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My question is straight forward. Is a kilonova bigger than a supernova?
How does a kilonova differ from a nova in terms of…
- volume of space occupied by the ejecta
- speed of the ejecta
- other metrics?
Although it's a little tricky to say what "bigger" means in this context, the answer is, in most senses, no.
A supernova puts out about ten to a hundred times as much energy in the form of light, and hundred or more times as much matter is ejected. (A core-collapse supernova undoubtedly puts out much more energy in the form of neutrinos as well.) What matter is ejected by a kilonova does go out faster (30-60,000 km/s, versus about 10,000 km/s for supernova ejecta).
On the other hand, a kilonova puts out much more energy in the form of gravitational waves, so they're bigger in that sense.
Eleven billion years ago, two massive stars were born. They both lived short, brilliant lives, dying in supernova explosions and leaving behind two neutron stars orbiting each other. After a billion-year cosmic dance, these neutron finally stars merged, sending a ripple of gravitational waves through space and time. These gravitational waves travelled more than a hundred million light years and were finally felt on August 17, 2017 by Advanced LIGO and Virgo using their incredibly sensitive detectors.
Credit: Dark Energy Survey
Our team, and others around the world, jumped into action. As soon as the sun set on the deserts of Chile — less than twelve hours after the waves were detected — observations began using the Dark Energy Camera on the 4-meter Victor Blanco Telescope at the Cerro Tololo Inter-American Observatory.
For the first time in history, we have connected these elusive gravitational waves with an electromagnetic companion: a kilonova.
Why do kilonovae matter? As well as allowing us to study extreme physics in the densest objects in the Universe, these events are thought to be responsible for producing most of the heavy elements such as gold and platinum.
Credit: P. S. Cowperthwaite / E. Berger / DECam
Most importantly, this is just the beginning. The discovery of this “multi-messenger”, visible in both light and gravitational waves, marks the beginning of a new era in physics and astronomy, and a new way to learn about the Universe.
You can read more about our work in our technical description for experts or by checking out our eight papers listed below. Our Press Kit page features our team’s official press release as well as video interviews with some of our team members.
'Kilonova' detection is astronomical gold mine, here's why
Monday, October 16, 2017, 12:13 PM - For the first time ever, astronomers have spotted a 'kilonova', an elusive, previously only theoretical stellar explosion, and this discovery is not only important for the science of gravitational waves, but may also solve another puzzle of the universe.
130 million of years ago, in another galaxy, two neutron stars orbiting each other came so close together that they merged. The titanic forces produced by this merger set off ripples across space-time, known as gravitational waves, and very shortly thereafter, it also caused an immense explosion, 1,000 times brighter than a typical stellar nova - a kilonova.
On August 17, 2017, the gravitational waves from this merger were picked up by both the LIGO and VIRGO detectors. This was the fifth gravitational wave detection made, known as GW170817, but it was the first detected from a pair of neutron stars, and it is now the first ever where astronomers also spotted the kilonova explosion that went with it.
WATCH THE VIDEO BELOW TO LEARN MORE
Nova, supernova, kilonova?
Two types of explosions associated with stars - novae and supernovae - are well known and have been observed numerous times by astronomers. A nova occurs when a white dwarf - the 'dead' remnant of a Sun-like star - pulls matter off a larger companion star, and the intense gravity at the surface of the white dwarf causes that stolen matter to fuse, ignite and expand out into space. The pair brightens significantly from this eruption, and they can appear as a new star in our night sky, thus inspiring the name 'nova' (which means "new"). A supernova is a much more energetic explosion, a million times brighter than a nova. It can be caused by the collapse of a massive star, into either a neutron star or a black hole. It can also happen in a similar way to a nova, except that rather than only the stolen matter fusing, nearly the entire mass of the white dwarf undergoes fusion, resulting in a colossal explosion that blows the entire remnant apart.
Over the past 30 years, theoretical physicists have investigated how other stellar remnants - a pair of neutron stars, a pair of black holes, or a paired neutron star and black hole - could interact and merge. This work gave us the ideas behind gravitational waves, and what they would look like if we detected them, but it also gave us an idea of what an explosion from the merger of two neutron stars should look like - a 'kilonova', or what some call a 'macronova'.
These kilonova explosions are thought to be responsible for dispersing heavy elements, such as gold and platinum, throughout the Universe.
Up until now, astronomers had not actually seen one of these kilonovas, though. With the detection of the burst of light from GW170817, they appear to have the first.
