Santa Barbara, CA, United States
Santa Barbara, CA, United States

Time filter

Source Type

It was early Thursday morning when astronomer Matt Muterspaugh noticed something strange with the star he had been observing for the last year and a half. Telescope data taken from the night before showed that the brightness of the star had dipped significantly. He contacted other astronomers who had also been observing the same star, to let them know what he had seen and to keep an eye on it for any more changes. Then by the following morning, the star had dimmed even more. That’s when he and the others knew it was time to signal the alarm: the weirdest star in our galaxy was acting weird again. And it was time for everyone to look at this distant celestial body — to figure out what the hell is going on. “As far as I can tell, every telescope that can look at it right now is looking at it right now,” Muterspaugh, a professor at Tennessee State University, tells The Verge. “As far as I can tell, every telescope that can look at it right now is looking at it right now.” The star Muterspaugh has been looking at is KIC 8462852, though it’s also known as Tabby’s Star. That’s because Tabetha Boyajian, an astronomer at Louisiana State University, first noticed this strange star a couple years ago after looking through archive data from Kepler — a NASA spacecraft that’s been hunting for planets that exist outside of our Solar System. Boyajian was part of a citizen science project called Planet Hunters, where volunteers can analyze Kepler data to look for planets, and they alerted her to the wonky star. “Our users flagged it to be something really interesting,” Boyajian tells The Verge. “They came to the science team and asked, ‘What is this? That’s not a planet clearly.’” The data showed that KIC 8462852 experienced some extreme fluctuations in brightness, way more than what a passing planet would cause. At one point, the star’s light dimmed by up to 20 percent. It was a huge dip, like nothing that had ever been seen before, indicating something big and irregular may be orbiting around the star. Then in late 2015, astronomer Jason Wright from Penn State suggested a tantalizing scenario for the dips. Perhaps large megastructures created by an alien civilization were orbiting around the star, explaining the weird changes. “Aliens should always be the very last hypothesis you consider,” Wright told The Atlantic at the time, “but this looked like something you would expect an alien civilization to build.” That’s when Tabby’s Star became popularly known as the “alien megastructure” star. Of course, astronomers are more focused on a natural explanation: perhaps a huge swarm of giant comets periodically orbits the star. The only way to narrow down the possibilities is to observe the star in real time as the dimming is happening. And all we had were past observations of the fluctuations caught by Kepler. “We were kind of stuck in a spot where we couldn’t do anything,” says Boyajian. “We had all the data we could and to learn anything more we needed to catch it in action again.” The problem, though, is that Tabby’s star is unpredictable. The fluctuations aren’t exactly repetitive and don’t seem to follow any known pattern — making it hard to know when the strange star will be strange again. “Things that change the brightness of a star happen in a very regular pattern,” says Muterspaugh. “And from what we can tell so far, [this star] is not periodic. We cannot predict when it happens, and that makes it very weird.” astronomers have been observing the star basically around the clock That’s why astronomers have been observing the star basically around the clock since they first learned of its dimming behavior. To do this, Boyajian started a Kickstarter campaign called “Where’s the Flux?” to secure funding for enough telescope time to continuously monitor the star. The campaign successfully raised more than $100,000, which helped Boyajian and others set up a year-long observation program through the Las Cumbres Observatory, which has telescopes stationed throughout the world. At the same time, Muterspaugh independently set up an observation campaign with the robotic telescopes at the Fairborn Observatory in Arizona. These telescopes are essentially automatic, observing certain targets in the sky on their own when the rest of us are sleeping. Muterspaugh had programmed one of these telescopes to constantly keep an eye on Tabby’s Star. And for the most part, the star has been quiet, behaving more or less like normal. Then on April 24th, data from Fairborn indicated that the star had dimmed ever so slightly. It wasn’t enough of a change for astronomers to think the star was acting up again, but everyone was still on their guard. There was an idea that this small dip could be a preliminary event before the real thing. And sure enough, nearly a month later, the huge dimming that Kepler saw seems to be happening again. And it’s really the moment that everyone has been waiting for with Tabby’s Star. It gives astronomers the opportunity to use their entire arsenal of telescopes to observe these fluctuations as they occur. Kepler only observed the light fluctuations in just one broad range of light colors. Now, we can use telescopes to observe the star’s light in numerous colors and light spectrums, and that can give us a better idea of the types of chemicals that are present when these changes occur or the properties of the objects that are blocking the light. For instance, if it is just a bunch of comets, then they’re going to be very close to the star and super hot, according to Jason Wright, and that’s something we can pick up by observing in the infrared spectrum. If it’s the other theory — the alien one — then it’s unclear what we’ll see. Maybe we’ll see some kind of artificial element associated with the blockage. No one is making any definitive statements just yet, since now is the time to simply observe, and it’s going to be a while before astronomers decode what they see this weekend. So all the theories are still on the table — including the alien megastructures. “That theory is still a valid one,” says Muterspaugh. “We would really hate to go to that, because that’s a pretty major thing. It’d be awesome of course, but as scientists we’re hoping there’s a natural explanation.” But the good news is we’re going to get a lot of data. Boyajian says the response from the science community has been overwhelming, and everyone who can help right now is doing their watch and document changes. “It’s neat to see it turn full circle from citizen scientists who discovered the star and then an opportunity for folks interested in science to follow up and learn more about what this star is,” Boyajian says. “It’s really humbling to work with all these science enthusiasts and have this support for this really interesting star.” Update May 20th, 11:30AM ET: This post was updated to include quotes and information from Tabetha Boyajian.


