Astronomers Confirm First 'Lone' Black Hole Discovery - and It's in the Milky Way (sciencenews.org) 24
For the first time, astronomers have confirmed the existence of a lone black hole," reports Science News — "one with no star orbiting it."
It's "the only one so far," says Kailash Sahu, an astronomer at the Space Telescope Science Institute in Baltimore. In 2022, Sahu and his colleagues discovered the dark object coursing through the constellation Sagittarius. A second team disputed the claim, saying the body might instead be a neutron star. New observations from the Hubble Space Telescope now confirm that the object's mass is so large that it must be a black hole, Sahu's team reports in the April 20 Astrophysical Journal.... [And that second team has revised its assessment and now agrees: the object is a black hole.]
While solitary black holes should be common, they are hard to find. The one in Sagittarius revealed itself when it passed in front of a dim background star, magnifying the star's light and slowly shifting its position due to the black hole's gravity. This passage occurred in July 2011, but the star's position is still changing. "It takes a long time to do the observations," Sahu says. "Everything is improved if you have a longer baseline and more observations." The original discovery relied on precise Hubble measurements of star positions from 2011 to 2017. The new work incorporates Hubble observations from 2021 and 2022 as well as data from the Gaia spacecraft.
The upshot: The black hole is about seven times as massive as the sun, give or take 0.8 solar masses.... Located 5,000 light-years from Earth, this black hole is much closer than the supermassive one at the Milky Way's center, which also lies in Sagittarius but about 27,000 light-years from us. The star-rich region around the galactic center provides an ideal hunting ground for solitary black holes passing in front of stars. Sahu hopes to find additional lone black holes by using the Nancy Grace Roman Space Telescope, slated for launch in 2027.
While solitary black holes should be common, they are hard to find. The one in Sagittarius revealed itself when it passed in front of a dim background star, magnifying the star's light and slowly shifting its position due to the black hole's gravity. This passage occurred in July 2011, but the star's position is still changing. "It takes a long time to do the observations," Sahu says. "Everything is improved if you have a longer baseline and more observations." The original discovery relied on precise Hubble measurements of star positions from 2011 to 2017. The new work incorporates Hubble observations from 2021 and 2022 as well as data from the Gaia spacecraft.
The upshot: The black hole is about seven times as massive as the sun, give or take 0.8 solar masses.... Located 5,000 light-years from Earth, this black hole is much closer than the supermassive one at the Milky Way's center, which also lies in Sagittarius but about 27,000 light-years from us. The star-rich region around the galactic center provides an ideal hunting ground for solitary black holes passing in front of stars. Sahu hopes to find additional lone black holes by using the Nancy Grace Roman Space Telescope, slated for launch in 2027.
I thought black holes were stars⦠(Score:2)
Re:I thought black holes were stars⦠(Score:5, Informative)
âoeâ¦one with no star orbiting itâ¦â I admit, Iâ(TM)m no astrophysicist, but I thought a black hole was a star in its final stage of life. Is that not the case?
No, a black hole is a black hole, typically originated from the collapse of a massive star. It may have started as a star, but once it reaches about ~4.34 × 1030 kilograms (about 2.17 times the mass of our sun) it exceeds the Chandrasekhar limit and collapses into a black hole, which is way more dense than any star and does not emit light as light cannot escape its mass.
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Saying a star is defined by its orbital mechanics is stupid (The gases around black holes can emit light) as is conflating hawking radiation with thermal emission of a black body.
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I think you missed the point. Let's agree you're right a black holes isn't a star but USED to be a star. The question is WHY they say there is most frequently a star orbiting a black hole. Is it that it's the only way for a star to grow above the limit is to suck matter from stars orbiting it? But then how would solitary black holes exist at all, just out of random enough matter happened to be there without it being a star and immediately collapsing into a black hole seems weird. As you can guess I'm not as
Re:I thought black holes were stars⦠(Score:5, Funny)
But then how would solitary black holes exist at all
It finished all its orbiting stars. [Burp]
Flip it. (Score:5, Informative)
I think you misunderstood.
It isn't that black holes mostly have an orbiting star, its that most of the black holes we spot have one because it is like having a light bulb right next to it.
Black holes without are dark and need a lucky coincidence like this one to spot. So rarely seen.
Re:I thought black holes were stars⦠(Score:5, Informative)
It's not that black holes frequently have orbiting stars, it's that these are the only type of black holes we can easily detect.
Black holes with an orbiting star steel matter from their companion. This matter forms an acretion disk around the black hole that heats-up to insane temperatures that make them glow as far up in the EM spectrum as x-rays, making them easy to detect, and distinguish from ordinary stars.
Solitary black holes are likely very common, probably as common as solitary stars are to multiple stars, but having no acretion disk, they're basically "black" and almost impossible te detect. These researchers say they detected this one almost by chance when it passed in front of an ordinary star, modifying its light in a way that is consistent with the effect of a gravitational lens.
As for how these stellar mass solitary black holes form, it's probably the same way any other stellar mass black hole forms: A star that goes supernovae, its core collapsing into either a neutron star or a black hole, depending on the original mass of the star.
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Continued existence in gravitational and electrically bound form is not conducive with being hit with that kind of energy. The ones that survive are going to receive enough momentum from the star as to potentially exceed escape velocity.
Doesn't seem that weird to me.
Of course it's in the Milky Way (Score:3, Informative)
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" There probably is no realistic way to detect a solo black hole in another galaxy."
At least for a stellar mass black hole. We can detect SMBHs and UMBHs in other galaxies.
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We can detect SMBHs and UMBHs in other galaxies.
But can you detect, or rule out an orbiting star(s) around them? Cyclical Doppler shift of the emissions from the accretion disk might work to detect an orbiting star. But that data would probably be noisy. And a very small signal unless the orbiting object were itself super massive.
5,000 light-years from Earth is still too far ... (Score:2)
for us to be able to chuck our current batch of politicians into :-(
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And Veritasium just came out with a video showing that energy is not conserved, so hurling them toward the black hole into the void may not get them there either. Bummer. The video: https://www.youtube.com/watch?... [youtube.com]
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Really? I've found many of his videos to be rather enlightening. Why do you consider this one click bait?
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It is pretty bold to simply say it is not conserved, and if this person has "shown" this, they either don't know what they're talking about, or have picked a set of definitions and convinced you they're the only ones (probably by omission).
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From your perspective, the politicians are hauling more and more ass away from you, but also from your perspective, the difference in velocity between your politicians and the black hole decreases as the expansion of the universe accelerates. Whether or not this counts as a loss of energy is a matter of how you
Re: 5,000 light-years from Earth is still too far (Score:3)
Re: 5,000 light-years from Earth is still too far (Score:3)
lone black hole in the White House...... (Score:2)
7 times as massive? (Score:1)
"The black hole is about seven times as massive as the sun, give or take 0.8 solar masses"
How does 7xSun equal 0.8 solar masses?