A Couple Of Aussies Helped Find A Light-Sucking Supermassive Black Hole In A Dwarf Galaxy

This Hubble Space telescope image shows the gargantuan galaxy M60 in the center, and the ultracompact dwarf galaxy M60-UCD1 below it and to the right, and also enlarged as an inset. M60-UCD1 is the smallest known galaxy with a supermassive black hole at its centre. Image: NASA/Space Telescope Science Institute/European Space Agency.

Two Australian astronomers are part of an international team which has found a supermassive black hole inside the smallest known galaxy.

A partnership between the Australian Astronomical Observatory and Macquarie University supported the key roles played by Dr Richard McDermid and Dr Lee Spitler in making the discovery, led by University of Utah astronomer Anil Seth.

Seth, McDermid and Spitler’s star team discovered that an ultracompact dwarf galaxy known as M60-UCD1 harbours a supermassive black hole. It’s the smallest galaxy known to contain such a massive light-sucking object.

“This object is bizarre – it is the smallest thing we’ve ever found to harbour such a large black hole,” says Spitler.

“Even the Milky Way, which is 500 times larger than M60-UCD1, has a smaller black hole.”

The size of a supermassive black hole usually relates to the size of the galaxy it lives in.

M60-UCD1 is a supermassive black hole way out of proportion, about 1500 times larger than expected.

“What we think happened was that M60-UCD1 was once a normal galaxy, probably a little bigger than the Milky Way,” says Spitler.

“The old M60-UCD1 likely had a head-on collision with another, much larger galaxy called M60.

“All that is left of M60-UCD1 is just its core – the rest of it was ripped apart. So we think
we found the dense stellar core of a destroyed galaxy.”

As part of the international science team, the two joint Macquarie-Australian Astronomical Observatory staff members contributed access to the Gemini North Observatory, an 8 metre telescope in Hawaii funded by Australia as part of an international partnership.

The video simulation below shows how this small galaxy, named M60-UCD1, was formed from a larger, normal galaxy.

The find is announced in the journal Nature.

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