Giant galactic explosion exposes galaxy pollution in action
Astronomers have produced the first high-resolution map of a massive explosion in a nearby galaxy, providing important clues on how the space between galaxies is polluted with chemical elements.
INTERNATIONAL CENTRE FOR RADIO ASTRONOMY RESEARCH
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GALAXY NGC 4383 EVOLVING STRANGELY. GAS IS FLOWING FROM ITS CORE AT A RATE OF OVER 200 KM/S. THIS MYSTERIOUS GAS ERUPTION HAS A UNIQUE CAUSE: STAR FORMATION.
view moreCREDIT: CREDIT: ESO/A. WATTS ET AL
A team of international researchers studied galaxy NGC 4383, in the nearby Virgo cluster, revealing a gas outflow so large that it would take 20,000 years for light to travel from one side to the other.
The discovery was published today in the journal Monthly Notices of the Royal Astronomical Society.
Lead author Dr Adam Watts, from The University of Western Australia node at the International Centre for Radio Astronomy Research (ICRAR), said the outflow was the result of powerful stellar explosions in the central regions of the galaxy that could eject enormous amounts of hydrogen and heavier elements.
The mass of gas ejected is equivalent to more than 50 million Suns.
“Very little is known about the physics of outflows and their properties because outflows are very hard to detect,” Dr Watts said.
“The ejected gas is quite rich in heavy elements giving us a unique view of the complex process of mixing between hydrogen and metals in the outflowing gas.
“In this particular case, we detected oxygen, nitrogen, sulphur and many other chemical elements.”
Gas outflows are crucial to regulate how fast and for how long galaxies can keep forming stars. The gas ejected by these explosions pollutes the space between stars within a galaxy, and even between galaxies, and can float in the intergalactic medium forever.
The high-resolution map was produced with data from the MAUVE survey, co-led by ICRAR researchers Professors Barbara Catinella and Luca Cortese, who were also co-authors of the study.
The survey used the MUSE Integral Field Spectrograph on the European Southern Observatoryʼs Very Large Telescope, located in northern Chile.
"We designed MAUVE to investigate how physical processes such as gas outflows help stop star formation in galaxies,” Professor Catinella said.
"NGC 4383 was our first target, as we suspected something very interesting was happening, but the data exceeded all our expectations.
“We hope that in the future, MAUVE observations reveal the importance of gas outflows in the local Universe with exquisite detail.”
MAUVE survey finds galaxies ej [VIDEO] |
JOURNAL
Monthly Notices of the Royal Astronomical Society
METHOD OF RESEARCH
Meta-analysis
ARTICLE TITLE
MAUVE: A 6 kpc bipolar outflow launched from NGC4383, one of the most Hi-rich galaxies in the Virgo cluster
ARTICLE PUBLICATION DATE
22-Apr-2024
SwRI-led eclipse projects shed new light on solar corona
Airborne, ground-based observations provide unique data and engage the public
SOUTHWEST RESEARCH INSTITUTE
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ACROSS THE COUNTRY, 35 TEAMS INCLUDING MORE THAN 200 VOLUNTEERS COLLECTED ECLIPSE DATA USING TELESCOPES PROVIDED THROUGH THE SWRI-LED CITIZEN CATE 2024 EXPERIMENT. THERESA COSTILOW, CARLYN ROCAZELLA AND SUSAN AND BOB BENEDICT DONNED ECLIPSE 2024 WEAR AND ENJOYED THEMED MOON PIE TREATS WHILE OBSERVING THE APRIL 8 EVENT FROM CAMPGROUND IN KINGSVILLE, OHIO.
view moreCREDIT: SOUTHWEST RESEARCH INSTITUTE/CITIZEN CATE 2024
SAN ANTONIO — April 22, 2024 —Teams led by Southwest Research Institute successfully executed two groundbreaking experiments — by land and air — collecting unique solar data from the total eclipse that cast a shadow from Texas to Maine on April 8, 2024. The Citizen Continental-America Telescopic Eclipse (CATE) 2024 experiment engaged more than 200 community participants in a broad, approachable and inclusive attempt to make a continuous 60-minute high-resolution movie of this exciting event. A nearly simultaneous investigation used unique equipment installed in NASA’s WB-57F research aircraft to chase the eclipse shadow, making observations only accessible from a bird’s eye view.
