Scientists working with CSIRO's Australia Telescope Compact Array have found a new kind of black hole that would make Goldilocks quite happy: By not being too big, nor too small, it falls within a new class of "middleweight" black holes. The discovery indicates that black holes can take on a larger variety of sizes than previously assumed — and that they might be the younger version of something bigger yet to come.


Prior to the discovery, we believed that black holes only came in two major varieties. Supermassive black holes are typically be found in the center of galaxies and have a million to a billion times the mass of our sun. And then there are stellar mass black holes, which are anywhere from three to 30 times our sun's mass.


But by observing distant outbursts of super-hot gas, astronomers believe they have stumbled upon a black hole that's anywhere from 20,000 to 90,000 times the mass of our sun — placing it squarely within an intermediate class of black holes.

Called HLX-1 ("hyper-luminous X-ray source 1"), the black hole is about 300 million light-years away. The object was discovered by Natalie Webb from Université de Toulouse and her research team, which included astronomers from France, Australia, the UK and the USA.

The object is described as being "hyper-luminous" because it is giving off a tremendous amount of X-rays. Astronomers theorize that the black hole is consuming either a gas cloud or an entire star — and when black holes suck up all this energy it is heated to extreme temperatures causing it to shine bright in X-rays.

It was this exact observation that led Farrell and his team to conclude that there must be a black hole responsible for the hyper luminosity. But at 10 times the brightness of other similar objects, the team concluded that a very special kind of black hole must be responsible — one that's about 3,000 times bigger than regular stellar black holes.


The researchers suspect that a star is responsible for the X-ray bursts. Because the X-ray flashes happen at fairly regular intervals, about once every day or so, they theorize that the black hole is in the process of consuming an orbiting companion sun.

The researchers are particularly excited by the discovery of this new black hole because it could explain where supermassive black holes come from. They're positing the idea that middleweight black holes eventually graduate to supermassive class given the right circumstances.


Since this is the first black hole discovered of its kind, the astronomers are hoping to find more, and this is where they will focus their future research.

You can check out the entire paper in Science.

All images via CSIRO.