of how young star clusters in our galactic neighborhood are interconnected, much like members of a family or ‘bloodlines’", says lead author Cameren Swiggum, a doctoral student at the University of Vienna. "By examining the 3D movements and past positions of these star clusters, we can identify their common origins and locate the regions in our galaxy where the first stars in these respective star clusters formed up to 40 million years ago."
These Massive Explosions Likely Also Created Our "Local Bubble"
The study found that over 200 supernova explosions must have occurred within these three star cluster families, releasing enormous amounts of energy into their surroundings. The authors concluded that this energy likely had a significant impact on the gas distribution in the local Milky Way. "This could explain the formation of a superbubble, a giant bubble of gas and dust with a diameter of 3,000 light-years around the Cr135 family," explains Swiggum. Our solar system is also embedded in such a bubble, the so-called Local Bubble, which is filled with very thin and hot gas. "The Local Bubble is probably also linked to the history of one of the three star cluster families," adds Swiggum. "And it has likely left traces on Earth, as suggested by measurements of iron isotopes (60Fe) in the Earth's crust."
"We can practically turn the sky into a time machine that allows us to trace the history of our home galaxy," says João Alves. "By deciphering the genealogy of star clusters, we also learn more about our own galactic ancestry." In the future, João Alves' team plans to investigate more precisely whether and how our solar system has interacted with interstellar matter in our home galaxy, the Milky Way.
This research was supported by the ERC Advanced Grant ISM-FLOW (Alves), the Austrian Research Promotion Agency (FFG), the German Research Foundation (DFG), and NASA.
Most nearby young star clusters formed in three massive complexes.
ARTICLE PUBLICATION DATE
10-Jun-2024
The Collinder 135 star cluster: An optical image of the Collinder 135 star cluster from the second Digitized Sky Survey (DSS-II). This cluster is one of the earliest formed in the Collinder 135 family and is the namesake of the family.
The Messier 6 star cluster: An optical image of the Messier 6 star cluster, also known as the "Butterfly cluster", from the second Digitized Sky Survey (DSS-II). This cluster is one of the earliest formed in the Messier 6 family and is the namesake of the family.
The IC 2391 star cluster: An optical image of the IC 2391 star cluster, also known as the "Omicron Velorum cluster", from the second Digitized Sky Survey (DSS-II). It is a member of the Messier 6 family.
The IC 2602 star cluster: An optical image of the IC 2602 star cluster, also known as the "Southern Pleiades", from the second Digitized Sky Survey (DSS-II). It is a member of the Alpha Persei family.
The NGC 2451A star cluster: An optical image of the NGC 2415A star cluster from the second Digitized Sky Survey (DSS-II). It is a member of the Messier 6 family.
THE NGC 2547 STAR CLUSTER: AN OPTICAL IMAGE OF THE NGC 2547 STAR CLUSTER FROM THE SECOND DIGITIZED SKY SURVEY (DSS-II). IT IS A MEMBER OF THE COLLINDER 135 FAMILY.
CREDIT
ESO/STScI Digitized Sky Survey II
Lone Star State: Tracking a low-mass star as it speeds across the Milky Way
A newly discovered L subdwarf is on an unusual journey through our galaxy
A SIMULATION OF A POSSIBLE EXPLANATION FOR AN L SUBDWARF NAMED CWISE J124909+362116.0'S SPEED SHOWS IT AS A PART OF A WHITE DWARF BINARY PAIR THAT ENDED WITH THE WHITE DWARF EXPLODING INTO A SUPERNOVA.
It may seem like the Sun is stationary while the planets in its orbit are moving, but the Sun is actually orbiting around the Milky Way galaxy at an impressive rate of about 220 kilometers per second — almost half a million miles per hour. As fast as that may seem, when a faint red star was discovered crossing the sky at a noticeably quick pace, scientists took notice.
Thanks to the efforts of a citizen science project called Backyard Worlds: Planet 9 and a team of astronomers from around the country, a rare hypervelocity L subdwarf star has been found racing through the Milky Way. More remarkably, this star may be on a trajectory that causes it to leave the Milky Way altogether. The research, led by University of California San Diego Professor of Astronomy and Astrophysics Adam Burgasser, was presented today at a press conference during the 244th national meeting of the American Astronomical Society (AAS) in Madison, Wisconsin.