“Total solar eclipses are relatively rare, offering unique opportunities for scientists to study the hot atmosphere above the Sun’s visible surface,” said Dr. Amir Caspi, principal investigator of both projects. “But more than that, through CATE 2024, the eclipse offered a bonding experience between scientists and communities along the path, sharing in this incredible awe-inspiring event. We hope the public experienced a new interest in, and appreciation of, the Sun and its mysteries.”
Total solar eclipses allow scientists to view the complex and dynamic features of the Sun’s outer atmosphere in ways that aren’t possible or practical by any other means, opening new windows into our understanding of the solar corona. The faint light from the corona is usually overpowered by the intense brightness of the Sun itself, and some wavelengths of light are blocked by Earth’s atmosphere.
CATE 2024 deployed a network of 35 teams of community participants, or “citizen scientists,” representing local communities along the eclipse path, deploying a “bucket brigade” of small telescopes following the eclipse’s cross-country path. CATE 2024’s scientific objectives required measuring the polarization of light, or the orientation of oscillating light waves, in the corona.
“You are familiar with this because sometimes you wear a polarizing filter right on your face — sunglasses that filter out certain angles of polarized light,” Caspi said. “The Citizen CATE 2024 telescopes have a polarizing filter baked onto every pixel of the sensor, allowing us to measure four different angles of polarization everywhere in the corona, providing a lot more information than just measuring the brightness of the light.”
Caspi also led an airborne project to observe the corona during the eclipse from 50,000 feet. These high-altitude observations both provide measurements that can’t be made from the ground and avoid any weather-related risks. Caspi’s team deployed a new suite of sensitive, high-speed, visible-light and infrared imagers, built by the SCIFLI team at NASA’s Langley Research Center, installed in the nose cone of a WB-57 jet.
Looking at complex motion in the solar corona, at new wavelengths and with new polarization measurements, will help scientists understand why it is so hot. The corona is millions of degrees Celsius, hundreds of times hotter than the visible surface below, a curious paradox that is a longstanding scientific mystery. The corona is also one of the major sources of eruptions that cause geomagnetic storms around Earth. These phenomena damage satellites, cause power grid blackouts and disrupt communication and GPS signals, so it’s important to better understand them as the world becomes increasingly dependent on such systems.
“Combining the airborne mobile data with the CATE 2024 hour-long string of observations will provide a more complete picture of the Sun’s mysterious corona,” said SwRI co-investigator Dr. Dan Seaton, who serves as the science lead for both projects.
“Both experiments required an enormous effort and precise timing to get the data we need,” Caspi said. “I am honored and in awe of the exceptionally talented teams that worked so diligently together. I can hardly wait to dig into the data we collected.”
The SwRI-led airborne team includes scientists from the National Center for Atmospheric Research High Altitude Observatory, NASA Langley Research Center, and Predictive Sciences Inc., with collaborators at the Smithsonian Astrophysical Observatory. The SwRI-led CATE 2024 project, funded by NSF and NASA, includes scientists from the National Center for Atmospheric Research, the National Solar Observatory, the Laboratory for Atmospheric and Space Physics at the University of Colorado, and the Space Science Institute, with collaborators at New Mexico State University and the Livelihoods Knowledge Exchange Network, community leaders at Rice University, Indiana University Bloomington, and the University of Maine, and over 200 community participants in 35 communities along the eclipse path.
For more about these projects, please see: https://youtu.be/ca_GzURad1I?si=RgSjNvHBzLK0tHnC or https://eclipse.boulder.swri.edu.
For more information, visit https://www.swri.org/heliophysics.
This high-res processed image of the April 8 eclipse shows the Sun’s corona, its outermost atmosphere, in artificial colors that indicate the polarization or orientation of the light. Citizen scientists in Dallas collected these data through the SwRI-led Citizen Continental-America Telescopic Eclipse (CATE) 2024 experiment.
