Supermassive black holes to collide in a century - what impact will it have on Earth?

Astronomers have detected what seem to be two supermassive black holes on a collision course within a century, generating immense gravitational waves that will reach Earth.

This unusual event involves the black holes engaged in a ‘death spiral’ that will lead to a remarkable merger, and occurs in the galaxy Markarian 501, about 500 million light-years away.

Although it was previously classified as a blazar, a luminous galactic core usually driven by a single black hole, new analysis of years of radio telescope data reveals a more intricate scenario.

Researchers identified evidence of two strong jets of particles emanating from the galaxy’s core, each likely powered by a separate black hole, with masses estimated between 100 million and one billion times that of the Sun.

The findings, published in the journal Monthly Notices of the Royal Astronomical Society, reveal that the two black holes orbit each other approximately every 121 days. They are separated by a distance of just 250 to 540 times the distance between the Earth and the Sun, which is remarkably close considering their tremendous size.

Further support for the binary black hole theory came from observations in June 2022, when the system’s alignment caused light from one jet to be bent by the foreground black hole’s gravity, forming an Einstein ring.

This effect strengthened the case for the presence of two supermassive black holes.

Scientists believe that when the pair of black holes eventually merges, it will create powerful gravitational waves that can be detected from Earth, much stronger than those previously observed from smaller black hole collisions.

This merger would provide a unique opportunity to study extreme physics on a cosmic scale. However, any direct effects from the merger would be far beyond Earth, so we are safe for now.