An unconventionally bright star has disappeared into a stellar mystery of cosmic magnitude, according to new research published Tuesday in Monthly notices from the Royal Astronomical Society.
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The giant star disappears without a trace
A stellar object within the Kinman dwarf galaxy has disappeared from view. A gigantic and extraordinarily bright blue star was supposed to exist, based on astronomical observations that occurred between 2001 and 2011.
But as of sometime in 2019, no one else could detect it.
The authors of the study, led by Andrew Allan of Trinity College Dublin, have put forward two explanations: The star has experienced a sharp drop in luminosity and is momentarily hiding behind stardust, or has collapsed into a new unexploded black hole. in A supernova.
If the latter is the case, it would mark the second known failed supernova.
Kinman’s dwarf galaxy is 75 million light years from Earth, in other words: far, far away. In this range, astronomers generally cannot tell one star from another. But the hypothetical star (now disappeared) is a luminous blue variable (LBV), which can be observed even at extreme distances. LBVs are massive stars whose behavior is difficult to predict near the end of their useful lives.
The unpredictability of this star as it moves through brightness and variable spectra can be seen from Earth. Plus, the star is maddeningly 2.5 million times brighter than the Sun, reports Gizmodo.
Or at least, it used to be.
Possible destinations of the fleeing star
Astronomers gathered observations from 2001 to 2011, and concluded that this star was likely a late-stage LBV in the Kinman dwarf galaxy. In 2019, they were recorded with the bright star using the Very Large Telescope of the European Southern Observatory. But to his surprise, there seemed to be nothing there, a discovery that was both exciting and daunting.
“We were pleasantly surprised to discover that the star’s signature was not present in our observation taken in August 2019 using the ESPRESSO instrument from ESO’s Very Large Telescope,” Allan told Gizmodo. “Initially we were expecting a higher resolution observation that resembled past observations, which we would use for our models.”
At first astronomers thought something must be wrong with ESPRESSO, so Allan and his colleagues took another look with the telescope’s X-shooter instrument.
“We reviewed ESPRESSO’s observation several times, but were unable to detect the star’s signature,” Allan told Gizmodo. “As conditions were not perfect on the day this observation was made, we wanted to make sure the signature was really absent. This time we used the Very Large Telescope’s X-Shooter instrument and were pleased to discover that this also pointed towards the disappearing star. “
MIA after a big starburst
Seeing nothing there, the team suddenly had in their possession a great cosmic mystery that begged for it to be solved. So they went into the archives, looking for earlier observations of the dwarf galaxy that could give context to the observation.
Indeed, the suspected giant star experienced a major explosion period that ended around 2011. LBVs often cause huge tantrums, causing sudden mass losses and sharp drops in brightness.
In the wake of the 2011 burst period, astronomers think, “We are seeing the end of an LBV eruption of a surviving star, with a slight drop in luminosity, a change to higher effective temperatures, and some darkening of the dust.” So while the star may still be active, it may simply be too dim for astronomers to observe.
Ghost Black Hole
It could also be a newly formed black hole, without the typical supernova explosion that normally precedes such transformations. This is called a failed supernova.
“This would be consistent with some of the current computer simulations that predict that some stars will not produce a bright supernova when they die,” Allan told Gizmodo. “This happens when a massive black hole forms, and it is not spinning very fast. However, a collapse to a black hole without producing a supernova has only been observed once in the past, in galaxy NGC 6946 where it looked like a star. Massive smaller to disappear without a brilliant supernova explosion. “
If this is the case, it would be the first known black hole formed without a supernova from a massive star in a low-metallic galaxy. This is significant because it represents a finding that “could contain important clues about how stars could collapse into a black hole without producing a bright supernova,” Allan added.
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