It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Long a controversial energy source, nuclear has been facing a renaissance in space.
So far, nuclear reactions have been mainly used to provide electricity for spacecraft, but researchers want to use these reactions to propel them forward
Nuclear power is experiencing a renaissance on Earth, and in space. Whether we’re talking about lunar bases or space exploration, nuclear might be the key to pushing beyond our current boundaries.
On the 25th of August 2012, the lonely Voyager 1 space probe crossed the threshold into interstellar space. At the time it was 18 billion km (11 million miles) away from the sun, far beyond all the planets of our solar system.
The Voyager 1 was launched in 1977. Almost 50 years later, it’s still going and sending back information, penetrating ever deeper into space. It can do that because it’s powered by nuclear energy.
Long a controversial energy source, nuclear has been experiencing renewed interest on Earth to power our fight against climate change. But behind the scenes, nuclear has also been facing a renaissance in space.
In July, the US National Aeronautics and Space Administration (NASA) and Defense Advanced Research Projects Agency (DARPA) jointly announced that they plan to launch a nuclear-propelled spacecraft by 2025 or 2026. The European Space Agency (ESA) in turn is funding a range of studies on the use of nuclear engines for space exploration. And last year, NASA awarded a contract to Westinghouse to develop a concept for a nuclear reactor to power a future moon base.
“There’s a lot of interest in nuclear for space applications at the moment,” said Dr Ramy Mesalam, programme director of spacecraft engineering at the University of Leicester. “The deeper we explore our solar system and beyond, the more attractive nuclear will become.”
Lunar night
One participant in this new boom is Zeno Power, a United States startup founded in 2018. A team led by them recently received a $15m award to develop so-called radioisotope nuclear power systems for use on the moon’s surface by NASA. These small, lightweight nuclear power systems have a long history of use in space, and can potentially use nuclear waste to power themselves.
NASA and international partners such as the European Space Agency (ESA) want to have a lunar base up and running before the end of the decade. This base will most likely partly use nuclear reactors for power and heat.
Illustration of the DRACO spacecraft that is being developed by Lockheed Martin for DARPA and that will demonstrate thermal nuclear engine technology
[Lockheed Martin/Business Wire/AP Photo]
Nuclear power is particularly attractive for use on the moon because of the harsh conditions on the lunar surface. Darkness is a particular concern for longer-duration missions. “The lunar night lasts 14 Earth days”, said Tyler Bernstein, co-founder and CEO of Zeno Power. “There are also permanently shadowed regions, like craters. Generating solar power is impossible in the dark, and temperatures in some places can reach beyond -200 degrees Celsius.”
Bernstein hopes to have the first reactors ready by 2025. Nuclear explosion
Space travel, however, is an inherently risky pursuit, particularly with nuclear materials on board. Rockets destined for space regularly explode, potentially spreading nuclear debris across space or even Earth. That’s a sobering reality that professor Dale Thomas of the University of Alabama in Huntsville is facing.
He works on nuclear-powered propulsion. Instead of powering a rocket through a chemical reaction, we would power it through a nuclear one.
So far we have mainly used nuclear reactions to provide electricity for spacecraft, but researchers like Thomas want to use these reactions to propel them forward.
That holds great potential to push us further into space, but also forces us to review the way we test rocket engines. Usually, these engines are tested on the ground, where they sometimes explode or suffer failures. This gives engineers key information to improve their designs. That model of testing and fixing, however, needs to be adapted to nuclear propulsion.
“Failing a nuclear engine on the test stand is not a good idea”, Thomas told Al Jazeera. “Its failure modes are much more catastrophic than those of chemical propulsion.”
Building a nuclear engine, in other words, requires researchers to be more cautious, and make sure no failure takes place. This in turn slows down development.
A similar situation is present in sending nuclear reactors up to space to power spacecraft and moon bases. Before we do so, they need to meet high safety standards, and even be ready to withstand explosions. Luckily, we have figured out how to do this. The first nuclear reactor was launched into space as early as 1965.
“The safety aspect is a challenge”, Mesalam said. “That’s always at the heart of a nuclear power system design. But the good news is that we have almost 60 years of experience in doing this safely.”
Interplanetary species
In the future, spacecraft might be powered by nuclear engines. We would probably propel them into an orbit around the Earth using chemical engines, and then turn on their nuclear propulsion to push them on missions far beyond our own planet.
“Chemical propulsion can get us off the Earth, and even to the moon”, said Thomas. “But when you’re going to Mars and beyond, it runs into its limits. Atomic propulsion will be key to going beyond that barrier.”
On top of that, nuclear propulsion would open up different ways of exploring space. Today, flights to places like Mars and the planets beyond are limited by time windows. Space organisations like NASA calculate complex trajectories that slingshot spacecraft off planets’ gravity fields, to save fuel. If higher-capacity and more powerful nuclear engines were available, this wouldn’t be such a high priority, giving us more flexibility when to launch these craft.
“A Ferrari will go faster than a Volkswagen because it has a more powerful engine”, said Thomas. “That’s what nuclear propulsion is to chemical propulsion.”
Before we get nuclear propulsion, however, we might need some time. Thomas argues that these craft will probably only really take off around 2030.
Once we have them, though, they might be a game changer. “Nuclear power and propulsion will be a huge foundational technology for bringing humans to Mars and beyond”, said Bernstein. “It will be key to making humanity an interplanetary species.”
SOURCE: AL JAZEERA
Thursday, February 22, 2024
SPACE
Little groundwater recharge in ancient Mars aquifer, according to new models
Mars was once a wet world. The geological record of the Red Planet shows evidence for water flowing on the surface – from river deltas to valleys carved by massive flash floods.
But a new study shows that no matter how much rainfall fell on the surface of ancient Mars, very little of it seeped into an aquifer in the planet’s southern highlands.
A graduate student at The University of Texas at Austin made the discovery by modeling groundwater recharge dynamics for the aquifer using a range of methods – from computer models to simple back-of-the-envelope calculations.
No matter the degree of complexity, the results converged on the same answer – a miniscule .03 millimeters of groundwater recharge per year on average. That means that wherever rain fell in the model, only an average of .03 millimeters per year could have entered the aquifer and still produced the landforms remaining on the planet today.
For comparison, the annual rate of groundwater recharge for the Trinity and Edwards-Trinity Plateau aquifers that provide water to San Antonio generally ranges from 2.5 to 50 millimeters per year, or about 80 to 1,600 times the Martian aquifer recharge rate calculated by the researchers.
There are a variety of potential reasons for such low groundwater flow rates, said lead author Eric Hiatt, a doctoral student at the Jackson School of Geosciences. When it rained, the water may have mostly washed across the Martian landscape as runoff. Or it may have just not rained very much at all.
These findings can help scientists constrain the climatic conditions capable of producing rainfall on early Mars. They also suggest a very different water regime on the Red Planet than what exists on Earth today.
