A Naked Black Hole Is Screaming Through the Universe


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A Naked Black Hole Is Screaming Through the Universe

11/03/16 10:24am

Artist’s conception of how the “nearly naked” supermassive black hole originated. Image: Bill Saxton, NRAO/AUI/NSF

Millions of years ago, B3 1715+425 was just an ordinary supermassive black hole. It had a comfortable life, of devouring stars and belching deadly x-rays, at the center of its distant galaxy. Now, starless and alone, it’s screaming through space at 2,000 kilometers per second—and it may never stop.

BC 1715+425’s troubles began when its galaxy bumped up against another. This isn’t all that unusual: in fact, astronomers believe that the largest galaxies in our universe formed during ancient mergers. Normally, when two galaxies collide, the supermassive black holes at their centers start to orbit one another, moving closer and closer together in an inescapable gravitational attraction.

Eventually, those black holes can fuse, releasing a burst of energy as gravitational waves and completing the cosmic joining.

Most of the time, this process seems to work out for all parties involved, judging from the fact that nearly all supermassive black holes reside at the center of galaxies, and nearly all galactic centers contain a supermassive black hole. But every now and then, something goes wrong and cosmic wreckage ensues. B3 1715+425, speeding away from the core of a bloated galactic merger 2 billion light years from Earth, is living proof of this.

The strange object was discovered by astronomers using the Very Long Baseline Array (VLBA), a network of ten 25-meter dish antennas located around the world and operated out of New Mexico.

“We were looking for orbiting pairs of supermassive black holes, with one offset from the center of a galaxy, as telltale evidence of a previous galaxy merger,” said James Condon, the astronomer at the National Radio Astronomy Observatory who led the study. “Instead, we found this black hole fleeing from the larger galaxy and leaving a trail of debris behind it.”

The working theory is that millions of years ago, B3 1715+425’s galaxy passed through a much larger galaxy (one that had formed during many previous mergers) and got shredded to bits, a bit like a paper airplane flying into a hurricane. The leftovers include a faint galactic remnant, just 3,000 light years across, and the supermassive black hole itself, nearly naked and hemorrhaging ionized gas as it tears through the void.

Astronomers believe the cosmic carnage will become invisible in about a billion years, as the galactic remnant ceases to form new stars.

“We’ve not seen anything like this before,” Condon said.

Have other galaxies and supermassive black holes met the same unfortunate fate? It seems likely. Condon and his team will continue to investigate the matter using the VLBA, and with high-resolution optical telescopes in the future.

Update: As several readers have pointed out, Condon says in the video that the black hole is moving 2,000 kilometers per second. While a press release states that the black hole is moving at 2,000 miles per second, we have updated the post to reflect Condon’s statement, because after all, the experts know best.

Maddie is the science editor at Gizmodo

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First Ever Supernova ‘Shock Breakout’ Captured in Visible Light


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First Ever Supernova ‘Shock Breakout’ Captured in Visible Light

3/22/16 6:10am

When a star dies and erupts as a supernova it can produce a short, sharp shockwave that astronomers call a “shock breakout.” For the first time ever, astronomers have captured such an event as optical light.

When a red supergiant star runs out of fuel and can no longer sustain itself, gravity causes its core to collapse in on itself. This creates what’s known as a Type II Supernova, as the star explodes in a fiery death. While the process of the explosion can take weeks to reach full brightness, it often begins with a short, sharp blast of light, created as the shockwave generated by the collapsing core reaches the surface of the star. The artist’s representation above shows what happens during the breakout.

A team from University of Notre Dame in Indiana has been studying reams of data captured by the Kepler space telescope, inspecting as many as 50 trillion stars in the process. During that study, they came across a shock breakout event occurring within the star KSN 2011d. You can see the short burst of brightness in the graph below, which occurs before the steady increase associated with the growth of the supernova.

It’s kind of amazing that the team managed to catch it when you look at this time axis in the graph: The whole thing was over within just 20 minutes. The research is published in Astrophysical Journal.

Getting to grips with how and why these events occur is an important part of understanding the formation of our Universe. “All heavy elements in the universe come from supernova explosions. For example, all the silver, nickel, and copper in the earth and even in our bodies came from the explosive death throes of stars,” explained Steve Howell, one of the researchers, in a press release. “Life exists because of supernovae.”

[Astrophysical Journal via NASA]

Contributing Editor at Gizmodo. An ex-engineer writing about science and technology.

