Scientists observe flattest explosion ever seen in space
Astronomers have observed an explosion 180 million light years away which challenges our current understanding of explosions in space, that appeared much flatter than ever thought possible
Peer-Reviewed PublicationIMAGE: SLIM BOOM view more
CREDIT: PHIL DRURY, UNIVERSITY OF SHEFFIELD
Scientists observe flattest explosion ever seen in space
- Astronomers have observed an explosion 180 million light years away which challenges our current understanding of explosions in space, that appeared much flatter than ever thought possible
- Explosions are almost always expected to be spherical, as the stars themselves are spherical, but this one is the flattest ever seen
- The explosion observed was an extremely rare Fast Blue Optical Transient (FBOT) - known colloquially amongst astronomers as “the cow” - only four others have ever been seen, and scientists don’t know how they occur, but this discovery has helped solve part of the puzzle
- A potential explanation for how this explosion occurred is that the star itself may have been surrounding by a dense disk or it may have been a failed supernova
An explosion the size of our solar system has baffled scientists, as part of its shape - similar to that of an extremely flat disc - challenges everything we know about explosions in space.
The explosion observed was a bright Fast Blue Optical Transient (FBOT) - an extremely rare class of explosion which is much less common than other explosions, such as supernovas. The first bright FBOT was discovered in 2018 and given the nickname “the cow”.
Explosions of stars in the universe are almost always spherical in shape, as the stars themselves are spherical. However, this explosion, which occurred 180 million light years away, is the most aspherical ever seen in space, with a shape like a disc emerging a few days after it was discovered. This section of the explosion may have come from material shed by the star just before it exploded.
It’s still unclear how bright FBOT explosions occur, but it’s hoped that this observation, published in Monthly Notices of the Royal Astronomical Society, will bring us closer to understanding them.
Dr Justyn Maund, Lead Author of the study from the University of Sheffield’s Department of Physics and Astronomy, said: “Very little is known about FBOT explosions - they just don’t behave like exploding stars should, they are too bright and they evolve too quickly. Put simply, they are weird, and this new observation makes them even weirder.
“Hopefully this new finding will help us shed a bit more light on them - we never thought that explosions could be this aspherical. There are a few potential explanations for it: the stars involved may have created a disc just before they died or these could be failed supernovas, where the core of the star collapses to a blackhole or neutron star which then eats the rest of the star.
“What we now know for sure is that the levels of asymmetry recorded are a key part of understanding these mysterious explosions, and it challenges our preconceptions of how stars might explode in the Universe.”
Scientists made the discovery after spotting a flash of polarised light completely by chance. They were able to measure the polarisation of the blast - using the astronomical equivalent of polaroid sunglasses - with the Liverpool Telescope (owned by Liverpool John Moores University) located on La Palma.
By measuring the polarisation, it allowed them to measure the shape of the explosion, effectively seeing something the size of our Solar System but in a galaxy 180 million light years away. They were then able to use the data to reconstruct the 3D shape of the explosion, and were able to map the edges of the blast - allowing them to see just how flat it was.
The mirror of the Liverpool Telescope is only 2.0m in diameter, but by studying the polarisation the astronomers were able to reconstruct the shape of the explosion as if the telescope had a diameter of about 750km.
Researchers will now undertake a new survey with the international Vera Rubin Observatory in Chile, which is expected to help discover more FBOTs and further understand them.
Ends
For more information contact: Amy Huxtable, Media Relations Officer at the University of Sheffield, a.l.huxtable@sheffield.ac.uk or mediateam@sheffield.ac.uk
JOURNAL
Monthly Notices of the Royal Astronomical Society
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
A flash of polarized optical light points to an aspherical “cow”
ARTICLE PUBLICATION DATE
31-Mar-2023
AI algorithm unblurs the cosmos
Tool produces faster, more realistic images than current methods
Peer-Reviewed PublicationIMAGE: A SIMULATED IMAGE TO MATCH THE PARAMETERS OF THE VERA C. RUBIN OBSERVATORY’S LEGACY SURVEY OF SPACE AND TIME (LSST). TO SIMULATE THE IMAGE, RESEARCHERS TOOK HIGH-RESOLUTION, ATMOSPHERE-FREE IMAGES FROM THE HUBBLE SPACE TELESCOPE (IN THE COSMOS DATASET), SIMULATED THE ATMOSPHERIC EFFECTS USING A SOFTWARE PACKAGE CALLED GALSIM WITH LSST PARAMETERS PLUGGED IN, AND THEN DOWNSAMPLED TO THE LOWER RESOLUTION OF THE LSST. view more
CREDIT: EMMA ALEXANDER/NORTHWESTERN UNIVERSITY
- Images from ground-based telescopes look blurry due to Earth’s atmosphere
- Scientists must remove blur to obtain accurate and precise physical measurements of astronomical objects
- To improve blur removal, computer scientists adapted a computer-vision algorithm typically used to sharpen photos
- Researchers trained new tool on data simulated to match Vera C. Rubin Observatory’s imaging parameters, so it will be ready to unblur its images
EVANSTON, Ill. — The cosmos would look a lot better if Earth’s atmosphere wasn’t photo bombing it all the time.
