[Artist's conception of a black with material swirling around it in an accretion disk, and also a jet of matter blasting away from it. Until recently, it was thought that a star had to supernova to create a black hole, but evidence is mounting it may not. Credit:NASA/JPL-Caltech]
One of the basic truisms in astronomy is that, when a massive star ends its life, it goes out with a bang. A big one. A supernova.
This titanic explosion is triggered when the star runs out of nuclear fuel in its core. The core collapses in a heartbeat, and the energy generated in that collapse is so immense that it blows the outer layers off. This explosion is so colossal it can outshine an entire galaxy! In the meantime,the collapsed core can form an exotic neutron star, or may even squeeze itself down into a black hole.
Now, Ive skipped some steps there, but thats the general picture (if you want more, check out my Crash Course Astronomy episode on high mass stars and supernovae). If you want a black hole, you have to blow up a massive star.
Except, maybe not. It turns out theres a loophole that could allow a star to bypass the supernova part. It collapses directly down to a black hole without the explosion. Some energy is released, but not much compared to a supernova, and in the end what you get is a now-you-see-it-now-you-dont situation: The star is there, and then suddenly ... it isnt.
The idea of a failed supernova is an interesting theoretical astrophysical problem, and one scientists have been working on for a while now. But theres been a new an exciting development: Astronomers now think theyve seen one!
The star in question is called N6946-BH1, and it was found in a very cool survey specifically designed to look for failed supernovae. Using the Large Binocular Telescope in Arizona, 27 galaxies all within about 30 million light-years of Earth were observed over and over again. Each image was painstakingly compared to the others to look for transients: objects that have changed brightness. Even using rather stringent criteria, thousands were found stars change brightness for a lot of reasons,but most are not due to them going supernova ... or, in this case, failing to supernova.
Eventually,the number of interesting objects was whittled down to just 15. Six of them turned out to be run-of-the-mill exploding stars (if the titanic explosion of a few octillion tons of star screaming outward at a substantial fraction of the speed of light can be called ho-hum), but nine of them turned out to be more interesting.
Of these, all but one were likely unusual events, like two stars merging, which can cause a very big (and very pretty) eruption, but again falls short of the outcome of a massive star dying. When all was said and done, after searching 27 galaxies for seven years, only one object was left: N6946-BH1.
In earlier images, the star is there, clearly seen in the galaxy NGC 6946, a lovely face-on spiral galaxy roughly 20 million light-years away (and one that has had no fewer than 10 recorded supernovae in the past century; by coincidence one was seen just this year). Then, in later images, its gone. Like, gone: Disappeared. Poof.
If it had exploded as a supernova it wouldve been seen in the images. Instead, in 2009, it briefly got somewhat brighter, glowing at about a million times brighter than the Sun; then it faded so much it was only about 2% of its previous brightness (that is, pre-collapse) by 2015. And yes, in human terms, a million times the Suns luminosity is terrifyingly bright, but in terms of a supernova, its barely worth mentioning; a typical one will shine many billions of times brighter than the Sun! So this was, at best, a bit of a pop.
So, how do we know it wasnt some sort of weird supernova, maybe obscured by lots of dust in the host galaxy? This material is dark and opaque, and can completely block the light from even a normal supernova. Follow-up observations using Spitzer Space Telescope should reveal that, because infrared light can pierce through the dust. Spitzer did see some IR light from the event, roughly 20003000 times the Suns luminosity. Again, thats a lot, but nowhere near what youd expect from a supernova. Even a stellar merger would produce more than that.
It really looks like whats left is what the astronomers had been looking for all along: a failed supernova.
If true, this is very interesting, indeed. Why? Because of physics.
It takes a massive star to explode; it has to have enough pressure in the core (caused by the mass of the star above it squeezing down on it) to fuse successively heavier elements over time. First,hydrogen fuses into helium.Then, when that runs out, helium is fused into carbon, and so on, until the core builds up iron. When iron fuses, it doesnt release energy; it absorbs it. Thats a big problem, because its that release of fusion energy that holds the star up (in a similar fashion that hot air causes a balloon to expand). Once the star tries to fuse iron, the core collapses. If the core has a mass up to about 2.8 times that mass of the Sun, it forms a neutron star, but if it has more, it forms a black hole.
And in general, either way, the core collapse triggers the supernova in the outer layers, and kaboom.