News Article | May 23, 2017
Site: www.cnet.com

We're not saying it's aliens, but I also can't tell you it's definitely not aliens. Late last week, astronomers around the world prepared to work through the weekend observing one of the most enigmatic stars known to humanity: KIC 8462852, better known as Tabby's Star, Boyajian's Star or the "alien megastructures star." Amateur and pro star watchers trained telescopes on the star some 1,400 light-years away, and now we're able to get an early look at those observations and take a few tiny, tentative steps toward solving the mystery of this very weird star. The alert went out on Friday that the odd dips in the brightness of the star first discovered in Kepler data via a crowdsourced effort were happening once again -- these dips have yet to be explained, giving rise to all sorts of theories, including far-out ideas like huge megastructures built by an advanced alien civilization. Astrophysicist Tabetha Boyajian, who led the citizen science project and for whom the star is named, predicted last year that the star's brightness might dip again as soon as May 2017. When her prediction began to come true last week, she notified major observatories and amateur astronomy groups via social media and other channels, and many swung their lenses in the direction of the constellation Cygnus and the mysterious star. By Sunday, we were beginning to learn more about the latest "dimming event" going on with KIC 8462852. What makes this star so bizarre is that its dips in brightness don't seem to follow any obvious patterns. When planets or even comets pass in front of their stars, it tends to happen at regular, predictable intervals and they usually block out the same amount of a star's light as the last time they made a pass. But the dips seen in the brightness of KIC 8462852 don't occur on a very tight schedule and they vary in how much they dim the star's light: anywhere from three to more than 20 percent. To make things even weirder, old observations of the star show it has also dimmed slowly over the course of the past century. So in addition to these odd short term dips where something seems to pass in front of the star, it's also getting noticeably less bright over the long term, as if someone is turning down its energy output like you might with your living room lights using a dimmer switch. We just don't see many, if any, other stars behaving this way. So back to the latest observations: by May 19, the light seen from KIC 8462853 had dropped by as much as 3 percent over a period of around 24 hours. This according to new data from the Las Cumbres Observatory in California that Boyajian discussed with fellow scientist David Kipping from Columbia University in the below livestream recorded Sunday. By Monday morning, astronomer Jason Wright (who was the first to put forward the idea that alien megastuctures could explain the unpredictable dips) noted that the dip seemed to be over and the star was returning to its normal brightness. As it turns out, the dip seen over the weekend is roughly similar to a 3 percent dip observed by the Kepler Space Telescope a few years back, leading Boyajian and others to wonder if it might repeat or follow some other sort of pattern after all. "We're still quite unsure if it is in fact a duplicate of that event, meaning that it's the same object that's passing in front of (the star). It could be a different object or even the same object that's (rotated) to have a different contrast or signature against the star," she explains. The new observations will be analyzed more rigorously over the coming days and weeks and hopefully provide some new insights into the mystery of the star. In fact, if the weird dips in brightness do follow a pattern, this could be just the beginning of the latest round of them. As Wright points out in the tweeted graph below, if this is a repeat of previous dips, then more action from Boyajian's Star is just around the corner. The black line on the graph shows Kepler data from previous dips overlaid on the multicolor data from multiple telescopes showing last week's dip. Note that if we're seeing a repeating pattern, more and deeper dips could happen this week. If that happens, then we could really begin to get to the bottom of the mystery. But for now, the new observations already provide some very interesting food for thought. If the dip seen last week is actually the shadow of something passing in front of the star on a regular basis, it's something pretty massive. In fact, Kipping estimates it would be about five times the radius of our own sun and bigger than KIC 8462853 itself. And while the odds that whatever is getting in between the star and our telescopes is artificial are still very low, that possibility still can't be ruled out. What's more, Boyajian herself (who has always been hesitant to fan the hungry flame of the alien megastructures hypothesis) notes that it appears the large object blocking the star's light could even be within the habitable zone of the solar system. "I think it's an interesting coincidence," she says. "You can imagine some Death Star blowing up a planet that was inhabited perhaps and this is the pieces of shrapnel from the planet that is orbiting around the star and blocking the light. You can imagine it, but the data doesn't quite fit the alien hypothesis perfectly. A more likely explanation might be a huge cloud of dust, perhaps from some big time colliding comets or even planets, but who knows at this point. Boyajian, for one, says she's keeping an open mind about what could be causing the weird observations of the star that now carries her name. Meanwhile, telescopes around the world will continue to keep a close eye on this very weird star, including the SETI Institute's Allen Telescope Array, which continues to listen for signs of intelligent life from Boyajian's star. So far, any aliens that might be building a massive Dyson sphere around the star seem to be doing their work with their radios turned off, because SETI researchers have yet to pick up signs of life from the star. Technically Literate: Original works of short fiction with unique perspectives on tech, exclusively on CNET.