“The fact that the groundwater isn’t as big of a process could mean that other things are,” Hiatt said. “It might magnify the importance of runoff, or it could mean that it just didn’t rain as much on Mars. But it’s just fundamentally different from how we think about [water] on Earth.”
The results were published in the journal Icarus. The paper’s co-authors are Mohammad Afzal Shadab, a doctoral student at the Jackson School and faculty members Sean Gulick, Timothy Goudge and Marc Hesse.
The models used in the study work by simulating groundwater flow in a “steady state” environment where inflow and outflow of water into the aquifer is balanced. Scientists then changed the parameters affecting the flow – for example, where rain falls or the average porosity of the rock – and observed what other variables would have to change to maintain the steady state and how plausible those charges are.
While other researchers have simulated groundwater flow on Mars using similar techniques, this model is the first to incorporate the influence of the oceans that existed on the surface of Mars more than three billion years ago in the Hellas, Argyre, and Borealis basins.
The study also incorporates modern topographical data collected by satellites. The modern landscape, Hiatt said, still preserves one of the planet’s oldest and most influential topographical features – an extreme difference in elevation between the northern hemisphere – the lowlands – and the southern hemisphere – the highlands – known as the “great dichotomy.” The dichotomy preserves signs of past groundwater upwelling in which groundwater rose up from the aquifer to the surface. The researchers used geological markers of these past upwelling events to evaluate different model outputs.
Across different models, the researchers found the mean groundwater recharge rate of .03 millimeters per year to match most closely with what’s known about the geologic record.
The research isn’t just about understanding the Red Planet’s past. It has implications for future Mars exploration too. Understanding groundwater flow can help inform where to find water today, Hiatt said. Whether you’re looking for signs of ancient life, trying to sustain human explorers, or making rocket fuel to get back home to Earth, it’s essential to know where the water would most likely be.
The research was funded by NASA, the University of Texas Institute for Geophysics, and the UT Center for Planetary Habitability.
UNIVERSITY OF CINCINNATI GRADUATE STUDENT ANDREA CORPOLONGO, LEFT, AND ASSOCIATE PROFESSOR ANDY CZAJA POSE IN FRONT OF A TELESCOPE AT THE CINCINNATI OBSERVATORY. THEY SERVE ON THE NASA SCIENCE TEAM EXPLORING MARS WITH THE PERSEVERANCE ROVER.
In the three years since NASA’s Perseverance rover touched down on Mars, the NASA science team has made the daily task of investigating the red planet seem almost mundane.
The rover and its helicopter sidekick Ingenuity have captured stunning images of Mars and collected 23 unique rock core samples along 17 miles of an ancient river delta.
One science team member, University of Cincinnati Associate Professor Andy Czaja, said he sometimes has to remind himself that the project is anything but ordinary.
“This is so cool. I’m exploring another planet,” he said.
Czaja teaches in the Department of Geosciences in UC’s College of Arts and Sciences. He is a paleobiologist and astrobiologist helping NASA look for evidence of ancient life on Mars using a rover outfitted with custom geoscience and imaging tools with three of his UC graduate students, Andrea Corpolongo, Brianna Orrill and Sam Hall.
Three years into the mission, the rover has performed like a champ, he said.
“Perseverance has excelled. It’s been fantastic. It has such capable instrumentation for doing the geology work. It’s able to explore distant objects with its zoom lens cameras and can focus on tiny objects at incredible resolution,” Czaja said.
Along the way, the mission has recorded a number of firsts: first powered flight, first recorded sounds of Mars, the longest autonomous drive (nearly a half-mile) and new discoveries about the planet’s geology, atmosphere and climate.
Czaja was part of the NASA team that decided where on Mars to land the rover. And he remained on the science team that would pore over its daily data and discoveries to decide what the rover should do next.
Among the new discoveries was finding primary igneous rocks in Jezero Crater. These rocks are the hardened result of liquid magma. They offer scientists promising clues about refining the known age of the planet.
Scientists suspect Mars once had long-lived rivers, lakes and streams. Today, water on Mars is found in ice at the poles and trapped below the Martian surface.
Czaja and his student Corpolongo were co-lead authors of a paper published in the Journal of Geophysical Research, Planets that revealed that Mars also may have had hydrothermal systems based on the hydrated magnesium sulfate the rover identified in the volcanic rocks.
“When those rocks cool off and fracture, they become a habitable environment for life,” Czaja said.
Corpolongo also led a similar research paper in the same journal co-authored by Czaja detailing the results of the rover’s analysis of samples using the SHERLOC deep ultraviolet Raman and fluorescence instrument. Both papers featured contributions from dozens of their fellow NASA researchers on the project.
Samples collected by the rover may finally answer the question about whether we are alone in the universe.
“We have not found any definitive evidence of life in these deposits yet. But if there were fossil microorganisms trapped in the rocks, they would be too small to see with the rover,” Czaja said.
Czaja is hopeful funding will be approved for the anticipated Mars Sample Return mission to retrieve the hermetically sealed titanium tubes scientists have spent three years filling with interesting rock cores.
“These hydrated minerals trap water within themselves and record the history of how and when they formed,” the study said. “Returning samples of these minerals to Earth would allow researchers to explore the history of Mars’ water and climate and possibly evidence of ancient life with the most sensitive instruments possible.”
But that was just the beginning. Perseverance began its deliberate exploration from the floor of the crater to the front of the delta, formed by an ancient river or drainage channel where it encountered sedimentary rocks that often contain trapped minerals and another avenue for evidence of ancient life.
And last year the rover made it to the crater’s margin in what used to be an enormous lake where it is exploring deposits of magnesium carbonate, which can form geologically or biologically from bacteria.
Czaja said the decision to send Perseverance to Jezero Crater appears to be paying off.
“Absolutely. There were other places we could have gone that might have been just as good,” he said. “You won’t know until you explore them all. But Jezero was picked for good reason and it has been completely justified.”
The helicopter Ingenuity’s flying days appear to be over after it sustained rotor damage in January after landing on its 72nd flight. But Perseverance is still going strong. It still has 15 sample tubes at its disposal to capture additional interesting geologic specimens.
Next the rover will make its way out of Jezero Crater to explore the wider area. Czaja said they are likely to find rocks dating back 4 billion years or more. And Mars could harbor stromatolites or rocks that contain evidence of ancient layered mats of bacteria visible to the naked eye. On Earth, these rocks are sometimes found in extreme environments such as geyser basins.
The horizon of discovery continues to expand daily before the science team.
“I hope that Perseverance has just whetted our appetite for more Martian exploration,” Czaja said. “And bringing back samples will allow us to study Mars and search for evidence of ancient life with instruments that haven’t even been invented yet for years and years to come.
University of Cincinnati graduate student Andrea Corpolongo, left, and Associate Professor Andy Czaja pose in front of a telescope at the Cincinnati Observatory. They serve on the NASA science team exploring Mars with the Perseverance rover.