Even images obtained by the world’s best ground-based telescopes are blurry due to the atmosphere’s shifting pockets of air. While seemingly harmless, this blur obscures the shapes of objects in astronomical images, sometimes leading to error-filled physical measurements that are essential for understanding the nature of our universe.
Now researchers at Northwestern University and Tsinghua University in Beijing have unveiled a new strategy to fix this issue. The team adapted a well-known computer-vision algorithm used for sharpening photos and, for the first time, applied it to astronomical images from ground-based telescopes. The researchers also trained the artificial intelligence (AI) algorithm on data simulated to match the Vera C. Rubin Observatory’s imaging parameters, so, when the observatory opens next year, the tool will be instantly compatible.
While astrophysicists already use technologies to remove blur, the adapted AI-driven algorithm works faster and produces more realistic images than current technologies. The resulting images are blur-free and truer to life. They also are beautiful — although that’s not the technology’s purpose.
“Photography’s goal is often to get a pretty, nice-looking image,” said Northwestern’s Emma Alexander, the study’s senior author. “But astronomical images are used for science. By cleaning up images in the right way, we can get more accurate data. The algorithm removes the atmosphere computationally, enabling physicists to obtain better scientific measurements. At the end of the day, the images do look better as well.”
The research will be published March 30 in the Monthly Notices of the Royal Astronomical Society.
Alexander is an assistant professor of computer science at Northwestern’s McCormick School of Engineering, where she runs the Bio Inspired Vision Lab. She co-led the new study with Tianao Li, an undergraduate in electrical engineering at Tsinghua University and a research intern in Alexander’s lab.
When light emanates from distant stars, planets and galaxies, it travels through Earth’s atmosphere before it hits our eyes. Not only does our atmosphere block out certain wavelengths of light, it also distorts the light that reaches Earth. Even clear night skies still contain moving air that affects light passing through it. That’s why stars twinkle and why the best ground-based telescopes are located at high altitudes where the atmosphere is thinnest.
“It’s a bit like looking up from the bottom of a swimming pool,” Alexander said. “The water pushes light around and distorts it. The atmosphere is, of course, much less dense, but it’s a similar concept.”
The blur becomes an issue when astrophysicists analyze images to extract cosmological data. By studying the apparent shapes of galaxies, scientists can detect the gravitational effects of large-scale cosmological structures, which bend light on its way to our planet. This can cause an elliptical galaxy to appear rounder or more stretched than it really is. But atmospheric blur smears the image in a way that warps the galaxy shape. Removing the blur enables scientists to collect accurate shape data.
“Slight differences in shape can tell us about gravity in the universe,” Alexander said. “These differences are already difficult to detect. If you look at an image from a ground-based telescope, a shape might be warped. It’s hard to know if that’s because of a gravitational effect or the atmosphere.”
To tackle this challenge, Alexander and Li combined an optimization algorithm with a deep-learning network trained on astronomical images. Among the training images, the team included simulated data that matches the Rubin Observatory’s expected imaging parameters. The resulting tool produced images with 38.6% less error compared to classic methods for removing blur and 7.4% less error compared to modern methods.
When the Rubin Observatory officially opens next year, its telescopes will begin a decade-long deep survey across an enormous portion of the night sky. Because the researchers trained the new tool on data specifically designed to simulate Rubin’s upcoming images, it will be able to help analyze the survey’s highly anticipated data.
For astronomers interested in using the tool, the open-source, user-friendly code and accompanying tutorials are available online.
“Now we pass off this tool, putting it into the hands of astronomy experts,” Alexander said. “We think this could be a valuable resource for sky surveys to obtain the most realistic data possible.”
The study, “Galaxy image deconvolution for weak gravitational lensing with unrolled plug-and-play ADMM,” used computational resources from the Computational Photography Lab at Northwestern University.