News Article | May 22, 2017
Site: www.sciencemag.org

Astronomers and alien life enthusiasts alike are buzzing over the sudden dimming of an otherwise unremarkable star 1300 light-years away in the constellation Cygnus. KIC 8462852 or “Tabby’s star” has dimmed like this several times before, prompting some researchers to suggest that the megastructures of an advanced alien civilization might be blocking its light. And now—based on new data from numerous telescopes—it’s doing it again. “This is the first clear dip we have seen since [2013], and the first we have ever caught in real time,” says Jason Wright, an astronomer at Pennsylvania State University in State College. If they can rope in more telescopes, astronomers hope to gather enough data to finally figure out what’s going on. “This could be the first of several dips about to come,” says astronomer David Kipping of Columbia University. “Many observers will be closely watching.” KIC 8462852 was first noticed to be dipping in brightness at seemingly random intervals between 2011 and 2013 by NASA’s Kepler telescope. Kepler, launched to observe the stellar dimmings caused when an exoplanet passes in front of its star, revealed that the dimming of Tabby’s star was much more erratic than a typical planetary transit. It was also more extreme, with its brightness sometimes dropping by as much as 20%. This was not the passage of a small circular planet, but of something much larger and more irregular. The team that made this discovery, led by Yale University astronomer Tabetha Boyajian—the star’s namesake—suggested a variety of explanations for its strange behavior, including that the star itself was variable, that it was surrounded by clouds of dust or dusty comets, or that planets around it had collided or were still forming. But KIC 8462852 hit the headlines when Wright and colleagues suggested that the star would be a good candidate to search for evidence of a large manufactured structure built by alien life. Further studies didn’t find the infrared “glow” expected from a large object orbiting close to its star. But neither did they confirm—or refute—any other explanations. Astronomers needed to observe the star closely and take spectra—the distribution of light emitted at various wavelengths—during a dimming. For that they had to wait. Kepler stopped looking at the sky around Tabby’s star in 2013, so Boyajian and her team have been keeping an eye on KIC 8462852 with the help of a network of amateur star watchers and, more recently, with the privately run Las Cumbres Observatory, a network of 18 robotic telescopes at six sites around the world. The first sign of the star’s recent dimming came on 24 April from Tennessee State University’s Fairborn Observatory in southern Arizona. But it wasn’t until late last week that astronomers were sure it had entered a new dip. It was 3% dimmer than its normal brightness on 19 and 20 May and is now moving back toward normal. “It looks like the dip has mostly ended,” Kipping says. “But … in the Kepler data we saw an episode of multiple dips clustered together over the span of a few weeks.” The progress of the dimming over the past few days also bears a passing resemblance to some detected by Kepler, supporting the idea that the same object is repeatedly passing in front of the star. Observers are ready for further changes. “There’s been an enormously positive response from the community,” says Boyajian, now at Louisiana State University in Baton Rouge, with people interrupting ongoing projects to take observations of KIC 8462852. Astronomers from about a dozen different observatories managed to capture spectra from the star during the dimming. So, just what is happening around the star? Boyajian says that combining the different spectra into a coherent picture across the wavelengths may take a while. “A physical interpretation of what’s going on will take more work. But the process has begun.”


