Giant Star That Failed To Explode In Supernova And Became A Black Hole

MessageToEagle.com | May 30, 2017 | Astronomy | No Comments

MessageToEagle.com – A dying star – 25 times as massive as our sun – should have exploded in a very bright supernova but instead it was reborn as a black hole.

This kind of event was made for the first time by astronomers, who were looking for failed supernovae in other galaxies, using the Large Binocular Telescope (LBT).

In the failed supernova of a red supergiant, the envelope of the star is ejected and expands, producing a cold, red transient source surrounding the newly formed black hole, as illustrated by the expanding shell (left to right). Some residual material may fall onto the black hole, as illustrated by the stream and the disk, potentially powering some optical and infrared emissions years after the collapse. Credit: NASA, ESA, P. Jeffries (STScI) — In the failed supernova of a red supergiant, the envelope of the star is ejected and expands, producing a cold, red transient source surrounding the newly formed black hole, as illustrated by the expanding shell (left to right). Some residual material may fall onto the black hole, as illustrated by the stream and the disk, potentially powering some optical and infrared emissions years after the collapse.
Credit: NASA, ESA, P. Jeffries (STScI)

“Massive fails” like this one in a nearby galaxy could explain why astronomers rarely see supernovae from the most massive stars, said Christopher Kochanek, professor of astronomy at The Ohio State University and the Ohio Eminent Scholar in Observational Cosmology.

“The typical view is that a star can form a black hole only after it goes supernova,” Kochanek explained.

“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 pair of visible-light and near-infrared Hubble Space Telescope photos shows the giant star N6946-BH1 before and after it vanished out of sight by imploding to form a black hole. The left image shows the 25 solar mass star as it looked in 2007. In 2009, the star shot up in brightness to become over 1 million times more luminous than our sun for several months. But then it seemed to vanish, as seen in the right panel image from 2015. A small amount of infrared light has been detected from where the star used to be. This radiation probably comes from debris falling onto a black hole. The black hole is located 22 million light-years away in the spiral galaxy NGC 6946. Credits: NASA, ESA, and C. Kochanek (OSU) — This pair of visible-light and near-infrared Hubble Space Telescope photos shows the giant star N6946-BH1 before and after it vanished out of sight by imploding to form a black hole. The left image shows the 25 solar mass star as it looked in 2007. In 2009, the star shot up in brightness to become over 1 million times more luminous than our sun for several months. But then it seemed to vanish, as seen in the right panel image from 2015. A small amount of infrared light has been detected from where the star used to be. This radiation probably comes from debris falling onto a black hole. The black hole is located 22 million light-years away in the spiral galaxy NGC 6946.
Credits: NASA, ESA, and C. Kochanek (OSU)

Among the galaxies they’ve been watching is NGC 6946, a galaxy 22 million light-years away that is nicknamed the “Fireworks Galaxy” because supernovae frequently takes place in this region.

Particularly one star named N6946-BH1 and located in the “Fireworks Galaxy” began to brighten weakly in 2009 and it finally vanished by 2015.

Using process of elimination, the researchers eventually concluded that the star must have become a black hole.

An interesting question is: how often stars experience massive fails?

A team of astronomers at The Ohio State University watched a star disappear and possibly become a black hole. Instead of becoming a black hole through the expected process of a supernova, the black hole candidate formed through a “failed supernova.” Credits: NASA’s Goddard Space Flight Center/Katrina Jackson

N6946-BH1 is the only likely failed supernova that we found in the first seven years of our survey,” said Scott Adams, a former Ohio State student who recently earned his Ph.D. doing this work. Adams was able to make a preliminary estimate.

“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,” he said.

Co-author, professor of astronomy at Ohio State, Krzystof Stanek, pointed out that the really interesting part of the discovery is the implications it holds for the origins of very massive black holes.

It doesn’t necessarily make sense, said Stanek, professor of astronomy at Ohio State, that a massive star could undergo a supernova — a process which entails blowing off much of its outer layers — and still have enough mass left over to form a massive black hole on the scale of those that LIGO detected.