SMALL FUNNEL FLOW - THE SAME EXPERIMENTS WERE SET UP IN, BOTH, SIMULATION AND REALITY TO SEE IF THE VIRTUAL REGOLITH BEHAVED REALISTICALLY. THIS TEST LOOKED AT HOW SMALL (16 G) SAMPLES OF MATERIAL FLOWED THROUGH NARROW FUNNELS.
A new computer model mimics Moon dust so well that it could lead to smoother and safer Lunar robot teleoperations.
The tool, developed by researchers at the University of Bristol and based at the Bristol Robotics Laboratory, could be used to train astronauts ahead of Lunar missions.
Working with their industry partner, Thales Alenia Space in the UK, who has specific interest in creating working robotic systems for space applications, the team investigated a virtual version of regolith, another name for Moon dust.
Lunar regolith is of particular interest for the upcoming Lunar exploration missions planned over the next decade. From it, scientists can potentially extract valuable resources such as oxygen, rocket fuel or construction materials, to support a long-term presence on the Moon.
To collect regolith, remotely operated robots emerge as a practical choice due to their lower risks and costs compared to human spaceflight. However, operating robots over these large distances introduces large delays into the system, which make them more difficult to control.
Now that the team know this simulation behaves similarly to reality, they can use it to mirror operating a robot on the Moon. This approach allows operators to control the robot without delays, providing a smoother and more efficient experience.
Lead author Joe Louca, based in Bristol’s School of Engineering Mathematics and Technology explained: “Think of it like a realistic video game set on the Moon – we want to make sure the virtual version of moon dust behaves just like the actual thing, so that if we are using it to control a robot on the Moon, then it will behave as we expect.
“This model is accurate, scalable, and lightweight, so can be used to support upcoming lunar exploration missions.”
This study followed from previous work of the team, which found that expert robot operators want to train on their systems with gradually increasing risk and realism. That means starting in a simulation and building up to using physical mock-ups, before moving on to using the actual system. An accurate simulation model is crucial for training and developing the operator’s trust in the system.
While some especially accurate models of Moon dust had previously been developed, these are so detailed that they require a lot of computational time, making them too slow to control a robot smoothly. Researchers from DLR (German Aerospace Centre) tackled this challenge by developing a virtual model of regolith that considers its density, stickiness, and friction, as well as the Moon’s reduced gravity. Their model is of interest for the space industry as it is light on computational resources, and, hence, can be run in real-time. However, it works best with small quantities of Moon dust.
The Bristol team’s aims were to, firstly, extend the model so it can handle more regolith, while staying lightweight enough to run in real-time, and then to verify it experimentally.
Joe Louca added: “Our primary focus throughout this project was on enhancing the user experience for operators of these systems – how could we make their job easier?
“We began with the original virtual regolith model developed by DLR, and modified it to make it more scalable.
“Then, we conducted a series of experiments – half in a simulated environment, half in the real world – to measure whether the virtual moon dust behaved the same as its real-world counterpart.”
As this model of regolith is promising for being accurate, scalable and lightweight enough to be used in real-time, the team will next investigate whether it can be used when operating robots to collect regolith.
They also plan to investigate whether a similar system could be developed to simulate Martian soil, which could be of benefit for future exploration missions, or to train scientists to handle material from the highly anticipated Mars Sample Return mission.
Paper:
‘Verification of a Virtual Lunar Regolith Simulant’ by Joe Louca, John Vrublevskis, Kerstin Eder and Antonia Tzemanaki in Frontiers in Space Technologies, Section Space Exploration.
Large Funnel Setup - The simulation was scaled up to test larger quantities of regolith. This example poured 0.5 kg of regolith through wider funnels, to compare against physical equivalents.
Regolith Sim Demo Video - The model can be adjusted to represent different materials: ball bearings, dry sand, and cohesive regolith simulant, under Earth’s or the Moon’s gravity. The stickiness virtual regolith makes it flow more slowly through the funnels.
JOURNAL
Frontiers in Space Technologies
METHOD OF RESEARCH
Computational simulation/modeling
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Verification of a Virtual Lunar Regolith Simulant
ARTICLE PUBLICATION DATE
22-Feb-2024
A new beginning: The search for more temperate Tatooines
New Haven, Conn. — Luke Skywalker’s childhood might have been slightly less harsh if he’d grown up on a more temperate Tatooine — like the ones identified in a new, Yale-led study.
According to the study’s authors, there are more climate-friendly planets in binary star systems — in other words, those with two suns — than previously known. And, they say, it may be a sign that, at least in some ways, the universe leans in the direction of orderly alignment rather than chaotic misalignment.
For the study, the researchers looked at planets in binary star systems — systems where individual planets orbit around a host star, with a second star, located nearby, that orbits the whole system. (The fictional desert planet Tatooine, from the “Star Wars” films, is in a binary star system.)
“We show, for the first time, that there is an unexpected pile-up of systems where everything is aligned,” said Malena Rice, an assistant professor of astronomy in the Yale Faculty of Arts and Sciences and lead author of the new study, which was published Feb. 22 in The Astronomical Journal. “The planets orbit precisely in the same direction that the first star rotates, and the second star orbits that system on the same plane as the planets.”
Rice’s team used a variety of sources, including the Gaia DR3 catalogue of high-precision stellar astrometry, the NASA Exoplanet Archive’s Planetary Systems Composite Parameters table, and the TEPCat catalogue of exoplanet spin-orbit angle measurements, to create 3D geometries of planets in binary star systems.
The researchers found that nine of the 40 systems they studied had “perfect” alignment.
“It could be an indication that planetary systems like to push toward an orderly configuration,” Rice said. “This is also good news for life forming in those systems. Stellar companions that are aligned differently can wreak havoc on planetary systems, toppling them over or flash heating planets over time.”
And just how would the world look on a more temperate Tatooine?
During some seasons of the year, it would be daytime continuously, with one star lighting up one side of the planet, while the other star was lighting the other half of the planet. But that sunlight would not always be blazing hot, because one of the stars would be much farther away.
In other seasons of the year, both suns would light up the same side of the planet, with one sun appearing much larger than the other.
Rice will give a presentation on the study in March at the Extreme Solar Systems conference in New Zealand.
Co-authors of the study are Konstantin Gerbig, a Yale Ph.D. student in astrophysics, and Andrew Vanderburg, an assistant professor of physics at MIT.
The research was funded, in part, by the Heising-Simons Foundation and the 51 Pegasi b Fellowship program.