CREDIT
Southwest Research Institute/Citizen CATE 2024/Ritesh Patel/Dan Seaton
These preliminary images from a new suite of sensitive, high-speed, visible-light and infrared imagers aboard one of NASA’s WB-57 jets show the corona and prominences visible during the April 8, 2024, eclipse in four wavelength ranges. Moving forward, SwRI scientists will significantly improve the images through processing and analysis of the rich and complex data.
CREDIT
Southwest Research Institute/NASA/Dan Seaton
written by Haygen Warren April 21, 2024
In December 2023 and February 2024, NASA’s Juno spacecraft, currently in orbit around and investigating Jupiter and the Jovian system, made several close flybys of the innermost of the Galilean moons, Io. During the flybys, Juno came as close as 1,500 kilometers from the surface of Io, during which extensive data and imagery of the moon were captured.
From the imagery and data, scientists were able to make the first up-close observations of the northern latitudes of Io, as well as sharp mountains and lava lakes. Furthermore, Juno’s recent flybys of Jupiter allowed scientists to refine their understanding of Jupiter’s polar cyclones and water abundance.
Io’s lava lakes and sharp mountains
Io is known to be one of the most extreme locations in the solar system, with the moon having the most geologic/volcanic activity of any planetary body in the solar system. Io’s immense volcanic activity has been recorded by several spacecraft, with images showing large plumes of sulfur and sulfur dioxide shooting as high as 500 kilometers above the surface.
Io’s volcanism is largely due to a two-to-one mean-motion orbital resonance with Europa, and a four-to-one mean-motion orbital resonance with Ganymede — meaning that Io completes two orbits of Jupiter with every orbit of Europa, and four orbits with every one orbit of Ganymede. These resonances expand and contract the surface of Io, which then allows Jupiter’s gravity to heat the interior of the moons, providing the heating needed for Io’s extreme geologic activity.
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“Io is simply littered with volcanoes, and we caught a few of them in action. We also got some great close-ups and other data on a 200-kilometer-long (127-mile-long) lava lake called Loki Patera. There is amazing detail showing these crazy islands embedded in the middle of a potentially magma lake rimmed with hot lava. The specular reflection our instruments recorded of the lake suggests parts of Io’s surface are as smooth as glass, reminiscent of volcanically created obsidian glass on Earth,” said Scott Bolton, Juno’s principal investigator.
Using the Juno data, the team was able to create two simulations that visualize the characteristics of the lava lake, Loki Patera, and sharp mountains, one of which is Steeple Mountain.
Additional data from the flyby using Juno’s Microwave Radiometer instrument (MWR) shows that Io’s surface is relatively smooth compared to the surfaces of the other three Galilean moons, which are Ganymede, Callisto, and Europa. Furthermore, MWR also found that Io’s poles are colder than the moon’s middle latitudes.
Juno successfully inserted itself into orbit around Jupiter in July 2016. The original mission plans had the spacecraft deorbit into Jupiter’s atmosphere after completing 32 orbits of Jupiter, where it would ultimately burn up and disintegrate. However, with the spacecraft remaining in good condition and all of its instruments still operating as expected, NASA awarded Juno and its team a mission extension in 2021 that would have the spacecraft complete 42 additional orbits of Jupiter. Juno is expected to complete its mission extension in September 2025.
Juno’s trajectory for its mission extension brings the spacecraft closer and closer to Jupiter’s north pole with each orbit. This trajectory allows for the MWR instrument to continuously improve its resolution of the planet’s north pole, which is filled with massive polar cyclones. The new data allows scientists to compare the poles and the cyclones in multiple wavelengths, and scientists have found that not all polar cyclones are created equally.
“Perhaps the most striking example of this disparity can be found with the central cyclone at Jupiter’s north pole. It is clearly visible in both infrared and visible light images, but its microwave signature is nowhere near as strong as other nearby storms. This tells us that its subsurface structure must be very different from these other cyclones. The MWR team continues to collect more and better microwave data with every orbit, so we anticipate developing a more detailed 3D map of these intriguing polar storms,” said Juno project scientist Steve Levin of NASA’s Jet Propulsion Laboratory in California.
Jupiter’s northern polar cyclones, seen in infrared by Juno.
