Listen to a star ‘twinkle’

New study is first to determine how much stars should innately twinkle

Peer-Reviewed Publication

NORTHWESTERN UNIVERSITY

 

VIDEO: VISUALIZATION OF "JUPITER" BY GUSTAV HOLST PLAYED THROUGH THREE SIZES OF MASSIVE STARS. view more 

CREDIT: NORTHWESTERN UNIVERSITY

Many people know that stars appear to twinkle because our atmosphere bends starlight as it travels to Earth. But stars also have an innate “twinkle” — caused by rippling waves of gas on their surfaces — that is imperceptible to current Earth-bound telescopes.

In a new study, a Northwestern University-led team of researchers developed the first 3D simulations of energy rippling from a massive star’s core to its outer surface. Using these new models, the researchers determined, for the first time, how much stars should innately twinkle. 

And, in yet another first, the team also converted these rippling waves of gas into sound waves, enabling listeners to hear both what the insides of stars and the “twinkling” should sound like. And it is eerily fascinating.

The study will be published on July 27, in the journal Nature Astronomy.

“Motions in the cores of stars launch waves like those on the ocean,” said Northwestern’s Evan Anders, who led the study. “When the waves arrive at the star’s surface, they make it twinkle in a way that astronomers may be able to observe. For the first time, we have developed computer models which allow us to determine how much a star should twinkle as a result of these waves. This work allows future space telescopes to probe the central regions where stars forge the elements we depend upon to live and breathe.”

Anders is a postdoctoral fellow in Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). He is advised by study coauthor Daniel Lecoanet, an assistant professor of engineering sciences and applied mathematics in Northwestern’s McCormick School of Engineering and member of CIERA.

Chaotic convection

All stars have a convection zone, a wild and disorderly place where gases churn to push heat outward. For massive stars (stars at least about 1.2 times the mass of our sun), this convection zone resides at their cores.

“Convection within stars is similar to the process that fuels thunderstorms,” Anders said. “Cooled air drops, warms and rises again. It’s a turbulent process that transports heat.”

It also makes waves — small rivulets that cause starlight to dim and brighten, producing a subtle twinkle. Because the cores of massive stars are shrouded from view, Anders and his team sought to model their hidden convection. Building upon studies that examined properties of turbulent core convection, characteristics of waves and possible observational features of those waves, the team’s new simulations include all relevant physics to accurately predict how a star’s brightness changes depending upon convection-generated waves.

‘Soundproofing’ stars

After convection generates waves, those waves bounce around inside of the simulated star. While some waves eventually emerge to the star’s surface to produce a twinkling effect, other waves become trapped and continue to bounce around. To isolate the waves that launch to the surface and create twinkling, Anders and his team built a filter that describes how waves bounce around inside of the simulations.

“We first put a damping layer around the star — like the padded walls you would have in a recording studio — so we could measure exactly how the core convection makes waves,” Anders explained. 

Anders compares it to a music studio, which leverages soundproof padded walls to minimize the acoustics of an environment so musicians can extract the “pure sound” of the music. Musicians then apply filters and engineer those recordings to produce the song how they want. 

Similarly, Anders and his collaborators applied their filter to the pure waves they measured coming out of the convective core. They then followed waves bouncing around in a model star, ultimately finding that their filter accurately described how the star changed the waves coming from the core. The researchers then developed a different filter for how waves should bounce around inside of a real star. With this filter applied, the resulting simulation shows how astronomers expect waves to appear if viewed through a powerful telescope.

“Stars get a little brighter or a little dimmer depending on various things happening dynamically inside the star,” Anders said. “The twinkling that these waves cause is extremely subtle, and our eyes are not sensitive enough to see it. But powerful future telescopes may be able to detect it.”

Music in the stars

Taking the recording studio analogy one step further, Anders and his collaborators next used their simulations to generate sound. Because these waves are outside the range of human hearing, the researchers uniformly increased the frequencies of the waves to make them audible.

Depending on how large or bright a massive star is, the convection produces waves corresponding to different sounds. Waves emerging from the core of a large star, for example, make sounds like a warped ray gun, blasting through an alien landscape. But the star alters these sounds as the waves reach the star’s surface. For a large star, the ray gun-like pulses shift into a low echo reverberating through an empty room. Waves at the surface of a medium-sized star, on the other hand, conjure images of a persistent hum through a windswept terrain. And surface waves on a small star sound like a plaintive alert from a weather siren.

Next, Anders and his team passed songs through different stars to listen to how the stars change the songs. They passed a short audio clip from “Jupiter”(a movement from “The Planets” orchestral suite by composer Gustav Holst) and from “Twinkle, Twinkle, Little Star” through three sizes (large, medium and small) of massive stars. When propagated through stars, all songs sound distant and haunting — like something from “Alice in Wonderland.”

“We were curious how a song would sound if heard as propagated through a star,” Anders said. “The stars change the music and, correspondingly, change how the waves would look if we saw them as twinkling on the star’s surface.”

The study, “The photometric variability of massive stars due to gravity waves excited by core convection,” was supported by CIERA, NASA and the National Science Foundation.

