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Thursday, December 24, 2009

Black hole is closer than we thought

It turns out that we’re only 7800 light years away from the black hole in the Cygnus constellation.  That’s just over half the distance we had thought it was.

V404 Cygni forms a binary pair with a black hole, a region from which nothing can escape, not even light.  Black holes can be detected from the radiation emitted as gas from nearby stars spirals into it. In this case, the black hole is stealing hot gas from its partner V404 Cgyni. An international team of astronomers used the High Sensitivity Array (HSA) telescopes to detect the emitted radio waves every three months for a year.

The cosmologists then used trigonometric parallax to determine the distance to the black hole.  This method relies on parallax shift, or the apparent shift in position of an object when viewed from a different vantage point.  You can see this for yourself by closing one eye and lining up a finger in front of a distant object.  If you switch eyes, the object will have appeared to jump to the side.  In this case, the Earth’s movement around the sun provided the different vantage points.

The new distance tells scientists that the black hole formed in a supernova, and that it and its partner star are speeding through space together at 40 km/second.

Concept drawing of black hole.