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from the a-proton-and-a-neutron-walk-into-a-black-hole dept.
Scientists propose plan to determine if Planet Nine is a primordial black hole:
Dr. Avi Loeb, Frank B. Baird Jr. Professor of Science at Harvard, and Amir Siraj, a Harvard undergraduate student, have developed the new method to search for black holes in the outer solar system based on flares that result from the disruption of intercepted comets. The study suggests that the LSST[*] has the capability to find black holes by observing for accretion flares resulting from the impact of small Oort cloud objects.
"In the vicinity of a black hole, small bodies that approach it will melt as a result of heating from the background accretion of gas from the interstellar medium onto the black hole," said Siraj. "Once they melt, the small bodies are subject to tidal disruption by the black hole, followed by accretion from the tidally disrupted body onto the black hole." Loeb added, "Because black holes are intrinsically dark, the radiation that matter emits on its way to the mouth of the black hole is our only way to illuminate this dark environment."
[...] The upcoming LSST is expected to have the sensitivity required to detect accretion flares, while current technology isn't able to do so without guidance. "LSST has a wide field of view, covering the entire sky again and again, and searching for transient flares," said Loeb. "Other telescopes are good at pointing at a known target, but we do not know exactly where to look for Planet Nine. We only know the broad region in which it may reside." Siraj added, "LSST's ability to survey the sky twice per week is extremely valuable. In addition, its unprecedented depth will allow for the detection of flares resulting from relatively small impactors, which are more frequent than large ones."
[*] LSST:
The Vera C. Rubin Observatory, previously referred to as the Large Synoptic Survey Telescope (LSST), is an astronomical observatory currently under construction in Chile. Its main task will be an astronomical survey, the Legacy Survey of Space and Time (LSST). The Rubin Observatory has a wide-field reflecting telescope with an 8.4-meter primary mirror that will photograph the entire available sky every few nights. The word synoptic is derived from the Greek words σύν (syn "together") and ὄψις (opsis "view"), and describes observations that give a broad view of a subject at a particular time. The observatory is named for Vera Rubin, an American astronomer who pioneered discoveries about galaxy rotation rates.
Journal Reference:
A. Siraj, A. Loeb. Searching for Black Holes in the Outer Solar System with LSST, https://arxiv.org/abs/2005.12280v2
(Score: 5, Insightful) by fyngyrz on Saturday July 11 2020, @06:26PM (6 children)
FFS, Planet 9 is Pluto [fyngyrz.com], IAU twits.
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(Score: 0) by Anonymous Coward on Saturday July 11 2020, @07:12PM
Would that be Plan 9?
(Score: 3, Touché) by Thexalon on Saturday July 11 2020, @08:43PM (3 children)
If Pluto should be a planet, then so should Ceres, so that would make Pluto planet 10, not planet 9.
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(Score: 2) by takyon on Saturday July 11 2020, @08:49PM (1 child)
Fourth-Largest Object in the Asteroid Belt, Hygiea, Could be Classified as a Dwarf Planet [soylentnews.org]
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(Score: 1) by khallow on Sunday July 12 2020, @12:13PM
The characteristic of planet is that it is physically large/massive enough that no matter what the would-be planet is made of, it has a strong enough gravity to pull itself into a spherical shape (ignoring rotation and tidal force distortions). Ceres is crudely of the minimal size and mass needed.
(Score: 3, Touché) by fyngyrz on Saturday July 11 2020, @10:56PM
Ya should have followed the link. 😊
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(Score: 2, Interesting) by Anonymous Coward on Sunday July 12 2020, @04:24PM
To quote one of my professors. "When the astronomers demoted Pluto, they did not consult the planetary geologists." Never heard his opinion on Ceres, but he did consider Pluto a planet type.
(Score: 2) by takyon on Saturday July 11 2020, @06:36PM
It could also just find any giant planets immediately after the survey begins, if they exist and are close enough.
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(Score: 0) by Anonymous Coward on Saturday July 11 2020, @06:39PM (1 child)
At bottom, basically need to watch a line in the sky
https://www.aanda.org/articles/aa/full_html/2016/03/aa28227-16/F6.html [aanda.org]
How hard can that be?
Maybe a preliminary starshot mission could look for it.
(Score: 2) by takyon on Saturday July 11 2020, @06:59PM
I don't think Starchips could find it unless you accidentally aimed one right at the object. I'm guessing preliminary starchips would be propelled by much weaker lasers than the Proxima/Alpha Centauri proposal and take decades to travel hundreds of AU.
We should just see what Rubin, Subaru, and other telescopes come up with by 2022. And a future successor to Rubin should be made larger and put in space to survey for even fainter objects.
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(Score: 4, Interesting) by Opportunist on Saturday July 11 2020, @07:32PM (12 children)
I don't claim to know a lot about nuclear physics, but so far I was under the impression that for a black hole to form, you would need a LOT of mass because the gravity of the object has to overcome the other forces that keep the matter from collapsing into itself, e.g. you'd have to have SO much gravity that it overpowers the mutual rejection of the positively charge nuclei.
How is this supposed to work with small objects?