"Twinkle, Twinkle, Little Star [VIDEO] | 

JOURNAL

Nature Astronomy

DOI

10.1038/s41550-023-02040-7 

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

The photometric variability of massive stars due to gravity waves excited by core convection

ARTICLE PUBLICATION DATE

27-Jul-2023

 

Twinkling of giant stars reveals how their innards churn in first-ever simulations

Astrophysicists at the Flatiron Institute and their colleagues have created the first computer simulations showing how convection in the cores of massive stars generates waves that result in flickering starlight.

Peer-Reviewed Publicatio

SIMONS FOUNDATION

 

VIDEO: A 3D SIMULATION OF HOW TURBULENT CONVECTION IN THE CORE OF A LARGE STAR (CENTER) CAN GENERATE WAVES THAT RIPPLE OUTWARD AND POWER RESONANT VIBRATIONS NEAR THE STAR’S SURFACE. BY STUDYING CHANGES IN THE STAR’S BRIGHTNESS CAUSED BY THE VIBRATIONS, SCIENTISTS COULD ONE DAY BETTER UNDERSTAND THE PROCESSES DEEP IN THE HEARTS OF LARGE STARS. view more 

CREDIT: E.H. ANDERS ET AL./NATURE ASTRONOMY 2023

Secrets hide in the twinkling of stars.

A research team led by scientists at the Flatiron Institute and Northwestern University has created first-of-their-kind computer simulations showing how churning deep in a star’s depths can cause the star’s light to flicker. This effect is different from the visible twinkling of stars in the night sky caused by Earth’s atmosphere.

By closely observing the innate twinkling of stars, astronomers could one day use the simulations to learn more about what goes on inside stars larger than our sun, the researchers report on July 27 in Nature Astronomy.

The effects are too small for current telescopes to pick up, says study co-author Matteo Cantiello, a research scientist at the Flatiron Institute’s Center for Computational Astrophysics (CCA) in New York City. That could change with improved telescopes. “We’ll be able to see the signature of the core,” Cantiello says, “which will be quite interesting because it will be a way to probe the very inner regions of stars.”

A better understanding of stellar innards will help astronomers learn how stars form and evolve, how galaxies assemble, and how heavy elements such as the oxygen we breathe are created, says study lead author Evan Anders, a postdoctoral researcher at Northwestern University.

“Motions in the cores of stars launch waves like those on the ocean,” Anders says. “When the waves arrive at the star’s surface, they make it twinkle in a way that astronomers may be able to observe. For the first time, we have developed computer models which allow us to determine how much a star should twinkle as a result of these waves. This work allows future space telescopes to probe the central regions where stars forge the elements we depend upon to live and breathe.”

Intriguingly, the new simulations also widen a years-long stellar mystery. Astronomers have consistently observed an unexplained pulsing — or ‘red noise’ — causing fluctuations in the brightness of hot, massive stars. A popular proposal was that convection in the stars’ cores causes this flickering. The new simulations, however, show that the twinkling induced by core convection is far too faint to match the observed red noise. Something else must be responsible, the researchers report in their new paper.

A Deep Squeeze

A star’s convection is powered by the nuclear reactor at its core. In the heart of a star, intense pressure squeezes hydrogen atoms together to form helium atoms plus a bit of excess energy. That energy generates heat, which causes clumps of plasma to rise like the goo in a lava lamp. But unlike a lava lamp, the convection is turbulent like a pot of boiling water. This movement generates waves just like those found in Earth’s oceans. Those waves then ripple outward to the star’s surface, where they compress and decompress the star’s plasma, causing brightening and dimming of the star’s light. By studying a star’s brightness, scientists realized they might be able to glean what’s going in the star’s core.

Simulating the wave generation and propagation in a computer is absurdly difficult, though, Cantiello says. That’s because while a wave-generating flow in the star’s core lasts a few weeks, the waves generated can linger for hundreds of thousands of years. Connecting those drastically different timescales — weeks and hundreds of millennia — posed a serious challenge.

The researchers took inspiration from a different form of waves: the sound waves that make up music. They realized that the convection-induced wave generation in the core is like a group of musicians in a concert hall. The musicians strumming their instruments produce a sound that is altered as it bounces around the venue. The researchers found they could first calculate the unaltered “song” of the convection-induced waves and then apply a filter that replicated the star’s acoustic properties — a similar process to that of a professional sound engineer.

The researchers tested their method using sound waves from real music, including “Jupiter” from Gustav Holst’s orchestral suite “The Planets” and, rather appropriately, “Twinkle, Twinkle, Little Star.” They simulated how those sound waves would bounce around inside stars of different sizes, producing a haunting result.

After this validation of their approach, the researchers simulated the convection-induced waves and resulting starlight fluctuations of stars whose masses are three, 15 and 40 times that of our sun. For all three sizes, the core convection did indeed cause flickering light intensity near the surface, but not at the frequencies or intensities characteristic of the red noise astronomers had seen.

