NASA discovers new black hole in Milky Way

While astronomers do not know its precise distance,they think the object resides about 20,000 to 30,000 light-years away in the galaxy8217;s inner region.

The satellite detected a rising tide of high-energy X-rays from a source toward the centre of Milky Way and the outburst,produced by a rare X-ray nova,announced the presence of the black hole.

8220;Bright X-ray novae are so rare that they8217;re essentially once-a-mission events and this is the first one Swift has seen,8221; said Neil Gehrels,the mission8217;s principal investigator,at NASA8217;s Goddard Space Flight Center.

8220;This is really something we8217;ve been waiting for,8221; Gehrels said.

An X-ray nova is a short-lived X-ray source that appears suddenly,reaches its emission peak in a few days and then fades out over a period of months.

The outburst arises when a torrent of stored gas suddenly rushes toward one of the most compact objects known,either a neutron star or a black hole.

Ground-based observatories detected infrared and radio emissions,but thick clouds of obscuring dust have prevented astronomers from catching Swift J1745-26 in visible light.

8220;The pattern we8217;re seeing is observed in X-ray novae where the central object is a black hole. Once the X-rays fade away,we hope to measure its mass and confirm its black hole status,8221; said Boris Sbarufatti,an astrophysicist at Brera Observatory in Milan,Italy.

The black hole must be a member of a low-mass X-ray binary LMXB system,which includes a normal,Sun-like star. A stream of gas flows from the normal star and enters into a storage disk around the black hole.

In most LMXBs,the gas in the disk spirals inward,heats up as it heads toward the black hole,and produces a steady stream of X-rays.