Water abundance within Jupiter
Understanding water abundance within Jupiter is one of the primary science goals for Juno’s mission. However, the team isn’t searching for liquid water, but rather investigating the presence of oxygen and hydrogen molecules — the molecules that make up water — within Jupiter’s massive atmosphere. Getting an estimate of Jupiter’s water abundance is crucial for understanding the formation of the solar system and Jupiter.
Scientists believe that Jupiter was the first planet to form, which means it likely contains most of the gas, dust, and other cosmic material left over from the formation of the Sun and our solar system. Having insight into the abundance of different molecules and materials within the planet gives scientists the chance to record what materials were present during the formation of our solar system.
Water abundance, specifically, is important for Jupiter’s meteorology, including the flow of wind currents, and the planet’s internal structure. Scientists have been trying to measure Jupiter’s water abundance for decades, with NASA’s Galileo mission collecting one of the first datasets on Jovian water abundance in 1995 during the spacecraft’s 57-minute entry into Jupiter’s atmosphere at the end of its mission. However, Galileo’s data created more confusion than clarity, as the spacecraft found that the planet’s atmosphere was hot and void of water.
“The probe did amazing science, but its data was so far afield from our models of Jupiter’s water abundance that we considered whether the location it sampled could be an outlier. But before Juno, we couldn’t confirm. Now, with recent results made with MWR data, we have nailed down that the water abundance near Jupiter’s equator is roughly three to four times the solar abundance when compared to hydrogen. This definitively demonstrates that the Galileo probe’s entry site was an anomalously dry, desert-like region,” Bolton said.
The northern and equatorial regions of Jupiter, imaged by Juno during its 10th flyby of the planet.
Juno’s new results on Jovian water abundance suggest very low water abundance—an unexpected result that scientists are still trying to understand. However, these results do support scientists’ theories that during the solar system’s formation, water-ice material was likely a driving force behind heavy element enrichment, the process by which chemical elements heavier than hydrogen and helium were accreted by Jupiter during its formation.
Additional data on Jovian water abundance collected by Juno during the remainder of its extended mission will help scientists compare Jupiter’s water abundance at polar regions and equatorial regions. Additional data will also help reveal the structure of the planet’s core.
Juno’s next flyby of Jupiter, the 61st of the mission, is planned for May 12.
(Lead image: Image of Io taken by Juno on October 15, 2023. Credit: NASA/JPL-Caltech/SwRI/MSSS/Ted Stryk)
To find life in the universe, look to deadly Venus
Earth-like but incapable of hosting life
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THIS LITHOGRAPH FEATURES IMAGES OF VENUS FROM THE PIONEER VENUS, MAGELLAN, TRACE, AND VENUS EXPRESS MISSIONS.
view moreCREDIT: NASA
Despite surface temperatures hot enough to melt lead, lava-spewing volcanoes, and puffy clouds of sulfuric acid, uninhabitable Venus offers vital lessons about the potential for life on other planets, a new paper argues.
“We often assume that Earth is the model of habitability, but if you consider this planet in isolation, we don’t know where the boundaries and limitations are,” said UC Riverside astrophysicist and paper first author Stephen Kane. “Venus gives us that.”
Published today in the journal Nature Astronomy, the paper compiles much of the known information about Earth and Venus. It also describes Venus as an anchor point from which scientists can better understand the conditions that preclude life on planets around other stars.
Though it also features a pressure cooker-like atmosphere that would instantly flatten a human, Earth and Venus share some similarities. They have roughly the same mass and radius. Given the proximity to that planet, it’s natural to wonder why Earth turned out so differently.
Many scientists assume that insolation flux, the amount of energy Venus receives from the sun, caused a runaway greenhouse situation that ruined the planet.
“If you consider the solar energy received by Earth as 100%, Venus collects 191%. A lot of people think that’s why Venus turned out differently,” Kane said. “But hold on a second. Venus doesn’t have a moon, which is what gives Earth things like ocean tides and influenced the amount of water here.”
In addition to some of the known differences, more NASA missions to Venus would help clear up some of the unknowns. Scientists don’t know the size of its core, how it got to its present, relatively slow rotation rate, how its magnetic field changed over time, or anything about the chemistry of the lower atmosphere.