The star, charmingly named CWISE J124909+362116.0 (“J1249+36”), was first noticed by some of the over 80,000 citizen science volunteers participating in the Backyard Worlds: Planet 9 project, who comb through enormous reams of data collected over the past 14 years by NASA's Wide-field Infrared Survey Explorer (WISE) mission. This project capitalizes on the keen ability of humans, who are evolutionarily programmed to look for patterns and spot anomalies in a way that is unmatched by computer technology. Volunteers tag moving objects in data files and when enough volunteers tag the same object, astronomers investigate.
J1249+36 immediately stood out because of the speed at which it is moving across the sky, initially estimated at about 600 kilometers per second (1.3 million miles per hour). At this speed, the star is fast enough to escape the gravity of the Milky Way, making it a potential “hypervelocity” star.
To better understand the nature of this object, Burgasser turned to the W.M. Keck Observatory in Maunakea, Hawaii to measure its infrared spectrum. These data revealed that the object was a rare L subdwarf — a class of stars with very low mass and temperature. Subdwarfs represent the oldest stars in the Milky Way.
The insight into J1249+36’s composition was made possible by a new set of atmosphere models created by UC San Diego alumnus Roman Gerasimov, who worked with UC LEADS scholar Efrain Alvarado III to generate models specifically tuned to study L subdwarfs. “It was exciting to see that our models were able to accurately match the observed spectrum,” said Alvarado, who is presenting his modeling work at the AAS meeting.
The spectral data, along with imaging data from several ground-based telescopes, allowed the team to accurately measure J1249+36’s position and velocity in space, and thereby predict its orbit through the Milky Way. “This is where the source became very interesting, as its speed and trajectory showed that it was moving fast enough to potentially escape the Milky Way,” stated Burgasser.
What gave this star a kick?
Researchers focused on two possible scenarios to explain J1249+36’s unusual trajectory. In the first scenario, J1249+36 was originally the low-mass companion of a white dwarf. White dwarfs are the remnant cores of stars that have depleted their nuclear fuel and died out. When a stellar companion is in a very close orbit with a white dwarf, it can transfer mass, resulting in periodic outbursts called novae. If the white dwarf collects too much mass, it can collapse and explode as a supernova.
“In this kind of supernova, the white dwarf is completely destroyed, so its companion is released and flies off at whatever orbital speed it was originally moving, plus a little bit of a kick from the supernova explosion as well,” said Burgasser. “Our calculations show this scenario works. However, the white dwarf isn’t there anymore and the remnants of the explosion, which likely happened several million years ago, have already dissipated, so we don’t have definitive proof that this is its origin.”
In the second scenario, J1249+36 was originally a member of a globular cluster, a tightly bound cluster of stars, immediately recognizable by its distinct spherical shape. The centers of these clusters are predicted to contain black holes of a wide range of masses. These black holes can also form binaries, and such systems turn out to be great catapults for any stars that happen to wander too close to them.
“When a star encounters a black hole binary, the complex dynamics of this three-body interaction can toss that star right out of the globular cluster,” explained Kyle Kremer, an incoming Assistant Professor in UC San Diego’s Department of Astronomy and Astrophysics. Kremer ran a series of simulations and found that on rare occasions these kinds of interactions can kick a low-mass subdwarf out of a globular cluster and on a trajectory similar to that observed for J1249+36.
“It demonstrates a proof of concept,” said Kremer, “but we don’t actually know what globular cluster this star is from.” Tracing J1249+36 back in time puts it in a very crowded part of the sky that may hide undiscovered clusters.
To determine whether either of these scenarios, or some other mechanism, can explain J1249+36’s trajectory, Burgasser said the team hopes to look more closely at its elemental composition. For example, when a white dwarf explodes, it creates heavy elements that could have “polluted” the atmosphere of J1249+36 as it was escaping. The stars in globular clusters and satellite galaxies of the Milky Way also have distinct abundance patterns that may reveal the origin of J1249+36.
“We’re essentially looking for a chemical fingerprint that would pinpoint what system this star is from,” said Gerasimov, whose modeling work has enabled him to measure the element abundances of cool stars in several globular clusters, work he is also presenting at the AAS meeting.
Whether J1249+36’s speedy journey was because of a supernova, a chance encounter with a black hole binary, or some other scenario, its discovery provides a new opportunity for astronomers to learn more about the history and dynamics of the Milky Way.
