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Archives for supernova

Collapsing stars are a rare thing to witness. And when astronomers are able to catch a star in the final phase of its evolution, it is a veritable feast for the senses. Ordinarily, this process consists of a star undergoing gravitational collapse after it has exhausted all of its fuel, and shedding its outer layers in a massive explosion (aka. a supernova). However, sometimes, stars can form black holes without the preceding massive explosion.

This process, what might be described as “going out not with a bang, but with a whimper,” is what a team of astronomers witnessed when observing N6946-BH1 — a star located in the Fireworks Galaxy (NGC 6946). Originally, astronomers thought that this star would explode because of its significant mass. But instead, the star simply fizzled out, leaving behind a black hole.

The Fireworks Galaxy, a spiral galaxy located 22 million light-years from Earth, is so-named because supernova are known to be a frequent occurrence there. In fact, earlier this month, an amateur astronomer spotted what is now designated as SN 2017eaw. As such, three astronomers from Ohio Sate University (who are co-authors on the study) were expecting N6946-BH1 would go supernova when in 2009, it began to brighten.

Visible-light and near-infrared photos from NASA’s Hubble Space Telescope showing the giant star N6946-BH1 before and after it vanished out of sight by imploding to form a black hole. Image Credit: NASA/ESA/C. Kochanek (OSU)

However, by 2015, it appeared to have winked out. As such, the team went looking for the remnants of it with the help of colleagues from Ohio State University and the University of Oklahoma. Using the combined power of the Large Binocular Telescope (LBT) and NASA’s Hubble and Spitzer space telescopes, they realized that the star had completely disappeared from sight.

The details of their research appeared in a study titled “The Search for Failed Supernovae with the Large Binocular Telescope: Confirmation of a Disappearing Star, which recently appeared in the Monthly Notices of the Royal Astronomical Society. Among the many galaxies they were watching for supernovas, they had their sights set on the Fireworks Galaxy to see what had become of N6946-BH1.

After it experienced a weak optical outburst in 2009, they had anticipated that this red supergiant would go supernova – which seemed logical given that it was 25 times as massive as our Sun. After winking out in 2015, they had expected to find that the star had merely dimmed, or that it had cast off a dusty shell of material that was obscuring its light from view.

Their efforts included an LBT survey for failed supernovae, which they combined with infrared spectra obtained by the Spitzer Space Telescope and optical data from Hubble. However, all the surveys turned up negative, which led them to only one possible conclusion: that N6946-BH1 must have failed to go supernova and instead went straight to forming a black hole.

Simulated view of a black hole. Image Credit: Bronzwaer/Davelaar/Moscibrodzka/Falcke, Radboud University

As Scott Adams — a former Ohio State student who is now an astrophysicist at the Cahill Center for Astrophysics (and the lead author of the study) — explained in a NASA press release:

N6946-BH1 is the only likely failed supernova that we found in the first seven years of our survey. During this period, six normal supernovae have occurred within the galaxies we’ve been monitoring, suggesting that 10 to 30 percent of massive stars die as failed supernovae. This is just the fraction that would explain the very problem that motivated us to start the survey, that is, that there are fewer observed supernovae than should be occurring if all massive stars die that way.

A major implication of this study is the way it could shed new light on the formation of very massive black holes. For some time now, astronomers have believed that in order to form a black hole at the end of its life cycle, a star would have to be massive enough to cause a supernova. But as the team observed, it doesn’t make sense that a star would blow off its outer layers and still have enough mass left over to form a massive black hole.

As Christopher Kochanek — a professor of astronomy at The Ohio State University, the Ohio Eminent Scholar in Observational Cosmology and a co-author of the team’s study — explained:

The typical view is that a star can form a black hole only after it goes supernova. If a star can fall short of a supernova and still make a black hole, that would help to explain why we don’t see supernovae from the most massive stars.

This information is also important as far as the study of gravitational waves goes. In February of 2016, scientists at the Laser Interferometer Gravitational-wave Observatory (LIGO) announced the first detection of this strange phenomena, which were apparently generated by a massive black hole. If in fact massive black holes form from failed supernova, it would help astronomers to track down the sources more easily.

Be sure to check out this video of the observations made of this failed SN and black hole:

The post Stars Don’t Always Go Supernova When They Die appeared first on Futurism.

“Sherlocking” our Galaxy

While scientists have already uncovered answers to some of the universe’s greatest mysteries, there’s still a great deal we don’t understand — the “alien megastructure” star, fast radio bursts (FRBs), and the (non-)existence of dark matter are just a few examples. Thanks to new research by a team of astronomers, we may now be able to exclude from this list the previously unexplained mystery of antimatter in the Milky Way.

Essentially, antimatter is matter with its electrical charge reversed. For example, an electron’s antiparticle is a positron, while a proton’s antiparticle is an antiproton. When a particle of matter meets its antimatter cohort, they release a burst of energy and annihilate each other.

Some 40 years ago, scientists detected gamma rays that suggested that around 1043 positrons were being annihilated in the Milky Way every second. They believe most were concentrated in the central bulge of the galaxy, which didn’t make sense as that area hosts less than half of the galaxy’s total mass. As Roland Crocker, particle astrophysicist at the Australian National Universitytold“The origin of these positrons is a 40-year-old mystery in astrophysics.”

That mystery may finally have a resolution, and it’s a relatively simple one. “You don’t need anything exotic like dark matter to explain the positrons,” claims Crocker. Instead, he and his research team suggest that the positrons may have come from just one kind of supernova. Their study has been published in Nature Astronomy.

Dead Stars, Lost Stars

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Crocker’s team thinks that dim supernovas known as SN 1991bg-like could create all of those unexplained positrons. These supernovas result from the merging of two superdense white dwarf stars, and they generate a huge number of radioactive isotopes known as titanium-44, which is capable of releasing the positrons being annihilated.

But why were these positrons concentrated at the interior of the Milky Way? The researchers explained that SN 1991bg-like supernovas — unlike those resulting from the death of young, massive stars — likely occur in galactic neighborhoods with stars roughly 3 billion to 6 billion years old. Our galaxy’s central bulge happens to have a population of stars older than those in its outer disk.

Of course, while the simplest explanation does often prove to be the right one, Crocker isn’t ruling out a more exciting solution to this decades-old mystery. “The most recent data show that there’s a positron source connected to the very center of the galaxy,” he said. “In our model, this is explained as due to the old stars distributed on roughly 200-parsec [650 light years] scales around the galaxy’s supermassive black hole, but the black hole itself is an interesting alternative source.”

The post Scientists May Have Found a Simple Solution to a 40-Year-Old Space Mystery appeared first on Futurism.


The post Planets of Doom: The Strange Worlds of Dead and Dying Stars [INFOGRAPHIC] appeared first on Futurism.