"The data we have so far are an amazingly close match to theory," said Stefano Covino, the lead author of a Nature Astronomy paper detailing the detection of the kilonova, according to ESO News. "It is a triumph for the theorists, a confirmation that the LIGO–VIRGO events are absolutely real, and an achievement for ESO to have gathered such an astonishing data set on the kilonova."
With this detection, astronomers were able to pinpoint the source, in the galaxy NGC 4993, some 130 million light years away. That makes this first kilonova not only the first confirmed light seen from a gravitational wave event, but it also confirms GW170817 as being the closest gravitational wave event so far, and also the closest gamma ray burst source ever.
This mosaic of images, taken by the VISTA infrared survey telescope at ESO's Paranal Observatory in Chile, shows how the kilonova in NGC 4993 - the bright dot to the upper left of the galaxy's center - brightened, became much redder in colour and then faded in the weeks after it was first detected, on August 17, 2017. Credit: ESO/N.R. Tanvir, A.J. Levan and the VIN-ROUGE collaboration
Another mystery solved?
Along with those discovery milestones, we may be able to add another.
Over the years, NASA’s Fermi Gamma-ray Space Telescope and the ESA’s INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL), have detected a number of very short bursts of gamma rays, the most energetic rays we find. These have lasted anywhere from milliseconds up to two seconds long, and have been observed all over the sky. It was speculated that these may be caused by the merger of two neutron stars, however their source has remained a mystery, since there has been no way to confirm that hypothesis. Regardless of the many short gamma ray bursts detected, astronomers lacked some kind of supporting evidence to link them to a source.
With this detection, it would appear that they now have that supporting evidence. Seeing the gravitational waves from a neutron star merger show up at the same time, and from the same location, as one of these short gamma ray bursts shows that they are linked.
Physicists predict neutron stars may be bigger than previously imagined
A composite image of the supernova 1E0102.2-7219 contains X-rays from Chandra (blue and purple), visible light data from VLT’s MUSE instrument (bright red), and additional data from Hubble (dark red and green). A neutron star, the ultra dense core of a massive star that collapses and undergoes a supernova explosion, is found at its center. Credit: NASA
When a massive star dies, first there is a supernova explosion. Then, what's left over becomes either a black hole or a neutron star.
That neutron star is the densest celestial body that astronomers can observe, with a mass about 1.4 times the size of the sun. However, there is still little known about these impressive objects. Now, a Florida State University researcher has published a piece in Physical Review Letters arguing that new measurements related to the neutron skin of a lead nucleus may require scientists to rethink theories regarding the overall size of neutron stars.
In short, neutron stars may be larger than scientists previously predicted.
"The dimension of that skin, how it extends further, is something that correlates with the size of the neutron star," said Jorge Piekarewicz, a Robert O. Lawton Professor of Physics.
Piekarewicz and his colleagues have calculated that a new measurement of the thickness of the neutron skin of lead implies a radius between 13.25 and 14.25 kilometers for an average neutron star. Based on earlier experiments on the neutron skin, other theories put the average size of neutron stars at about 10 to 12 kilometers.
Piekarewicz's work complements a study, also published in Physical Review Letters, by physicists with the Lead Radius Experiment (PREX) at the Thomas Jefferson National Accelerator Facility. The PREX team conducted experiments that allowed them to measure the thickness of the neutron skin of a lead nucleus at 0.28 femtometers—or 0.28 trillionths of a millimeter.
An atomic nucleus consists of neutrons and protons. If neutrons outnumber the protons in the nucleus, the extra neutrons form a layer around the center of the nucleus. That layer of pure neutrons is called the skin.
It's the thickness of that skin that has captivated both experimental and theoretical physicists because it may shed light on the overall size and structure of a neutron star. And though the experiment was done on lead, the physics is applicable to neutron stars—objects that are a quintillion (or trillion-million) times larger than the atomic nucleus.
Piekarewicz used the results reported by the PREX team to calculate the new overall measurements of neutron stars.
"There is no experiment that we can carry out in the laboratory that can probe the structure of the neutron star," Piekarewicz said. "A neutron star is such an exotic object that we have not been able to recreate it in the lab. So, anything that can be done in the lab to constrain or inform us about the properties of a neutron star is very helpful."
The new results from the PREX team were larger than previous experiments, which of course affects the overall theory and calculations related to neutron stars. Piekarewicz said there is still more work to be done on the subject and new advances in technology are constantly adding to scientists' understanding of space.
