Closest Black Hole To Earth Found 'Hiding in Plain Sight' (nationalgeographic.com) 38
The massive cosmic object lurks in a star system you can see with the naked eye. From a report: During winter in the Southern Hemisphere, a blue point of light in the constellation Telescopium gleams overhead. The brilliant pinprick on the sky, which looks like a bright star, is actually two stars in close orbit -- accompanied by the closest known black hole to Earth. The newly discovered black hole is about 1,011 light-years from our solar system in the star system HR 6819. Unveiled today in Astronomy & Astrophysics, the invisible object is locked in an orbit with two visible stars. It's estimated to be about four times the mass of the sun and roughly 2,500 light-years closer than the next black hole.
"It seems like it's been hiding in plain sight," says astronomer Kareem El-Badry, a Ph.D. student at the University of California, Berkeley, who specializes in binary star systems but wasn't involved with the study. "It's a bright enough star [system] that people have been studying it since the 80s, but it seems like it's had some surprises." On a human scale, a thousand light-years is an immense distance. If a model of the Milky Way were scaled so that Earth and the sun were only a hair's width apart, HR 6819 would be about four miles away. But in the grand scheme of the galaxy, which is more than 100,000 light-years across, HR 6819 is quite close, and it suggests the Milky Way is littered with black holes. "If you find one that is very close to you, and you assume you're not special, then they must be out there everywhere," says lead study author Thomas Rivinius, an astronomer at the European Southern Observatory (ESO) in Chile.
"It seems like it's been hiding in plain sight," says astronomer Kareem El-Badry, a Ph.D. student at the University of California, Berkeley, who specializes in binary star systems but wasn't involved with the study. "It's a bright enough star [system] that people have been studying it since the 80s, but it seems like it's had some surprises." On a human scale, a thousand light-years is an immense distance. If a model of the Milky Way were scaled so that Earth and the sun were only a hair's width apart, HR 6819 would be about four miles away. But in the grand scheme of the galaxy, which is more than 100,000 light-years across, HR 6819 is quite close, and it suggests the Milky Way is littered with black holes. "If you find one that is very close to you, and you assume you're not special, then they must be out there everywhere," says lead study author Thomas Rivinius, an astronomer at the European Southern Observatory (ESO) in Chile.
Well duh... (Score:4, Funny)
The two universal seasons (Score:4)
Winter and Roadwork.
Must be Roadwork if we're finding potholes. Interstellar travel is looking awfully unpleasant with the whole invisible-potholes-of-death thing.
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Black on black background. Of course you can't see it. Ya big dummy. :)
You can't see a black hole. But you can see the effects of a black hole: The radiation emitted by gases from the companion stars swirling into the black hole.
Re:Well duh... (Score:4, Insightful)
This is hardly a valid complaint.
There is always someone learning something new and to stop the flow of information because most people are expected to know something is part of societies problem for people knowing things.
Knock it off!
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Well, if (as I suspect you do) you want to be pedantic, you can't "see" anything. what you see is the effect the thing has on light that reaches your eyes or the sensor of your choice. So the phrase
"You can't see a black hole. But you can see the effects of a black hole:"
Works as
You can't see a tree. But you can see the effects of a tree:"
And on the point of pedantry
"The Earth rotates around the sun."
Well, no, the earth and sun both "rotates" around their shared center of mass. Though I would use orbit inst
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Obligatory:
Well, the thing about a black hole - its main distinguishing feature - is it's black. And the thing about space, the colour of space, your basic space colour, is black. So how are you supposed to see them?
Re:Well duh... (Score:4, Informative)
Red Dwarf quotes should get an automatic +5.
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It's like, how much more black could this be and the answer is none. None more black.
Nigel Tufnel
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Black on black background. Of course you can't see it. Ya big dummy. :)
Yep. It's like a modern web page, or a MacBook.
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>> If the galaxy were littered with black holes,
>> would that mean the estimated percentage of
>> galactic mass comprised of dark matter is off by a percent or two?
Black holes are considered a candidate _form_ of dark matter. If the galaxy is littered with black holes that will explain a (large?) portion of the dark matter in/around our galaxy. I don't know why bh are considered a candidate tho - they are dark, gravitate, and exist.
Re:Littered with black holes (Score:5, Informative)
They contribute to the galaxy's mass, but dark matter appears to be more diffuse. Black holes were rejected as candidates to explain the missing mass sometime ago. If black holes are far more common then that obviously explains some of the missing mass, but probably is only going to shift that amount down a fraction of a percentage. If black holes formed the halos of dark matter around galaxies, we'd know it by the gravitational lensing effects they'd produce.
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If black holes formed the halos of dark matter around galaxies, we'd know it by the gravitational lensing effects they'd produce.
The Massive Compact Halo Object (MACHO) hypothesis for dark matter has been pretty carefully tested, since we know such things exist, plus it's a really cool acronym to counter Weakly Interacting Massive Particles (WIMPS). Not just black holes, but white dwarfs, neutron stars, etc. The "Massive compact halo object" wikipedia page has an ok summary and links to papers and articles if you want a starting point to read more: short form, you watch distant stars in the Milky Way halo (for which you've got a c
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That's my understanding, that black holes and other massive objects are probably somewhat more numerous than current estimates would have it, but whatever is causing the significant gravitational effects we're measuring has to be very widespread, relatively evenly spread through galactic halos, but otherwise doesn't strongly interact with any other known forces. WIMPs are probably still the leader candidates, but with supersymmetical particles still an experimental no-show (which causes some problems, since
Small (Score:3)
Isn't 4 stellar masses pretty small for a black hole?
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Yes:
https://en.wikipedia.org/wiki/... [wikipedia.org]
Neutron star upper limit is 2.16 solar masses (Score:3)
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Short answer is no - at 2 and a bit solar masses a neutron star will collapse into a black hole. So 4 solar masses is not small.
https://en.wikipedia.org/wiki/... [wikipedia.org]
Compared to the billion stellar-mass black holes at the center of galaxies, yes 4 is small.
"Bright" to astronomers, not to ordinary people (Score:5, Informative)
The star system in question, HR 6819, is "bright" according to astronomers -- who can achieve very high signal-to-noise ratios even when breaking the light up with a high-resolution spectrograph. However, it is "faint" in ordinary human terms: at magnitude V = 5.4 or so, it would be barely visible if viewed from a rural site by someone who had been sitting outside in the dark for 10 or 20 minutes. It would be very difficult to pick out from other stars in the sky.
This message brought to you by "Pedants and Killjoys United."
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So if I have neighbor who has a pet macaque ... (Score:1)
that must mean that pet macaque's are common, or I'm special.
Yeah.
1,011 lightyears is very close! (Score:1)
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Almost everyone agreed on the Metric System, except the US and a few other flakes. There's always going to be flakes.
A semi-standard has formed around YYYY-MM-DD.
Neither is the private sector. Only friends are friends.
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I meant in terms of actual usage. An organization can label something as a "standard", but if too few use it, it's not really a standard.
This applies to *so many things* (Score:2)
- Partners
- Cars
- Jobs
- Unicorns. . .