Astronomers Detect a Supermassive Black Hole

A team of US based researchers led by Chinese astronomer Shen Zhiqing from Shanghai Astronomical Observatory in China claim to have identified a "supermassive" black hole with a diameter 20 times that of the sun at the center of the Milky Way galaxy.

Black holes are collapsed stars with a mass so dense whose gravitational pull is so strong that nothing, not even light, can escape. Supermassive black holes contain the mass of millions, if not billions, of suns.
By observing radio emissions from the object, astronomers have also been able to measure it more accurately than ever before.

The results indicate that the "hole" is as wide as the Earth’s orbit round the Sun - considerably smaller than previous estimates suggested. It appears to contain a mass equivalent to four million Suns.
The findings seem to rule out an alternative theory that the object, known as Sagittarius A (Sgr A), is a cluster of super-dense dead stellar remnants known as neutron stars.

Matter at such a high density level would be very short-lived, collapsing further into a black hole in only around 100 years.

Astronomers believe all the evidence points towards Sgr A being a black hole - a region of space in which gravity is so strong that nothing can escape from it, not even light.

Scientists used 10 radio telescopes spread across the US and working as one gigantic antenna to capture the radio waves. The technique is known as Very Long Baseline Interferometry (VLBI).

Black holes emit radiation from matter swirling round the edge of the event horizon - the "point of no return" after which there is no escape from their gravity.
The observations showed that the object is four million times more massive than the sun and is no bigger than Pluto’s orbit.