A massive unstable star suddenly disappeared from sight and astronomers are not sure if it collapsed into one black hole or is playing to peek behind the galactic dust.
The star was too far away to be found on its own, but it appeared in the spectrum, or light signature, of the dwarf galaxy Kinman, which is about 75 million light years from Earth. The spectrum showed that the distant galaxy contained an advanced blue variable star that is, 2.5 million times brighter than the sun. Stars of this type are known to be temperamental, with dramatic changes in their spectra and brightness (intrinsic brightness).
The signature of the blue variable star appeared in observations collected between 2001
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Additionally, Kinman Dwarf showed no signs of a supernova, or explosion of stars, in subsequent years – leading the team to speculate that the star may have collapsed directly into a black hole, instead of going to supernova first.
“We were surprised to find that the star had disappeared,” lead researcher Andrew Allan, a PhD. student at Trinity College Dublin in Ireland, said in an ESO statement. If the star had actually gone directly from being a star to being a black hole, Allan added, “this would be the first direct detection of such a monstrous star that would end his life in this way.”
To find out more, the team analyzed older data collected by X-shooter and VLT Ultraviolet and Visual Echelle Spectrograph between 2002 and 2009. (ESPRESSO was only installed in 2016). Other telescopes were also used for historical study; between VLT spectrographs and these other observers, astronomers easily confirmed the presence of the missing star in previous observations.
Archival research also revealed new information. The star, the old data suggested, may have been performing outburst which ended some time after the scientists’ last observation in 2011. The explosion would have produced a large rate of mass loss and would have caused a temporary increase in the brightness of the star.
This is what happened after this outbreak that left astronomers perplexed. If the star has actually collapsed into a black hole, this is an unusual life path for an advanced stage blue star like that of Kinman Dwarf. Usually, the sequence would see the star explode in a supernova before, before the strong gravity of the event dragged it into a black hole.
One potential explanation, astronomers think, is that perhaps the star has lost so much mass that it has become less bright and is now partially hidden by dust in the galaxy.
Astronomers plan to continue their work with a more powerful observatory when it is ready. ESO of Extremely large telescope will have a single 127-foot (39m) mirror, compared to the combined opening of the 107-foot (32m) mirror VLT through four telescopes. This would make it large enough to locate single stars in distant galaxies such as the dwarf Kinman. The new telescope is slated for first light in 2025.
A study based on the research it was published Tuesday (June 30) in the monthly communications of the Royal Astronomical Society.
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