News Article | December 12, 2016
Site: www.eurekalert.org

Back in 2015 when astronomers discovered an intense flare in a distant galaxy, they considered it the brightest supernova ever observed. Now, UC Santa Barbara astrophysicists and a group of international colleagues offer an entirely different interpretation based on new astronomical observation data from the Las Cumbres Observatory (LCO), a global robotic telescope network, and the Hubble Space Telescope. The new information indicates that the event, called ASASSN-15lh, is actually a tidal disruption event (TDE) -- the destruction of a star by a supermassive black hole. The findings appear in the inaugural issue of the journal Nature Astronomy. "Years ago we just wouldn't have been able to follow an event like this," said co-author Andy Howell, leader of the supernova group at the Goleta, California-based LCO and an adjunct professor in UCSB's Department of Physics. "This study shows that large-area surveys, a global robotic telescope network and a NASA satellite can come together to reveal dramatic new discoveries that wouldn't be possible without each piece of that puzzle." Using images from the Hubble Space Telescope that were not available when ASASSN-15lh was discovered, the scientists found that the event occurred at the center of the galaxy where the supermassive black hole resides. The black hole inferred to lie in this galaxy is more than 100 million times the mass of the sun. For a star to be tidally disrupted by such a massive black hole -- rather than swallowed whole -- the black hole must be spinning very rapidly. This discovery marks the first time that a TDE has been used to probe the spin of a black hole, a property that is very difficult to measure and is used to infer the existence of so-called Kerr black holes. ASASSN-15lh occurred when the star strayed too close to the supermassive black hole and was torn apart by the tides generated by the extreme gravity. The stellar material orbited around the black hole, collided with itself at high velocity and started falling into the black hole. This released copious amounts of energy and generated the bright flare astronomers observed as ASASSN-15lh. "We've only been studying the optical flares of tidal disruptions for the last few years," said co-author Iair Arcavi, principal investigator of the LCO program that's used to observe ASASSN-15lh and an Einstein postdoctoral fellow at UCSB. "ASASSN-15lh is similar in some ways to the other events we've been seeing but is different in ways we didn't expect. It turns out that these events -- and the black holes that make them -- are more diverse than we had previously imagined." "This is like discovering a new kind of dinosaur," Howell said. "Now that we have the right tools and know what to look for, we're going to find more and get a better sense of the population. It's exciting to have new ways of learning about black holes and stellar death."


