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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: 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.