"It's pushing the frontiers of knowledge," he said. "We all want to know where we've come from, what the universe is made of and what's the ultimate fate of the universe."
D. Adhikari et al. Accurate Determination of the Neutron Skin Thickness of Pb208 through Parity-Violation in Electron Scattering, Physical Review Letters (2021). DOI: 10.1103/PhysRevLett.126.172502
When a star dies it would go into a supernova and depending on its mass its core either collapses into a black hole or a neutron star or a white dwarf. A kilonova is 1000 times brighter than nova (but not much brighter than a supernova). It is usually produced when two massive stellar core collapses. In this case, the core is a neutron star. Neutron stars are small but extremely dense objects. To give a figure of that, 1 teaspoonful of neutron star would weigh 1 billion tons.
Below is a gif that shows what would happen if an object gets too close to a neutron star.
First, it shreds apart the joints and connections of that body and piece by piece rip of the whole body into atoms. It doesn’t end there. Those pieces form a stream of particles and collide onto the surface of the neutron star with a speed which is approximately 100,000 m/s.( More about the neutron star will be discussed later in another blog. )
On 17 August 2017, a galaxy named NGC 4993, 130 light-years away, baffled the scientists. A unique explosion that puzzled them. The one which they have never witnessed. A KILONOVA.
It was one of a kind. No one has ever observed this kind of event before. A whole new level of talks about what this event might be and what might have caused this event was raised among the scientific community during that time.
Until that moment, LIGO was observing gravitational waves from colliding black holes which are billions of miles away. But this was the first time that scientists were able to witness both the electromagnetic radiation and gravitational waves during a single event. GW170817 was the fifth detection by the LIGO.
Hubble picture of NGC 4993 with inset showing GRB 170817A over 6 days. Credit: NASA and ESA
“There are rare occasions when a scientist has the chance to witness a new era at its beginning,” said Elena Pian, an astronomer with INAF, Italy, and lead author of one of the Nature papers. “This is one such time!”
Taking this opportunity into the hand, 70 observatories from all around the world observed that event. It was also releasing Short GRBs or Gamma-Ray Burst (which was first thought to be “little green man”) which scientists then thought would be only emitted by objects like black holes.
The ripples in spacetime known as gravitational waves are created by moving masses, but only the most intense, created by rapid changes in the speed of very massive objects, can currently be detected. One such event is the merging of neutron stars, the extremely dense, collapsed cores of high-mass stars left behind after supernovae. These mergers have so far been the leading hypothesis to explain short gamma-ray bursts. An explosive event 1000 times brighter than a typical nova — known as a kilonova — is expected to follow this type of event. And this event produced Gamma-Ray Bursts just after 1.7 seconds after the detection of gravitational waves. GRBs are some of the most energetic events observed in the universe. They typically release as much energy in just a few seconds as our Sun will throughout its 10 billion-year life
Two neutron stars spiraling into a dance of death, each of mass varying from 1.36 to 1.60 solar masses for the bigger one and 1.17 to 1.36 solar masses for the other. They spiraled into each other until they collided in the most violent way sending out gravitational waves, electromagnetic waves all across space which lasted for over 100 seconds before fading along with short GRBs. This phenomenal event and its observation achieved the breakthrough of the year award in the year 2017. This was one of the loudest gravitational wave detection to date.
The merging of two neutron stars produces a violent explosion known as a kilonova. Such an event is expected to expel heavy chemical elements into space. This picture shows some of these elements, along with their atomic numbers.
The gravitational wave signal lasted for approximately 100 seconds starting from a frequency of 24 hertz. It covered approximately 3,000 cycles, increasing in amplitude and frequency to a few hundred hertz in the typical in spiral chirp pattern.
The neutron star merger event is thought to result in a kilonova, characterized by a short gamma-ray burst followed by a longer optical “afterglow” powered by the radioactive decay of heavy r-process nuclei. Kilonovae are candidates for the production of half the chemical elements heavier than iron in the Universe. A total of 16,000 times the mass of the Earth in heavy elements is believed to have formed, including approximately 10 Earth masses just of the two elements gold and platinum. This was a multi-messenger observation.
The scientific interest in this event was enormous! The scientific papers were released with more than over 4000 astronomy co-authors from more than over 900 institutions.