News Article | December 12, 2016
Site: www.rdmag.com

Back in 2015 when astronomers discovered an intense flare in a distant galaxy, they considered it the brightest supernova ever observed. Now, UC Santa Barbara astrophysicists and a group of international colleagues offer an entirely different interpretation based on new astronomical observation data from the Las Cumbres Observatory (LCO), a global robotic telescope network, and the Hubble Space Telescope. The new information indicates that the event, called ASASSN-15lh, is actually a tidal disruption event (TDE) -- the destruction of a star by a supermassive black hole. The findings appear in the inaugural issue of the journal Nature Astronomy. "Years ago we just wouldn't have been able to follow an event like this," said co-author Andy Howell, leader of the supernova group at the Goleta, California-based LCO and an adjunct professor in UCSB's Department of Physics. "This study shows that large-area surveys, a global robotic telescope network and a NASA satellite can come together to reveal dramatic new discoveries that wouldn't be possible without each piece of that puzzle." Using images from the Hubble Space Telescope that were not available when ASASSN-15lh was discovered, the scientists found that the event occurred at the center of the galaxy where the supermassive black hole resides. The black hole inferred to lie in this galaxy is more than 100 million times the mass of the sun. For a star to be tidally disrupted by such a massive black hole -- rather than swallowed whole -- the black hole must be spinning very rapidly. This discovery marks the first time that a TDE has been used to probe the spin of a black hole, a property that is very difficult to measure and is used to infer the existence of so-called Kerr black holes. ASASSN-15lh occurred when the star strayed too close to the supermassive black hole and was torn apart by the tides generated by the extreme gravity. The stellar material orbited around the black hole, collided with itself at high velocity and started falling into the black hole. This released copious amounts of energy and generated the bright flare astronomers observed as ASASSN-15lh. "We've only been studying the optical flares of tidal disruptions for the last few years," said co-author Iair Arcavi, principal investigator of the LCO program that's used to observe ASASSN-15lh and an Einstein postdoctoral fellow at UCSB. "ASASSN-15lh is similar in some ways to the other events we've been seeing but is different in ways we didn't expect. It turns out that these events -- and the black holes that make them -- are more diverse than we had previously imagined." "This is like discovering a new kind of dinosaur," Howell said. "Now that we have the right tools and know what to look for, we're going to find more and get a better sense of the population. It's exciting to have new ways of learning about black holes and stellar death."


A flash in the sky that earlier this year was called the brightest supernova ever detected—tens of times brighter than our entire Milky Way galaxy—may be something much more exotic: a supermassive black hole tearing apart—and consuming—a star that strayed too close, according to a new study. The flash was first spotted in 2015 by the All-Sky Automated Survey for SuperNovae (ASAS-SN), a network of small telescopes in Chile and Hawaii that monitors the sky for fast-changing objects. Astronomers assumed it was a superluminous supernova (SLSN), which occurs when a massive star collapses under its own gravity at the end of its life, spewing out a fireball of hot dust and gas that glows brightly for a short time before gradually fading. At the time, the event was twice as bright as the previous record holder. But ASASSN-15lh, as the event was named, was in the wrong sort of galaxy for an SLSN. The right sort is generally a young dwarf galaxy full of gas and dust where huge stars can form rapidly, burn brightly, and explode in a blaze of supernova glory. ASASSN-15lh, however, was in an old, burned-out galaxy with little evidence of star formation. “The minute they told me about this event, I was suspicious. It just didn’t seem right,” says Giorgos Leloudas, an astronomer at the Weizmann Institute of Science in Rehovot, Israel, who was not a member of the original team. Leloudas and his colleagues began gathering more data from a variety of sources, including the Swift gamma-ray satellite, the Las Cumbres Observatory global telescope network, the Hubble Space Telescope, and the European Southern Observatory’s Very Large Telescope and the New Technology Telescope, both based in Chile. Hubble data showed that the source of the flash was close to the center of its galaxy, whereas the rapid star formation that produces SLSNs typically happens farther out. Also, unlike a normal SLSN, ASASSN-15lh seemed to fade before getting brighter again weeks later, indicating a rise in temperature maintained for about 100 days, Leloudas says. A spectrum of the ultraviolet light from the event, recorded by Hubble, suggested a low-mass star in the prime of life, not on its deathbed. As the team reports today in , all these signs pointed to the idea that ASASSN-15lh might, in fact, be the dying gasp of a star that strayed too close to the supermassive black hole at the center of its galaxy and was ripped apart by the extreme gravitational field, a so-called tidal disruption event (TDE). TDEs are very rare—there are only about 10 such events currently suspected by astronomers. But, Leloudas says, the changes of output from ASASSN-15lh suggested a TDE: the initial flash from gravity tearing the star apart and heating its remains to high temperatures; the later burst from those remains being heated again as they were accreted onto the surface of the black hole. The one flaw in this argument is that the galaxy in question is thought to have a very massive black hole at its heart: more than 100 million times the mass of our sun. Theorists predict that such a leviathan would more likely swallow a star whole and only tear it up once it’s below the event horizon, where it can’t be seen. But the team realized there was a scenario in which the black hole would chew first and swallow later—if it were spinning. The gravitational field around a rotating black hole is different from a nonrotating one and would allow a visible TDE to occur. If it is confirmed that this was the fate of ASASSN-15lh, it will be the first verified rotating black hole at the center of a quiescent galaxy. The team will continue to observe ASASSN-15lh, hoping to learn more as its dazzle ceases to illuminate the rest of the galaxy. And because other candidate TDEs all occur around smaller black holes, ASASSN-15lh broadens the range of places TDEs may occur. “By adding to the diversity, we will learn more about the physics that happens during a disruption,” Leloudas says. “This whole new phenomenon of tidal disruption events gives us a unique opportunity to learn about supermassive black holes during their quiescent phase,” says astronomer Benny Trakhtenbrot of the Swiss Federal Institute of Technology in Zurich, who was not involved in the study. If you can determine how close the disrupted star passed to the black hole, he says, “that can directly tell us how fast the black hole is spinning.” And spin can reveal something of the formation history of otherwise inscrutable black holes, he says.