JOURNAL
The Astronomical Journal
ARTICLE PUBLICATION DATE
22-Feb-2024
Webb finds evidence for neutron star at heart of young supernova remnant
THE JAMES WEBB SPACE TELESCOPE HAS OBSERVED THE BEST EVIDENCE YET FOR EMISSION FROM A NEUTRON STAR AT THE SITE OF A WELL-KNOWN AND RECENTLY-OBSERVED SUPERNOVA KNOWN AS SN 1987A. AT LEFT IS A NIRCAM (NEAR-INFRARED CAMERA) IMAGE released in 2023. THE IMAGE AT TOP RIGHT SHOWS LIGHT FROM SINGLY IONIZED ARGON (ARGON II) CAPTURED BY THE MEDIUM RESOLUTION SPECTROGRAPH (MRS) MODE OF MIRI (MID-INFRARED INSTRUMENT). THE IMAGE AT BOTTOM RIGHT SHOWS LIGHT FROM MULTIPLY IONIZED ARGON CAPTURED BY THE NIRSPEC (NEAR-INFRARED SPECTROGRAPH). BOTH INSTRUMENTS SHOW A STRONG SIGNAL FROM THE CENTER OF THE SUPERNOVA REMNANT. THIS INDICATED TO THE SCIENCE TEAM THAT THERE IS A SOURCE OF HIGH-ENERGY RADIATION THERE, MOST LIKELY A NEUTRON STAR.
CREDIT: NASA, ESA, CSA, STSCI, CLAES FRANSSON (STOCKHOLM UNIVERSITY), MIKAKO MATSUURA (CARDIFF UNIVERSITY), M. BARLOW (UCL), PATRICK KAVANAGH (MAYNOOTH UNIVERSITY), JOSEFIN LARSSON (KTH)
NASA’s James Webb Space Telescope has found the best evidence yet for emission from a neutron star at the site of a recently observed supernova. The supernova, known as SN 1987A, was a core-collapse supernova, meaning the compacted remains at its core formed either a neutron star or a black hole. Evidence for such a compact object has long been sought, and while indirect evidence for the presence of a neutron star has previously been found, this is the first time that the effects of high-energy emission from the probable young neutron star have been detected.
Supernovae – the explosive final death throes of some massive stars – blast out within hours, and the brightness of the explosion peaks within a few months. The remains of the exploding star will continue to evolve at a rapid rate over the following decades, offering a rare opportunity for astronomers to study a key astronomical process in real time.
Supernova 1987A
The supernova SN 1987A occurred 160,000 light-years from Earth in the Large Magellanic Cloud. It was first observed on Earth in February 1987, and its brightness peaked in May of that year. It was the first supernova that could be seen with the naked eye since Kepler's Supernova was observed in 1604.
About two hours prior to the first visible-light observation of SN 1987A, three observatories around the world detected a burst of neutrinos lasting only a few seconds. The two different types of observations were linked to the same supernova event, and provided important evidence to inform the theory of how core-collapse supernovae take place. This theory included the expectation that this type of supernova would form a neutron star or a black hole. Astronomers have searched for evidence for one or the other of these compact objects at the center of the expanding remnant material ever since.
Indirect evidence for the presence of a neutron star at the center of the remnant has been found in the past few years, and observations of much older supernova remnants –such as the Crab Nebula – confirm that neutron stars are found in many supernova remnants. However, no direct evidence of a neutron star in the aftermath of SN 1987A (or any other such recent supernova explosion) had been observed, until now.
Claes Fransson of Stockholm University, and the lead author on this study, explained: “From theoretical models of SN 1987A, the 10-second burst of neutrinos observed just before the supernova implied that a neutron star or black hole was formed in the explosion. But we have not observed any compelling signature of such a newborn object from any supernova explosion. With this observatory, we have now found direct evidence for emission triggered by the newborn compact object, most likely a neutron star.”
Webb’s Observations of SN 1987A
Webb began science observations in July 2022, and the Webb observations behind this work were taken on July 16, making the SN 1987A remnant one of the first objects observed by Webb. The team used the Medium Resolution Spectrograph (MRS) mode of Webb’s MIRI (Mid-Infrared Instrument), which members of the same team helped to develop. The MRS is a type of instrument known as an Integral Field Unit (IFU).
IFUs are able to image an object and take a spectrum of it at the same time. An IFU forms a spectrum at each pixel, allowing observers to see spectroscopic differences across the object. Analysis of the Doppler shift of each spectrum also permits the evaluation of the velocity at each position.
Spectral analysis of the results showed a strong signal due to ionized argon from the center of the ejected material that surrounds the original site of SN 1987A. Subsequent observations using Webb’s NIRSpec (Near-Infrared Spectrograph) IFU at shorter wavelengths found even more heavily ionized chemical elements, particularly five times ionized argon (meaning argon atoms that have lost five of their 18 electrons). Such ions require highly energetic photons to form, and those photons have to come from somewhere.
“To create these ions that we observed in the ejecta, it was clear that there had to be a source of high-energy radiation in the center of the SN 1987A remnant,” Fransson said. “In the paper we discuss different possibilities, finding that only a few scenarios are likely, and all of these involve a newly born neutron star.”
More observations are planned this year, with Webb and ground-based telescopes. The research team hopes ongoing study will provide more clarity about exactly what is happening in the heart of the SN 1987A remnant. These observations will hopefully stimulate the development of more detailed models, ultimately enabling astronomers to better understand not just SN 1987A, but all core-collapse supernovae.
These findings were published in the journal Science.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
FIG. 1. COMBINATION OF A HUBBLE IMAGE OF SN 1987A AND THE COMPACT HIGHLY IONIZED ARGON SOURCE IN FIG. 2. THE FAINT BLUE SOURCE IN THE CENTRE WAS DETECTED BY THE NIRSPEC INSTRUMENT ON JWST. OUTSIDE OF THIS IS THE REST OF THE SUPERNOVA, WHICH CONTAINS THE MOST MASS AND IS EXPANDING AT THOUSANDS OF KILOMETERS EVERY SECOND. THE INNER BRIGHT "STRING OF PEARLS" IS GAS FROM THE STAR'S OUTER LAYERS THAT WAS EJECTED ABOUT 20,000 YEARS BEFORE THE EXPLOSION. THE COLLISION BETWEEN THE RAPIDLY EXPANDING SUPERNOVA REMNANT AND THE RING GIVES RISE TO THE HEATED CLUMPS IN THE RING. OUTSIDE THE INNER RING ARE TWO OUTER RINGS, WHICH PROBABLY AROSE AT THE SAME TIME AS THE INNER RING WAS FORMED. THE BRIGHT STARS TO THE LEFT AND RIGHT OF THE INNER RING ARE UNRELATED TO THE SUPERNOVA. (ILLUSTRATION: HST, JWST/NIRSPEC, J. LARSSON)
CREDIT: ILLUSTRATION: HST, JWST/NIRSPEC, J. LARSSON
Scientists can finally show that a neutron star formed from our most well-studied supernova, SN 1987A. The breakthrough was made possible thanks to the James Webb telescope.
Supernovae are the spectacular end result of the collapse of stars more massive than 8-10 times the mass of the sun. Besides being the main sources of chemical elements such as carbon, oxygen, silicon, and iron that make life possible, they are also responsible for creating the most exotic objects in the universe, neutron stars and black holes.