But thats where this gets funny. It may not always happen that way. For a range of core masses, theoretical calculations show that the explosion may stall. The outer layers get a decent kick, but not a huge one. They blow off, but its a more gentle event than the unfettered violence of a supernova.
That depends on a lot of factors, actually, but it tends to happen when the total star mass is roughly 25 times that of the Sun. Looking at the observations of N6946-BH1, thats just about the mass it had.
And theres more. We see lots of high-mass stars in galaxies being born, but there arent enough supernovae seen to account for them all. That implies failed supernovae happen relatively often.
Also, when we look at the masses of neutron stars and black holes, we find theres a gap between them; the lowest-mass black holes are still considerably more massive than the highest-mass neutron stars. If all these compact objects formed from regular supernovae, youd expect there to be a smooth transition. Thats because, in a supernova, a lot of the material in the star still lingers near the core, and that can fall back on the newly formed neutron star. If theres enough, the neutron star will then collapse to form a low-mass black hole. So youd expect to see lots of black holes right at the lower mass limit. But we dont.
Ah, but in the failed supernova scenario, theres a lot more material left over there wasnt enough energy in the event to blow away all the outer layers. This comes crashing back down and adds its mass to the neutron stars, making a far more massive black hole. So, in reality, the existence of failed supernovae explains a lot of different phenomena.
And now, very likely, weve seen one! More observations would be nice, though. For example, a newly formed black hole should emit lots of X-rays, as material heats up before falling in. If we see those X-rays, that would go a long way in understanding what were seeing.
And again, this is the first one that weve seen. Given the number of supernovae that were detected in the survey, it implies that something like 14% of all high-mass star deaths result in failed supernovae. If thats the case, then we need more eyes on the sky looking for these events. Supernovae are what create and distribute elements literally vital to our existence: iron, calcium and more. Without them, you and I would literally not exist.
In my opinion, that makes these events very much worthy of our study. Even when they fail.
See the rest here:
Bad Astronomy | Astronomers may have seen a star collapse directly ... - Blastr
- Astronomy clubs want to help you enjoy the eclipse safely - NPR - March 16th, 2024 [March 16th, 2024]
- You Can See a Rare, Bright Comet This Month. Will It Be Visible During the Solar Eclipse? - Smithsonian Magazine - March 16th, 2024 [March 16th, 2024]
- Solar Eclipse Path Map Shows States Where Sun Will Be Blocked Out - Newsweek - March 16th, 2024 [March 16th, 2024]
- Deep-space astronomy sensor peers into the heart of an atom - Space.com - March 16th, 2024 [March 16th, 2024]
- Physics and Astronomy Colloquium - Professor Paul Cassak; Department of Physics and Astronomy, West Virginia ... - The University of Iowa - March 16th, 2024 [March 16th, 2024]
- United Nations prioritizes discussion of Dark and Quiet Skies - Astrobites - March 16th, 2024 [March 16th, 2024]
- The burning acid behind ant stings was spotted around two stars - WAPT Jackson - March 16th, 2024 [March 16th, 2024]
- The oddities known as Centaurs may sprout their tales after jumping to new orbits - Astronomy Magazine - March 16th, 2024 [March 16th, 2024]
- Pair of astronomy brothers to host eclipse viewing event - KAIT - March 16th, 2024 [March 16th, 2024]
- How to watch the solar eclipse online - Astronomy Magazine - March 16th, 2024 [March 16th, 2024]
- How does a black hole get to the center of a galaxy, and does the galaxy revolve around it? - Astronomy Magazine - March 16th, 2024 [March 16th, 2024]
- The eclipse gives astronomy clubs an opportunity to shine - Voice Of Alexandria - March 16th, 2024 [March 16th, 2024]
- AI 'for all': How access to new models is advancing academic research, from astronomy to education - Source - Microsoft - March 16th, 2024 [March 16th, 2024]
- KU Department of Physics & Astronomy professor receives prestigious NSF award for black hole research - Salina Post - March 16th, 2024 [March 16th, 2024]