“Venus doesn’t have a detectable magnetic field. That could be related to the size of its core,” Kane said. “Core size also give us information about how a planet cools itself. Earth has a mantle circulating heat from its core. We don’t know what’s happening inside Venus.”
A terrestrial planet’s interior also influences its atmosphere. That is the case on Earth, where our atmosphere is largely the result of volcanic outgassing.
NASA does have twin missions to Venus planned for the end of this decade, and Kane is assisting with both of them. The DAVINCI mission will probe the acid-filled atmosphere to measure noble gases and other chemical elements.
“DAVINCI will measure the atmosphere all the way from the top to the bottom. That will really help us build new climate models and predict these kinds of atmospheres elsewhere, including on Earth, as we keep increasing the amount of CO2,” Kane said.
The VERITAS mission, led by NASA’s Jet Propulsion Laboratory, won’t land on the surface but it will allow scientists to create detailed 3D landscape reconstructions, revealing whether the planet has active plate tectonics or volcanoes.
“Currently, our maps of the planet are very incomplete. It’s very different to understand how active the surface is, versus how it may have changed through time. We need both kinds of information,” Kane said.
Ultimately, the paper advocates for missions like these to Venus for two main reasons. One is the ability, with better data, to use Venus to ensure inferences about life on farther-flung planets are correct.
“The sobering part of the search for life elsewhere in the universe is that we’re never going to have in situ data for an exoplanet. We aren’t going there, landing, or taking direct measurements of them,” Kane said.
“If we think another planet has life on the surface, we might not ever know we’re wrong, and we’d be dreaming about a planet with life that doesn’t have it. We are only going to get that right by properly understanding the Earth-size planets we can visit, and Venus gives us that chance.”
The other reason to research Venus is that it offers a preview of what Earth’s future could look like.
“One of the main reasons to study Venus is because of our sacred duties as caretakers of this planet, to preserve its future. My hope is that through studying the processes that produced present-day Venus, especially if Venus had a more temperate past that’s now devastated, there are lessons there for us. It can happen to us. It’s a question of how and when,” Kane said.
JOURNAL
Nature Astronomy
ARTICLE TITLE
Venus as an Anchor Point for Planetary Habitability
ARTICLE PUBLICATION DATE
22-Apr-2024
AI and physics combine to reveal the 3D structure of a flare erupting around a black hole
CALIFORNIA INSTITUTE OF TECHNOLOGY
VIDEO:
BASED ON RADIO TELESCOPE DATA AND MODELS OF BLACK HOLE PHYSICS, A TEAM LED BY CALTECH HAS USED NEURAL NETWORKS TO RECONSTRUCT A 3D IMAGE THAT SHOWS HOW EXPLOSIVE FLARE-UPS IN THE DISK OF GAS AROUND OUR SUPERMASSIVE BLACK HOLE, SAGITTARIUS A* (SGR A*), MIGHT LOOK.
THE 3D FLARE STRUCTURE FEATURES TWO BRIGHT, COMPACT FEATURES LOCATED ABOUT 75 MILLION KILOMETERS (OR HALF THE DISTANCE BETWEEN EARTH AND THE SUN) FROM THE CENTER OF THE BLACK HOLE. IT IS BASED ON DATA COLLECTED BY THE ATACAMA LARGE MILLIMETER ARRAY (ALMA) IN CHILE AFTER AN ERUPTION SEEN IN X-RAY DATA ON APRIL 11, 2017.
HERE, THE RECONSTRUCTED 3D STRUCTURE IS SEEN FROM A FIXED ANGLE AS THE MODEL EVOLVES OVER A SPAN OF ABOUT 100 MINUTES, SHOWING THE PATH THE TWO BRIGHT FEATURES TRACE AROUND THE BLACK HOLE.
view moreCREDIT: A. LEVIS/A. CHAEL/K. BOUMAN/M. WIELGUS/P. SRINIVASAN
Scientists believe the environment immediately surrounding a black hole is tumultuous, featuring hot magnetized gas that spirals in a disk at tremendous speeds and temperatures. Astronomical observations show that within such a disk, mysterious flares occur up to several times a day, temporarily brightening and then fading away. Now a team led by Caltech scientists has used telescope data and an artificial intelligence (AI) computer-vision technique to recover the first three-dimensional video showing what such flares could look like around Sagittarius A* (Sgr A*, pronounced sadge-ay-star), the supermassive black hole at the heart of our own Milky Way galaxy.
