Astronomers May Have Detected a 'Dark' Free-Floating Black Hole (berkeley.edu) 55
"If, as astronomers believe, the death of large stars leave behind black holes, there should be hundreds of millions of them scattered throughout the Milky Way galaxy," notes an announcement from the University of California at Berkeley. "The problem is, isolated black holes are invisible.
"Now, a team led by University of California, Berkeley, astronomers has for the first time discovered what may be a free-floating black hole by observing the brightening of a more distant star as its light was distorted by the object's strong gravitational field — so-called gravitational microlensing." The team, led by graduate student Casey Lam and Jessica Lu, a UC Berkeley associate professor of astronomy, estimates that the mass of the invisible compact object is between 1.6 and 4.4 times that of the sun. Because astronomers think that the leftover remnant of a dead star must be heavier than 2.2 solar masses in order to collapse to a black hole, the UC Berkeley researchers caution that the object could be a neutron star instead of a black hole. Neutron stars are also dense, highly compact objects, but their gravity is balanced by internal neutron pressure, which prevents further collapse to a black hole.
Whether a black hole or a neutron star, the object is the first dark stellar remnant — a stellar "ghost" — discovered wandering through the galaxy unpaired with another star.
"This is the first free-floating black hole or neutron star discovered with gravitational microlensing," Lu said. "With microlensing, we're able to probe these lonely, compact objects and weigh them. I think we have opened a new window onto these dark objects, which can't be seen any other way...." The analysis by Lam, Lu and their international team has been accepted for publication in The Astrophysical Journal Letters. The analysis includes four other microlensing events that the team concluded were not caused by a black hole, though two were likely caused by a white dwarf or a neutron star.
The team also concluded that the likely population of black holes in the galaxy is 200 million — about what most theorists predicted.
Notably, a competing team from the Space Telescope Science Institute (STScI) in Baltimore analyzed the same microlensing event and claims that the mass of the compact object is closer to 7.1 solar masses and indisputably a black hole. A paper describing the analysis by the STScI team, led by Kailash Sahu, has been accepted for publication in The Astrophysical Journal....
The astrometric data came from NASA's Hubble Space Telescope.... While surveys like these discover about 2,000 stars brightened by microlensing each year in the Milky Way galaxy, the addition of astrometric data is what allowed the two teams to determine the mass of the compact object and its distance from Earth.
"Now, a team led by University of California, Berkeley, astronomers has for the first time discovered what may be a free-floating black hole by observing the brightening of a more distant star as its light was distorted by the object's strong gravitational field — so-called gravitational microlensing." The team, led by graduate student Casey Lam and Jessica Lu, a UC Berkeley associate professor of astronomy, estimates that the mass of the invisible compact object is between 1.6 and 4.4 times that of the sun. Because astronomers think that the leftover remnant of a dead star must be heavier than 2.2 solar masses in order to collapse to a black hole, the UC Berkeley researchers caution that the object could be a neutron star instead of a black hole. Neutron stars are also dense, highly compact objects, but their gravity is balanced by internal neutron pressure, which prevents further collapse to a black hole.
Whether a black hole or a neutron star, the object is the first dark stellar remnant — a stellar "ghost" — discovered wandering through the galaxy unpaired with another star.
"This is the first free-floating black hole or neutron star discovered with gravitational microlensing," Lu said. "With microlensing, we're able to probe these lonely, compact objects and weigh them. I think we have opened a new window onto these dark objects, which can't be seen any other way...." The analysis by Lam, Lu and their international team has been accepted for publication in The Astrophysical Journal Letters. The analysis includes four other microlensing events that the team concluded were not caused by a black hole, though two were likely caused by a white dwarf or a neutron star.
The team also concluded that the likely population of black holes in the galaxy is 200 million — about what most theorists predicted.
Notably, a competing team from the Space Telescope Science Institute (STScI) in Baltimore analyzed the same microlensing event and claims that the mass of the compact object is closer to 7.1 solar masses and indisputably a black hole. A paper describing the analysis by the STScI team, led by Kailash Sahu, has been accepted for publication in The Astrophysical Journal....
