A rogue black hole has been found in the outer regions of the lenticular galaxy SDSS J141711.07+522540.8 (GJ1417+52 for short). Evidence suggests this black hole has a mass of approximately 100,000 solar masses, and was originally located in a dwarf satellite galaxy that collided and merged with a larger one.
Astronomers know that black holes ranging from about 10 times to 100 times the Sun’s mass are the remnants of dying stars, and that supermassive black holes, with some 100,000 to 10 billion times the Sun’s mass, inhabit the centers of most galaxies.
But scattered across the Universe are a few apparent black holes of a more mysterious type. Ranging from 100 to 100,000 solar masses, these intermediate-mass black holes are much harder to find.
According to scientists, both supermassive and intermediate-mass black holes may be found away from the center of a galaxy following a collision and merger with another galaxy containing a massive black hole.
As the stars, gas and dust from the second galaxy move through the first one, its black hole would move with it.
Now, a team of astronomers led by University of New Hampshire scientist Dacheng Lin has used NASA’s Chandra and ESA’s XMM-Newton X-ray observatories to discover a ‘wandering’ black hole in GJ1417+52, a lenticular galaxy located approximately 4.5 billion light-years away from us.
This object, dubbed 3XMM J141711.1+522541 (XJ1417+52 for short), is located at a projected offset of 17,000 light-years from the nucleus of GJ1417+52.
It was discovered during long observations of a special region, the so-called Extended Groth Strip, with XMM-Newton and Chandra data obtained between 2000 and 2002.
Its extreme brightness makes it likely that it is a black hole with a mass estimated to be about 100,000 times that of the Sun, assuming that the radiation force on surrounding matter equals the gravitational force.
The Chandra data show XJ1417+52 gave off a tremendous amount of X-rays, which classifies it as a hyperluminous X-ray source (HLX). These are objects that are 10,000 to 100,000 times more luminous in X-rays than stellar black holes, and 10 to 100 times more powerful than ultraluminous X-ray sources (ULXs).
At its peak XJ1417+52 is about 10 times more luminous than the brightest X-ray source ever seen for a wandering black hole. It is also about 10 times more distant than the previous record holder for a wandering black hole.
The bright X-ray emission from this type of black hole comes from material falling toward it. The X-rays from XJ1417+52 reached peak brightness between 2000 and 2002.
Dr. Lin and co-authors theorize that this outburst occurred when a star passed too close to the black hole and was torn apart by tidal forces.
The discovery is reported in the Astrophysical Journal (arXiv.org preprint).
Dacheng Lin et al. 2016. Discovery of the Candidate Off-nuclear Ultrasoft Hyper-luminous X-ray Source 3XMM J141711.1+522541. ApJ 821, 25; doi: 10.3847/0004-637X/821/1/25