Have astronomers discovered an invisible floating black hole?
Scientists believe after the death of giant stars, black holes are formed from the remains. Thus millions of black holes may be roaming in Milky Way.
Astronomers detect the presence of black holes from gravitational microlensing events where they begin to glow and distort the light coming from the star towards the centre of the galaxy. Using this technique, scientists have discovered a free-roaming black hole, for which they are gathering more data to confirm.
Millions of black holes in Milky Way
Scientists believe that after the death of giant stars, black holes are formed from their remains. If this theory is proved right, then it will be correct to believe that millions of black holes must be roaming in our Milky Way. But the biggest problem with them is that these black holes are not visible alone.
Team of astronomers from the University of California, Berkeley, has now discovered a free-floating black hole for the first time.
Distortion of light
Astronomers made this breakthrough by observing the brightness of light coming from a distant star. The light coming from there was being distorted by a body with a powerful gravitational field. This process is called Gravitational Microlensing.
Researchers led by Jessica Lu, associate professor of astronomy at UC Berkeley and graduate student Cassie Lam, estimated the mass of the body to be between 1.6 and 4.4, more massive than the Sun.
Possibility of a neutron star
Since astronomers think that the mass of a dead star must be more than 2.2 solar masses in order to collapse into a black hole, researchers are unable to rule out the possibility that this body could be a neutron star rather than a black hole. Neutron stars are also dense, and very condensed bodies, but their gravity is balanced due to internal neutron pressure and they do not compress further into black holes.
Whether it is a black hole or a neutron star, this body will be the first stellar 'monster' body with stellar remnants to move around the galaxy without being associated with another star. Lu said that this is the first free-floating black hole or neutron star discovered through gravitational microlensing.
Many secrets may be revealed
Researchers discovered this body through microlensing and also estimated its weight. They say that this will be an achievement to open a new dimension in the search for such lost bodies. Finding their number in the Galaxy will help astronomers understand the story of the evolution of stars.
This may also reveal why unseen black holes can be primordial black holes. Many astronomers think that primordial black holes were formed in large numbers during the Big Bang. The analysis of the researchers has been accepted for publication in the Astrophysical Journal Letters. It also includes four other microlensing events that did not involve black holes.
Another theory
Apart from this, the team of the Space Telescope Science Institute in Baltimore had also analysed the same event and claimed that the mass of this body would be about 7.1 solar masses and it must be a black hole. The paper of this study, led by Kailash Sahu, has also been accepted for publication in The Astrophysical Journal.
The interesting thing is that both the teams have used the same body data. Two different surveys had observed the same body, hence its two names. Not only this, both the observations have also derived different distances of this body from the Earth. In the new study, the researchers also found other indications such as the length of the lensing event, which indicate that this object may not be a black hole.