European Space Agency discovers 'missing link' black holes

Illustration of HLX-1 (blue star on the upper left ), an intermediate mass black hole. Credit: Heidi Sagerud/ESA

Astronomers with the European Space Agency have discovered a new category of black hole.

There’s one less secret of the universe today.

By digging through old observatory data obtained by a satellite launched in 1999, astronomers with the European Space Agency have discovered a mid-size black hole weighing more than 500 solar masses. The researchers consider the distant discovery a “missing link” between lighter stellar-mass and heavier super massive black holes. The discovery is reported in the July 2 issue of Nature.

In a July 1 statement, scientists from the ESA’s  XMM-Newton X-ray observatory said the discovery is “the best detection to date of a new class that has long been searched for: intermediate mass black holes.”

The XMM-Newton X-ray observatory team, led by Sean Farrell from the Centre d’Etude Spatiale des Rayonnements at the University of Leicester, UK, found the black hole while analyzing November 2004 data obtained by the satellite. They were looking for neutron stars and white dwarves when they noticed a peculiar object.

It’s called HLX-1 (Hyper-Luminous X-ray source 1) and it lies towards the outskirts of the galaxy ESO 243-49, approximately 290 million light years from earth.

Analyzing the light originating from HLX-1 -- its X-rays peak at 260 million times the luminosity of the sun -- the astronomers said the find was consistent with only one object: a black hole.

The team observed HLX-1 again in November 2008 to confirm it was truly a single astronomical object.

Scientists already know of the existence of stellar-mass black holes (three to 20 times larger than the sun) and super massive black holes (up to several thousand million times larger than the sun).

But until now the existence of a mid-size group of black holes like HLX-1 was just speculation. ESA astronomists believe they’ve now put that question to rest.

Launched in December 1999 (Ariane-5 at Kourou, French Guiana), the XMM-Newton is Europe’s largest science satellite. It derives its name from its X-ray Multi-Mirror design and Sir Isaac Newton (1642-1727), the English physicist and mathematician who advanced theories of gravitation and optics, built the first working reflecting telescope and discovered how to split light into its components to study its spectrum.