Convection may still be responsible for red noise, Cantiello says, but it would likely be far nearer to the star’s surface and therefore less telling of what’s going on in the star’s deep interior.

The researchers are now improving their simulations to consider additional effects, such as the rapid spinning of a star around its axis, a common feature of stars more massive than our sun. They’re curious if fast-spinning stars have a strong enough flickering induced by core convection to be picked up by current telescopes. “It’s an interesting question we’re hoping to get an answer to,” Cantiello says.

Surface Waves [AUDIO] | EurekAlert! 

Unaltered Audio [AUDIO] | EurekAlert! 

Audio (Three Solar Masses) [AUDIO] |

Audio (15 Solar Masses) [AUDIO] |

Audio (40 Solar Masses) [AUDIO] |

ABOUT THE FLATIRON INSTITUTE

The Flatiron Institute is the research division of the Simons Foundation. The institute's mission is to advance scientific research through computational methods, including data analysis, theory, modeling and simulation. The institute's Center for Computational Astrophysics creates new computational frameworks that allow scientists to analyze big astronomical datasets and to understand complex, multi-scale physics in a cosmological context.

---

JOURNAL

Nature Astronomy

DOI

10.1038/s41550-023-02040-7 

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

The photometric variability of massive stars due to gravity waves excited by core convection

ARTICLE PUBLICATION DATE

27-Jul-2023

 

James Webb Space Telescope sees Jupiter moons in a new light

Hydrogen peroxide detected at Ganymede's poles; sulfur monoxide from Io's volcanos

Peer-Reviewed Publication

UNIVERSITY OF CALIFORNIA - BERKELEY

 

IMAGE: A SPECTROSCOPIC MAP OF GANYMEDE DERIVED FROM JWST MEASUREMENTS SHOWS LIGHT ABSORPTION AROUND THE POLES CHARACTERISTIC OF THE MOLECULE HYDROGEN PEROXIDE. THE CIRCLE OUTLINES THE SURFACES OF THE MOON. view more 

CREDIT: SAMANTHA TRUMBO, CORNELL

With its sensitive infrared cameras and high-resolution spectrometer, the James Webb Space Telescope (JWST) is revealing new secrets of Jupiter's Galilean satellites, in particular Ganymede, the largest moon, and Io, the most volcanically active.

In two separate publications, astronomers who are part of JWST's Early Release Science program report the first detection of hydrogen peroxide on Ganymede and sulfurous fumes on Io, both the result of Jupiter's domineering influence.

"This shows that we can do incredible science with the James Webb Space Telescope on solar system objects, even if the object is really very bright, like Jupiter, but also when you look at very faint things next to Jupiter," said Imke de Pater, professor emerita of astronomy and earth and planetary science at the University of California, Berkeley. De Pater and Thierry Fouchet from the Paris Observatory are co-principal investigators for the Early Release Science solar system observation team, one of 13 teams given early access to the telescope.

Samantha Trumbo, a 51 Pegasi b postdoctoral fellow at Cornell University, led the study of Ganymede, which was published July 21 in the journal Science Advances. Using measurements captured by the near infrared spectrometer (NIRSpec) on JWST, the team detected the absorption of light by hydrogen peroxide — H2O2 — around the north and south poles of the moon, a result of charged particles around Jupiter and Ganymede impacting the ice that blankets the moon.

"JWST revealing the presence of hydrogen peroxide at Ganymede’s poles shows for the first time that charged particles funneled along Ganymede’s magnetic field are preferentially altering the surface chemistry of its polar caps," Trumbo said.

The astronomers argue that the peroxide is produced by charged particles hitting the frozen water ice around the poles and breaking the water molecules into fragments — a process called radiolysis — which then recombine to form H2O2. They suspected that radiolysis would occur primarily around the poles on Ganymede because, unlike all other moons in our solar system, it has a magnetic field that directs charged particles toward the poles.

"Just like how Earth’s magnetic field directs charged particles from the sun to the highest latitudes, causing the aurora, Ganymede’s magnetic field does the same thing to charged particles from Jupiter’s magnetosphere," she added. "Not only do these particles result in aurorae at Ganymede, as well, but they also impact the icy surface."

Trumbo and Michael Brown, professor of planetary astronomy at Caltech, where Trumbo recently received her Ph.D., had earlier studied hydrogen peroxide on Europa, another of Jupiter's four Galilean satellites. On Europa, however, the peroxide was detectable over much of the surface, perhaps, in part, because it has no magnetic field to protect the surface from the fast-moving particles zipping around Jupiter.

"This is likely a really important and widespread process," Trumbo said. "These observations of Ganymede provide a key window to understand how such water radiolysis might drive chemistry on icy bodies throughout the outer solar system, including on neighboring Europa and Callisto (the fourth Galilean moon)."

"It helps to actually understand how this so-called radiolysis works and that, indeed, it works as people expected, based on lab experiments on Earth," de Pater said.

A JWST infrared image of Io shows hot volcanic eruptions at Kanehekili Fluctus (center) and Loki Patera (right). The circle outlines the surface of the moon.