The astrometric data came from NASA's Hubble Space Telescope.... While surveys like these discover about 2,000 stars brightened by microlensing each year in the Milky Way galaxy, the addition of astrometric data is what allowed the two teams to determine the mass of the compact object and its distance from Earth.
Interstellar travel hazard (Score:1)
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Or not. They make for some good gravity assisted slingshots, maybe...
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Or not. They make for some good gravity assisted slingshots, maybe...
So if you had a cluster of them, you could make the Kessel run in under 12 parsecs?
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So if you had a cluster of them, you could make the Kessel run in under 12 parsecs?
A beowulf cluster of them you say?
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Neeerd!
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I'd worry more about rogue planets [wikipedia.org]. They are 'dark' as well. But they have a physical radius that is larger then the 'safe approach distance' to a stellar black hole.
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As rough estimate, if we assume the danger radii were the same, the estimate is that the rogue planet count might be in "the trillions" so if it is 2 trillion, the threat is 10,000 times larger. Not sure what a good figure for the 'safe approach distance' to a stellar black hole is, but for a 10 solar mass black hole the tidal force at 1000 km is about 500 g's, and at 10,000 km it is 0.5 g's. So at some multiple of 1000 km, and the since the radius of solar planets ranges from 2440 km (Mercury) to 71500 km
Re:Interstellar travel hazard (Score:4, Interesting)
I suspect the "safe approach distance" of a black hole would be mostly irrelevant for purposes of any sort of realistic interstellar travel:
If you pass within many AU of one it's going to significantly alter your trajectory. Which given the mind-bogglingly enormous amounts of kinetic energy involved in interstellar voyages that take less than millenia, means that unless you've got a warp drive, or some other some sort of science fiction reactionless drive to correct your trajectory (and an enormous amount of excess stored energy on board to power it), you're unlikely to ever approach another star within the service life of your space craft.
You won't die right away, but you could argue that a long slow death by resource/energy starvation while stranded in the interstellar void without hope of rescue is the crueler fate.
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No it is not. The gravity of the black hole from AU away is no higher than its original star's, unless it acquired mass some other way afterwards. So exception aside, it's the same as traveling a few AU from the star before it became a black hole .. actually slightly less.
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Exactly - passing anywhere near a star is going to divert your path substantially - and even a degree or two likely means you can no longer reach your destination.
The black hole just means you didn't see it coming to correct for it at launch time.
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1) It's unlikely interstellar travel with ever be a thing.
2) It create an on-going event that affects the entire solar system, rather than a one-off
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It appears that these things may be a travel hazard one day.
They would be very easy to detect moving through space to navigate across interstellar voids, they distort space itself which easy to detect. You’d need some kind of massive ultra crazy thick shield on the leading edge of a ship that is narrow and extremely long with a slight taper because it’s taking massive hits from just about anything and at speed.
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Do tell how "space distortion" is easy to detect.
"Space distortion" is gravity of course, and microlensing is not easy, and is the only way we have to detect "space distortion", err, dark gravitating objects at a great distance.
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"Space distortion" is gravity of course, and microlensing is not easy, and is the only way we have to detect "space distortion", err, dark gravitating objects at a great distance.
Absolutely flat out false. It has a gravity well the size and shape of a star at least twice as massive then the sun, using pulsar timing as a cosmic GPS to see you’re drifting off course is something we could do with today’s tech many AU from the system, in the future perhaps out light years. Further, outside what was the stars surface radius the gravity potential is identically the same, the safest approach distance before your ship and or passengers would suffer damage from differential f
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However, given the outlandish energy requirements for interstellar travel, if you pass close enough to an unspotted black hole for it to alter your trajectory enough to be spotted that way, the damage is already done.
