Core Concepts
The recent discovery of the most massive black hole, Gaia BH3, in the Milky Way galaxy provides insights into the formation and dynamics of black holes in the early universe and their potential encounters with Earth.
Abstract
The content discusses the recent discovery of the nearest black hole to Earth, called Gaia BH3, by the Gaia collaboration. Gaia BH3 has a mass of 33 times the Sun and is believed to have originated from the collapse of a star in the Milky Way's halo, where the oldest stars reside.
The author, Avi Loeb, provides context on the significance of this discovery. He notes that Gaia BH3's mass is similar to the first black holes detected through gravitational waves by LIGO in 2015, suggesting that the early universe was efficient at producing massive black holes. Loeb's past research has suggested that the first stars were much more massive than present-day stars, leading to the formation of these massive black holes.
Loeb also discusses the potential for black hole encounters with Earth. He estimates that the Milky Way's disk contains about 100 million black holes, and one of them likely came within the outer envelope of the Oort cloud during the lifetime of the Solar system. While a dormant black hole would have had a negligible impact, a black hole accreting mass from a companion star could have produced significant X-ray flux.
The content also explores the possibility of primordial black holes, which could have been produced shortly after the Big Bang and may have passed through Earth, though their impact would have been negligible. Loeb suggests that the nearest black hole that could be visited by interstellar tourists is about 30 light-years away, and a spacecraft made of sufficiently strong materials could withstand the gravitational stress of crossing the horizon of a black hole like Gaia BH3.
Ultimately, Loeb emphasizes that contemplating a journey to a black hole can have practical benefits, as it encourages a deeper appreciation for the preciousness of life.
Stats
Gaia BH3 has 33 times the mass of the Sun.
The first black holes detected by LIGO in 2015 had masses of 29 and 36 solar masses.
The iron-to-hydrogen ratio of Gaia BH3's companion is 320 times smaller than the solar value.
The Milky Way's disk is estimated to contain about 100 million black holes.
A black hole's encounter with the Oort cloud would have lasted tens of thousands of years.
A 10-meter scale spacecraft made of steel could withstand the gravitational stress at the horizon of a 33 solar mass black hole.
Quotes
"This black hole, called Gaia BH3, has 33 times the mass of the Sun, in striking resemblance to the masses of the first black holes detected through gravitational waves by LIGO in 2015 involving a merger of 29 and 36 solar masses."
"After formation, these black holes followed the collision-free dynamics of the dark matter and assembled into the extended halos of galaxies like the Milky Way."
"If primordial black holes make a significant contribution to dark matter and they have masses of mile-scale asteroids, then some of them may have passed through Earth during its lifespan."