CREDIT

Imke de Pater, UC Berkeley

Io's sulfurous environment

In a second paper, accepted for publication in the journal JGR: Planets, a publication of the American Geophysical Union, de Pater and her colleagues report new Webb observations of Io that show several ongoing eruptions, including a brightening at a volcanic complex called Loki Patera and an exceptionally bright eruption at Kanehekili Fluctus. Because Io is the only volcanically active moon in the solar system — Jupiter's gravitational push and pull heats it up — studies like this give planetary scientists a different perspective than can be obtained by studying volcanos on Earth.

For the first time, the researchers were able to link a volcanic eruption — at Kanehekili Fluctus — to a specific emission line, a so-called “forbidden” line, of the gas sulfur monoxide (SO).

Sulfur dioxide (SO2) is the main component of Io's atmosphere, coming from sublimation of SO2 ice, as well as ongoing volcanic eruptions, similar to the production of SO2 by volcanos on Earth. The volcanos also produce SO, which is much harder to detect than SO2. In particular, the forbidden SO emission line is very weak because SO is in such low concentrations and produced for only a short time after being excited. Moreover, the observations can only be made when Io is in Jupiter’s shadow, when it is easier to see the glowing SO gases. When Io is in Jupiter's shadow, the SO2 gas in Io’s atmosphere freezes out onto its surface, leaving only SO and newly emitted volcanic SO2 gas in the atmosphere.

"These observations with Webb show for the first time that the SO actually did come from a volcano," de Pater said.

De Pater had made previous observations of Io with the Keck Telescope in Hawaii and found low levels of the forbidden SO emission over much of the moon, but she was unable to tie SO hotspots specifically to an active volcano. She suspects that much of this SO, as well as the SO2 seen during an eclipse, is coming from so-called stealth volcanoes, which erupt gas but not dust, which would make them visible.

Twenty years ago, de Pater and her team proposed that this excited state of SO could only be produced in hot volcanic vents, and that the tenuous atmosphere allowed this state to stick around long enough — a few seconds — to emit the forbidden line. Normally, excited states that produce this emission are quickly damped out by collisions with other molecules in the atmosphere and never seen. Only in parts of the atmosphere where the gas is sparse do such excited states last long enough to emit forbidden lines. The greens and reds of Earth's auroras are produced by forbidden transitions of oxygen in the tenuous upper atmosphere.

"The link between SO and volcanoes ties in with a hypothesis we had in 2002 to explain how we could see SO emission at all," she said. "The only way we could explain this emission is if the SO is excited in the volcanic vent at a temperature of 1500 Kelvin or so, and that it comes out in this excited state, loses its photon within a few seconds, and that is the emission we see. So these observations are the first that actually show that this is the most likely mechanism of why we see that SO."

Webb will observe Io again in August with NIRSpec. The upcoming observation and the earlier one, which took place on Nov. 15, 2022, were taken when Io was in the shadow of Jupiter so that light reflected from the planet did not overwhelm the light coming from Io.

De Pater noted, too, that the brightening of Loki Patera was consistent with the observed period of eruptions at the volcano, which brighten, on average, about every 500 Earth days, with the brightening lasting for a couple of months. She determined this because it was not bright when she observed the moon with Keck in August and September 2022, nor was it bright when another astronomer observed it from April through July 2022. Only the JWST captured the event.

"The Webb observations showed that actually eruptions had started, and that it was much brighter than what we had seen in September," she said.

While De Pater is primarily focused on the Jovian system — its rings, small moons and the larger moons Ganymede and Io — she and other members of the early science team of some 80 astronomers are also using JWST to study the planetary systems of Saturn, Uranus and Neptune.

JWST measurements obtained in November 2022 overlaid on a map of Io's surface. Thermal infrared measurements (left) show a brightening of Kanekehili Fluctus, a large and, during the observation period, very active volcanic area on Io. Spectral measurements (right) show forbidden infrared emissions from sulfur monoxide centered on the volcanic area. The coincidence confirms a theory that SO is produced in volcanic vents and, in the very thin atmosphere of Io, remain around long enough to emit the forbidden line that would normally be suppressed by collisions with other molecules in the atmosphere.

CREDIT

Chris Moeckel and Imke de Pater, UC Berkeley; Io map courtesy of USGS

---

JOURNAL

Science Advances

DOI

10.1126/sciadv.adg3724 

ARTICLE TITLE

Hydrogen Peroxide at the Poles of Ganymede

ARTICLE PUBLICATION DATE

27-Jul-2023

Boeing's Starliner program racks up $1.4B in losses

Story by Daniella Genovese • FOX NEWS

 Boeing took a massive financial hit stemming from the planned crew launch of its Starliner spacecraft this month. 

The Starliner program incurred a $257 million loss during the second quarter "primarily due to the impacts of the previously announced launch delay," Boeing reported Wednesday. 

It pushes Boeing's total charges for the program to about $1.4 billion, Boeing confirmed with FOX Business on Thursday.

