Astronomers observe black hole bound stars in Milky Way

December 10th, 2008 - 12:55 pm ICT by ANI  

Washington, Dec 10 (ANI): Astronomers have observed the motions of 28 stars orbiting the Milky Ways most central region, which has helped them to study the supermassive black hole lurking there.

The 16-year long study has been conducted by a team from the Max-Planck-Institute for Extraterrestrial Physics in Garching near Munich, in Germany.

The new research marks the first time that the orbits of so many of these central stars have been calculated precisely and reveals information about the enigmatic formation of these stars, and about the black hole to which they are bound.

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, explained Reinhard Genzel, leader of the team from the Max-Planck-Institute for Extraterrestrial Physics.

The interstellar dust that fills the Galaxy blocks our direct view of the Milky Ways central region in visible light. So, astronomers used infrared wavelengths that can penetrate the dust to probe the region.

The Galactic Centre harbours the closest supermassive black hole known. Hence, it is the best place to study black holes in detail, said the studys first author, Stefan Gillessen.

The team used the central stars as test particles by watching how they move around Sagittarius A star, the name assigned to the black hole.

Just as leaves caught in a wintry gust reveal a complex web of air currents, so does tracking the central stars show the nexus of forces at work at the Galactic centre.

These observations can then be used to infer important properties of the black hole itself, such as its mass and distance.

The new study also showed that at least 95 percent of the mass sensed by the stars has to be in the black hole.

There is thus little room left for other dark matter.

Undoubtedly, the most spectacular aspect of our long term study is that it has delivered what is now considered to be the best empirical evidence that supermassive black holes do really exist. The stellar orbits in the Galactic Centre show that the central mass concentration of four million solar masses must be a black hole, beyond any reasonable doubt, said Genzel.

The observations also allow astronomers to pinpoint our distance to the centre of the Galaxy with great precision, which is now measured to be 27,000 light-years. (ANI)

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