Astronomers solve mystery of strange bright burst in space
Around midday on June 13 last year, my colleagues and I were scanning the skies when we thought we had discovered a strange and exciting new object in space. Using a huge radio telescope, we spotted a blindingly fast flash of radio waves that appeared to be coming from somewhere inside our galaxy.
After a year of research and analysis, we have finally pinned down the source of the signal – and it was even closer to home than we had ever expected.
Our instrument was located at Inyarrimanha Ilgari Bundara – also known as the Murchison Radio-astronomy Observatory – in remote Western Australia, where the sky above the red desert plains is vast and sublime.
We were using a new detector at the radio telescope known as the Australian Square Kilometre Array Pathfinder – or ASKAP – to search for rare flickering signals from distant galaxies called fast radio bursts.
We detected a burst. Surprisingly, it showed no evidence of a time delay between high and low frequencies – a phenomenon known as 'dispersion'.
This meant it must have originated within a few hundred light years of Earth. In other words, it must have come from inside our galaxy – unlike other fast radio bursts which have come from billions of light years away.
Fast radio bursts are the brightest radio flashes in the Universe, emitting 30 years' worth of the Sun's energy in less than a millisecond – and we only have hints of how they are produced.
Some theories suggest they are produced by 'magnetars' – the highly magnetised cores of massive, dead stars – or arise from cosmic collisions between these dead stellar remnants. Regardless of how they occur, fast radio bursts are also a precise instrument for mapping out the so-called 'missing matter' in our Universe.
When we went back over our recordings to take a closer look at the radio burst, we had a surprise: the signal seemed to have disappeared. Two months of trial and error went by until the problem was found.
ASKAP is composed of 36 antennas, which can be combined to act like one gigantic zoom lens six kilometres across. Just like a zoom lens on a camera, if you try to take a picture of something too close, it comes out blurry. Only by removing some of the antennas from the analysis – artificially reducing the size of our 'lens' – did we finally make an image of the burst.
We weren't excited by this – in fact, we were disappointed. No astronomical signal could be close enough to cause this blurring.
This meant it was probably just radio-frequency 'interference' – an astronomer's term for human-made signals that corrupt our data.
It's the kind of junk data we'd normally throw away.
Yet the burst had us intrigued. For one thing, this burst was fast. The fastest known fast radio burst lasted about 10 millionths of a second. This burst consisted of an extremely bright pulse lasting a few billionths of a second, and two dimmer after-pulses, for a total duration of 30 nanoseconds.
So, where did this amazingly short, bright burst come from?
We already knew the direction it came from, and we were able to use the blurriness in the image to estimate a distance of 4,500 km. And there was only one thing in that direction, at that distance, at that time – a derelict 60-year-old satellite called Relay 2.
Relay 2 was one of the first ever telecommunications satellites. Launched by the United States in 1964, it was operated until 1965, and its onboard systems had failed by 1967.
But how could Relay 2 have produced this burst?
Some satellites, presumed dead, have been observed to reawaken. They are known as 'zombie satellites'.
But this was no zombie. No system on board Relay 2 had ever been able to produce a nanosecond burst of radio waves, even when it was alive.
We think the most likely cause was an 'electrostatic discharge'. As satellites are exposed to electrically charged gases in space known as plasmas, they can become charged – just like when your feet rub on carpet. And that accumulated charge can suddenly discharge, with the resulting spark causing a flash of radio waves.
Electrostatic discharges are common and are known to cause damage to spacecraft. Yet all known electrostatic discharges last thousands of times longer than our signal, and occur most commonly when the Earth's magnetosphere is highly active. And our magnetosphere was unusually quiet at the time of the signal.
Another possibility is a strike by a micrometeoroid – a tiny piece of space debris – similar to that experienced by the James Webb Space Telescope in June 2022.
According to our calculations, a 22 micro-gram micrometeoroid travelling at 20km per second or more and hitting Relay 2 would have been able to produce such a strong flash of radio waves. But we estimate the chance that the nanosecond burst we detected was caused by such an event to be about 1 per cent.
Ultimately, we can't be certain why we saw this signal from Relay 2. What we do know, however, is how to see more of them. When looking at 13.8 millisecond timescales – the equivalent of keeping the camera shutter open for longer – this signal was washed out, and barely detectable even to a powerful radio telescope such as ASKAP.
But if we had searched at 13.8 nanoseconds, any old radio antenna would have easily seen it. It shows us that monitoring satellites for electrostatic discharges with ground-based radio antennas is possible. And with the number of satellites in orbit growing rapidly, finding new ways to monitor them is more important than ever.
But did our team eventually find new astronomical signals? You bet we did. And there are no doubt plenty more to be found.