In 1987, supernova 1987A (SN 1987A) exploded in the Large Magellanic Cloud, which is located near the Milky Way. It was the first time in four centuries that a supernova became visible to the naked eye, giving astronomers an unprecedented close-up of a supernova explosion. Although SN 1987A is one of the most studied objects in the sky, the question of what was left after the explosion remains unanswered. Did it become a compact neutron star or a black hole? The detection of neutrinos, which are produced in the supernova, indicated that a super compact neutron star should have formed at the center of the SN 1987A. But even after three and a half decades of intensive observations with the best telescopes, no conclusive evidence of such a neutron star has been found, until now.
In a study published on February 22 in the journal Science, an international team of astronomers announced that they had detected signals from a neutron star from the centre of the nebula around SN 1987A. Using the James Webb Telescope (JWST), the authors were able to observe spectral lines that had either been created from the hot neutron star or from a so-called pulsar wind nebula around the neutron star.
“Thanks to the fantastic resolution and the new instruments at JWST, we have been able to examine the centre of the supernova and what was created after the explosion for the first time. We now know that there is a compact source of ionizing radiation there, which is likely a neutron star. This was predicted by the explosion models and we did simulations in 1992 that indicated how to observe this, but it was only with JWST that it became possible. However, the details offered several surprises,” says Claes Fransson, professor at the Department of Astronomy, Stockholm University and the Oskar Klein Centre and the lead author of the study.
“This is the latest in a series of surprises that this supernova has offered over the years. It was unexpected that the compact object would finally be detected through a very strong argon line, so it was a bit fun that it turned out this way,” says Josefin Larsson, professor at the Department of Physics, KTH Royal Institute of Technology and the Oskar Klein Centre and co-author of the study.
Read article in Science: Emission lines due to ionizing radiation from a compact object in the remnant of Supernova 1987A DOI: 10.1126/science.adj5796
Contact: Claes Fransson, professor at the Department of Astronomy, Stockholm University and the Oskar Klein Centre E-mail: claes@astro.su.se Phone: ++46701610333
Josefin Larsson, professor at the Department of Physics, KTH Royal Institute of Technology and the Oskar Klein Centre E-mail: josla@kth.se
------- Supernova (SN)1987A – the most studied supernova SN 1987A is the most studied and best observed supernova of all and therefore of particular importance to understanding these objects. Exploding on February 23, 1987 in the Large Magellanic Cloud in the southern sky at a distance of 160,000 light years, it was the closest supernova explosion since the supernova observed by Johannes Kepler in 1604. For several months, it was possible to see SN 1987A with the naked eye.
SN 1987A is the only supernova that has been observed via its neutrinos (almost massless particles with an extremely weak interaction with other matter). This was important because 99.9 percent of the enormous energy released in this event was predicted to be lost in these particles. The remaining 0.1 percent was sent away in the form of light and kinetic energy. Of the huge number (about 1058) of neutrinos emitted, about 20 were detected by three different detectors around the Earth. SN 1987A was also the first supernova in which the exploding star could be identified from images taken before the explosion. This allowed the mass of the star to be determined, which agreed well with theoretical models.
Black hole or neutron star was created Apart from the neutrinos, the most interesting consequence of the explosion is the prediction that it will collapse into a black hole or neutron star. This compact remnant was created by the collapsed star's core, and has a mass about 1.5 times that of the Sun. The remaining mass was pushed away at up to 10 percent of the speed of light, forming the expanding remnant we can observe today.
The astronomers studying SN 1987A suspected that a neutron star had formed after the explosion. The main indication came from the neutrino pulse's duration of 10 seconds. But despite further indications from radio and X-ray observations, no conclusive evidence for a neutron star has been found until now. An important reason is the large amount of dust that formed in the years after the explosion. This dust can block most of the visible light from the center, obscuring the compact object at visible wavelengths. Identifying the final product of the explosion was the main remaining unsolved problem for SN 1987A.
James Webb Space Telescope made breakthroughs possible The James Webb Space Telescope (JWST) can observe light at infrared wavelengths, which can more easily travel through the dust that blocks visible light. An international team of astronomers studied SN 1987A using two of the telescope's instruments, MIRI* and NIRSpec. They then saw a point source in the centre of the widespread supernova remnant, emitting light from argon and sulfur ions (see Figs. 1+3). Thanks to JWST's resolution, and the ability of its instruments to accurately determine the velocity of the emitting source, we know that this point source is very close to the centre of the supernova explosion.
While most of the exploding star's mass is expanding at up to 10,000 km/second and has therefore been spread over a large volume, the observed source is still close to the explosion site. This is what astronomers expect for the compact remnant after the explosion. The observed spectral lines from argon and sulfur come from ionized atoms, requiring high-energy photons from the compact object. How this can happen as a result of the ultraviolet and X-ray radiation from a neutron star was already predicted in 1992 by Roger Chevalier (University of Virginia) and Claes Fransson.
Two possible explanations The scientists do not see the neutron star directly. Instead, they infer its existence by observing how its radiation affects its surroundings. In their study, the authors discuss two main explanations for the observed spectral lines. They may have been created due to the radiation from either the hot, newborn neutron star, which has a surface temperature of more than a million degrees, or from energetic particles accelerated in the strong magnetic field of the rapidly rotating neutron star (which is also called a pulsar). This is the same mechanism that takes place around the pulsar at the centre of the famous Crab Nebula, which is the remnant of a supernova observed by Chinese astronomers in 1054.
Both of these explanatory models result in similar predictions for what kind of spectral lines are created. To distinguish between these two models, further observations with JWST and ground-based telescopes in visible light, as well as the Hubble telescope, are therefore required.
Regardless, the new JWST observations provide compelling evidence for the existence of a compact object, likely a neutron star, at the centre of SN 1987A. The radius of such a neutron star is approximately 10 km, which means that the density is as great as in an atomic nucleus. One cubic millimeter of such stellar matter weighs about as much as a supertanker!
In summary, the new JWST observations, along with previous observations of the exploding star and the neutrinos created in the explosion, provide a complete picture of this unique object.
The team behind these results consists of 34 authors from 12 countries in Europe and the USA. First author is Claes Fransson, professor at the Department of Astronomy at Stockholm University and the Oskar Klein Centre.
* MIRI is an instrument that researchers at Stockholm University helped develop.
Fig. 4. The star in the Large Magellanic Cloud before the explosion on 23 February 1987 (right) and immediately after the explosion (left). The image illustrates the enormous increase in the brightness of the supernova. Credit: David Malin Anglo Australian Telescope.
CREDIT
Credit: David Malin Anglo Australian Telescope
Fig. 3. Upper row. Left. Argon II image with MIRI/MRS at the velocity of the compact object. Middle: Corresponding image at ring speed. Right: The first image subtracted with the second image, showing how the compact object dominates the center. Bottom row: Same thing though for highly ionized argon with the NIRSpec instrument.