METHOD OF RESEARCH
Observational study
George Mason University announces its first NASA Space Mission which seeks to uncover the secrets of dark energy
$19.5M Landolt Mission will launch artificial star into
Earth's Orbit
GEORGE MASON UNIVERSITY
George Mason University will be the home of the $19.5 million recently approved Landolt NASA Space Mission that will put an artificial “star” in orbit around the Earth. This artificial star will allow scientists to calibrate telescopes and more accurately measure the brightness of stars ranging from those nearby to the distant explosions of supernova in far-off galaxies. By establishing absolute flux calibration, the mission will begin to address several open challenges in astrophysics including the speed and acceleration of the universe expansion.
"This mission marks another first for George Mason University, a milestone that proves our impact as a major public research university truly knows no bounds,” George Mason University President Gregory Washington said. “It's an honor for George Mason to lead this unique team seeking to expand the boundaries of knowledge through College of Science associate professor Peter Plavchan’s collaboration with NASA, one of George Mason's most prestigious research partners.”
Scientists know the universe is expanding, which is measured by calculating the brightness of numerous stars and by the number of photons-per-second they emit. According to Plavchan, a George Mason associate professor of physics and astronomy and the Landolt Mission principal investigator, more accurate measurements are needed for the next breakthroughs.
Named for late astronomer Arlo Landolt, who put together widely used catalogs of stellar brightness throughout the 1970s through the 1990s, this mission will launch a light into the sky in 2029 with a known emission rate of photons, and the team will observe it next to real stars to make new stellar brightness catalogs. The satellite (artificial star) will have eight lasers shining at ground optical telescopes in order to calibrate them for observations. The effort will not make the artificial stars so bright as to see with the naked eye, but one can see it with a personal telescope at home.
“This mission is focused on measuring fundamental properties that are used daily in astronomical observations,” said Eliad Peretz, NASA Goddard mission and instrument scientist and Landolt’s deputy principal investigator. “It might impact and change the way we measure or understand the properties of stars, surface temperatures, and the habitability of exoplanets.”
The artificial star will orbit earth 22,236 miles up, far enough away to look like a star to telescopes back on Earth. This orbit also allows it to move at the same speed of the Earth’s rotation, keeping it in place over the United States during its first year in space. “This is what is considered an infrastructure mission for NASA, supporting the science in a way that we’ve known we needed to do, but with a transformative change in how we do it,” Plavchan explained.
The payload, which is the size of the proverbial bread box, will be built in partnership with the National Institute of Standards and Technology (NIST), a world leader in measuring photon emissions. “This calibration under known laser wavelength and power will remove effects of atmosphere filtration of light and allow scientists to significantly improve measurements,” explained Peter Pachowicz, associate professor in Mason’s Department of Electrical and Computer Engineering, who is leading this component of the mission.
George Mason faculty and students from Mason’s College of Science and College of Engineering and Computing will work together with the NASA and NIST and nine other organizations for a first-of-its-kind project for a university in the Washington, D.C., area. Pachowicz added, “This is an incredibly exciting opportunity for George Mason and our students. Our team will design, build, and integrate the payload, which—because it’s going very high into geostationary orbit—must handle incredible challenges.”
With mission control based at George Mason on its Fairfax Campus, the team also includes Blue Canyon Technologies; California Institute of Technology; Lawrence Berkeley National Laboratory; Mississippi State University; Montreal Planetarium and iREx/University of Montreal; the University of Florida; the University of Hawaiʻi; the University of Minnesota, Duluth; and the University of Victoria.
With more accurate measurements, experts will use the improved data from the project to enhance understanding of stellar evolution, habitable zones or exoplanets in proximity to Earth, and refine dark energy parameters, setting a foundation for the next great leaps in scientific discovery. “When we look at a star with a telescope, no one can tell you today the rate of photons or brightness coming from it with the desired level of accuracy,” Plavchan, who is also the director of Mason’s Observatories in Fairfax, said. “We will now know exactly how many photons-per-second come out of this source to .25 percent accuracy.”
"Flux calibration is essential for astronomical research.” explained NIST’s Susana Deustua, a Physical Scientist in the NIST Remote Sensing Group. “We constantly ask: ‘How big? How bright? How far?’ and then ponder: ‘What is the universe made of? Are we alone?’ Accurate answers require precise measurements and excellent instrument characterization,” Deustua said.
