- Astronomy researchers have identified what may be the first identification of a single black hole drifting through the galaxy.
- Two teams of studied researchers studied six years of data from the Hubble Space Telescope to locate the potential black hole.
- This data revealed how the potential black hole changed the starlight of a star in the background as it passed in front of it.
Of course, you know about black holes. But did you know there could be millions of them drifting like ghosts in our galaxy?
Since black holes are invisible, they are identified by statistical means or by seeing the effects of a black hole on another star or a second black hole. But moving black holes – ghostly remnants of collapsed stars – have been incredibly elusive.
Astronomers estimate that there could be 100 million black holes roaming our galaxy, based on the 100 billion stars in the Milky Way (some of which eventually collapse and become black holes). Two astronomy research teams have announced that they have used data from the Hubble Space Telescope to find, for the first time, what appears to be a moving black hole in our galaxy.
What sets a black hole in motion? When a star explodes as a supernova, gravity crushes its core and creates a black hole. However, an asymmetric explosion can send the black hole “spinning through our galaxy like a blasted cannonball,” according to a description of the new findings on NASA’s Hubble site.
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Researchers were alerted to the possible black hole after telescopes monitoring changes in star brightness captured anomalies about 5,000 light-years away in our galaxy’s Carina-Sagittarius spiral arm, NASA said.
The two research teams – one based at the Space Telescope Science Institute in Baltimore, Maryland, the other at the University of California, Berkeley – studied six years of Hubble Telescope data to investigate more closely, using a technique called gravitational microlensing.
Since a black hole distorts the surrounding space, it distorts and amplifies the light from any stars in the background. Accurate Hubble recordings helped researchers measure how the light from a background star 19,000 light-years away had been altered by the potential black hole passing in front of it. It also helped them determine the black hole’s mass, distance and speed, NASA said.
The isolated black hole is moving at around 100,000 mph – fast enough to travel from Earth to the Moon in less than three hours, the Space Telescope Science Institute research team said.
The Hubble data included 270 days during which light from the background star was amplified as the black hole passed in front of it. Hubble also revealed how the image of the star was deviated by a milliarcsecond, comparable to the diameter of a 25-cent piece in Los Angeles seen from New York, NASA said.
Another unrelated star nearby made measurements difficult, astronomer Kailash Sahu, who led the Space Telescope Science Institute team, said in a statement posted on the NASA website.
“It’s like trying to measure the tiny movement of a firefly next to a bright light bulb,” he said. “We had to meticulously subtract the light from the nearby bright star to accurately measure the deviation from the faint source.”
His team estimated that the black hole weighed the equivalent of seven of our suns. Their research, published on the arXiv Archive of Scientific Research, has been accepted for publication in The Astrophysical Journal, Sahu told USA TODAY.
But there is some disagreement over the size of the black hole – or even if it is a black hole. Researchers at the University of California, Berkeley estimate the mass of the object between 1.6 and 4.4 times that of our sun, NASA said. At the lower end of this range, the object could actually be a neutron star, the researchers say.
The team’s research, also published on arXiv, has been accepted for publication in The Astrophysical Journal Letters, according to Science Daily.
Like black holes, neutron stars also form when a star collapses. However, these stellar objects stop short of becoming black holes, whose gravity is so strong that light cannot escape.
“While we’d like to say it’s definitely a black hole, we should point out all allowed solutions. This includes both lower-mass black holes and possibly even a neutron star,” said said Jessica Lu, associate professor at the University of California, Berkeley. of astronomy, said in a statement on the NASA site and the UC Berkeley site.
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Both research teams have analyzed additional Hubble data — and that, along with future discoveries — will help scientists better understand our galaxy and perhaps lead to a definitive discovery about this particular object.
For now, the researchers can be congratulated on their discovery, which NASA considered the equivalent of “galactic research with a needle in a haystack.”
Casey Lam, a graduate student who led the UC Berkeley team, told the NASA website: “In any event, the object is the first dark stellar remnant discovered wandering the galaxy without be accompanied by another star.”
Follow Mike Snider on Twitter: @mikesnider.