Researchers used the AI algorithm to remove the simulated atmospheric blur, revealing the true-to-life image.
CREDIT
Emma Alexander/Northwestern University
JOURNAL
Monthly Notices of the Royal Astronomical Society
METHOD OF RESEARCH
Computational simulation/modeling
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Galaxy image deconvolution for weak gravitational lensing with unrolled plug-and-play ADMM
ARTICLE PUBLICATION DATE
30-Mar-2023
The brightest explosion ever seen
IMAGE: ARTIST'S ILLUSTRATION OF A GAMMA-RAY BURST RESULTING FROM A COLLAPSING STARS, EJECTING PARTICLES AND RADIATION IN A NARROW JET. view more
CREDIT: SOHEB MANDHAI
Gamma-ray bursts are the most energetic and luminous events known to occur in the Universe. Short-lived flashes of gamma-rays that typically last from a a tenth of a second to less than an hour, gamma-ray bursts may for a brief period of time outshine entire galaxies. The explosions are believed to be caused by the collapse of massive stars, the collision of neutron stars, or the merging of a neutron star and a black hole.
Although we have known about their existence for 60 years, there is still much to learn about these fascinating events. Not only are they transient and occur at random locations in the sky; gamma-rays are also mostly absorbed by our atmosphere impeding their detection from Earth.
To detect them, scientists therefore use space-based gamma-ray telescopes that, when triggered, send automatic instant messages to Earth. This allows the astronomers to follow up the detections with Earth-based telescopes, to look for a less energetic "afterglow" that often follows the gamma-rays.
Outshining an entire galaxy
On 9 October 2022, ESA's INTEGRAL, NASA's Swift and Fermi satellites, and other space observatories detected the gamma-ray burst which was, accordingly, named GRB 221009A. This led Daniele Bjørn Malesani, astronomer at Radboud University in the Netherlands and affiliated scientist at the Cosmic Dawn Center, to point the Very Large Telescope (VLT) in Chile toward the direction of GRB 221009A.
Using the X-shooter spectrograph mounted at the VLT, the resulting spectrum allowed Malesani and his team to measure the exact distance to GRB 221009A. Although the host galaxy of the burst turned out to lie more than two billion lightyears away, this actually makes it one of the most nearby bursts. Moreover, with a secure distance the team were also able to calculate the total amount of energy released from the burst.
"Gamma-ray bursts are always energetic, but this one was absolutely astonishing: During the 290 seconds that it lasted, GRB 221009A released roughly 1,000 times as much energy as our Sun has emitted during all of its lifetime of 4,5 billion years," says Malesani.
Another way to put it is that the burst for a brief period of time was more luminous that the combined light of all the hundreds of billions of stars in the Milky Way.
As is normal, this calculation assumes that GRB 221009A has emitted the same amount of energy in all directions. More likely though, the energy in "concentrated" in a narrow beam, in the direction of which we happen to lie. The total energy is therefore somewhat smaller, although still extremely high.
And in any rate, it is the most energetic gamma-ray burst ever detected, 70 times brighter than ever seen before. It was even reported to affect the Earth's ionosphere.
"Theoretically, we would expect such a powerful event to happen only once in 10,000 years," explains Malesani. "This makes us wonder if our detection is just sheer luck, of if there's something we're misunderstanding about the nature of gamma-ray bursts."
Followed up with James Webb
GRB 221009A was also followed up at longer wavelengths with the James Webb Space Telescope. These observations were led by Andrew Levan, also at Radboud University, although Malesani and other DAWNers also were a part of the team.
These observation allowed the astronomers to further characterize the gamma-ray burst. The James Webb telescope was particularly useful because the burst happens to lie, by an unlucky chance, behind a thick layer of cosmic dust inside the Milky Way galaxy. This has nothing to do with the burst itself, but makes it harder to interpret the results, as it dims the light from the burst. Webb looked at the afterglow in the mid infrared, which is much less affected by dust, offering a better view of the event.
But even Webb has shortcomings
Kasper Heintz, assistant professor at the Cosmic Dawn Center, participated in both studies. He explains: "Gamma-ray bursts like GRB 221009A are expected to explode together with a supernova whose light should ‘add’ to the burst itself. But for this burst, despite Webb's huge mirror it couldn't find convincing evidence for a bright supernova."
So, was the supernova just fainter than normal, or was it missing altogether? The jury is still out, and there are more surprises to come from this once-in-a-lifetime mysterious event.
The articles have just been accepted for publication in, respectively, Astronomy & Astrophysics and Astrophysical Journal Letters.
