An unusual source of light has been found in a galaxy some 90 million light-years away. The object’s odd properties make it a good match for a supermassive black hole ejected from its home galaxy after merging with another giant black hole, or the source, called SDSS1133, might be the remnant of a massive star that erupted for a record period of time before destroying itself in a supernova explosion. Whether it’s a rogue supermassive black hole or the closing act of a rare star, SDSS1133 has been a persistent source for more than 60 years. This sequence of archival astronomical imagery, taken through different instruments and filters, shows that the source is detectable in 1950 and brightest in 2001.

One possible explanation for this source is a very unusual type of star known as a Luminous Blue Variable (LBV). These massive stars undergo episodic eruptions that through off large amounts of matter into space long before they explode. If this be the case, SDSS1133 would have displayed the longest period of LBV eruptions ever observed.

The object could also be a supermassive black hole ejected from its home galaxy after merging with another giant black hole. The collision merger of two galaxies disrupts their shapes and results in new episodes of star formation. If each galaxy possesses a central supermassive black hole, the two black holes will form a bound binary pair at the center of the merged galaxy before ultimately coalescing themselves. The kick may be strong enough to hurl the merged black hole entirely out of its home galaxy, drifting as a rogue through intergalactic space. More likely, it will go into an elongated orbit around the galaxy, retaining the hot gas trapped around it which will continue to shine until all of it is consumed.

This simulation zooms into galaxy Markarian 177 and object SDSS1133 and suggests how they compare with a simulated galaxy collision. When the central black holes in these galaxies combine, a “kick” launches the merged black hole on a wide orbit taking it far from the galaxy’s core.