Partners weigh in on the magnitude and opportunity with this critical Landolt Mission: NIST scientists S. Deustua, J. Rice, and B. Alberding will apply their expertise to the calibration of Landolt-emitted light. This will be critical, as precise calibration enables astronomers to better answer pressing questions like: “Are there other Earths? What is the history of the Universe?"
"Major new telescopes – like NASA’s Nancy Grace Roman Space Telescope and the Vera C. Rubin Observatory – intend to measure the expansion history of the universe using the brightnesses of supernovae. However, errors in brightness calibration across wavelengths could lead to incorrect measurements. Landolt will solve this problem by providing telescopes with light of known brightness," said Greg Aldering of Lawrence Berkeley National Laboratory's Physics Division, who will serve on the Landolt science team to ensure that it is designed and performs as needed for precision cosmology measurements. Once the Landolt satellite is in orbit, Aldering and his team plan to observe the calibrated light from Landolt with ground-based instruments, including the SuperNova Integral Field Spectrograph (SNIFS) in Hawaii, built in part by Lawrence Berkeley National Laboratory, and the Vera C. Rubin Observatory in Chile, equipped with a 3.2 billion pixel camera built by DOE.
“Being a part of this space mission along with brilliant experts by contributing to target selection and data analysis is an exciting prospect,” said Canada’s Jonathan Gagné, scientific advisor at the Planétarium | Montréal Space for Life, adjunct professor at Université de Montréal, and member of the Trottier Institute for Research on Exoplanets (iRex). “The impact that the Landolt mission will have in different areas of astrophysics, notably in exoplanet characterization and in measuring the accelerating expansion of the Universe, will be particularly important,” Gagné explained.
"The measurements by Landolt will enable tremendous progress for a wide range of ground-based astronomical observations,” said Daniel Huber, associate professor at the University of Hawaiʻiʻs Institute for Astronomy. The University of Hawaiʻi will provide access to the UH88 telescope located atop of Maunakea, Hawaiʻi, one of the ground stations that will observe Landolt during its mission. Maunakea is one of the best sites for ground-based astronomy in the world.
“The University of Victoria is excited to be an institutional collaborator on the NASA Landolt mission. We will leverage what we've learned from the CSA-funded, UVic-led ORCASat CubeSat satellite mission and are greatly looking forward to contributing to the success of this new mission,” said Justin Albert, professor of physics and astronomy at University of Victoria.
“This project is tackling a truly fundamental problem in astronomy in a very novel way,” said Dan Stevens, PhD, an assistant professor of Astronomy at the University of Minnesota Duluth. “By creating an "artificial star,” measuring its brightness in the laboratory, and launching it into space, our team will then be able to take lab-calibrated measurements of real stars' actual, absolute brightnesses. This level of accuracy wasn’t possible before, and it will allow us to overcome decades-long sources of uncertainty in how well we measure the fundamental properties of stars and the planets they host.”
“Landolt is an exciting opportunity to enable absolute calibration in astronomy at an unprecedented level,” said David Ciardi, Chief Scientist for NASA Exoplanet Science Institute (NExScI) at Caltech/IPAC. “For as long as people have looked up at the night sky, a fundamental question has always been: ‘What is the true brightness of that star?’ Landolt has the opportunity to change astronomy for the relatively minimal cost of a NASA Astrophysics Pioneer program,” Ciardi explained.
NExScI, responsible for the Landolt data archiving and contributing to the ground support through Palomar Observatory suggests, “Even with today’s modern instruments, true brightness calibration has only been good to a few percent, and Landolt will enable an improvement by more than a factor of 10. Understanding the true brightness of stars allows to understand the stars better – and, perhaps more importantly, understand the planets that orbit the stars better.
The solar system may have passed through dense interstellar clouds 2 million years ago, altering Earth’s climate
Astrophysicists calculate the likelihood that Earth was exposed to cold, harsh interstellar clouds, a phenomenon not previously considered in geologic climate models
Around two million years ago, Earth was a very different place, with our early human ancestorsliving alongside saber-toothed tigers, mastodons, and enormous rodents. And, depending on where they were, they may have been cold: Earth had fallen into a deep freeze, with multiple ice ages coming and going until about 12,000 years ago. Scientists theorize that ice ages occur for a number of reasons, including the planet’s tilt and rotation, shifting plate tectonics, volcanic eruptions, and carbon dioxide levels in the atmosphere. But what if drastic changes like these are not only a result of Earth’s environment, but also the sun’s location in the galaxy?