(Score: 5, Informative) by HiThere on Saturday July 11 2020, @08:02PM (2 children)
That's why they said "primordial". If the big bang hypothesis is correct, and there's a lot of supporting evidence, then there's an argument that a lot of really small black holes of varying mass should have been produced during the process.
Personally, I think these primordial black holes unlikely, because many of them would have been evaporating over the recent millennia, and they'd emit radiation that hasn't been detected. OTOH, possibly this wouldn't happen. There's a chance that when a hole gets small enough, it stops being able to emit particles, and since it's now too small to swallow anything (well, perhaps a neutrino) it's in stasis. In that case the radiation wouldn't be emitted, because the holes never finish evaporating. Notice the large number of "possibly"s in this paragraph. And I'm not a physicist of any stripe. I can hear arguments made, but I can't really evaluate them.
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(Score: 0) by Anonymous Coward on Saturday July 11 2020, @11:47PM (1 child)
black holes evaporating? Evaporating into where?
(Score: 2) by takyon on Sunday July 12 2020, @11:13AM
Hawking radiation [wikipedia.org]. The "evaporation" process is the black hole gradually converting mass into energy (emitted particles), while shrinking in radius, until it's all gone.
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(Score: 4, Interesting) by Anonymous Coward on Saturday July 11 2020, @09:29PM (5 children)
You can make a black hole of any size. You just have to squeeze it down to smaller than the Schwarzschild radius for the amount of mass you are using. r = 2GM / c2 . The gravitational constant G is pretty small and c2 is pretty big, so that makes r really tiny unless M is huge.
Black holes emit Hawking radiation in inverse proportion to their size, so small ones radiate faster, leading to a runaway effect where little ones go bang. Practical minimum size is about a planetary mass. A lunar mass one would be in rough equilibrium with outgoing Hawking radiation matched with CMB radiation falling in.
Theory says any number of them of all sizes could have been formed during the big bang, but the counterargument is that we should be seeing occasional unexplained explosions as the smaller ones hit the runaway point. Astronomy has yet to detect any such explosions.
(Score: 1) by khallow on Sunday July 12 2020, @04:40AM
(Score: 2) by Opportunist on Sunday July 12 2020, @10:50AM (3 children)
The problem is the "squeeze it down" part. Normal black holes (well, as normal as objects as crazy as these can be) do this by gravity, but with such small ones, gravity alone won't cut it. So what squeezes them down?
(Score: 0) by Anonymous Coward on Sunday July 12 2020, @11:55AM (2 children)
The Big Bang supposedly had sufficient pressure to do it in the first few micro? milli? seconds. Not for long anyway. Hence primordial - nothing since has made small black holes, except possibly some Kardeshev II or III aliens.
(Score: 2) by Opportunist on Sunday July 12 2020, @05:33PM (1 child)
And one of those superspecialawesome black holes made it to our solar system? Erh... yeah.
(Score: 0) by Anonymous Coward on Sunday July 12 2020, @06:01PM
Not really my field but as I understand it, if it made any at all then the Big Bang should have made lots of them. If there were lots of them then we should see more gravitational lensing events. We don't, so people tend to assume that there were none.
(Score: -1, Troll) by Anonymous Coward on Saturday July 11 2020, @09:44PM (2 children)
OK, I can explain. For starters we're calling them Black holes now instead of black holes to show respect for all the African-American astrophysicists killed the the police. As for your question, the Black hole forms when one particle kneels on another until it overcomes the opposing force.
(Score: 0) by Anonymous Coward on Saturday July 11 2020, @11:51PM
Well... That cracker shit name still be totally racist. They should be called ebony chasms.
(Score: 2) by Opportunist on Sunday July 12 2020, @10:53AM
And here I was thinking it got its name from the smelly place you pulled that shit out of.
(Score: 1, Informative) by Anonymous Coward on Sunday July 12 2020, @07:19PM
Shouldn't a primordial black hole of the sizes that have been hypothesised be emitting copious amounts of Hawking radiation? One about the mass of a small asteroid, say 10 billion kilograms, would have a temperature of some 12 trillion kelvin, giving it a radiation peak at 7e23 Hz (very high energy gamma) emitted at something like three terawatts. I'd think that Chandra and other similar instruments would have already noticed such a powerful source of high energy gamma radiation even if it is out in the Oort Cloud.
More massive primordial black holes are rather a hard sell though. They're supposed to have been formed from irregularities in the early universe, but the best evidence is that space-time of the early universe was very close to being flat and homogeneous. If planet nine exists it's much more likely to be a regular planet of some sort.
(Score: 2) by bzipitidoo on Monday July 13 2020, @11:18PM
Primordial black hole is the most far out idea I've heard yet for what Planet 9 could be.
Someone else proposed a ring of material. Basically, the mass of Planet 9 spread out over Planet 9's orbit.
I am thinking of notions such as, could Planet 9 be a double planet? Instead of one planet of 5 Earth masses, two planets of 3 Earth and 2 Earth masses respectively, orbiting one another as far apart as 1 AU. That would certainly make the system harder to find. There's really no reason to suppose it could be a double planet, I just thought it was a fun idea.