BOEING STARLINER DOCKS WITH INTERNATIONAL SPACE STATION FOR FIRST TIME

Boeing will work to launch the Starliner capsule, with astronauts, to and from the International Space Station (ISS) for the first time. 

The capsule was scheduled to have a test flight in July with two astronauts. However, the test flight, already behind schedule, was halted yet again when final reviews uncovered issues with the parachute lines and other problems that were present on last year’s test flight with no one on board. Officials said the issues should have been caught years ago.

During the second quarter, Boeing's Defense, Space, & Security division suffered a $527 million loss in part because of the issues with the Starliner. 

A search and rescue training exercise with the Boeing CST-100 Starliner training capsule is shown at the Army Wharf at Cape Canaveral Air Force Station in Florida on April 23, 2019. 

Paul Hennessy / NurPhoto via Getty Images

Boeing further noted that its Defense, Space & Security second-quarter operating margin was "primarily driven by losses on certain fixed-price development programs, as well as continued operational impacts of labor instability and supply chain disruption on other programs."

Boeing said it is working with NASA to determine a new launch date.

BOEING'S STARLINER RETURNS FROM SPACE STATION

Boeing Program Manager Mark Nappi previously said the test flight could happen by year's end, although he doesn't "want to commit to any dates or time frames" until the problems get fixed.

NASA hired Boeing and SpaceX to transport astronauts to and from the space station, though NASA Commercial Crew Program Manager Steve Stich pleaded for another provider for crew transportation.

SpaceX has now completed 10 crew flights, three of them private. Boeing had to repeat its 2019 test flight without a crew because of software and other issues.

Following a successful test flight with astronauts, NASA previously said it "will begin the final process of certifying the Starliner spacecraft and systems for regular crew rotation flights to the space station."

The goal is to have one SpaceX and one Boeing taxi flight to the station each year.

The Associated Press contributed to this report.

Blue Origin, Astrobotic, Varda Space and others win NASA funding to develop advanced space tech


Image Credits: Blue Origin 

Aria Alamalhodaei
Tue, July 25, 2023 

NASA awarded new funding to 11 companies today for advanced space tech projects ranging from advanced power generation on the lunar surface to additive manufacturing for space habitats.

The awards, which total $150 million across all 11 companies, were announced as part of the space agency’s Tipping Point program. According to NASA, a technology is a “tipping point” if an investment in a demonstration would significantly mature the technology and bring it to market, for both future NASA missions and commercial customers.

In a statement, Prasun Desai, acting associate administrator for NASA’s Space Technology Mission Directorate, said that the awards are meant “to push crucial technologies over the finish line.”

“Our partnerships with industry could be a cornerstone of humanity's return to the Moon under Artemis,” he said.

Five of the 11 awards are for technologies to support long-term exploration of the moon. Those include a $34.7 million award to Blue Origin to continue advancing its solution to process solar cells from lunar regolith, a process the company says “would bootstrap unlimited electricity and power transmission cables anywhere on the surface of the Moon.” The project is part of Blue Origin’s Blue Alchemist initiative it unveiled earlier this year.

Astrobotic, a company that hopes to send a lander to the moon in the fourth quarter of this year, was awarded $34.6 million to demonstrate a new power and transmission system on the lunar surface. The LunaGrid-Lite demonstration will aim to generate solar power and transmit it across a one-kilometer-long power cable on the moon.

“LunaGrid-Lite will pave the way for power generation and distribution services on the Moon, and change the game for lunar surface systems like landers, rovers, habitats, science suits, and in-situ resource utilization pilot plants,” Astrobotic CEO John Thornton said in a statement. “With renewable, uninterrupted commercial power service, both crewed and robotic operations can be made sustainable for long-term operations.”

The other six projects to have received Tipping Point awards are focused on other areas of space technology. Those include a $1.9 million project from in-space manufacturing startup Varda Space Industries to mature and commercialize an advanced thermal protection system material first developed by NASA. United Launch Alliance was awarded $25 million to continue development of an inflatable heat shield technology, which could possibly be used to return portions of a rocket booster from space.

This is the agency’s sixth Tipping Point award cycle. The full list of awardees and NASA’s total contribution to each project can be found here.

NASA gives Blue Origin $34.7M to work on technology for making solar cells on moon

Alan Boyle

GeekWire:
Tue, July 25, 2023 

The Blue Alchemist project aims to produce solar cells from lunar materials.

 (Blue Origin Photo)

Jeff Bezos’ Blue Origin space venture has won $34.7 million in funding from NASA to support the development of a system that could produce solar cells on the moon from materials that are available on site.

The Blue Alchemist project is one of 11 proposals winning support from the space agency’s Tipping Point program, which partners with commercial ventures to back technologies that could contribute to long-term space exploration.

“Harnessing the vast resources in space to benefit Earth is part of our mission, and we’re inspired and humbled to receive this investment from NASA to advance our innovation,” Pat Remias, vice president for Blue Origin’s Capabilities Directorate, Space Systems Development, said today in a news release. “First we return humans to the moon, then we start to ‘live off the land.’”

