The Wandering Black Hole

Don’t panic, but scientists believe there may be a Jupiter-sized black hole wandering around our galaxy.

In December 2018, scientist Shunya Takekawa at the National Astronomical Observatory of Japan and his colleagues published a report claiming to have found ripples in interstellar gas clouds that may be caused by a wandering intermediate-mass black hole (an IMBH). The black hole in question, if it exits, can be found far from our own solar system, somewhere near the supermassive black hole at the centre of the Milky Way.

Black holes as we currently know them come in two categories: stellar-mass, housing the mass of a collapsed star; and supermassive, housing the mass of millions or billions of starts. Though currently elusive, intermediate-mass varieties with the mass of several stars combined could provide the missing link between the two, the scientists say.

‘Many efforts have been made to confirm the existence of IMBHs’, wrote Takekawa and his colleagues in their report; ‘however, these results have been argued upon, and therefore, none of the IMBH candidates are accepted as definitive’.

He then explains that certain interstellar clouds called HVCC (High-velocity compact clouds) may also provide possible hints of IMBHs. Recently, using the Atacama Large Millimeter Array (ALMA) telescope in Chile, they discovered a peculiar HVCC more compact and with less luminosity than expected, which apparently ‘can be explained by the high-velocity plunge of an invisible compact object into a molecular cloud … The driving source may be an inactive and isolated black hole’.

“When I checked the ALMA data for the first time,” Takekawa told New Scientist, “I was really excited because the observed gas showed obvious orbital motions, which strongly suggest an invisible massive object lurking.”

The theorised reason why this black hole is ‘wandering’ goes something like this: this black hole may essentially be leftover shrapnel from a dwarf galaxy merger with our own Milky Way that, while much of the dwarf galaxy’s stars were consumed by the suermassive black hole, this black hole or star did not plunge all the way, and instead orbited it, and there remains, like a basketball circling a hoop, sucking up all the other mass it encounters on its way.

Pure speculation on the part of this author: if there is one of these, might there be more? Can we imagine a stream or whirlpool populated by these things near the heart of the Milky Way, spiralling there for millennia to come?

To summarise, the moral of this fascinating story might be this: if you ever take a trip to the galactic core, be careful where you’re flying.



New Scientist

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