Littlefair S.P.,University of Sheffield | Naylor T.,University of Exeter | Mayne N.J.,University of Exeter | Saunders E.,Las Cumbres Observatory | Jeffries R.D.,Keele University
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2011

We present an analysis of the rotation of young stars in the associations Cepheus OB3b, NGC 2264, 2362 and the Orion Nebula Cluster (ONC). We discover a correlation between rotation rate and position in a colour-magnitude diagram (CMD) such that stars which lie above an empirically determined median pre-main sequence rotate more rapidly than stars which lie below this sequence. The same correlation is seen, with a high degree of statistical significance, in each association studied here. If position within the CMD is interpreted as being due to genuine age spreads within a cluster, then the stars above the median pre-main sequence would be the youngest stars. This would in turn imply that the most rapidly rotating stars in an association are the youngest, and hence those with the largest moments of inertia and highest likelihood of ongoing accretion. Such a result does not fit naturally into the existing picture of angular momentum evolution in young stars, where the stars are braked effectively by their accretion discs until the disc disperses. Instead, we argue that, for a given association of young stars, position within the CMD is not primarily a function of age, but of accretion history. We show that this hypothesis could explain the correlation we observe between rotation rate and position within the CMD. © 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS.


Barnes J.W.,University of Idaho | Linscott E.,Oklahoma Baptist University | Shporer A.,University of California at Santa Barbara | Shporer A.,Las Cumbres Observatory
Astrophysical Journal, Supplement Series | Year: 2011

We model the asymmetry of the KOI-13.01 transit lightcurve assuming a gravity-darkened rapidly rotating host star in order to constrain the system's spin-orbit alignment and transit parameters. We find that our model can reproduce the Kepler lightcurve for KOI-13.01 with a sky-projected alignment of λ = 23° 4° and with the star's north pole tilted away from the observer by 48° 4° (assuming M * = 2.05 M ⊙). With both these determinations, we calculate that the net misalignment between this planet's orbit normal and its star's rotational pole is 56° ± 4°. Degeneracies in our geometric interpretation also allow a retrograde spin-orbit angle of 124° ± 4°. This is the first spin-orbit measurement to come from gravity darkening and is one of only a few measurements of the full (not just the sky-projected) spin-orbit misalignment of an extrasolar planet. We also measure accurate transit parameters incorporating stellar oblateness and gravity darkening: R * = 1.756 ± 0.014 R⊙, R p = 1.445 ± 0.016 RJup, and i = 859 04. The new lower planetary radius falls within the planetary mass regime for plausible interior models for the transiting body. A simple initial calculation shows that KOI-13.01's circular orbit is apparently inconsistent with the Kozai mechanism having driven its spin-orbit misalignment; planet-planet scattering and stellar spin migration remain viable mechanisms. Future Kepler data will improve the precision of the KOI-13.01 transit lightcurve, allowing more precise determination of transit parameters and the opportunity to use the Photometric Rossiter-McLaughlin effect to resolve the prograde/retrograde orbit determination degeneracy. © 2011. The American Astronomical Society. All rights reserved.


