Four-in-one: telescopes join forces to spot a dim star in a black hole’s clutches

Technique could help to determine the spin of the supermassive black hole at the centre of our Galaxy.

A ‘super telescope’ that combines the powers of four separate telescopes has spotted a dim star dancing close to the supermassive black hole at the Milky Way’s centre.

To observe objects near the black hole, the GRAVITY instrument at the Very Large Telescope in Chile combines infrared light from the facility’s four eight-metre telescopes to achieve better sensitivity and resolution than can be provided by the individual components. Feng Gao, then at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, Thibaut Paumard at the Paris Observatory and their colleagues borrowed an algorithm from radio astronomy to help process GRAVITY’s signals from the galactic centre.

The faint star the researchers spotted is called S62. It has been observed before, but only when it appeared to be farther from the black hole and so was easier to see against the glare of radiation emitted by material spiralling into the black hole.

The team says the approach might make it possible to find new stars orbiting so close to the black hole that they could provide a long-awaited revelation: how fast it spins.


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