Astronomers believe they've found a new type of black hole, following observations of the most extreme ultra-luminous X-ray source yet discovered.
The X-ray source, HLX-1, is located in the galaxy ESO 243-49, around 300 million light years from the Earth. It's ten times more luminous than the next brightest X-ray source, leading scientists to believe that it may contain an intermediate mass black hole.
Using the European Southern Observatory's (ESO's) Very Large Telescope (VLT) in Chile, the team was able to work out exactly how far away the object is.
"We could see on images taken with big telescopes that a faint optical source was present at the location of the X-ray source, located near the core of a large and bright galaxy," says Dr Klaas Wiersema of the University of Leicester.
"Much to our delight we saw in the resulting measurements exactly what we were hoping for: the characteristic light of hydrogen atoms was detected allowing us to accurately measure the distance to this object. This provided conclusive proof that the black hole was indeed located inside the big, bright galaxy, and that HLX-1 is the brightest ultra-luminous X-ray source known."
The data proves that HLX-1 is not in our own galaxy, nor is it a super-massive black hole in the centre of a distant background galaxy. It also confirms that the object really is as bright as they thought it was.
Whether all ultra-luminous X-ray sources contain intermediate mass black holes is still quite uncertain. The team has now been granted time on the Hubble Space Telescope to take the highest-ever resolution images of this host galaxy, which will allow a detailedinvestigation of the environment around HLX-1 and the galaxy which hosts it.
The next step will be to find out how many intermediate mass black holes might be out there, and where they are likely to appear.