Monster black hole lurking in our galaxy
A super-massive object at the heart of the Milky Way is almost certainly a monster black hole, scientists said today.
New evidence appears to confirm that the black hole thought to lurk at the centre of our galaxy is real.
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.
Yet 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.
Writing in the journal Nature, the astronomers, led by Zhi-Qiang Shen, from Shanghai Astronomical Observatory in China, said the new radio image provided “strong evidence that Sgr A is a super-massive black hole”.
In an accompanying article, astronomer Christopher Reynolds, from the University of Maryland in College Park, USA, said scientists were now a step closer to the goal of actually taking a snapshot of a black hole.
The ultimate proof that black holes exist would be to obtain an image of the “shadow” produced by the event horizon, he said.
“The predicted diameter of the event horizon’s shadow for Sgr A is just 30 micro-arc seconds, or 120 millionth of a degree,” he said.
“This would be the apparent size of a tennis ball on the Moon when viewed from the Earth, and is about a factor of four smaller than the scales probed by the current VLBI experiments.”