Brightest Supernova Ever Seen Was Actually Something Much Darker


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Brightest Supernova Ever Seen Was Actually Something Much Darker

Yesterday 11:00am

Artist’s impression of a rapidly spinning supermassive black hole surrounded by an accretion disc—one consisting of the shredded remains of a Sun-like star. (Image: ESO, ESA/Hubble, M. Kornmesser)

Last year, astronomers recorded the brightest supernova explosion ever seen. Follow up observations now suggest this cataclysmic event wasn’t a supernova at all, but rather, an extremely rare celestial phenomenon involving a supermassive black hole and a rather unfortunate star.

In 2015, astronomers participating in the the All Sky Automated Survey for SuperNovae (ASAS-SN) witnessed what they thought was an unusually bright supernova. Dubbed ASASSN-15lh, it was twice as bright as the previous record holder, shining 20 times brighter than the total light output of the entire Milky Way galaxy. A supernova is the brilliant, dying gasp of a large star that can no longer balance the tremendous forces keeping it together, producing a shockwave that blows the star’s outer shell into space with tremendous force.

A new follow-up study published in the journal Nature Astronomy casts doubt on this initial assessment, proposing that ASASSN-15lh isn’t a superluminous supernova at all, but instead the consequence of a Sun-like star that ventured too close to a rapidly spinning supermassive black hole—an exceptionally rare cosmological event known as a tidal disruption.

Artist’s impression of the Sun-like star as it careens towards the supermassive black hole. (Image: ESO, ESA/Hubble, M. Kornmesser)

“We observed the source for 10 months following the event and have concluded that the explanation is unlikely to lie with an extraordinarily bright supernova,” noted lead investigator Giorgos Leloudas, an astronomer at Israel’s Weizmann Institute of Science, in a statement. “Our results indicate that the event was probably caused by a rapidly spinning supermassive black hole as it destroyed a low-mass star.”

During a tidal disruption, the extreme gravitational forces of a supermassive black hole “spaghettifies” and rips apart a star when it wanders too close. The shocks produced by the colliding debris, along with the tremendous amount of heat generated, produces an incredibly brilliant burst of light. This particular event transpired in a galaxy four billion light-years from Earth, and it’s only the tenth tidal disruption ever recorded.

Above: An animation showing how the ASASSN-15lh most likely happened.

During the ten months that followed the outburst, the astronomers watched as ASASSN-15lh went through a series of phases consistent with a tidal disruption. The object lit up in ultraviolet light and experienced a temperature increase—features that are not consistent with a supernova event. What’s more, the location of the outburst in a red, massive and passive galaxy is not the usual home for a superluminous supernova explosion, which typically happens in blue, star-forming dwarf galaxies.

The researchers based these conclusions on observations made from the Very Large Telescope at ESO’s Paranal Observatory, the New Technology Telescope at ESO’s La Silla Observatory, and the Hubble Space Telescope.

Above: This simulation shows a star getting torn apart by the gravitational tides of a supermassive black hole. The star gets “spaghettified,” and after several orbits creates an accretion disc. The view on the right is from the side, and at left from face on. (Credit: ESO, ESA/Hubble, N. Stone, K. Hayasaki)

That said, this particular tidal disruption—if that’s what it really is—is quite unique, requiring a special set of circumstances to make it happen.

“The tidal disruption event we propose cannot be explained with a non-spinning supermassive black hole,” explained Nicholas Stone from Columbia University. “We argue that ASASSN-15lh was a tidal disruption event arising from a very particular kind of black hole.”

The supermassive black hole at the core of this galaxy features a mass about 100 million times that of our Sun. Normally, a black hole of this size wouldn’t be able to disrupt stars outside of its event horizon—that fateful boundary within which nothing is able to escape. But if this black hole happens to be a so-called Kerr black hole—a black hole that features a rapid spin—this limit no longer applies, and the black hole is able to suck up any star that ventures within a certain radius.

The researchers aren’t fully confident that the outburst came from a tidal disruption, but the clues certainly fit that scenario. Further observations will be needed to make a definitive case.

[Nature Astronomy]

George is a contributing editor at Gizmodo and io9.

Plate Tectonics and Continental Drift (Infographic)


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Plate Tectonics and Continental Drift (Infographic)

 

New Test Could Improve Diagnosis of Rare, Fatal Brain Disorder


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Underwater Hebrew Tablet Reveals Biblical-Era Ruler of Judea


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Underwater Hebrew Tablet Reveals Biblical-Era Ruler of Judea