The 3D flare structure features two bright, compact features located about 75 million kilometers (or half the distance between Earth and the Sun) from the center of the black hole. It is based on data collected by the Atacama Large Millimeter Array (ALMA) in Chile over a period of 100 minutes directly after an eruption seen in X-ray data on April 11, 2017.
"This is the first three-dimensional reconstruction of gas rotating close to a black hole," says Katie Bouman, assistant professor of computing and mathematical sciences, electrical engineering and astronomy at Caltech, whose group led the effort described in a new paper in Nature Astronomy.
Aviad Levis, a postdoctoral scholar in Bouman's group and lead author on the new paper, emphasizes that while the video is not a simulation, it is also not a direct recording of events as they took place. "It is a reconstruction based on our models of black hole physics. There is still a lot of uncertainty associated with it because it relies on these models being accurate," he says.
Using AI informed by physics to figure out possible 3D structures
To reconstruct the 3D image, the team had to develop new computational imaging tools that could, for example, account for the bending of light due to the curvature of space-time around objects of enormous gravity, such as a black hole.
The multidisciplinary team first considered if it would be possible to create a 3D video of flares around a black hole in June 2021. The Event Horizon Telescope (EHT) Collaboration, of which Bouman and Levis are members, had already published the first image of the supermassive black hole at the core of a distant galaxy, called M87, and was working to do the same with EHT data from Sgr A*. Pratul Srinivasan of Google Research, a co-author on the new paper, was at the time visiting the team at Caltech. He had helped develop a technique known as neural radiance fields (NeRF) that was then just starting to be used by researchers; it has since had a huge impact on computer graphics. NeRF uses deep learning to create a 3D representation of a scene based on 2D images. It provides a way to observe scenes from different angles, even when only limited views of the scene are available.
The team wondered if, by building on these recent developments in neural network representations, they could reconstruct the 3D environment around a black hole. Their big challenge: From Earth, as anywhere, we only get a single viewpoint of the black hole.
The team thought that they might be able to overcome this problem because gas behaves in a somewhat predictable way as it moves around the black hole. Consider the analogy of trying to capture a 3D image of a child wearing an inner tube around their waist. To capture such an image with the traditional NeRF method, you would need photos taken from multiple angles while the child remained stationary. But in theory, you could ask the child to rotate while the photographer remained stationary taking pictures. The timed snapshots, combined with information about the child's rotation speed, could be used to reconstruct the 3D scene equally well. Similarly, by leveraging knowledge of how gas moves at different distances from a black hole, the researchers aimed to solve the 3D flare reconstruction problem with measurements taken from Earth over time.
With this insight in hand, the team built a version of NeRF that takes into account how gas moves around black holes. But it also needed to consider how light bends around massive objects such as black holes. Under the guidance of co-author Andrew Chael of Princeton University, the team developed a computer model to simulate this bending, also known as gravitational lensing.
With these considerations in place, the new version of NeRF was able to recover the structure of orbiting bright features around the event horizon of a black hole. Indeed, the initial proof-of-concept showed promising results on synthetic data.
A flare around Sgr A* to study
But the team needed some real data. That's where ALMA came in. The EHT's now famous image of Sgr A* was based on data collected on April 6–7, 2017, which were relatively calm days in the environment surrounding the black hole. But astronomers detected an explosive and sudden brightening in the surroundings just a few days later, on April 11. When team member Maciek Wielgus of the Max Planck Institute for Radio Astronomy in Germany went back to the ALMA data from that day, he noticed a signal with a period matching the time it would take for a bright spot within the disk to complete an orbit around Sgr A*. The team set out to recover the 3D structure of that brightening around Sgr A*.
