What do people think about when lying back and looking out into the night sky? Heavens above, that’s the ultimate multi-choice answer. That Orion? No, can’t be. It’s summer. Grass a bit itchy. Wonder where that plane’s going? Red lights look a bit sci-fi i in the sky. I should have invited Phil but, damn, that guy could talk all the ears off an Iowa cornfield. Can you believe my third grade teacher Mrs Philpot said that to me all those years ago? Wasn’t even my pencil. Hmmm….really dark up there. Wonder where the nearest black hole is?
Although we can’t say with certainty, we can at least tell you where the nearest black hole is located! And, brace yourself with both arms, it’s much closer than once believed.
Who the devil just said that?
With a mass 8,200 times that of the Sun, what might well be the nearest of the known black holes could lurk a mere 18,000 light years from Earth. Tucked away within Omega Centauri, the largest and arguably most beautiful of all the Milky Way’s globular clusters, this celestial welterweight, if it exists, would be the first known example of what are called ‘intermediate black holes.’ Astronomers have found many stellar mass black holes, those with masses 5 – 150 times greater than the sun. They’ve also found an ample supply of supermassive black holes with masses exceeding 100,000 solar masses. (One will find such SMBH in the nuclei of all galaxies.) However, astronomers have yet to verify the existence of black holes with masses between those two extremes, aptly named “intermediates.’ Perhaps they soon will now that they found a prime candidate within Omega Centauri.
In April, a research team published a paper entitled “Photometry and Proper Motion for 1.4 Million Stars in Omega Centauri and its Rotation in the Plane of the Sky.” After having observed more than 500 photographs of Omega Centauri captured by the Hubble Space Telescope, this team discovered seven stars that are moving so quickly they should have been ejected by Omega Centauri. In other words, these stars seem to exhibit speeds that are greater than the cluster’s escape velocity. The very fact that they have remained within the cluster while still traveling so fast might indicate the presence of a black hole with a mass more than 8,000 times that of the Sun. Such a black hole could maintain a hold on these stars while causing them to move so rapidly.*
Astronomers who study Omega Centauri have long suspected that it might harbor a black hole. First, with a stellar population of nearly 10 million, it has been thought by many to be a remnant of a dwarf galaxy the Milky Way cannibalized a long time ago. Secondly, the unusual density of stars within the center of Omega Centauri could also be evidence that a gravitationally powerful entity such as a black hole could be hidden deep within it. As far back as 2008, astronomers were searching for a large black hole that they thought would explain this unusual density. However, some researchers believed that a cluster of stellar mass black holes could explain the stellar distribution within Omega Centauri just as easily as an intermediate mass black hole.
However, the observation of those seven stars provides the most compelling evidence yet in support of the notion that the Milky Way’s largest globular cluster harbors an intermediate black hole deep within it. As is generally the case in matters such as these, more observations will be required before astronomers can claim with certainty that they’ve found their first IMBH so close to our shores. Fortunately, the research team will soon be granted access to the James Webb Space Telescope, the worthy successor to the Hubble.
Soon we might be able to look up into the sky and know that a black hole is lurking a mere 18,000 light years away. While it is certainly possible that many isolated black holes might be veering closer to us than the one in Omega Centauri, we might never find them, at least not with the technology that we currently possess. However, perhaps it is best not to think about those. Why make a star gazing session any more anxiety-inducing than it already is.
*When it comes to orbiting bodies, speed and mass are directly related. For instance, if the Sun’s mass increased, the orbital velocities of the planets would increase, as well. It was by observing the velocities of stars close to the Milky Way’s center that astronomers were able to discover the supermassive black hole Sagittarius A* inside the galactic nucleus.
Quote of the day
“We forfeit three-fourths of ourselves to be like other people.”
-Arthur Schopenhauer
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