Blue Alchemist would use lunar regolith — the dust and crushed rock that covers the moon’s surface — as the raw material for solar cells and electrical transmission wire. Oxygen, iron, silicon and aluminum would be extracted through a process known as molten regolith electrolysis, and fed into the manufacturing process. The oxygen could be used for life support or for rocket propulsion.

Kent, Wash.-based Blue Origin has been working on the technology over the past couple of years, with Earth-produced simulants taking the place of lunar regolith.

Blue Origin is also on the team for another Tipping Point project, led by Washington, D.C.-based Zeno Power Systems. Zeno was awarded $15 million for Project Harmonia, which aims to create a new type of radioisotope power supply for the Artemis moon program that uses americium-241 as fuel.

An artist’s conception shows Zeno Power Systems’ radioisotope power supply as a purple-tinged box in a cutaway view of a lunar rover.

 (Zeno Power Systems Illustration)

Other partners on Project Harmonia include Intuitive Machines, NASA Glenn Research Center, NASA Marshall Flight Center, Sunpower and the University of Dayton Research Institute. Zeno plans to have its technology ready for a lunar surface demonstration in 2027. Theoretically, the team’s Stirling generators could provide continuous power to lunar bases for years, using radioactive material that’s currently classified as nuclear waste.

“Project Harmonia will provide the technology to transform the moon from a location darkened by night and shadow to one enlightened by science and exploration, ultimately for the good of the nation and humankind,” Tyler Bernstein, CEO and co-founder of Zeno Power, said in a news release.

This is NASA’s sixth round of Tipping Point grants. Each company receiving a grant is expected to cover a minimum percentage of the total project cost — at least 10% to 25%, based on company size. NASA’s investment in this newest round is expected to amount to $150 million over the course of a period lasting up to four years.

“Partnering with the commercial space industry lets us at NASA harness the strength of American innovation and ingenuity,” NASA Administrator Bill Nelson said in a news release. “The technologies that NASA is investing in today have the potential to be the foundation of future exploration.”

In addition to Blue Origin and Zeno Power, the newly announced Tipping Point awardees include:

Astrobotic Technology of Pittsburgh, $34.6 million – Astrobotic will demonstrate the robotic deployment of one kilometer of cable, and power transmission through that cable across the lunar surface. A CubeRover delivered by Astrobotic’s Griffin lander will deploy the power line. The demonstration will advance power generation and distribution technologies, including a high-voltage power converter and cable, plus a cable reel system.

Big Metal Additive of Denver, $5.4 million – The company will advance materials, manufacturing processes, equipment and facilities for metal hybrid additive manufacturing. The project aims to increase technology readiness and reduce lead time, material waste and cost to enable a range of structural products, including space habitats.

Freedom Photonics of Santa Barbara, California, $1.6 million – Freedom Photonics will develop a new tyupe of direct diode laser source that could enable more efficient lidar systems. The system could better detect methane in Earth’s atmosphere and improve scientists’ understanding of climate change.

Lockheed Martin of Littleton, Colorado, $9.1 million – The company will demonstrate in-space component joining and inspection technologies for structural, electrical and fluid systems. The capability would reduce risk and advance the maturity and reliability of in-space assembly architectures.

Redwire of Jacksonville, Florida, $12.9 million – The company will develop a grader, compactor and microwave emitter into a scalable platform that removes rocks, compacts loose regolith, and melts or sinters regolith into a solid surface. This technology could enable dust mitigation areas, habitat foundations, roads and landing pads.

Protoinnovations of Pittsburgh, $6.2 million – Protoinnovations will advance modular, flight-ready mobility control software for lunar rovers and robots

Psionic of Hampton, Virginia, $3.2 million – Partnering with Draper Laboratory, Psionic will conduct a flight demonstration of its Navigation Doppler Lidar and terrain contour matching system. Crewed and robotic missions could utilize the high-precision navigation system to land at various planetary destinations, including the moon.

United Launch Alliance of Centennial, Colorado, $25 million – The company will continue to evolve a proven Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology design. ULA will develop a larger 10-meter HIAD that leverages a two-piece structure to enable effective load distribution for even larger inflatable decelerators.

Varda Space Industries of El Segundo, California, $1.9 million – Varda will mature Conformal Phenolic Impregnated Carbon Ablator (C-PICA), a cost-effective and mass-efficient thermal protection system material developed by NASA. The project will put C-PICA through a flight test and start commercial production of the material.

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Milky Way galaxy's spiral arms revealed in stunning detail by chemical mapping


Robert Lea

SPACE
Wed, July 26, 2023 

An illustration of the Milky Way with red and blue spots showing areas with few (blue) and many (red) heavy elements

Never-before-seen details of the Milky Way's spiral arms have been revealed through chemical mapping.

This pioneering technique, called chemical cartography, has unveiled new regions of our galaxy's stunning radial features populated by dense patches of young stars. Headed by Keith Hawkins, an assistant professor at The University of Texas at Austin, the research team's work could be crucial for astronomers seeking to understand our galaxy's evolution, shape and structure.