ALMA is one of the most powerful radio telescopes in the world. However, because of the vast distance to the galactic center (more than 26,000 light-years), even ALMA does not have the resolution to see Sgr A*'s immediate surroundings. What ALMA measures are light curves, which are essentially videos of a single flickering pixel, which are created by collecting all of the radio-wavelength light detected by the telescope for each moment of observation.
Recovering a 3D volume from a single-pixel video might seem impossible. However, by leveraging an additional piece of information about the physics that are expected for the disk around black holes, the team was able to get around the lack of spatial information in the ALMA data.
Strongly polarized light from the flares provided clues
ALMA doesn’t just capture a single light curve. In fact, it provides several such "videos" for each observation because the telescope records data relating to different polarization states of light. Like wavelength and intensity, polarization is a fundamental property of light and represents which direction the electric component of a light wave is oriented with respect to the wave's general direction of travel. "What we get from ALMA is two polarized single-pixel videos," says Bouman, who is also a Rosenberg Scholar and a Heritage Medical Research Institute Investigator. "That polarized light is actually really, really informative."
Recent theoretical studies suggest that hot spots forming within the gas are strongly polarized, meaning the light waves coming from these hot spots have a distinct preferred orientation direction. This is in contrast to the rest of the gas, which has a more random or scrambled orientation. By gathering the different polarization measurements, the ALMA data gave the scientists information that could help localize where the emission was coming from in 3D space.
Introducing Orbital Polarimetric Tomography
To figure out a likely 3D structure that explained the observations, the team developed an updated version of its method that not only incorporated the physics of light bending and dynamics around a black hole but also the polarized emission expected in hot spots orbiting a black hole. In this technique, each potential flare structure is represented as a continuous volume using a neural network. This allows the researchers to computationally progress the initial 3D structure of a hotspot over time as it orbits the black hole to create a whole light curve. They could then solve for the best initial 3D structure that, when progressed in time according to black hole physics, matched the ALMA observations.
The result is a video showing the clockwise movement of two compact bright regions that trace a path around the black hole. "This is very exciting," says Bouman. "It didn't have to come out this way. There could have been arbitrary brightness scattered throughout the volume. The fact that this looks a lot like the flares that computer simulations of black holes predict is very exciting."
Levis says that the work was uniquely interdisciplinary: "You have a partnership between computer scientists and astrophysicists, which is uniquely synergetic. Together, we developed something that is cutting edge in both fields—both the development of numerical codes that model how light propagates around black holes and the computational imaging work that we did."
The scientists note that this is just the beginning for this exciting technology. "This is a really interesting application of how AI and physics can come together to reveal something that is otherwise unseen," says Levis. "We hope that astronomers could use it on other rich time-series data to shed light on complex dynamics of other such events and to draw new conclusions."
The new paper is titled, "Orbital Polarimetric Tomography of a Flare Near the Sagittarius A* Supermassive Black Hole." The work was supported by funding from the National Science Foundation, the Carver Mead New Adventures Fund at Caltech, the Princeton Gravity Initiative, and the European Research Council.
Viewing a Reconstructed 3D Structure Around a Black Hole From All Angles
Viewing a Reconstructed 3D Str [VIDEO] |
Based on radio telescope data and models of black hole physics, a team led by Caltech has used neural networks to reconstruct a 3D image that shows how explosive flare-ups in the disk of gas around our supermassive black hole, Sagittarius A* (Sgr A*), might look.
The 3D flare structure features two bright, compact features located about 75 million kilometers (or half the distance between Earth and the Sun) from the center of the black hole. It is based on data collected by the Atacama Large Millimeter Array (ALMA) in Chile after an eruption seen in X-ray data on April 11, 2017.
Here, the reconstructed 3D structure is shown at a single time (9:20 UT), directly after a flare was detected in X-ray, with the view rotating to help visualize the structure from all angles.
CREDIT
A. Levis/A. Chael/K. Bouman/M. Wielgus/P. Srinivasan
JOURNAL
Nature Astronomy
ARTICLE TITLE
Orbital Polarimetric Tomography of a Flare Near the Sagittarius A* Supermassive Black Hole
ARTICLE PUBLICATION DATE
22-Apr-2024
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