It's almost certainly far too late for you to correct your trajectory to rendevouz with your target star (or any other) with your available energy and reaction mass. Which means you'll be permanently stranded in interstellar space, facing death by resource starvation without any realistic hope
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In reality, it’s simply not possible for humans to travel interstellar distances between star systems on ships, even if you carry a large percentage of your mass as antimatter and react it somehow with matter you fin
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There's a number of ideas on how it could work - perhaps the simplest simply being world-ships. If we postulate a future where O'Neill cylinders are commonplace, it's only a matter of time until someone decides they don't like the neighbors and leave our Oort cloud for another star's. It might take thousands of years, but once you've mastered living in a mostly-closed system it's only a matter of ambition, and stocking up on enough supplies (especially energy) to tide you over until you can restock at the
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Your post did not make any sense at all.
Considering you claimed a few posts back that you can detect a black hole, and your parent asked "how?" - you completely failed to explain how you think you can detect one.
Regarding your "conservative guess" how big a "black hole is": you can calculate that with simple Newtonian math.
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Your post did not make any sense at all.
Considering you claimed a few posts back that you can detect a black hole, and your parent asked "how?" - you completely failed to explain how you think you can detect one.
It’s at a minimum twice as massive as our sun. As a star it was likely surrounded by a cloud of gas and debris, like earth, possibly still having some planets orbiting as well. It would be disrupting orbits and sending things off at odd trajectories within at least a few hundred AU, so it would be easy to detect from that perspective. Even if it is completely away from any matter, the mass will *massively* pull your ship off course, something that could be detected from how your ship moves through
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so it would be easy to detect from that perspective.
No it would not.
And no, itâ(TM)s not determined by Newtonian equations Lmafo. ... lol.
Yes it is, you only need Newton to determine how large the gravity is
I said a million mile diameter because if your ship was a kilometer long at that distance the tidal forces would start putting about 2000lbs of tensile force on the hull
No, it won't.
As long as you are not "inside" of the black hole, nothing special is happening.
For your damn space ship it is no dam
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so it would be easy to detect from that perspective. No it would not.
From the linked article you didn’t read: “The European Space Agency has explored the concept in recent years, with researchers calculating that a spacecraft could use pulsars to locate itself with a margin of error of 2 kilometres, even when flying 30 times farther from Earth than the Earth is from the Sun(1)” if you can’t understand that something that weighs 2x as much as our sun would cause accelerations that add up to more than a kilometer over the years of interstellar travel th
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I suggest to read some books about phyisics.
Or, improve your argumentation skills.
What exactly is wrong here:
No, it won't. As long as you are not "inside" of the black hole, nothing special is happening.
For your damn space ship it is no damn difference if an object of 2 solar masses 200 million miles away is:
a) a standard sun
b) a neutron star
c) a black hole
It is all the same: just gravity (the exact same gravity)
There is nothing wrong! Either learn physics, or at least make a lame attempt to argue against t
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I have no idea what a tide denier is.
I'm a sailor, I probably know more about tides than you do.
But feel free to explain "tide denier" to me.
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“ For your damn space ship it is no damn difference if an object of 2 solar masses 200 million miles away is:
a) a standard sun
b) a neutron star
c) a black hole“
It is all the same: just gravity (the exact same gravity)”
And after being told that the same forces the sun and moon put on the earth as tides are worse with a black hole because there is no surface anymore and they get strong enough to rip apart any matter before hitting the event horizon goes
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Perhaps you should read up how gravity works.
It is simple: the mass in question is the "problem". And you can/should calculate that in tons, mega tons or gazzilion amounts of tons.
Again:
it does not matter of that mass is:
a) a standard sun
b) a neutron star
c) a black hole
Because: the mass is the same, can't be so hard to grasp.
If you think otherwise, you have a lack of knowledge about physics :P
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tides are just an effect of gravity not being uniform because they get weaker with distance
Correct. And why are you telling me that?
That was never the topic.
Solar tidal forces on earth are large enough to make entire oceans move, at just above the suns surface (1m mile sphere) itâ(TM)s 6.5 million times our current tides and would squeeze the entire earth from the sides while even more force stretches it out like a piece of spaghetti. ...