Emission lines due to ionizing radiation from a compact object in the remnant of Supernova 1987A
Maynooth University partners in study published in Science that finds evidence of elusive neutron star
A new study, published in Science and co-authored by Dr Patrick Kavanagh of Maynooth University’s Experimental Physics Department, has provided the first conclusive evidence for the presence of the elusive neutron star produced in the supernova SN 1987A
CREDIT: C. FRANSSON (STOCKHOLM UNIVERSITY), M. J. BARLOW (UNIVERSITY COLLEGE LONDON), P. J. KAVANAGH (MAYNOOTH UNIVERSITY), J. LARSSON (KTH ROYAL INSTITUTE OF TECHNOLOGY)
A new study, published in Science and co-authored by Dr Patrick Kavanagh of Maynooth University’s Department of Experimental Physics in Ireland, has provided the first conclusive evidence for the presence of the elusive neutron star produced in the supernova SN 1987A.
Supernovae are the spectacular end result of the collapse of stars more massive than eight to ten times the mass of the sun. Besides being the main sources of chemical elements such as the carbon, oxygen, silicon, and iron that make life possible, they are also responsible for creating the most exotic objects in the universe, neutron stars and black holes.
Supernova 1987A (or SN 1987A for short) was the first naked eye supernova in four centuries and provided astronomers with an unprecedented close-up view of a supernova explosion with modern observatories. Despite being one of the most studied objects in the sky, SN 1987A is not without its mysteries, with the most enduring question being ‘what did the explosion leave behind?’
The detection of neutrinos, unimaginably small sub-atomic particles produced in the supernova, indicated that a neutron star must have formed. However, whether or not the neutron star persisted or collapsed into a black hole has been one of the biggest unknowns regarding SN 1987A.
Even after three and a half decades of intense monitoring with cutting-edge, world-class observatories, no conclusive evidence for the presence of a neutron star at the centre of SN 1987A has been found, until now.
In a study published on February 22 in the journal Science, an international team of astronomers announced their discovery with the James Webb Space Telescope (JWST) of narrow emission lines from ionized argon and sulphur atoms located at the centre of a nebula around SN 1987A.
“It was so exciting looking at the JWST observations of SN 1987A for the first time,” said Dr Kavanagh, an SFI-IRC Pathway Fellow at Maynooth University in Ireland. “As we checked the MIRI and NIRSpec data, the very bright emission from argon at the centre of SN 1987A jumped out. We knew immediately that this was something special that could finally answer the question on the nature of the compact object.”
The authors of the study show that the emission line strengths observed by JWST must be triggered by radiation from the hot neutron star or from a pulsar wind nebula around the neutron star.
“Thanks to the superb spatial resolution and excellent instruments on JWST we have for the first time been able to probe the center of the supernova and what was created there,” said Claes Fransson of Stockholm University, the lead author of the study.
“We now know that there is a compact source of ionizing radiation, most likely by a neutron star. We have been looking for this from the time of the explosion, but had to wait for JWST to be able to verify the predictions.”
About Supernova (SN) 1987A
SN 1987A is the most studied and best observed supernova of all and therefore of special importance for understanding these objects. Exploding on 23 February 1987 in the Large Magellanic Cloud in the southern sky at a distance of 160,000 light years, it was the closest supernova since the last naked eye supernova observed by Johannes Kepler in 1604.
For several months before it faded SN 1987A could be seen with the naked eye even at this distance. Even more importantly, it is the only supernova to have been detected via its neutrinos. This is highly significant since 99.9 % of the enormous energy emitted in this event was predicted to be lost as these extremely weakly interacting particles.
The remaining 0.1 % appears in the expansion energy of the remnant and as light. Of the huge number -- about 1058 -- of neutrinos emitted, about 20 were detected by three different detectors around the Earth, from the collapse in the core of the star on February 23 at 7:35:35 UT.
SN 1987A was also the first supernova where the star which exploded could be identified from images that had been taken before the explosion.
Besides the neutrinos, the most interesting result of the collapse and explosion is the prediction that a black hole or neutron star was created. This constitutes only the central core of the collapsed star, with a mass of 1.5 times that of the Sun. The rest is expelled with a velocity up to 10% of the speed of light, forming the expanding remnant we observe directly today.
The ‘long’ 10-second duration of the neutrino burst indicated the formation of a neutron star, but despite several interesting indications from radio and X-ray observations, no conclusive evidence for a compact object had been found until now, and was the main remaining unsolved problem for SN 1987A.
An important reason for this may be the large mass of dust particles that we know was formed during the years after explosion. This dust could block most of the visible light from the center and therefore hide the compact object at visible wavelengths. This has now changed with the observation of SN 1987A at infrared wavelengths by a team using the James Webb Space Telescope.
AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)
Astronomers using the James Webb Space Telescope (JWST) have found conclusive evidence of a neutron star in the remnant of Supernova 1987A, the only supernova visible to the naked eye in the last 400 years and the most studied supernova in history. Although Supernova 1987A has been observed for more than three decades, scientists have not seen the compact object expected to have been produced during the explosion. Some indirect evidence had suggested that the supernova produced a neutron star, but a black hole wasn’t ruled out, so the nature of the compact object has remained a topic of debate. Core-collapse supernovae occur when stars more than 8 times the mass of the Sun explode at the end of their lives. They are the main source of some chemical elements, including oxygen, silicon, and magnesium. The expired core of these exploding stars can leave behind a much smaller neutron star, composed of the densest material in the Universe, or can produce a black hole. Supernova 1987A, located in a neighboring dwarf galaxy, was the nearest and brightest supernova seen for four centuries. Neutrinos were produced in the explosion and detected on Earth a few hours before light from the supernova arrived, indicating that a neutron star probably formed, though might have later collapsed into a black hole. However, neither a neutron star nor a black hole have been directly detected, because the expanding debris from the explosion hides the compact object in dense gas and dust. Now, researchers led by Claes Fransson have observed the supernova remnant at infrared wavelengths with JWST, using spectroscopy to examine the gas composition and motions. They found emission lines from highly ionized argon and sulfur gas located close to where the star exploded. The gas composition and ionization can only be explained if there is a bright source of ultraviolet and X-ray radiation from a neutron star, either directly or indirectly; a black hole would not produce the observed lines. The JWST observations provide compelling evidence for a neutron star in the remnant of Supernova 1987A.
Emission lines due to ionizing radiation from a compact object in the remnant of Supernova 1987A
ARTICLE PUBLICATION DATE
23-Feb-2024
Astronomers find first strong evidence of neutron star remnant of exploding star
An international team of astronomers including UCL’s Professor Mike Barlow has discovered the first conclusive evidence that a neutron star exists at the centre of Supernova 1987A, a star explosion observed 37 years ago.
