Mark Megahan
Astronomers somehow managed to lose a black hole. Only two short years ago they announced the discovery of the closest black hole to Earth. Only 1,000 light-years away. Now, they can’t seem to find it but they did find a “stellar vampire” in it’s place.
Vampire star in space
Astronomers were convinced that an invisible black hole was lurking in the HD 6819 system when they described it as a “triple.” After looking closer with better instruments they realized they were wrong.
While there may not be a dark singularity in the area, they found something “rarer” and just as exciting. A stellar vampire caught in the act of feeding.
When skeptics in the scientific community challenged the black hole announcement they realized what they were really looking at was a two star system “orbiting each other in a rare and short-lived stage of their evolution, with one weak and emaciated after being fed upon.”
The Vampire got a “sugar rush” from the influx of energy.
As one star “transferred material to its companion star and was stripped of its outer envelope,” the other “received at least some of this material and was spun up, just like a spinning top.” We were lucky to catch the vampire in the very act of feeding.
“The phase we are currently observing is very short in comparison to the lifetime of the entire system, which makes it very difficult to catch by observations.”
Currently interacting
According to researcher Julia Bodensteiner, “astronomers call a binary system a vampire system if the two stars are currently interacting.”
That means that “the two stars are so close to each other that one star basically sucks the outer envelope of the second star, similarly to vampires which are said to suck blood.”
The latest survey indicates the pair in HD 6819 “are now believed to circle each other with a 40-day orbit.” The vampire star already “stripped the other’s upper layers of material.” This means “that this donor star had at some point in the past lost a huge amount of mass.”
Team member Abigail Frost adds that “stars like those in HR 6819 are very important players in the Universe, creating lots of complicated materials like iron, oxygen, and more that we find on Earth.”
ESO astronomer Thomas Rivinius explains how they missed the vampire behind the ghost of a black hole. “We basically had two competing scenarios. We knew there were two sources of light in the system, so the question was what relation they are in?” If they were orbiting each other it would be “a very unusual star, caught in a brief state of transition after an interaction.”
The more plausible explanation was “a third, dark body, purely supplying a source of gravity for one of the two luminous stars to orbit around. Which means a black hole.” They solved the mystery by “obtaining a clearer picture of HD 6819, which the joint team was able to do by using ESO’s Very Large Telescope and Very Large Telescope Interferometer.“