- Inspect impressive Mare Imbrium Astronomy Now - Astronomy Now Online - March 16th, 2024 [March 16th, 2024]
- The Sky This Week from March 15 to 22: A conjunction of Venus and Saturn - Astronomy Magazine - March 16th, 2024 [March 16th, 2024]
- Pons-Brooks and M31 - Astronomy Magazine - March 16th, 2024 [March 16th, 2024]
- The slightly weird mathematical coincidence behind an eclipse - Astronomy Magazine - March 16th, 2024 [March 16th, 2024]
- APOD: 2024 March 17 NGC 7714: Starburst after Galaxy Collision - Astronomy Picture of the Day - March 16th, 2024 [March 16th, 2024]
- How to Safely View the Eclipse National Radio Astronomy Observatory - National Radio Astronomy Observatory - March 16th, 2024 [March 16th, 2024]
- NOIRLab releases jaw-dropping images, video of remnants from massive star explosion | Astronomy.com - Astronomy Magazine - March 16th, 2024 [March 16th, 2024]
- JWST spots oceans' worth of water evaporating from a distant disk - Astronomy Magazine - March 16th, 2024 [March 16th, 2024]
- Radiation is vaporizing a young star's disk in the Orion Nebula - Astronomy Magazine - March 16th, 2024 [March 16th, 2024]
- APOD: 2024 March 12 A Galaxy Shaped Rocket Exhaust Spiral - Astronomy Picture of the Day - March 16th, 2024 [March 16th, 2024]
- Best laptops for astronomers and astrophotographers in 2024 - Space.com - March 16th, 2024 [March 16th, 2024]
- Why astronomers are worried about 2 major telescopes right now - Space.com - March 16th, 2024 [March 16th, 2024]
- The People Behind Webb | Webb - WebbTelescope.org - March 16th, 2024 [March 16th, 2024]
- X-ray image of universe reveals almost 1 million high-energy objects: 'These are mind-blowing numbers' - Space.com - February 1st, 2024 [February 1st, 2024]
- Galaxy named 'Nube' is almost invisible, baffling astronomers Earth.com - Earth.com - February 1st, 2024 [February 1st, 2024]
- Giant Star Seen 150 Days Before it Exploded as a Supernova - Universe Today - February 1st, 2024 [February 1st, 2024]
- UH astronomer named to prominent national astronomical society | University of Hawaii System News - University of Hawaii - February 1st, 2024 [February 1st, 2024]
- The Art of SeeingStates of Astronomy - Announcements - E-Flux - February 1st, 2024 [February 1st, 2024]
- Pluto isn't really a planet, but it might be Arizona's official state planet - Arizona Mirror - February 1st, 2024 [February 1st, 2024]
- Did You Know? Stars Near and Far Reveal Their Secrets to CSUN Scientists - California State University, Northridge - February 1st, 2024 [February 1st, 2024]
- Top 10 space stories of 2023 - Astronomy Magazine - February 1st, 2024 [February 1st, 2024]
- How we found the Milky Way's bar: This Week in Astronomy with Dave Eicher - Astronomy Magazine - February 1st, 2024 [February 1st, 2024]
- The best telescope to use with a smartphone - Astronomy Magazine - February 1st, 2024 [February 1st, 2024]
- JWST releases 19 awe-inspiring images of spiral galaxies - Astronomy Magazine - February 1st, 2024 [February 1st, 2024]
- Learning Shines Brightly at SuperKnova National Radio Astronomy Observatory - National Radio Astronomy Observatory - February 1st, 2024 [February 1st, 2024]
- The Crafoord Prize 2024 goes to three ERC grantees for their pioneering contributions to astronomy and mathematics ... - European Research Council - February 1st, 2024 [February 1st, 2024]
- The Moon's south pole is likely not the safest place for manned missions - Astronomy Magazine - February 1st, 2024 [February 1st, 2024]
- The moon could be perfect for cutting-edge telescopes but not if we don't protect it - Space.com - February 1st, 2024 [February 1st, 2024]
- February Astronomy: Spot the Milky Way and the Zodiacal Light While the Skies Are Darkest - Coachella Valley Independent - February 1st, 2024 [February 1st, 2024]
- You can stream an asteroid whizzing past Earth this weekend - Astronomy Magazine - February 1st, 2024 [February 1st, 2024]
- Chinese Astronomy at the Royal Observatory | Royal Observatory | Things to do in London - Time Out London - February 1st, 2024 [February 1st, 2024]
- Astronomers in Chile to scour universe with car-sized mega camera - - February 1st, 2024 [February 1st, 2024]