COMBINATION OF A HUBBLE SPACE TELESCOPE IMAGE OF SN 1987A AND THE COMPACT ARGON SOURCE. THE FAINT BLUE SOURCE IN THE CENTRE IS THE EMISSION FROM THE COMPACT SOURCE DETECTED WITH THE JWST/NIRSPEC INSTRUMENT. OUTSIDE THIS IS THE STELLAR DEBRIS, CONTAINING MOST OF THE MASS, EXPANDING AT THOUSANDS OF KM/SECOND. THE INNER BRIGHT “STRING OF PEARLS” IS THE GAS FROM THE OUTER LAYERS OF THE STAR THAT WAS EXPELLED ABOUT 20,000 YEARS BEFORE THE FINAL EXPLOSION. THE IS THE FAST DEBRIS ARE NOW COLLIDING WITH THE RING, EXPLAINING THE BRIGHT SPOTS. OUTSIDE OF THE INNER RING ARE TWO OUTER RINGS, PRESUMABLY PRODUCED BY THE SAME PROCESS AS FORMED THE INNER RING. THE BRIGHT STARS TO THE LEFT AND RIGHT OF THE INNER RING ARE UNRELATED TO THE SUPERNOVA.
CREDIT: HUBBLE SPACE TELESCOPE WFPC-3/JAMES WEBB SPACE TELESCOPE NIRSPEC/J. LARSSON
An international team of astronomers including UCL’s (University College London's) Professor Mike Barlow has discovered the first conclusive evidence that a neutron star exists at the centre of Supernova 1987A, a star explosion observed 37 years ago.
Supernovae are the spectacular end result of the collapse of stars more massive than 8-10 times the mass of the sun. They are the main sources of chemical elements (such as carbon, oxygen, silicon, and iron) that make life possible. The collapsed core of these exploding stars can result in much smaller neutron stars, composed of the densest matter in the known universe, or black holes.
Supernova 1987A, located in the Large Magellanic Cloud, a neighbouring dwarf galaxy, was the nearest, brightest supernova seen in the night sky in 400 years.
Neutrinos, unimaginably small sub-atomic particles, were produced in the supernova and detected on Earth (23 February, 1987) the day before the supernova was seen, indicating that a neutron star must have formed. However, it has not been known whether the neutron star persisted or collapsed into a black hole, as the star has been obscured by dust that formed after the explosion.
In the new study, published in the journal Science, researchers used two instruments on the James Webb Space Telescope (JWST), MIRI and NIRSpec, to observe the supernova at infrared wavelengths and found evidence of heavy argon and sulphur atoms whose outer electrons had been stripped off (i.e. the atoms had been ionised) close to where the star explosion occurred.
The team modelled various scenarios and found that these atoms could only have been ionised by ultra-violet and X-ray radiation from a hot cooling neutron star or, alternatively, from the winds of relativistic particles accelerated by a rapidly rotating neutron star and interacting with surrounding supernova material (pulsar wind nebula).
If the former scenario is true, the surface of the neutron star would be about a million degrees, having cooled down from 100 billion degrees or so at the moment of formation at the core of the collapse more than 30 years earlier.
Co-author Professor Mike Barlow (UCL Physics & Astronomy) said: “Our detection with James Webb’s MIRI and NIRSpec spectrometers of strong ionised argon and sulphur emission lines from the very centre of the nebula that surrounds Supernova 1987A is direct evidence of the presence of a central source of ionising radiation. Our data can only be fitted with a neutron star as the power source of that ionising radiation.
“This radiation can be emitted from the million degree surface of the hot neutron star, as well as by a pulsar wind nebula that could have been created if the neutron star is rapidly spinning and dragging charged particles around it.
“The mystery over whether a neutron star is hiding in the dust has lasted for more than 30 years and it is exciting that we have solved it.
“Supernovae are the main sources of chemical elements that make life possible – so we want to get our models of them right. There is no other object like the neutron star in Supernova 1987A, so close to us and having formed so recently. Because the material surrounding it is expanding, we will see more of it as time goes on.”
Professor Claes Fransson (Stockholm University, Sweden), the lead author of the study, said: “Thanks to the superb spatial resolution and excellent instruments on JWST we have, for the first time, been able to probe the centre of the supernova and what was created there.
“We now know that there is a compact source of ionising radiation, most likely by a neutron star. We have been looking for this from the time of the explosion, but had to wait for JWST to be able to verify the predictions.”
Dr Patrick Kavanagh (Maynooth University, Ireland), another author of the study, said: “It was so exciting looking at the JWST observations of SN 1987A for the first time. As we checked the MIRI and NIRSpec data, the very bright emission from argon at the centre of SN 1987A jumped out. We knew immediately that this was something special that could finally answer the question on the nature of the compact object.”
Professor Josefin Larsson (Royal Institute of Technology (KTH), Sweden), a co-author of the study, said: “This supernova keeps offering us surprises. Nobody had predicted that the compact object would be detected through a super strong emission line from argon, so it's kind of amusing that that’s how we found it in the JWST.”
Models indicate that heavy argon and sulphur atoms are produced in great abundance due to nucleosynthesis inside massive stars immediately before they explode.
While most of the mass of the exploding star is now expanding at up to 10,000 km/second, and is distributed over a large volume, the ionised argon and sulphur atoms were observed at close to the centre where the explosion occurred.
The ultraviolet and X-ray radiation which is thought to have ionised the atoms was predicted in 1992 as a unique signature of a newly created neutron star.
These ionised atoms were detected by James Webb’s MIRI and NIRSpec instruments using a technique called spectroscopy, where light is dispersed into a spectrum, enabling astronomers to measure light at different wavelengths to determine an object’s physical properties, including its chemical composition.
A UCL team at the Mullard Space Science Laboratory designed and built NIRSpec’s Calibration Source, which allows the instrument to make more precise measurements by providing an even, reference illumination of its detectors.
The new study involved researchers from the UK, Ireland, Sweden, France, Germany, the United States, the Netherlands, Belgium, Switzerland, Austria, Spain and Denmark.
About Supernova (SN) 1987A
SN 1987A is the most studied and best observed supernova of all.
Exploding on February 23 1987 in the Large Magellanic Cloud in the southern sky at a distance of 160,000 light years, it was the closest supernova since the last naked eye supernova observed by Johannes Kepler in 1604. For several months before it faded SN 1987A could be seen with the naked eye even at this distance.
Even more importantly, it is the only supernova to have been detected via its neutrinos. This is highly significant since 99.9 % of the enormous energy emitted in this event was predicted to be lost as these extremely weakly interacting particles.
The remaining 0.1 % appears in the expansion energy of the remnant and as light. Of the huge number (about 10 to the power 58) of neutrinos emitted, about 20 were detected by three different detectors around the Earth, from the collapse in the core of the star on February 23 at 7:35:35 UT.
SN 1987A was also the first supernova where the star which exploded could be identified from images that had been taken before the explosion. Besides the neutrinos, the most interesting result of the collapse and explosion is the prediction that a black hole or neutron star was created. This constitutes only the central core of the collapsed star, with a mass of 1.5 times that of the Sun. The rest is expelled with a velocity up to 10% of the speed of light, forming the expanding remnant we observe directly today.