Clancy William James is a Senior Lecturer (astronomy and astroparticle physics) at Curtin University.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Astronomers solve mystery of strange bright burst in space
Around midday on June 13 last year, my colleagues and I were scanning the skies when we thought we had discovered a strange and exciting new object in space. Using a huge radio telescope, we spotted a blindingly fast flash of radio waves that appeared to be coming from somewhere inside our galaxy. After a year of research and analysis, we have finally pinned down the source of the signal – and it was even closer to home than we had ever expected. Our instrument was located at Inyarrimanha Ilgari Bundara – also known as the Murchison Radio-astronomy Observatory – in remote Western Australia, where the sky above the red desert plains is vast and sublime. We were using a new detector at the radio telescope known as the Australian Square Kilometre Array Pathfinder – or ASKAP – to search for rare flickering signals from distant galaxies called fast radio bursts. We detected a burst. Surprisingly, it showed no evidence of a time delay between high and low frequencies – a phenomenon known as 'dispersion'. This meant it must have originated within a few hundred light years of Earth. In other words, it must have come from inside our galaxy – unlike other fast radio bursts which have come from billions of light years away. Fast radio bursts are the brightest radio flashes in the Universe, emitting 30 years' worth of the Sun's energy in less than a millisecond – and we only have hints of how they are produced. Some theories suggest they are produced by 'magnetars' – the highly magnetised cores of massive, dead stars – or arise from cosmic collisions between these dead stellar remnants. Regardless of how they occur, fast radio bursts are also a precise instrument for mapping out the so-called 'missing matter' in our Universe. When we went back over our recordings to take a closer look at the radio burst, we had a surprise: the signal seemed to have disappeared. Two months of trial and error went by until the problem was found. ASKAP is composed of 36 antennas, which can be combined to act like one gigantic zoom lens six kilometres across. Just like a zoom lens on a camera, if you try to take a picture of something too close, it comes out blurry. Only by removing some of the antennas from the analysis – artificially reducing the size of our 'lens' – did we finally make an image of the burst. We weren't excited by this – in fact, we were disappointed. No astronomical signal could be close enough to cause this blurring. This meant it was probably just radio-frequency 'interference' – an astronomer's term for human-made signals that corrupt our data. It's the kind of junk data we'd normally throw away. Yet the burst had us intrigued. For one thing, this burst was fast. The fastest known fast radio burst lasted about 10 millionths of a second. This burst consisted of an extremely bright pulse lasting a few billionths of a second, and two dimmer after-pulses, for a total duration of 30 nanoseconds. So, where did this amazingly short, bright burst come from? We already knew the direction it came from, and we were able to use the blurriness in the image to estimate a distance of 4,500 km. And there was only one thing in that direction, at that distance, at that time – a derelict 60-year-old satellite called Relay 2. Relay 2 was one of the first ever telecommunications satellites. Launched by the United States in 1964, it was operated until 1965, and its onboard systems had failed by 1967. But how could Relay 2 have produced this burst? Some satellites, presumed dead, have been observed to reawaken. They are known as 'zombie satellites'. But this was no zombie. No system on board Relay 2 had ever been able to produce a nanosecond burst of radio waves, even when it was alive. We think the most likely cause was an 'electrostatic discharge'. As satellites are exposed to electrically charged gases in space known as plasmas, they can become charged – just like when your feet rub on carpet. And that accumulated charge can suddenly discharge, with the resulting spark causing a flash of radio waves. Electrostatic discharges are common and are known to cause damage to spacecraft. Yet all known electrostatic discharges last thousands of times longer than our signal, and occur most commonly when the Earth's magnetosphere is highly active. And our magnetosphere was unusually quiet at the time of the signal. Another possibility is a strike by a micrometeoroid – a tiny piece of space debris – similar to that experienced by the James Webb Space Telescope in June 2022. According to our calculations, a 22 micro-gram micrometeoroid travelling at 20km per second or more and hitting Relay 2 would have been able to produce such a strong flash of radio waves. But we estimate the chance that the nanosecond burst we detected was caused by such an event to be about 1 per cent. Ultimately, we can't be certain why we saw this signal from Relay 2. What we do know, however, is how to see more of them. When looking at 13.8 millisecond timescales – the equivalent of keeping the camera shutter open for longer – this signal was washed out, and barely detectable even to a powerful radio telescope such as ASKAP. But if we had searched at 13.8 nanoseconds, any old radio antenna would have easily seen it. It shows us that monitoring satellites for electrostatic discharges with ground-based radio antennas is possible. And with the number of satellites in orbit growing rapidly, finding new ways to monitor them is more important than ever. But did our team eventually find new astronomical signals? You bet we did. And there are no doubt plenty more to be found. Clancy William James is a Senior Lecturer (astronomy and astroparticle physics) at Curtin University. This article is republished from The Conversation under a Creative Commons license. Read the original article.