FACT BOX: The enigmatic gamma-ray bursts
Gamma-ray bursts were first discovered in 1967 by the Vela satellite, built to monitor the sky for possible tests of nuclear weapons, which would be a violation of the 1963 Nuclear Test Ban Treaty. First thought to originate from nearby sources within our own galaxy, more sensitive space observatories revealed, in the 1990’s, that they must come from far outside the Milky Way, distributed over the whole Universe.
The transient nature of the bursts made them difficult to study, but since the late 1990’s astronomers have been able to detect also their less energetic afterglow, from X-rays to optical light, to the infrared, helping to establish a theory of their origin.
JOURNAL
The Astrophysical Journal Letters
ARTICLE TITLE
The First JWST Spectrum of a GRB Afterglow: No Bright Supernova in Observations of the Brightest GRB of all Time, GRB 221009A
First successful simulations of how various shapes of galaxies are formed
IMAGE: GALAXIES BY INTERMITTENT RING RELEASES OF STELLAR SEEDS FROM TWO ATTACHED GALACTIC SEEDS (DOUBLE DISC GALAXY, TYPE 3–1). (A) NO ROTATION OF THE TWO GALACTIC SEEDS Ω1.1 = 0, (B) —(E) ROTATION BY Ω1.1 = Î /12, Î /8, Î /6, Î /4. view more
CREDIT: AUTHOR
The standard cosmology can answer almost nothing about how the structure of a galaxy is formed. It expects a supermassive black hole at the center and dark matter in the halo to explain the circulation of stars and its velocity. However, why the visible matters are distributed in such a thin plane by the interaction with the black hole while dark matter results in a spherical distribution is a critical open question for a disc galaxy. The formation process of elliptical, ring, and long–barred galaxies also remains unknown.
The Energy Circulation Theory (ECT) claims that there is a force working between momentums whereas the effects of gravitational force is based on magnitudes of energies. The new force is named as the fundamental force, presentations of which are electric, magnetic, strong, and weak forces. Energy movements form energy circulations according to the fundamental force. As the space expands, an early energy circulation decomposes to local circulations simultaneously on the whole circumference, called the cyclic decomposition. After plural rounds of cyclic decomposition, the resulting energy circulations, which are named as the galactic seed, start to release daughter circulations, known as stellar seeds.
A high energy galactic seed separates into two galactic seeds as the space expands. There are three types of galaxies as the origin of stellar seed release; isolated single galactic seed, binary rotating seeds, and two attached seeds. There are two types of stellar seed releases; the linear release and the ring release, where stellar seeds are released simultaneously on the entire circumference. Depending on the type of galactic seeds and the linear or ring releases of stellar seeds, various shapes of stellar distribution are obtained.
Intermittent ring releases of a single galactic seed gave a disc galaxy. Two attached galactic seeds showed typical patterns of spiral disc galaxies after intermittent ring releases (double disc galaxy). If the two seeds are rotating, spiral arms came out. (See the attached figure.)
Galaxies by intermittent ring releases of stellar seeds from two attached galactic seeds (double disc galaxy, Type 3–1). (a) no rotation of the two galactic seeds Ω1.1 = 0, (b) —(e) rotation by Ω1.1 = Ï€/12, Ï€/8, Ï€/6, Ï€/4.
These should be worthwhile to be checked and validated by physicists because there is no other model that has theoretically and systemically demonstrated the observed features of the universe.
The corresponding author for this study is Shigeto Nagao (snagao@lilac.plala.or.jp).
The paper First Successful Simulations of How Various Shapes of Galaxies are Formed https://www.worldscientific.com/doi/10.1142/S2424942422500049 can be found in the Reports in Advances of Physical Sciences https://www.worldscientific.com/worldscinet/raps journal.