- Dark Matter Might Help Explain How Supermassive Black Holes Can Merge - Universe Today - February 1st, 2024 [February 1st, 2024]
- How far away is the sun? They went on a perilous journey to find out. - National Geographic - February 1st, 2024 [February 1st, 2024]
- Scientists spotted an asteroid hours before it burned up over Germany - Astronomy Magazine - February 1st, 2024 [February 1st, 2024]
- XRISM Unveils the Invisible: A New Era in X-Ray Astronomy - SciTechDaily - January 10th, 2024 [January 10th, 2024]
- New Astronomy Finding Uncovers the Mystery of Star Formation at the Edge of Galaxies - SBU News - Stony Brook News - January 10th, 2024 [January 10th, 2024]
- The Future Of Astronomy Lies In Artificial Intelligence - Forbes - January 10th, 2024 [January 10th, 2024]
- The 'Super Bowl of Astronomy' begins next week in New Orleans - Space.com - January 10th, 2024 [January 10th, 2024]
- Scientific American proposes policing the language of astronomy to make it beautiful and elegant, as well as ... - Why Evolution Is True - January 10th, 2024 [January 10th, 2024]
- 'Blob-like' home of farthest-known fast radio burst is collection of seven galaxies - Northwestern Now - January 10th, 2024 [January 10th, 2024]
- Astronomers revealed mysterious star formation by hearts of molecular clouds - Tech Explorist - January 10th, 2024 [January 10th, 2024]
- Spectroscopic sizing of interstellar icy grains with JWST - Nature.com - January 10th, 2024 [January 10th, 2024]
- Kip Thorne and the mind-bending science of Interstellar | Astronomy.com - Astronomy Magazine - January 10th, 2024 [January 10th, 2024]
- Here There Be DRAGNs National Radio Astronomy Observatory - National Radio Astronomy Observatory - January 10th, 2024 [January 10th, 2024]
- Unistellar's latest smart telescopes take the hassle out of backyard astronomy - Engadget - January 10th, 2024 [January 10th, 2024]
- 20 of the best places to view the 2024 total solar eclipse - Astronomy Magazine - January 10th, 2024 [January 10th, 2024]
- Northern Arizona astronomy: How old is our third generation sun? - Grand Canyon News - January 10th, 2024 [January 10th, 2024]
- Evidence builds that Kamo'oalewa is a chunk of the Moon accompanying Earth - Astronomy Magazine - January 10th, 2024 [January 10th, 2024]
- The Sky This Week from January 5 to 12: Visitors to the Scorpion - Astronomy Magazine - January 10th, 2024 [January 10th, 2024]
- AAS 243 NRAO Press Announcement - National Radio Astronomy Observatory - January 10th, 2024 [January 10th, 2024]
- Your guide to the sky in 2024 - Astronomy Magazine - January 10th, 2024 [January 10th, 2024]
- The best binoculars for astronomy in 2024 - Popular Science - January 10th, 2024 [January 10th, 2024]
- Are we visible to alien astronomers? This study makes the case - Astronomy Magazine - January 10th, 2024 [January 10th, 2024]
- Mystery of Star Formation Revealed by Hearts of Molecular Clouds - National Radio Astronomy Observatory - January 10th, 2024 [January 10th, 2024]
- Astronomers Solve the Mystery of Giant Radio Circles - AZoQuantum - January 10th, 2024 [January 10th, 2024]
- Early Evolution of Planetary Disk Structures Seen for the First Time - National Radio Astronomy Observatory - January 10th, 2024 [January 10th, 2024]
- XRISM's Revolutionary Insights into X-Ray Astronomy - AZoQuantum - January 10th, 2024 [January 10th, 2024]
- Vatican's chief astronomer talks about stars, beauty, truth - Aleteia - January 10th, 2024 [January 10th, 2024]
- Explore the cosmos in EAC Payson Campus astronomy workshops - Payson Roundup - January 10th, 2024 [January 10th, 2024]
- Neptune is more of a greenish blue than is commonly depicted - NPR - January 10th, 2024 [January 10th, 2024]
- First Yale Gravitational Wave Symposium sparks research innovation | Department of Physics - Yale University - January 10th, 2024 [January 10th, 2024]
- The best expensive telescopes for those ready to splurge - Astronomy Magazine - January 10th, 2024 [January 10th, 2024]
- Dinosaurs and a touch of astronomy | Education | paysonroundup.com - Payson Roundup - January 10th, 2024 [January 10th, 2024]
- Astronomical Illusions: New Images Reveal What Neptune and Uranus Really Look Like - SciTechDaily - January 10th, 2024 [January 10th, 2024]
- Book Review: Things That Go Bump in the Universe, by C. Rene James - The New York Times - December 16th, 2023 [December 16th, 2023]