Scientists have finally pinned down a monster black hole lurking at the heart of the Milky Way. The cosmic plughole has long been suspected but is hidden behind vast clouds of interstellar dust in our galaxy.
It revealed that it is four million times the mass, or size, of the sun. The discovery also provided an accurate measurement of the distance to the centre of the galaxy – 27,000 light-years.
The German team made the breakthrough by watching the movements of 28 stars in orbit around the centre of the galaxy. This allowed them to measure the violent forces being exerted by the black hole, which astronomers call Sagittarius A*.
They carried out their observations in the infrared region of the spectrum to allow them to penetrate the dusty veil in the Milky Way. They compare their studies to watching swirling leaves caught by a gust of wind which reveal powerful air currents.
One of the stars was seen to be circling the black hole so quickly that it completed one orbit within the 16 years of the project, according to the report to be published in the Astrophysical Journal.
The astronomers are puzzled as to how the stars came to be in the orbits observed. They are much too young to have travelled far, but are not thought able to have formed in their current orbits within the powerful tidal pull of the black hole.
Team member Stefan Gillessen said: “The Galactic Centre harbours the closest supermassive black hole known. Hence, it is the best place to study black holes in detail.” The astronomers began their observations in 1992 using the SHARP camera attached to European Southern Observatory’s 3.5-metre New Technology Telescope at the La Silla observatory in Chile.
More observations have subsequently been made since 2002 using two instruments mounted on ESO’s 8.2-metre Very Large Telescope. Astronomers are developing other techniques, including a form of cosmic shades, to observe these enigmatic monsters.
In March we revealed that space telescopes have combined to take a snapshot of the sky revealing the presence of 1,000 massive black holes.
Picture: The central region of our galaxy as observed in the near-infrared with ESO’s Very Large Telescope. (Credit: ESO/S. Gillessen et al).
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