THIS WAS ONE HELL OF A COLLISION. THE MOST SPECTACULAR AND VIOLENT ONE, BY THE NEUTRON STARS.
Astronomers detect rare kilonova explosion
Astronomers studying short-lived gamma-ray bursts (GRBs) have detected a rare kilonova explosion in which two neutron stars appear to have merged to form a larger neutron star called a magnetar.
“I’ve been studying these short gamma-ray bursts for a decade now,” says Wen-fai Fong, an astrophysicist at Northwestern University, US. “Just when you think you understood them, they throw a new twist at you. The Universe produces such a diversity of explosions.”
Short GRBs are brief flashes of gamma-rays, heralding exciting events in distant galaxies. “We think they come from the merger of two neutron stars,” Fong says. As the name implies, they happen quickly: there and gone in the course of a couple of seconds. But they can be followed by an afterglow of everything from X-rays to radio and infrared emissions.
That means that when a short GRB is detected, it’s all hands on deck to turn as many types of astronomical instruments on it as possible, before the afterglow fades. “It is a fast-fading signal,” Fong says. “The burst is fading from the time you eat lunch to the time you eat dinner,” (though there’s usually still time to study it for a few days).
This afterglow, she says, suggests that some short GRBs are from kilonova explosions, in which the merger of the neutron stars ejects part of those stars’ mass into space. (The name means that they are about 1000 times more powerful than stellar nova explosions, though much less powerful than the supernova explosions that mark the deaths of giant stars.)
Fong compares it to what would happen if you tried to make a smoothie and forgot to put the lid on the blender – though in this case, it’s chunks of neutron star that get blasted out all over the place.
These neutrons rapidly coalesce into unstable isotopes of heavy elements that then quickly decay into more stable ones, releasing heat, light, X-rays, and radio waves in the process. But for a short GRB detected on 22 May (called GRB 200522A), something didn’t fit the model.
When the Hubble Space Telescope was free to pause other observations and turn toward GRB 200522A’s source, three-and-a-half days after the GRB, astronomers found that it was emitting 10 times more infrared light than a normal kilonova. “Given what we know about the radio and X-rays from this blast, it just didn’t match up,” Fong says.
Gradually, her team realised they’d seen something truly unusual.
Normally, neutron star mergers produce black holes. But the only explanation her team could come up with for how such a merger could produce an afterglow ten times too bright in the infrared was that they had witnessed the birth of a magnetar.
Magnetars are neutron stars with extremely strong magnetic fields. As it spun rapidly after the collision that created it, this magnetar’s field would transfer energy to the debris created by the kilonova explosion, heating it up and causing it to glow in exactly the manner observed by the Hubble.
That in itself is exciting enough. But even though GRB 200522A is in a galaxy far, far away, the finding is also relevant to our lives here on Earth.
Scientists once thought that nuclear reactions in supernova explosions were what created elements heavier than iron, many of which later found their way into planets.
But that theory is passé. Now, scientists think, if you have a gold ring, odds are that its atoms were forged in the brief fires of something akin to a long-ago kilonova. “We think a lot of our heavy elements come from these neutron-star mergers,” Fong says.
The next step will be the launch of NASA’s James Webb Space Telescope in October 2021. That instrument, she says, will be sensitive enough that if there’s another burst like GRB 200522A, it will not only be able to observe its afterglow, but obtain a spectrum of it, thereby picking out the specific elements being created in the kilonova.
Meanwhile, Fong’s team’s research is scheduled to be published in The Astrophysical Journal and available now on the pre-print arXiv.
Richard A Lovett
Richard A Lovett is a Portland, Oregon-based science writer and science fiction author. He is a frequent contributor to Cosmos.
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When Neutron Stars Collide: Scientists Spot Kilonova Explosion from Epic 2016 Crash
Scientists recently spotted a gold-and-platinum factory in space, the remains of a massive collision of stellar corpses.
The precious elements were formed in a "kilonova," or an epic explosion that likely happened when two very dense stars (called neutron stars) slammed into each other. (A kilonova is an even stronger type of explosion than the typical supernova that happens when large stars blow up.)
The kilonova's power comes from colliding superdense neutron stars, where bizarre physics reigns. These objects are the remnants of large stars &mdash once many times the mass of our sun &mdash that exploded, leaving behind a dense core. Although neutron stars are only the size of a city, their mass is about 1.4 times that of our sun. Because they are so dense, when these neutron stars collide, their echoes are visible across a large stretch of space.