That sentence does not really make any sense
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No, the sentence before made no sense, because it makes no sense. :P
I'm an expert about tides
Next to the suns surface (at 2x mass), at a half million miles from its center tides are 6.5 million times stronger than normal, the sun would rapidly destroy and spaghetify the entire earth like clay in a childâ(TM)s squeezing hand ... hint: https://en.wikipedia.org/wiki/... [wikipedia.org]
No it would not. The earth would simply drop into the sun
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Assuming you mean "microlensing is not easy to detect," that statement needs a lot of qualification. We detected microlensing in 1919 (and would have done in 1912 except for rain). The experiment has been duplicated by at least one amateur, using a 10 cm scope, but could be done using a 5-6 cm scope you can buy at Wal-Mart or pick up at a garage sale.
Detecting a black hole close enough to be a navigational problem would be easier because a) you'd be in space, no atmospheric distortion to worry about; b) it'
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If the black hole is close enough to significantly alter your course, wouldn't it also cause a lensing effect on your target star? I am no physicist, and frankly at the speeds involved, you might not be able to see in front well enough due to the risk of damage to the scope, but that would be one way to detect a black hole near your path.
Re: Interstellar travel hazard (Score:1)
Initial response (Score:1)
This is (Score:2)
Comforting. Imagine if one of these wandering black holes made its way near our solar system
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Comforting. Imagine if one of these wandering black holes made its way near our solar system
On the plus side, all of us would get to explore deep space.
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Yeah, while we freeze to death
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As a hazard to the solar system they are much less so than regular stars, which in addition to having gravity, emit a lot of heat and far more numerous.
One of the 200 million loose black holes has no more power to disrupt the Oort Cloud (say) than a regular star of similar mass. The disruption threat scales as the 2/3 power of mass (essentially its effective collision area), so a typical stellar black hole of 10 solar masses is only about 20 times more disruptive than a typical galactic star which would be
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You can see a star coming, you can't see a black hole
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So what? It's not like the solar system can dodge.
And either way you'll be able to see any deflected Oort-cloud objects decades before they reach the inner system (at least assuming we have the technology to do anything about it). In fact spotting them might be a lot easier without them being hidden in the glare of a passing sun.
I think it's cooler if it's a neutron star. (Score:3)
I won't be disappointed if this ends up narrowing to the low end of the mass range, indicating a neutron star rather than a black hole, because spotting one of those via microlensing is itself an achievement worth celebrating.
Black holes are not singularities (Score:4, Insightful)
Nope.
I was a long-time holdout against the idea that black holes could actually form, but between the gravitational wave detections from mergers, and the direct imaging of nearby supermassive black holes (as computer enhanced as they are), it's becoming an increasingly untenable position.
Black holes refer specifically to objects having an event horizon from which no events (including light emissions) can escape. And we have a whole lot of evidence that such things do in fact exist. Most compellingly to my thinking, we've detected the distinctive "ring-out" of black hole mergers - something that no other merging supermassive objects would generate.
What happens *within* that event horizon is the realm of pure speculation, and singularities are only one of many plausible options of what lies inside. Others include the holographic principle (all mass and information gets "embedded" in the event horizon itself) and "superstring fuzzballs" (in which the event horizon doesn't *technically* exist - instead the quantum wavefunctions are unable to collapse *quite* enough to form an event horizon, but all emitted photons are still near-infinitely red-shifted, so the observed result is much the same). Regardless, nothing that goes in can get out, so the question is academic.
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Have you noticed how much the "bloop" of the gravitational wave detection resembles the sound of an Euler disc finally running out of energy and falling flat? I mean it's not that surprising in a way, the loss of energy and ensuing increase in rotation kind of work in a similar fashion, but that wasn't enough to make me expect the similarity, and it's quite substantial.
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Just saying singularities don't exist without explaining why is not convincing.
How much mass does this add to the 'verse? (Score:2)
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Not even close. These are objects that were already mostly accounted for as "unseen conventional matter", and if I remember correctly, they constitute enough to make up about one percent of the "missing mass" at most.
Essays on social problems (Score:1)
baffled by the "free-floating" distinction (Score:2)
Implies that some black holes are stationary... relative to what?