The ‘long’ 10 second duration of the neutrino burst indicated the formation of a neutron star, but despite several interesting indications from radio and X-ray observations, no conclusive evidence for a compact object had been found until now, and was the main remaining unsolved problem for SN 1987A.
An important reason for this may be the large mass of dust particles that we know was formed during the years after explosion. This dust could block most of the visible light from the centre and therefore hide the compact object at visible wavelengths.
Two scenarios of neutron star
In their study the authors discuss two main possibilities: either radiation from the hot, million degree newly born neutron star or, alternatively, radiation from energetic particles accelerated in the strong magnetic field from the rapidly rotating neutron star (pulsar). This is the same mechanism as operates in the famous Crab nebula with its pulsar in the centre, which is the remnant of the supernova observed by Chinese astronomers in 1054.
Models of these two scenarios result in similar predictions for the spectrum, which agree well with the observations, but are difficult to distinguish. Further observations with JWST and ground-based telescopes in visible light, as well as the Hubble Space Telescope, may be able to distinguish these models.
In either case, these new observations with JWST provide compelling evidence for a compact object, most likely a neutron star, at the centre of SN 1987A.
In summary, these new observations by JWST, together with the previous observations of the progenitor and neutrinos, provide a complete picture of this unique object.
Combination of a Hubble Space Telescope image of SN 1987A and the compact argon source. The faint blue source in the centre is the emission from the compact source detected with the JWST/NIRSpec instrument. Outside this is the stellar debris, containing most of the mass, expanding at thousands of km/second. The inner bright “string of pearls” is the gas from the outer layers of the star that was expelled about 20,000 years before the final explosion. The is the fast debris are now colliding with the ring, explaining the bright spots. Outside of the inner ring are two outer rings, presumably produced by the same process as formed the inner ring. The bright stars to the left and right of the inner ring are unrelated to the supernova.
CREDIT
Hubble Space Telescope WFPC-3/James Webb Space Telescope NIRSpec/J. Larsson
THIS ARTIST’S IMPRESSION SHOWS THE RECORD-BREAKING QUASAR J059-4351, THE BRIGHT CORE OF A DISTANT GALAXY THAT IS POWERED BY A SUPERMASSIVE BLACK HOLE. USING ESO’S VERY LARGE TELESCOPE (VLT) IN CHILE, THIS QUASAR HAS BEEN FOUND TO BE THE MOST LUMINOUS OBJECT KNOWN IN THE UNIVERSE TO DATE. THE SUPERMASSIVE BLACK HOLE, SEEN HERE PULLING IN SURROUNDING MATTER, HAS A MASS 17 BILLION TIMES THAT OF THE SUN AND IS GROWING IN MASS BY THE EQUIVALENT OF ANOTHER SUN PER DAY, MAKING IT THE FASTEST-GROWING BLACK HOLE EVER KNOWN.
Using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), astronomers have characterised a bright quasar, finding it to be not only the brightest of its kind, but also the most luminous object ever observed. Quasars are the bright cores of distant galaxies and they are powered by supermassive black holes. The black hole in this record-breaking quasar is growing in mass by the equivalent of one Sun per day, making it the fastest-growing black hole to date.
The black holes powering quasars collect matter from their surroundings in a process so energetic that it emits vast amounts of light. So much so that quasars are some of the brightest objects in our sky, meaning even distant ones are visible from Earth. As a general rule, the most luminous quasars indicate the fastest-growing supermassive black holes.
“We have discovered the fastest-growing black hole known to date. It has a mass of 17 billion Suns, and eats just over a Sun per day. This makes it the most luminous object in the known Universe,” says Christian Wolf, an astronomer at the Australian National University (ANU) and lead author of the study published today in Nature Astronomy. The quasar, called J0529-4351, is so far away from Earth that its light took over 12 billion years to reach us.
The matter being pulled in toward this black hole, in the form of a disc, emits so much energy that J0529-4351 is over 500 trillion times more luminous than the Sun [1]. “All this light comes from a hot accretion disc that measures seven light-years in diameter — this must be the largest accretion disc in the Universe," says ANU PhD student and co-author Samuel Lai. Seven light-years is about 15 000 times the distance from the Sun to the orbit of Neptune.
And, remarkably, this record-breaking quasar was hiding in plain sight. “It is a surprise that it has remained unknown until today, when we already know about a million less impressive quasars. It has literally been staring us in the face until now,” says co-author Christopher Onken, an astronomer at ANU. He added that this object showed up in images from the ESO Schmidt Southern Sky Survey dating back to 1980, but it was not recognised as a quasar until decades later.
Finding quasars requires precise observational data from large areas of the sky. The resulting datasets are so large, researchers often use machine-learning models to analyse them and tell quasars apart from other celestial objects. However, these models are trained on existing data, which limits the potential candidates to objects similar to those already known. If a new quasar is more luminous than any other previously observed, the programme might reject it and classify it instead as a star not too distant from Earth.
An automated analysis of data from the European Space Agency’s Gaia satellite passed over J0529-4351 for being too bright to be a quasar, suggesting it to be a star instead. The researchers identified it as a distant quasar last year using observations from the ANU 2.3-metre telescope at the Siding Spring Observatory in Australia. Discovering that it was the most luminous quasar ever observed, however, required a larger telescope and measurements from a more precise instrument. The X-shooter spectrograph on ESO’s VLT in the Chilean Atacama Desert provided the crucial data.
The fastest-growing black hole ever observed will also be a perfect target for the GRAVITY+ upgrade on ESO’s VLT Interferometer (VLTI), which is designed to accurately measure the mass of black holes, including those far away from Earth. Additionally, ESO’s Extremely Large Telescope (ELT), a 39-metre telescope under construction in the Chilean Atacama Desert, will make identifying and characterising such elusive objects even more feasible.
Finding and studying distant supermassive black holes could shed light on some of the mysteries of the early Universe, including how they and their host galaxies formed and evolved. But that’s not the only reason why Wolf searches for them. “Personally, I simply like the chase,” he says. “For a few minutes a day, I get to feel like a child again, playing treasure hunt, and now I bring everything to the table that I have learned since.”
Notes
[1] A few years ago, NASA and the European Space Agency reported that the Hubble Space Telescope had discovered a quasar, J043947.08+163415.7, as bright as 600 trillion Suns. However, that quasar’s brightness was magnified by a ‘lensing’ galaxy, located between us and the distant quasar. The actual luminosity of J043947.08+163415.7 is estimated to be equivalent to about 11 trillion Suns (1 trillion is a million million: 1 000 000 000 000 or 1012).
More information
This research was presented in a paper titled “The accretion of a solar mass per day by a 17-billion solar mass black hole” to appear in Nature Astronomy (doi:10.1038/s41550-024-02195-x).
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