Now, scientists think they have spotted such a kilonova in previously gathered data that had stumped observers at the time. Astronomers spotted a burst of ultrabright gamma-rays in the sky in August 2016, but they didn't understand initially what was going on.
Then a little thing called LIGO happened. The incredibly productive Laser Interferometer Gravitational-Wave Observatory (whose founding scientists had already won a Nobel Prize for a discovery made by the observatory in 2015) made a historic observation in 2017 when it recorded the first direct observation of two neutron stars merging. Scientists tracked the event in every wavelength imaginable, as well as through the gravitational waves that showed disturbances in space.
Inspired by LIGO, scientists revisited their strange 2016 data and had a pleasant surprise. Initially, the observations in 2016 didn't match what models of the day predicted for a kilonova event that was because "barely any signal remained" after 10 days, lead author Eleonora Troja, an astronomer and research scientist at the University of Maryland, said in a statement.
"We were all so disappointed," Troja recalled of their initial observations of the 2016 event. But LIGO's detection allowed them to look at the old data with new understanding. "[We] realized we had indeed caught a kilonova in 2016," Troja added. "It was a nearly perfect match."
In infrared wavelengths, both the 2016 and 2017 events had similar luminosities (or intrinsic brightness) happening at exactly the same time. While scientists observed the latter event in far more detail than the 2016 event, what sets the earlier one apart is that there is information about the first few hours of the kilanova explosion. That's because NASA's Neil Gehrels Swift Observatory tracked the 2016 gamma-ray burst just minutes after it was detected, whereas observations of the 2017 burst were delayed by about 12 hours.
By comparing the two events, the researchers concluded that the 2016 observations were likely also of a kilonova formed by two colliding neutron stars. That said, scientists aren't sure yet whether such an explosion would also form when a black hole and a neutron star merge, and if so what it would look like.
Troja and her colleagues plan to examine other past explosions inspired by this finding, and to create a fresh approach to future observations. In particular, they will focus on events that are strong in infrared light, which suggests that the explosion is producing heavy metals such as gold and platinum.
A paper based on the new research was published on Aug. 27 in the journal Monthly Notices of the Royal Astronomical Society.
Hubble sees the brightest kilonova yet
Artist’s concept of short gamma-ray burst 200522A, the result of what scientists have confirmed to be the brightest kilonova ever recorded, at 10 times brighter than the next closest observed event. Image via Center for Astrophysics/ NASA/ ESA/ D. Player (STScI).
A team of scientists said earlier this month (November 12, 2020) that they’ve observed the most luminous kilonova candidate yet discovered. Kilo means a thousand, and a kilonova bears its name for its dramatic peak brightness, which might be 1,000 times greater than an ordinary classical nova (but only a fraction as bright as a supernova). This one was associated with a short gamma ray burst – labeled GRB 200522A – seen on May 22, 2020. Observations by the Hubble Space Telescope, made in the days after the discovery, showed that the radiation from this distant cosmological event didn’t fit the profile scientists had come to expect from typical kilonovae. It shone as much as 10 times brighter most kilonovae in the near-infrared, as viewed from Hubble three days after the first observations.
Gamma rays bursts are believed to be caused when two neutron stars merge in a violent explosion, and the radiation from hot elements created in the explosion creates what is seen from Earth as a kilonova.
Artist’s concept of a neutron star. The star’s tiny size and great density give it incredibly powerful gravity at its surface. Image via Raphael.concorde/ Daniel Molybdenum/ NASA/ Wikimedia Commons.
According to the paper, to be published in The Astrophysical Journal and currently available at arXiv, the infrared light associated with GRB 200522A is:
… significantly more luminous than any kilonova candidate for which comparable observations exist.
Led by Wen-fai Fong of Northwestern University, the team combined observations from Hubble, the Very Large Array, the Las Cumbres Observatory Global Telescope and the W.M. Keck Observatory. However, Fong said:
Hubble really sealed the deal in the sense that it was the only one to detect infrared light. Amazingly, Hubble was able to take an image only three days after the burst. Hubble’s spectacular resolution was also key in quantifying the amount of light coming from the merger.
Edo Berger, professor of astronomy at the Center for Astrophysics | Harvard & Smithsonian, explained:
The Hubble observations were designed to search for infrared emission that results from the creation of heavy elements – like gold, platinum, and uranium – during a neutron star collision. Surprisingly, we found much brighter infrared emission than we ever expected, suggesting that there was additional energy input from a magnetar [a neutron star with a super strong magnetic field] that was the remnant of the merger.