In a new paper published in Nature Astronomy, lead authorand astrophysicist Merav Opher—an astronomy professor at Boston University and fellow at Harvard Radcliffe Institute— found evidence that some two million years ago, the solar system encountered an interstellar cloud so dense that it could have interfered with the sun’s solar wind. Opher and her co-authors believe this shows that the sun’s location in space might shape Earth’s history more than previously considered.
Our whole solar system is swathed in a protective plasma shield that emanates from the sun, known as the heliosphere. It’s made from a constant flow of charged particles, called solar wind, that stretch well past Pluto, wrapping the planets in what NASA calls a “a giant bubble.” It protects us from radiation and galactic rays that could alter DNA, and scientists believe it’s part of the reason life evolved on Earth as it did. According to the latest paper, the cold cloud compressed the heliosphere in such a way that it briefly placed Earth and the other planets in the solar system outside of the heliosphere’s influence.
“This paper is the first to quantitatively show there was an encounter between the sun and something outside of the solar system that would have affected Earth’s climate,” says Opher, who is an expert on the heliosphere. Her models have quite literally shaped our scientific understanding of the heliosphere, and how the bubble is structured by the solar wind pushing up against the interstellar medium—which is the space in between stars and beyond the heliosphere in our galaxy. Her theory is that the heliosphere is shaped like a puffy croissant, an idea that shook the space physics community. Now, she’s shedding new light on how the heliosphere, and where the sun moves through space, could affect Earth’s atmospheric chemistry.
“Stars move, and now this paper is showing not only that they move, but they encounter drastic changes,” says Opher. She first discovered and began working on this study during a yearlong fellowship at Harvard Radcliffe Institute.
To study this phenomenon, Opher and her collaborators essentially looked back in time, using sophisticated computer models to visualize where the sun was positioned two million years in the past—and, with it, the heliosphere, and the rest of the solar system. They also mapped the path of the Local Ribbon of Cold Clouds system, a string of large, dense, very cold clouds mostly made of hydrogen atoms. Their simulations showed that one of the clouds close to the end of that ribbon, named the Local Lynx of Cold Cloud, could have collided with the heliosphere.
If that had happened, says Opher, Earth would have been fully exposed to the interstellar medium, where gas and dust mix with the leftover atomic elements of exploded stars, including iron and plutonium. Normally, the heliosphere filters out most of these radioactive particles. But without protection, they can easily reach Earth. According to the paper, this aligns with geological evidence that shows increased 60Fe (iron 60) and 244Pu (plutonium 244) isotopes in the ocean, on the moon, Antarctic snow, and ice cores from the same time period. The timing also matches with temperature records that indicate a cooling period.
“Only rarely does our cosmic neighborhood beyond the solar system affect life on Earth,” says Avi Loeb, director of Harvard University’s Institute for Theory and Computation and coauthor on the paper. “It is exciting to discover that our passage through dense clouds a few million years ago could have exposed the Earth to a much larger flux of cosmic rays and hydrogen atoms. Our results open a new window into the relationship between the evolution of life on Earth and our cosmic neighborhood.”
The outside pressure from the Local Lynx of Cold Cloud could have continually blocked out the heliosphere for a couple of hundred years to a million years, Opher says—depending on the size of the cloud. “But as soon as the Earth was away from the cold cloud, the heliosphere engulfed all the planets, including Earth,” she says. And that’s how it is today.
It’s impossible to know the exact effect the cold clouds had on Earth—like if it could have spurred an ice age. But there are a couple of other cold clouds in the interstellar medium that the sun has likely encountered in the billions of years since it was born, Opher says. And it will likely stumble across more in another million years or so. Opher and her collaborators are now working to trace where the sun was seven million years ago, and even further back. Pinpointing the location of the sun millions of years in the past, as well as the cold cloud system, is possible with data collected by the European Space Agency’s Gaia mission, which is building the largest 3D map of the galaxy and giving an unprecedented look at the speed stars move.
