Mass of a black hole
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Mass of a Black Hole: Insights from Recent Research
Stellar-Mass Black Holes: Observations and Measurements
GW170104: A 50-Solar-Mass Binary Black Hole Coalescence
The gravitational-wave event GW170104, observed on January 4, 2017, provided significant insights into the masses of stellar-mass black holes. The event was caused by the merger of two black holes with masses of approximately 31.2 and 19.4 solar masses (M☉) . This observation highlights the typical mass range for stellar-mass black holes formed from the collapse of massive stars.
Methods for Measuring Stellar-Mass Black Holes
The mass of stellar-mass black holes in X-ray binaries is often measured using the dynamical method, which relies on Kepler’s laws. This method has been instrumental in understanding the mass distribution of these black holes, which typically range from a few to several tens of solar masses .
Intermediate-Mass Black Holes: Bridging the Gap
GW190521: A Binary Black Hole Merger with a Total Mass of 150 M☉
The event GW190521, detected on May 21, 2019, revealed the merger of two black holes with masses of 85 and 66 solar masses, resulting in a remnant black hole of approximately 142 solar masses . This discovery is significant as it provides evidence for the existence of intermediate-mass black holes (IMBHs), which bridge the gap between stellar-mass black holes and supermassive black holes.
Formation and Growth of Intermediate-Mass Black Holes
Intermediate-mass black holes are thought to form through the merger of smaller black holes or through the collapse of massive stars in dense star clusters. The detection of GW190521 supports the theory that IMBHs can form through the merger of stellar-mass black holes .
Supermassive Black Holes: Limits and Growth
Physical Limits to Black Hole Mass
There is a theoretical upper limit to the mass of a black hole, beyond which it cannot grow through luminous accretion of gas. This limit is approximately 5 × 10^10 M☉ for typical parameters, but can reach up to 2.7 × 10^11 M☉ in extreme cases . This limit is crucial for understanding the growth of supermassive black holes in the centers of galaxies.
Early Universe Quasars and Supermassive Black Holes
Observations of quasars at high redshifts (z ≈ 5.8 to 7.5) have revealed black hole masses around 4.6 × 10^9 M☉. These black holes are over-massive relative to their host galaxies, suggesting rapid growth in the early universe . The accretion rates and Eddington ratios of these quasars indicate that supermassive black holes can grow quickly, leading the formation of massive galaxies.
Primordial Black Holes: Constraints and Implications
Constraints on Primordial Black Holes
Primordial black holes (PBHs) are hypothesized to have formed in the early universe and can have a wide range of masses. Current constraints suggest that PBHs can constitute a significant fraction of dark matter in specific mass windows, such as around 25-100 M☉ . These constraints are essential for understanding the role of PBHs in cosmology and their potential contribution to dark matter.
Conclusion
The mass of black holes spans a wide range, from stellar-mass black holes formed from collapsing stars to supermassive black holes in the centers of galaxies. Recent observations, such as GW170104 and GW190521, have provided valuable insights into the masses and formation mechanisms of these enigmatic objects. Understanding the mass limits and growth processes of black holes is crucial for unraveling the mysteries of their origins and their role in the universe.
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