How likely are Primordial Black Holes to form in the early universe?
Answers
Answered by
0
mordial black holes are a hypothetical type of black hole that formed soon after the Big Bang. In the early universe, high densities and inhomogeneous conditions could lead sufficiently dense regions to undergo gravitational collapse, forming black holes. Yakov Borisovich Zel'dovich and Igor Dmitriyevich Novikov in 1966[1] first proposed the existence of such black holes, but the theory behind their origins was first studied in depth by Stephen Hawking in 1971.[2] Since primordial black holes did not form from stellar gravitational collapse, their masses can be far below stellar mass (c. 2×1030 kg). Hawking calculated that primordial black holes could weigh as little as 10−8 kg, about the weight of a human ovum.
Theoretical historyEdit
Depending on the model, primordial black holes could have initial masses ranging from 10−8 kg (the so-called Planck relics) to more than thousands of solar masses. However, primordial black holes with a mass lower than 1011 kg would have evaporated due to Hawking radiation in a time much shorter than the age of the Universe, so they cannot have survived until the present Universe. A noticeable exception is the case of Planck relics that could eventually be stable.[clarification needed]The abundance of primordial black holes could be as important as the one of dark matter, to which they are a plausible candidate. Primordial black holes are also good candidates for being the seeds of the supermassive black holes at the center of massive galaxies, as well as of intermediate-mass black holes.[3]
Primordial black holes belong to the class of massive compact halo objects (MACHOs). They are naturally a good dark matter candidate: they are (nearly) collision-less and stable (if sufficiently massive), they have non-relativistic velocities, and they form very early in the history of the Universe (typically less than one second after the Big Bang). Nevertheless, tight limits on their abundances have been set up from various astrophysical and cosmological observations, so that it is now excluded that they contribute importantly to the dark matter over most of the plausible mass range.
In March 2016, one month after the announcement of the detection by Advanced LIGO/VIRGO of gravitational waves emitted by the merging of two 30 solar mass black holes (about 6×1031 kg), three groups of researchers proposed independently that the detected black holes had a primordial origin.[4][5][6][7] Two of them found that the merging rates inferred by LIGO are consistent with a scenario in which all the dark matter is made of primordial black holes, if a non-negligible fraction of them are somehow clustered within halos such as faint dwarf galaxies or globular clusters, as expected by the standard theory of cosmic structure formation. The third group claimed that these merging rates are incompatible with an all-dark-matter scenario and that primordial black holes could only contribute to less than one percent of the total dark matter. The unexpected large mass of the black holes detected by LIGO has strongly revived the interest for primordial black holes with masses in the range of 1 to 100 solar masses. It is however still unclear and debated whether this range is excluded or not by other observations, such as the absence of micro-lensing of stars, the cosmic microwave background anisotropies, the size of faint dwarf galaxies, and the absence of correlation between X-ray and radio sources towards the galactic center.
In May 2016, Alexander Kashlinsky suggested that the observed spatial correlations in the unresolved gamma-ray and X-ray background radiations could be due to primordial black holes with similar masses, if their abundance is comparable to the one of dark matter.[8]
plzz mark as brainliest answer
Theoretical historyEdit
Depending on the model, primordial black holes could have initial masses ranging from 10−8 kg (the so-called Planck relics) to more than thousands of solar masses. However, primordial black holes with a mass lower than 1011 kg would have evaporated due to Hawking radiation in a time much shorter than the age of the Universe, so they cannot have survived until the present Universe. A noticeable exception is the case of Planck relics that could eventually be stable.[clarification needed]The abundance of primordial black holes could be as important as the one of dark matter, to which they are a plausible candidate. Primordial black holes are also good candidates for being the seeds of the supermassive black holes at the center of massive galaxies, as well as of intermediate-mass black holes.[3]
Primordial black holes belong to the class of massive compact halo objects (MACHOs). They are naturally a good dark matter candidate: they are (nearly) collision-less and stable (if sufficiently massive), they have non-relativistic velocities, and they form very early in the history of the Universe (typically less than one second after the Big Bang). Nevertheless, tight limits on their abundances have been set up from various astrophysical and cosmological observations, so that it is now excluded that they contribute importantly to the dark matter over most of the plausible mass range.
In March 2016, one month after the announcement of the detection by Advanced LIGO/VIRGO of gravitational waves emitted by the merging of two 30 solar mass black holes (about 6×1031 kg), three groups of researchers proposed independently that the detected black holes had a primordial origin.[4][5][6][7] Two of them found that the merging rates inferred by LIGO are consistent with a scenario in which all the dark matter is made of primordial black holes, if a non-negligible fraction of them are somehow clustered within halos such as faint dwarf galaxies or globular clusters, as expected by the standard theory of cosmic structure formation. The third group claimed that these merging rates are incompatible with an all-dark-matter scenario and that primordial black holes could only contribute to less than one percent of the total dark matter. The unexpected large mass of the black holes detected by LIGO has strongly revived the interest for primordial black holes with masses in the range of 1 to 100 solar masses. It is however still unclear and debated whether this range is excluded or not by other observations, such as the absence of micro-lensing of stars, the cosmic microwave background anisotropies, the size of faint dwarf galaxies, and the absence of correlation between X-ray and radio sources towards the galactic center.
In May 2016, Alexander Kashlinsky suggested that the observed spatial correlations in the unresolved gamma-ray and X-ray background radiations could be due to primordial black holes with similar masses, if their abundance is comparable to the one of dark matter.[8]
plzz mark as brainliest answer
Similar questions