Since it was first launched in 1990, the Hubble Space Telescope has shed light on many mysteries of our universe. And after more than 30 years, it continues to impress. Most recently, it discovered what astronomers believe is the first of its kind—a roving black hole left free to wander the galaxy.
Usually, black holes sit at the center of a galaxy or are paired with associated stars. However, the black hole that Hubble has spotted is going it alone and traveling 100,000 miles per hour around the Milky Way. Located 5,000 light-years away in the Carina-Sagittarius spiral arm of our galaxy, it's just one of 100 million estimated black holes that populate the Milky Way.
As NASA explains, black holes roaming our galaxy are born from rare, monstrous stars (less than one-thousandth of the galaxy's stellar population) that are at least 20 times more massive than our Sun. These stars explode as supernovae, and the remnant core is crushed by gravity into a black hole. Because the self-detonation is not perfectly symmetrical, the black hole may get a kick, and go careening through our galaxy like a blasted cannonball.
And while telescopes can't photograph black holes (since they don't emit light), they can image the starlight that gets warped when a black hole lines up behind it. By studying this warping of space, which is called gravitational microlensing, researchers were both able to identify and size the wandering black hole.
Two sets of studies looked at the data Hubble provided and estimated that the mass of the invisible compact object is between 1.6 and 4.4 times that of the Sun. At the high end of this range, the object would be a black hole; at the low end, it would be a neutron star, which is the collapsed core of a supergiant star. Either way, it's an exciting discovery.
“Detections of isolated black holes will provide new insights into the population of these objects in our Milky Way,” shared Kailash Sahu of the Space Telescope Science Institute in Baltimore, Maryland. Sahu led one of the two teams that analyzed Hubble's data, which was composed of six years of observations.
Six years of observations by the Hubble Space Telescope show a black hole wandering on its own through the Milky Way.
In order to “see” and measure the black hole, researchers look at how it bends starlight.
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