“This cloud was indeed in our past, and if we crossed something that massive, we were exposed to the interstellar medium,” Opher says. The effect of crossing paths with so much hydrogen and radioactive material is unclear, so Opher and her team at BU’s NASA-funded SHIELD (Solar wind with Hydrogen Ion Exchange and Large-scale Dynamics) DRIVE Science Center are now exploring the effect it could have had on Earth’s radiation, as well as the atmosphere and climate.
“This is only the beginning,” Opher says. She hopes that this paper will open the door to much more exploration of how the solar system was influenced by outside forces in the deep past and how these forces have in turn shaped life on our planet.
A possible direct exposure of the Earth to the cold dense interstellar medium 2–3 Myr ago
ARTICLE PUBLICATION DATE
10-Jun-2024
In new experiment, scientists record Earth’s radio waves from the moon
UNIVERSITY OF COLORADO AT BOULDER
On Feb. 22, a lunar lander named Odysseus touched down near the Moon’s South Pole and popped out four antennas to record radio waves around the surface—a moment University of Colorado Boulder astrophysicist Jack Burns hails as the “dawn of radio astronomy from the Moon.”
It was a major achievement for the tenacious lander, which was built by the Houston-based company Intuitive Machines and had to overcome a series of technical difficulties to make it to the lunar surface. Burns is co-investigator on the radio experiment that flew aboard Odysseus called Radio wave Observations at the Lunar Surface of the photo Electron Sheath (ROLSES).
He’ll give an update on the ROLSES data, and will share what’s in store for future radio astronomy from the Moon, this week at the 244th Meeting of the American Astronomical Society in Madison, Wisconsin. A press conference will take place Monday, June 10 at 10:15 a.m. Central Time.
“It was heroic for Intuitive Machines to land under these conditions, and to deploy our antennas, take some data and get that data back to Earth,” said Burns, professor emeritus in the Department of Astrophysical and Planetary Sciences at CU Boulder.
Natchimuthuk Gopalswamy at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, led the ROLSES experiment. The instrument, which included the antennas and a device called a radio spectrometer, was designed to record a wide range of radio emissions near the Moon and deep in space.
Despite the challenges of the mission, ROLSES managed to view Earth in a unique way.
“We viewed Earth as an exoplanet, or a planet orbiting another star,” Burns said. “That enables us to ask: What would our radio emissions from Earth look like if they came from an extraterrestrial civilization on a nearby exoplanet?”
Earth selfie
Odysseus traveled to the Moon as part of NASA’s Commercial Lunar Payload Services (CLPS) program, an ambitious effort to land spacecraft built by private companies on the lunar surface. It was the first such mission to achieve what NASA calls a “soft landing,” although it tipped onto its side in the process.
But it almost didn’t happen. Among other challenges, Odysseus wasn’t able to use its laser-guided navigation system to land on the Moon’s craggy surface. Instead, operators at Intuitive Machines relied entirely on the lander’s optical camera system—an impressive feat of maneuvering.
As Odysseus was traveling to the Moon, one of the ROLSES antennas slightly overheated and popped out of its housing on the lander. (A selfie from the spacecraft shows the antenna sticking out in space). It turned out to be a stroke of good luck, Burns said.
The team used the accident to look back at Earth and record radio waves emanating from the planet for nearly an hour-and-a-half. Human technologies, including cell phones and broadcast towers, churn out radio radiation on a near constant basis. Astronomer Carl Sagan spearheaded a similar experiment from NASA’s Galileo spacecraft in the 1990s, but the ROLSES data were more exhaustive.
Burns noted that scientists may be able to look for similar fingerprints coming from planets far away from our own—a potential sign of intelligent life.
Moonrise
He and his colleagues are just getting started. NASA has already greenlit a second ROLSES experiment, which will fly on another CLPS lander, likely in 2026.
The astrophysicist is also part of a third CLPS experiment, known as the Lunar Surface Electromagnetics Experiment-Night (LuSEE-Night), scheduled to arrive at the Moon in 2026. The instrument will land on the far side of the Moon, a quiet spot that human radio emissions can’t reach. From there, it will gaze at radio emissions coming not from Earth but from the earliest days of the Universe before the first stars formed called the Dark Ages—shedding more light on how the cosmos evolved during this crucial junction its history.
“Because NASA is going to send two or three landers to the Moon every year, we have a way to upgrade our instruments and learn from what goes wrong in a way we haven’t been able to do since the early days of the space program,” Burns said.
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