News Article | December 13, 2016
Site: www.gizmag.com

In 2015, astronomers detected what they believed to be the most luminous supernova ever recorded, which shone 20 times brighter than the light output of the entire Milky Way. However, fresh research suggests that the event, which has since been named ASASSN–15lh, might not have been a supernova at all, but instead the light signature of a vast, fast-spinning black hole devouring a Sun-like star. For the new study, an international team of astronomers made use of a number of famous ground and space-based observatories including the Hubble Space Telescope, and the European Southern Observatory's Very Large Telescope, located at the Paranal Observatory, Chile. The telescope data revealed that in the ten months following the supposed supernova event, ASASSN-15lh experienced a significant increase in both temperature and the emission of ultraviolet light. According to the researchers, these characteristics make it unlikely that the 2015 event took the form of a superluminous supernova. Instead the team suggest that the light signature detected in 2015 was created when a Sun-like star orbiting in close proximity to the supermassive black hole located at the centre of ASASSN -15lh's host galaxy was torn apart, or "spaghettified" by the gravity of the black hole. For the black hole to rip the star apart as it orbited beyond its event horizon, it must have been spinning incredibly fast. The extreme gravitational influence of such a fast spinning black hole, known as a Kerr black hole, could have created a tidal disruption event capable of destroying a star orbiting beyond its event horizon. Only 10 tidal disruption events have been observed to date, making it a rare occurrence. The researchers believe that the 2015 light signature was created when the remnants of a star destroyed by a tidal disruption event collided as they fell towards the event horizon of the supermassive black hole, which has at least 100 times the mass of our own sun. This process would have led to the release of an enormous amount of energy, a portion of which was released in the form of ASASSN-15lh. The nature of the galaxy in which ASASSN-15lh was discovered, and the close proximity of the event to the supermassive black hole's event horizon further supports the tidal disruption theory. Superluminous supernovae are typically discovered in galaxies that are alight with the activity of star creation. However, ASASSN-15lh was found in a passive, red galaxy, which exhibits a relatively low-level of star formation. "We've only been studying the optical flares of tidal disruptions for the last few years," said co-author Iair Arcavi, principal investigator of the Las Cumbres Observatory program used to observe ASASSN-15lh. "ASASSN-15lh is similar in some ways to the other events we've been seeing but is different in ways we didn't expect. It turns out that these events — and the black holes that make them — are more diverse than we had previously imagined." Scroll down to see a simulation of the supermassive black hole thought to reside at the centre of ASASSN-15lh's host galaxy destroying a Sun-like star via spaghettification.


Trimble V.,University of California at Irvine | Trimble V.,Las Cumbres Observatory
Scientometrics | Year: 2011

It has been shown that papers in stem cell research submitted from institutions in the USA are accepted faster than those submitted from elsewhere and that the cause might at least partly be some bias in the refereeing process. We investigate whether there is a similar difference in time scale for papers in astronomy, astrophysics, and cosmology and look briefly at some of the possible causes. We find a publication time lag of 3.8 days (out of a median time of 105 days) while in the stem cell case it is 24 days out of a median of 83 days. One of many possible causes is a difference in how useful the papers are to the community, and we will assess this in a second paper making use of citation analysis. © 2011 Akadémiai Kiadó, Budapest, Hungary.

Loading Las Cumbres Observatory collaborators
Loading Las Cumbres Observatory collaborators