Chemical cartography shows the distribution of elements throughout the Milky Way — from lighter elements, such as hydrogen and helium, to heavier ones, such as carbon, nitrogen and oxygen. For context, astronomers refer to any elements heavier than helium as metals. This, therefore, allows astronomers to locate stars according to their chemical compositions rather than merely the light they emit.

Over the course of their lives, stars fuse hydrogen to create helium, then fuse that helium to create other metals. This means metal levels associated with individual stars can give astronomers information about their ages. Chemical cartography thus allowed Hawkins and fellow scientists to spot where the Milky Way's young stars are concentrated. In short, the researchers found them to be abundant in our galaxy’s spiral arms.

Related: Alien's-eye view of the Milky Way: Our galaxy is unusual but not unique

"Much like the early explorers, who created better and better maps of our world, we are now creating better and better maps of the Milky Way," Hawkins said. "Those maps are revealing things we thought to be true but still need to check."

Chemical cartography isn't really a new process, but only recently did scientists manage to develop telescopes with enough observing power to get significant results using the technique.
Finding where the Milky Way's hot young stars hang out

For at least seven decades, astronomers have understood that our galaxy has spiral arms that extend out from the dense concentration of stars, gas, and dust which lie at its heart, known as the "central bulge."

However, the exact shape of this striking structure — down to the number of arms our galaxy has — remains uncertain.

The difficulty in assessing the Milky Way's morphology comes from the fact that we live in it. We're basically analyzing it from the inside, with Earth sitting in the Orion Arm around two-thirds of the way from the central bulge.

We simply can't get far enough to observe our galaxy from an outsider's perspective.

"It's like being in a big city," Hawkins explained. "You can look around at the buildings and you can see what street you’re on, but it’s hard to know what the whole city looks like unless you’re in a plane flying above it."

This hasn't prevented scientists from modeling intricate models of the shape of the Milky Way, but Hawkins wanted to verify the accuracy of those models while simultaneously investigating whether chemical cartography can offer an even better view of the Milky Way's arms in general.

The arch of Milky Way shining bright above Lut desert, in Kerman, Iran.

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One traditional way of mapping the Milky Way involves monitoring the concentrations of young stars that are created as the galaxy's very dense spiral arms rotate. As this rotation occurs, it compresses gas and dust to ultimately trigger star births.

In other words, identifying an overabundance of young stars implies the location of a spiral arm.

Though young stars can be detected by tracking the bright blue light they emit, observations of this kind can be obscured by thick clouds of dust which present a challenge to even the most advanced telescopes. That means some regions of the Milky Way’s spiral arms go unobserved.
No more metal

One way of working around this dust veil is by observing exactly how metal-rich the stars that lurk in hidden regions are.

This so-called metalicity serves as an age measurement because the early cosmos was filled with hydrogen and helium, but little in the way of metals. That means the oldest stars are also composed of mostly hydrogen and helium and are thus "low metalicity" or "metal-poor."

During their lives, these older stars forge heavier elements via nuclear fusion — but when they run out of such fuel, are ripped apart by supernova explosions that spread the metals throughout their cosmic environment. Therefore, when metal-enriched clouds of dust and gas collapse to birth stars, this next generation of stars is richer in metals than the last.

This stellar cycle of life and death has continued throughout the 13.8 billion-year history of the universe, with every subsequent generation of stars being more metal-rich than the last. Thus, young stars are expected to be "metal-rich" or hold a "high metalicity."

If the Milky Way's spiral arms trigger star births as predicted, then they should be marked by young stars, aka metal-rich stars. Conversely, spaces between the arms should be marked by metal-poor stars.

To confirm this theory, as well as create his overall map of metalicity, Hawkins first looked at our solar system's galactic backyard, which include stars about 32,000 light years from the sun. In cosmic terms, that represents our stellar neighborhood's immediate vicinity.

Taking the resultant map, the researcher compared it to others of the same area of the Milky Way created by different techniques, finding that the positions of the spiral arms lined up. And, because he used metalicity to chart the spiral arms, hitherto unseen regions of the Milky Way's spiral arms showed up in Hawkins' map.

"A big takeaway is that the spiral arms are indeed richer in metals," Hawkins explained. "This illustrates the value of chemical cartography in identifying the Milky Way's structure and formation. It has the potential to fully transform our view of the Galaxy."
The future is bright for chemical cartography

To reach his conclusions, Hawkins used data from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) and the Gaia space telescope, with new data from the latter proving particularly useful.

Since Gaia launched in 2013, the spacecraft has observed around 2 billion cosmic objects allowing astronomers to considerably widen their view of the universe. It dropped its latest and third data release in June 2022, which was especially important for Hawkins’ chemical cartography because it offers the most precise and comprehensive survey of the Milky Way ever conducted.

"The sheer volume of data available from Gaia allows us to do chemical cartography at a galactic scale now," Hawkins said. "Data on both the positions for billions of stars and their chemical makeup wasn’t available until recently."