Why do scientists find GRB 200522A different from other potential kilonovae? Fong said:
Given what we know about the radio and X-rays from this blast, it just doesn’t match up. The infrared emission that we’re finding with Hubble is way too bright. In terms of trying to fit the puzzle pieces of this gamma-ray burst together, one puzzle piece is not fitting correctly.
Several possibilities exist. Berger stated:
What is left behind in such a collision? A more massive neutron star? A black hole? The fact that we see this infrared emission, and that it is so bright, shows that short gamma-ray bursts indeed form from neutron star collisions, but surprisingly the aftermath of the collision may not be a black hole, but rather likely a magnetar.
A magnetar is part of the neutron star family: an ultra-dense star with a magnetic field stronger than Earth’s by a trillion times. Magnetars are short-lived (by cosmic standards) – perhaps 10,000 years – and are the probable source of fast radio bursts (FRBs). Follow-up observations in radio a few years down the line will be able to confirm whether it is indeed a magnetar behind this unexpectedly bright observation.
Bottom line: Hubble Space Telescope observations of a possible kilonova explosion associated with a gamma-ray burst revealed unexpectedly high levels of infrared light. Scientists speculate that the radiation comes from a magnetar – a highly magnetized neutron star – formed by the merger of two neutron stars.
For the First Time, We've Spotted a Superpowerful Neutron Star Collision
A neutron star merger sent literal waves through space-time.
Something big went boom in a distant galaxy. It's wasn't a nova. It's wasn't a supernova. It was a kilonova, and it burst forth with enough energy that four different telescopes monitoring virtually the entire spectrum of energy picked it up. And before astronomers saw any visual evidence of this cataclysmic collision, their instruments picked up the movement of gravitational waves sending ripples through the fabric of space-time.
In research published in three different journals today (Nature, Nature Astronomy and Astrophysical Journal Letters), hundreds of physicists and collaborators outline a first-of-its-kind observation: the elusive neutron star merger.
"Because we've seen this light show that accompany the gravitational wave event we believe at least one of the objects had to be a neutron star," says Nergis Mavalvala, an MIT professor and collaborator with the Laser Interferometer Gravitational-Wave Observatory (LIGO). The team believes both objects were neutron stars, "but as scientists we can't say for certain" that the heavier object wasn't a small black hole.
Neutron stars are the dense cores of stars that have previously gone supernova and shed their outer material. If the remaining core of the star is less than two-and-a-half times the mass of the sun, it becomes a six-mile diameter ball of dense, all-neutron matter. Any more massive, and the star will collapse into a black hole. Neutron stars are the second densest known objects in the universe after black holes, and both form under similar circumstances.
"The uncertainty comes from the fact that there's no hard boundaries between what mass a neutron star should have and what mass a black hole should have," says Mavalvala.
When the explosion from a neutron star merger occurred in the galaxy NGC 4993, which is 130 million light-years away, it sent physical ripples through the fabric of space-time. These gravitational waves were strong enough that the two LIGO observatories and the European sister station, Virgo, all picked up the signals. Seconds later, the Fermi Gamma-ray Space Telescope saw a bright flash called a short gamma ray burst that lasted two seconds. Then the fireworks of the explosion set off, viewed by several ground-based observatories.
This is the fourth gravitational wave event documented by LIGO in the last two years, although the newest cosmic event is unique. The previous three detections of gravitational waves came from black hole mergers, while this neutron star merger involved much smaller objects and had an optical component as researchers detected the gamma ray burst and light from the the kilonova explosion moments after the gravitational waves.
The collaborative effort between LIGO, Virgo, and multiple additional observatories demonstrates the power of these instruments to find smaller and smaller gravitational events. The Virgo interferometer in Europe was critical to pinpoint the origin of the merger because it's oriented differently from LIGO, allowing the gravitational waves to be traced to the source. If more neutron star mergers occur, collaboration between LIGO and Virgo can allow ground observatories to immediately point their telescopes to the event epicenter like during the NGC 4993 merger.
The new detection of gravitational waves also serves as a benchmark in a new era of astronomy where violent but nearly-invisible cataclysms can be "felt" as they rip through the fabric of space itself.
