They discover the first ‘stellar ghost’: it is possibly a floating black hole

Floating black holes currently only exist theoretically.


Astronomers have discovered for the first time what may be a  floating black hole , theorized as resulting from the death of a large isolated star, which until now are invisible.

The finding by a UC Berkeley-led team came from observing the brightness of a more distant star as its light is distorted by the object’s strong gravitational field, hence called gravitational microlensing.

two theories

The team, led by graduate student Casey Lam and Jessica Lu, an associate professor of astronomy, estimates the invisible compact object’s mass to be between 1.6 and 4.4 times that of the Sun.

Because astronomers think the leftover remnant of a dead star must weigh more than 2.2 solar masses to collapse into a black hole , the researchers caution that the object could be a neutron star rather than a black hole . Neutron stars are also very compact, dense objects, but their gravity is balanced by the internal pressure of the neutrons, preventing further collapse into a black hole.

Whether a black hole or a neutron star, the object is the first dark stellar remnant, a stellar “ghost”, discovered wandering the galaxy without pairing with another star.

“This is the first free-floating black hole or neutron star discovered with gravitational microlensing,” Lu said in a statement. “Using microlensing, we can probe these solitary, compact objects and weigh them. I think we’ve opened a new window on these dark objects, which can’t be seen any other way.”

Determining how many of these compact objects populate the Milky Way galaxy will help astronomers understand the evolution of stars, in particular how they die, and of our galaxy, and perhaps reveal whether any of the unseen black holes are black holes . primordial , which some cosmologists believe were produced in large numbers during the Big Bang.

The analysis by Lam, Lu and their international team has been accepted for publication in The Astrophysical Journal Letters .

Photometric data came from two microlensing studies: the Optical Gravitational Lensing Experiment (OGLE), which employs a 1.3-meter telescope in Chile operated by the University of Warsaw, and the Microlensing Observations in Astrophysics (MOA) experiment. , which is mounted on a 1.8-meter telescope in New Zealand operated by Osaka University. (EuropePress)