###
JOURNAL
Reports in Advances of Physical Sciences
METHOD OF RESEARCH
Computational simulation/modeling
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Formation of major types of galaxies based on the energy circulation theory
‘Taffy galaxies’ collide, leave behind bridge of star-forming material
Gemini North captures sprawling aftermath of head-on collision between a pair of galaxies
Reports and ProceedingsIMAGE: THE GEMINI NORTH TELESCOPE, ONE HALF OF THE INTERNATIONAL GEMINI OBSERVATORY, OPERATED BY NSF’S NOIRLAB, CAPTURED THIS DAZZLING IMAGE OF THE SO-CALLED TAFFY GALAXIES — UGC 12914 AND UGC 12915. THEIR TWISTED APPEARANCE IS THE RESULT OF A HEAD-ON COLLISION THAT OCCURRED ABOUT 25 MILLION YEARS PRIOR TO THEIR APPEARANCE IN THIS IMAGE. A BRIDGE OF HIGHLY TURBULENT GAS DEVOID OF SIGNIFICANT STAR FORMATION SPANS THE GAP BETWEEN THE TWO GALAXIES. view more
CREDIT: INTERNATIONAL GEMINI OBSERVATORY/NOIRLAB/NSF/AURA IMAGE PROCESSING: M. RODRIGUEZ (NSF’S NOIRLAB), T.A. RECTOR (UNIVERSITY OF ALASKA ANCHORAGE/NSF’S NOIRLAB), J. MILLER (GEMINI OBSERVATORY/NSF’S NOIRLAB), M. RODRIGUEZ (GEMINI OBSERVATORY/NSF’S NOIRLAB), M. ZAMANI (NSF’S NOIRLAB) & D. DE MARTIN (NSF’S NOIRLAB) ACKNOWLEDGMENT: PI: A. S. CASTELLI (UNIVERSIDAD NACIONAL DE LA PLATA)
Galaxy collisions are transformative events, largely responsible for driving the evolution of the Universe. The mixing and mingling of stellar material is an incredibly dynamic process that can lead to the formation of molecular clouds populated with newly forming stars. But, a head-on collision between the two galaxies UGC 12914 (left) and UGC 12915 (right) 25–30 million years ago appears to have resulted in a different kind of structure — a bridge of highly turbulent material spanning the two galaxies. Though this intergalactic bridge is teeming with star-forming material, its turbulent nature is suppressing star formation.
This pair of galaxies, nicknamed the Taffy Galaxies, is located about 180 million light-years away in the direction of the constellation Pegasus.
This new image, captured with Gemini North [1], one half of the International Gemini Observatory, operated by NSF’s NOIRLab, showcases the fascinating feature that gave them their name. A tenuous bridge composed of narrow molecular filaments, shown in brown, and clumps of hydrogen gas, shown in red, can be seen between the two galaxies. Its complex web structure resembles taffy being stretched as the pair slowly separates.
Galaxy collisions can happen out of a variety of different scenarios, often involving a larger galaxy and a smaller satellite galaxy. As they drift near one another, the satellite galaxy can attract one of the larger galaxy’s primary spiral arms, pulling it out of its orbit. Or the satellite galaxy can actually intersect with the larger galaxy, causing significant distortions to its own structure. In other cases, a collision can lead to a merger if neither member has enough momentum to continue on after colliding. In all these scenarios, stellar material from both galaxies mixes through a gradual combining and redistribution of gas, like two puddles of liquid that are slowly bleeding into each other. The resulting collecting and compression of the gas can then trigger star formation.
A head-on collision, however, would be more like pouring liquid from two separate cups into a shared bowl. When the Taffy Galaxies’ collided, their galactic disks and gaseous components smashed right into each other. This resulted in a massive injection of energy into the gas, causing it to become highly turbulent. As the pair emerged from their collision, high-velocity gas was pulled from each galaxy, creating a massive gas bridge between them. The turbulence of the stellar material throughout the bridge is now prohibiting the collection and compression of gas that are required to form new stars.
The Gemini North observations of this object were led by AnalÃa Smith Castelli, an astronomer with the Instituto de AstrofÃsica de La Plata in Argentina. Argentina is one of the partners in the International Gemini Observatory.
Notes
[1] The data for this image were acquired before the Gemini North primary mirror was taken offline for repairs. https://noirlab.edu/public/announcements/ann22030/
More information
NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory), the US center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.
Cosmoview: ‘Taffy Galaxies’ Co [VIDEO]
The Gemini North telescope, one half of the International Gemini Observatory, operated by NSF’s NOIRLab, captured this dazzling image of the so-called Taffy Galaxies — UGC 12914 and UGC 12915. Their twisted appearance is the result of a head-on collision that occurred about 25 million years prior to their appearance in this image. A bridge of highly turbulent gas devoid of significant star formation spans the gap between the two galaxies.
CREDIT
Images and Videos: International Gemini Observatory/NOIRLab/DOE/NSF/AURA, T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), J. Miller (Gemini Observatory/NSF’s NOIRLab), M. Rodriguez (Gemini Observatory/NSF’s NOIRLab), M. Zamani & D. de Martin (NSF’s NOIRLab), ESA/Hubble/L. Calcada, D. Munizaga, N. Bartmann Music: Stellardrone - In Time
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