The event is technically still in progress as researchers continue to measure the incoming gravitational waves here on Earth. The LIGO and Virgo teams don't quite know what is being created at at the center of the cataclysm&mdashit could be a larger neutron star, or the accumulated mass may be enough to collapse into a black hole. Mavalvala says it's hard to even speculate right now because the neutron star merger is the first such event ever observed.
"We're still culling the data," Mavalvala says. "It's just too early to say, and I'm not holding back."
5 Better Candidates Than Betelgeuse For Our Galaxy’s Next Supernova
This five-image composite shows the Crab Nebula as viewed in different wavelengths of light. The . [+] purple X-rays reveal short-wavelength radiation the cooler, redder colors trace out longer wavelength, lower-temperature material. Today we see the Crab Nebula as the expanding gaseous remnant from a star that self-detonated as a supernova, briefly shining as brightly as 400 million suns. The explosion took place 6,500 light-years away.
NASA, ESA, G. Dubner (IAFE, CONICET-University of Buenos Aires) et al. A. Loll et al. T. Temim et al. F. Seward et al. VLA/NRAO/AUI/NSF Chandra/CXC Spitzer/JPL-Caltech XMM-Newton/ESA and Hubble/STScI
Betelgeuse, a nearby red supergiant, will someday explode.
The black hole at the center of the Milky Way should be comparable in size to the physical extent of . [+] the red giant star Betelgeuse: larger than the extent of Jupiter's orbit around the Sun. Betelgeuse was the first star of all beyond our Sun to be resolved as more than a point of light, but other red supergiants, such as Antares and VY Canis Majoris, are known to be larger.
A. Dupree (CfA), R. Gilliland (STScI), NASA
One of our brightest stars, its recent dimming portends an eventual supernova.
The constellation Orion as it would appear if Betelgeuse went supernova in the very near future. The . [+] star would shine approximately as brightly as the full Moon, but all the light would be concentrated to a point, rather than extended over approximately half a degree.
Wikimedia Commons user HeNRyKus / Celestia
A “stellar burp” ejected matter, causing Betelgeuse’s temporary, routine faintening.
These four images show Betelgeuse in the infrared, all taken with the SPHERE instrument at the ESO's . [+] Very Large Telescope. Based on the faintening observed in detail, we can reconstruct that a "burp" of dust caused the dimming. Although variability remains larger than it was previously, Betelgeuse has returned to its original, early-2019-and-before brightness.
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Meanwhile, these 5 Milky Way candidates could easily go supernova first.
The atmosphere of Antares, by temperature and size, as inferred from ALMA and VLA data. Whereas . [+] Betelgeuse is large, larger than Jupiter's orbit around the Sun, the extent of Antares goes almost to Saturn as measured by the end of the upper chromosphere, but the luminous Wind Acceleration Zone goes all the way out almost to the extent of Uranus's orbit.
1.) Antares. Closer and larger than Betelgeuse, massive Antares is
This simulation of a red supergiant's surface, sped up to display an entire year of evolution in . [+] just a few seconds, shows how a "normal" red supergiant evolves during a relatively quiet period with no perceptible changes to its interior processes. There are multiple "dredge-up" periods where material from the core gets transferred to the surface, and this results in the creation of at least a fraction of the Universe's lithium.
Bernd Freytag with Susanne Höfner & Sofie Liljegren
This red supergiant should explode within
The Carina Nebula, with Eta Carina, the brightest star inside it, on the left. What appears to be a . [+] single star was identified as a binary back in 2005, and it's led some to theorize that a third companion was responsible for triggering the supernova impostor event.
ESO/IDA/Danish 1.5 m/R.Gendler, J-E. Ovaldsen, C. Thöne, and C. Feron
2.) Eta Carinae. This famous “supernova impostor” has brightened, historically, numerous times.
The 'supernova impostor' of the 19th century precipitated a gigantic eruption, spewing many Suns' . [+] worth of material into the interstellar medium from Eta Carinae. High mass stars like this within metal-rich galaxies, like our own, eject large fractions of mass in a way that stars within smaller, lower-metallicity galaxies do not. Eta Carinae might be over 100 times the mass of our Sun and is found in the Carina Nebula, but other known stars are more than twice as massive. Some supernova impostors remain stable for centuries others have been caught exploding after only a few years.
NASA, ESA, N. Smith (University of Arizona, Tucson), and J. Morse (BoldlyGo Institute, New York)
Its remaining lifetime could span centuries, or merely years.
