Posted on behalf of Ashley Yeager
For 16 years, astronomers have meticulously tracked the motions of 28 stars orbiting the Milky Way’s most central region. Two individual teams now say they have discovered indisputable evidence that a supermassive black hole sits at the heart of the galaxy.
“The centre of the galaxy is a unique laboratory where we can study the fundamental processes of strong gravity, stellar dynamics and star formation that are of great relevance to all other galactic nuclei, with a level of detail that will never be possible beyond our galaxy,” says Reinhard Genzel, leader of the team from the Max-Planck-Institute for Extraterrestrial Physics in Garching, Germany (European Southern Observatory press release).
He explained the long-term study provides the best empirical evidence that supermassive black holes do exist and allowed the two teams to peg the mass of the central black hole at four million solar masses. At that size, the central object “must be a black hole, beyond any reasonable doubt", says Genzel.
“We had the luxury of ignorance. It’s like we went from a teenager to an adult,” she says.
The two studies focused on a set of stars that orbit near the black hole because direct observation of a black hole is impossible, but the data also allowed the US and European groups to recalculate the distance to the centre of the galaxy to be 27,000 light-years. The research of both groups will appear in upcoming issues of the Astrophysical Journal.
Image: central parts of the Milky Way / ESO/S. Gillessen et al.