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There's a giant ball of ice barreling through the solar system right now, and it's bigger than any we've seen before. It poses no threat to Earth, but this comet, called C/2014 UN271 (Bernardinelli-Bernstein), has enraptured astronomers ever since its discovery in 2021. The hulking object, sometimes jovially called a 'megacomet,' is 100 times bigger than most comets we see in the solar system. And now we're learning more about it than ever before as it zooms toward its closest approach to our sun in 2031. In a study published in the Astrophysical Journal Letters on June 12, Nathan Roth of American University and his colleagues report the first conclusive detection of carbon monoxide on the megacomet. That's a crucial finding because it might tell us more about the object's origins, history and likely upcoming behavior as it dives deeper into the solar system. 'We wanted to test what drives activity in this comet,' Roth says. 'It's so far from the sun and so cold that trying to explain what makes a comet 'work' at these distances is difficult.' C/2014 UN271 was first imaged by chance in observations from 2014. Seven years later, when astronomers actually spotted it in their archives, the comet was at more than 20 times the Earth-sun distance, inside the orbit of Neptune. But they also found that it is on a path that will bring it nearly to Saturn's orbit in 2031 before it heads out again. The comet's orbit is huge, extending out to about 55,000 times the Earth-sun distance—87 percent of a light-year and well out into the Oort Cloud of icy objects that surrounds our sun. On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. Following the comet's discovery astronomers used various telescopes, including the James Webb Space Telescope and the Hubble Space Telescope, to scrutinize it from afar. The object was initially thought to be as big as 370 kilometers (230 miles) across. Revised observations showed it to be about 140 kilometers (87 miles) wide. But that's still the biggest anyone has ever seen—most comets in the solar system are only one or two kilometers across. 'It's huge,' says Quanzhi Ye, an astronomer at the University of Maryland, who was not involved in Roth's study. 'It represents a part of the cometary spectrum that we don't understand.' Some of those observations revealed bursts of activity from the comet, which sprouted an enormous, enveloping 'coma' of expelled gas that stretches some 250,000 kilometers (155,000 miles) across (more than half the distance from the Earth to the moon). To find out the cause of this activity, Roth and his team used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to observe the comet in radio waves for about eight hours in March 2024. They found a clear trace of carbon monoxide spewing from the comet, suggesting that its sprawling coma is fueled, at least in part, by carbon monoxide ice sublimating—turning from solid to gas—as the comet approaches the sun. The carbon monoxide appears to be vented in jets from spots on the object's surface, possibly the result of the overhead sun heating a localized region and causing the ice to sublimate. 'If you were standing on the comet, and the sun was right overhead, this is the area where the sun is heating the surface the most and the jet originates from,' Roth says. What's not clear so far, however, is how fast the comet is spinning and whether the location of the jets is changing over time. 'Are there different jets being activated at different times? We don't know yet,' Roth says. As C/2014 UN271 gets closer, other ices that are often found on comets, such as methane and hydrogen sulfide ice, might start to sublimate, too, and add their own contributions to the object's activity. 'As we continue to monitor it, we'll be able to get a better idea of the chemical fingerprint that's preserved inside the comet,' Roth says. Rosita Kokotanekova, an astronomer at the Rozhen National Astronomical Observatory in Bulgaria, who was not part of Roth's research team, says the detection of carbon monoxide is useful because it is 'important to identify what prompts activity at these large distances.' Researchers have witnessed gas venting from other, much smaller comets at a similar distance, 'which was very puzzling,' she adds. 'People were trying to figure out what exactly is causing this activity [so far from the sun].' C/2014 UN271's size makes it an especially alluring target for study. The presence of carbon monoxide ice is doubly interesting: Analysis of available data about the comet revealed that it exhibited signs of activity when it was more than 25 times as far out as the Earth-sun distance. But according to theoretical models, its carbon monoxide ice should have been sublimated by the sun's rays when the object was even farther out in the solar system. This discrepancy may mean the comet made a pass of the sun before, with sublimation first eating away at layers of ice on its surface and its current activity only being kickstarted at closer distances, when heat from sunlight reached ice deeper within the object. Finding a behemoth like C/2014 UN271, Kokotanekova says, could hint at the existence of a whole class of gigantic progenitor comets. Such comets might have been the first large, icy objects to coalesce in the solar system, after which they may could have eventually broken apart to form smaller comets. 'It's possible that the small objects are mostly fragments, while the large ones, like UN271, have never collided with anything,' she says. That might mean there are more primordial megacomets awaiting discovery. If so, the recently completed Vera C. Rubin Observatory in Chile, which will begin a 10-year panoramic survey of the heavens later this year, could find more of them. 'It's so sensitive that it will certainly pick up comets of this size, quite probably even further away from us,' Ye says. Rubin's wide eye on the sky should also give us more information on C/2014 UN271 itself, says Meg Schwamb, an astronomer at Queen's University Belfast uninvolved with this latest finding. 'Rubin's going to watch it come in,' she says. That could help us get a better handle on its activity, in partnership with telescopes like ALMA. 'You need both of those pieces of information—if it got brighter, and whether the amount of carbon monoxide changed—to tell you what's going on,' Schwamb says. For now Comet UN271 remains a fascinating target of study, a giant comet like no other that is giving us a unique window into the dark frontiers of the outer solar system. 'This is just an incredibly exciting object,' Roth says. And, for astronomers eager to learn more about this and other mega comets, the best is yet to come.