The Wolf-Rayet star WR 102 is the hottest star known, at 210,000 K. In this infrared composite from . [+] WISE and Spitzer, it's barely visible, as almost all of its energy is in shorter-wavelength light. The blown-off, ionized hydrogen, however, stands out spectacularly.
Judy Schmidt, based on data from WISE and Spitzer/MIPS1 and IRAC4
3.) WR 102. Wolf-Rayet stars represent the final evolutionary phases for massive stars expelling their outer layers.
The extremely high-excitation nebula shown here is powered by an extremely rare binary star system: . [+] a Wolf-Rayet star orbiting an O-star. The stellar winds coming off of the central Wolf-Rayet member are between 10,000,000 and 1,000,000,000 times as powerful as our solar wind, and illuminated at a temperature of 120,000 degrees. (The green supernova remnant off-center is unrelated.) Systems like this are estimated, at most, to represent 0.00003% of the stars in the Universe.
WR 102 is the hottest: 210,000 K, foreshadowing a stellar cataclysm.
The red arrow points to WR 142: a single, X-ray emitting star at temperatures of 200,000 K. WR 142 . [+] shows an overabundance of oxygen in its spectrum, indicating that the star has cooked up elements up to oxygen in its core, and is well on its way to the iron catastrophe which will trigger the violent death of the star.
L. M. Oskinova, W.-R. Hamann, A. Feldmeier, R. Ignace, Y-H. Chu and ESA
4.) WR 142. The second-hottest Wolf-Rayet star, WR 142’s demise is inevitable.
The Crescent Nebula in Cygnus is powered by the central massive star, WR 136, where the hydrogen . [+] expelled during the red giant phase is shocked into a visible bubble by the hot star at the center. As the star's hydrogen and then helium layers are blown off, it heats up, and as it fuses through heavier successive elements, it gets hotter still. Unless mass loss is severe enough, a supernova will result.
Wikimedia Commons user Hewholooks
Two different ways to make a Type Ia supernova: the accretion scenario (L) and the merger scenario . [+] (R). The merger scenario is responsible for the majority of many of the heavy elements in the Universe, but the accretion mechanism is also responsible for Type Ia events. The system T Coronae Borealis is a red giant-white dwarf combo, where the white dwarf has a mass of 1.37 solar masses: perilously close to the Chandrasekhar limit.
5.) T Coronae Borealis. White dwarfs siphoning mass from red giants can trigger type Ia supernovae.
When a denser, more compact star or stellar remnant comes into contact with a less dense, more . [+] tenuous object, like a giant or supergiant star, the denser object can siphon mass off of the larger one, accreting it onto itself. If the mass exceeds a critical threshold governed by the Pauli Exclusion Principle, a cataclysmic explosion will occur.
David A. Aguilar (Harvard-Smithsonian Center for Astrophysics)
T Coronae Borealis’s white dwarf now approaches this critical mass threshold.
When a white dwarf close to the Chandrasekhar mass limit accretes enough matter off of a binary . [+] companion, a runaway nuclear fusion reaction will get triggered. This will not only create a Type Ia supernova, but will destroy the white dwarf in the process.
Similarly, 5 common “next supernova” candidates are relatively unlikely.
The Wolf-Rayet star WR 124 and the nebula M1-67 which surrounds it both owe their origin to the same . [+] originally massive star that blew off its outer layers. The central star is now far hotter than what came before, but WR 124 is not the hottest class of Wolf-Rayet star: those are the ones that are depleted of hydrogen and helium but heavily enhanced with oxygen.
ESA/Hubble & NASA Acknowledgement: Judy Schmidt (geckzilla.com)
When two stars or stellar remnants merge, they can trigger a cataclysmic reaction, including . [+] supernovae, gamma-ray bursts, or they can lead to the creation of a hotter, bluer more massive star. In the case of V Sagittae, however, it is not well-accepted that the stars will inspiral and merge later this century, despite recent assertions.
MELVYN B. DAVIES, NATURE 462, 991-992 (2009)
Our next supernova might deliver a multi-messenger trifecta:
A supernova explosion enriches the surrounding interstellar medium with heavy elements. This . [+] illustration, of the remnant of SN 1987a, showcases how the material from a dead star gets recycled into the interstellar medium. In addition to light, we also detected neutrinos from SN 1987a. With the LIGO and Virgo detectors now functional, it's possible that the next supernova within the Milky Way will yield a triple multi-messenger event, delivering particles (neutrinos), light, and gravitational waves all together.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less smile more.