But as impressive as Gaia’s chemical data is, its observations still represent just around 1% of the Milky Way. Going forward, not only will Gaia continue to scour our galaxy collecting this data, but new telescopes are also coming online to collect data ripe for chemical cartography endeavors.

a disc-shaped spacecraft in space

As telescope technology becomes more advanced, the power of chemical cartography will also increase, meaning astronomers stand to learn more about the structure of our galaxy and its previously obscured regions.

The Milky Way and its chemical composition will thus deliver insights that can be applied to other galaxies, with this new map offering a hint at the revelations that are yet to come.

“It’s a completely new era,” Hawkins concluded.

The team's research was published in the April issue of the journal Monthly Notices of the Royal Astronomical Society.

A supermassive black hole is spitting a high-energy jet toward Earth

Robert Lea

SPACE
Tue, July 25, 2023 

a jet of white light shooting through space

A NASA mission has observed a supermassive black hole pointing its highly energetic jet straight toward Earth. Don't panic just yet, though. As fearsome as this cosmic event is, it's located at a very safe distance of about 400 million light-years away.

Actively feeding supermassive black holes, including the one at hand, are surrounded by swirling disks of matter called accretion disks which gradually feed them over time. Some of the material they don't swallow is then channeled toward their poles, where it's subsequently blasted out at near-light, or relativistic, speed. This creates highly energetic and extremely bright electromagnetic radiation. In some cases, like with NASA's latest muse, that jet is pointed straight at Earth. Those events are known as blazars.

This blazar, designated Markarian 421 and located in the constellation Ursa Major, was observed with NASA's Imaging X-ray Polarimetry Explorer (IXPE), which launched in December 2021. IXPE observes a property of magnetic fields called polarization, which refers to the fields' orientation. The polarization of the jet blasted out by Markarian 421 revealed a surprise for astronomers, showing that the part of the jet where particles are being accelerated is also home to a magnetic field with a helical structure.
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Blazar jets can stretch across space for millions of light-years, but the mechanisms that launch them aren't yet well-understood. However, these new discoveries surrounding the jet of Markarian 421 could shed some light on this extreme cosmic phenomenon.

Related: X-ray view shows how supermassive black holes speed up particles in jets

"Markarian 421 is an old friend for high-energy astronomers," lead researcher behind the discovery and Italian Space Agency astrophysicist, Laura Di Gesu, said in a statement. "We were sure the blazar would be a worthwhile target for IXPE, but its discoveries were beyond our best expectations, successfully demonstrating how X-ray polarimetry enriches our ability to probe the complex magnetic field geometry and particle acceleration in different regions of relativistic jets."
IXPE dives deeper into the twisted structure of blazar jets

The main reason jets of feeding supermassive black holes are so bright is that particles approaching the speed of light give off tremendous amounts of energy and behave according to the physics of Einstein’s theory of special relativity.

Blazar jets also get an extra boost to such brightness because their orientation towards us causes wavelengths of light associated with their jets to "bunch up," increasing both their frequencies and energies. This is similar to how sound waves from the siren of an approaching ambulance "bunch up" to cause an increase in frequency that makes it sound more high-pitched.

As a result of these two effects, blazars can often outshine the combined light of every star in the galaxies that house them. And now, IXPE has used that light to paint a picture of the physics going on at the heart of Markarian 421's jet and even identify the glowing beam's point of origin.

Previously, models of blazar jets had hinted that they're accompanied by helical magnetic fields, almost like DNA in living cells, except single- rather than double-stranded. What wasn’t predicted, however, was the fact that the magnetic helix would host areas where particles are being accelerated.

a T-shaped satellite in space

"We had anticipated that the polarization direction might change, but we thought large rotations would be rare, based on previous optical observations of many blazars,” research co-author and Massachusetts Institute of Technology physicist, Herman Marshal, said. "So, we planned several observations of the blazar, with the first showing a constant polarization of 15%."

Even more remarkably, analysis of IXPE's data showed that the polarization of the jet dropped to 0% between its first and second observations. This showed the team the magnetic field was turning like a corkscrew.

"We recognized that the polarization was actually about the same but its direction literally pulled a U-turn, rotating nearly 180 degrees in two days," Marshall said. "It then surprised us again during the third observation, which started a day later, to observe the direction of polarization continuing to rotate at the same rate."

a jet of light streaking through space

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During these maneuvers, measurements of electromagnetic radiation in the form of optical, infrared and radio light showed no effect on the stability and structure of the jet itself, even when X-ray emissions did change. This implied a shockwave traveling along the twisted magnetic field from Markarian 421.

Hints of such a phenomenon have once been seen in the jet of another blazar witnessed by IXPE, Markarian 501, but the team's new findings represent more clearcut evidence that a helical magnetic field does indeed contribute to a traveling shockwave that's accelerating jet particles to relativistic speeds.

The team behind the work intends to continue studying Markarian 421 as well as identify other blazars to find some with similar qualities in pursuit of revealing a mechanism that powers the extreme and bright outflows characteristic of these phenomena.

"Thanks to IXPE, it's an exciting time for studies of astrophysical jets," Di Gesu concluded.

The team"s research was published on Monday (July 17) in the journal Nature Astronomy.