Most massive black hole

The most massive observed black hole is TON 618, which has an estimated mass of 66 billion times the mass of the Sun.

TON 618 is located near the border of the constellations Canes Venatici and Coma Berenices, 10.8 billion light years from Earth.

It is a hyper-luminous quasar – a supermassive black hole at the centre of a distant galaxy, whose brightness is fuelled by gas traveling as fast as 7,000 km/s as it falls into the black hole.

Shining over 140 trillion times more brilliantly than the Sun, TON 618 is one of the brightest known objects in the universe.

It can be seen in the centre of the above image, captured by the Sloan Digital Sky Survey Data Release 9 (DR9), where it appears as the bluish-white dot.

TON 618 is ~2600 AU (approximately 390 billion kilometres) from one side of its event horizon to the other. With an average distance of 30 AU from the Sun to Neptune, this means TON 618 is big enough to swallow all the planets in our solar system more than 40 times over.

It is also 15,300 times more massive than Sagittarius A*, the black hole at the centre of the Milky Way.

Due to TON 618's extraordinary mass, some astronomers have proposed a new classification of “ultramassive black hole” for it.

TON 618 was first noted in a 1957 survey of faint blue stars by Mexican astronomers Braulio Iriarte and Enrique Chavira at the Tonantzintla Observatory. As quasars were not recognized until 1963, the exact nature of TON 618 remained a mystery to the astronomers, who listed it as entry number 618 in the Tonantzintla Catalogue.

In 1970, radio emissions coming from TON 618 were discovered, indicating that it was a quasar.

This was then confirmed by Marie-Helene Ulrich at the McDonald Observatory in Texas, USA, who obtained optical spectra of TON 618 showing emission lines typical of a quasar.

Header image credit: Sloan Digital Sky Survey