Alternate Names

IL Lupi

Type

Stellar mass

Location

In the constellation Lupus

Distance

25,000 light-years (7500 parsecs)

Mass

9 times the mass of the Sun

Size

Diameter roughly equal to the size of a large city

Discovery Methods

• Detection of an accretion disk

4U 1543-47

Once every decade or so, the star system 4U 1543-47 erupts, producing a powerful torrent of X-rays. The first eruption was recorded by the Uhuru X-ray satellite in 1971, with subsequent bursts in 1983, 1992, and 2002. At its maximum, the system shines up to 20 million times brighter in X-rays during these outbursts than during the years-long quiet time between them.

The system consists of the black hole plus a companion star, discovered after the 1983 eruption, that is roughly twice as massive as the Sun. The two orbit each other once every 1.1 days.

Because they are so close together, the gravity of the black hole distorts the shape of its companion star, making it taper toward the black hole so that its profile resembles an egg. The tapered end is so close to the black hole that hot gas flows off the star's surface and toward the black hole. The material forms a thin spiral known as an accretion disk.

The gas continues to build up in the accretion disk until it reaches a critical density. The gas then quickly heats up, making the accretion disk shine brighter. Gas in the inner portion of the disk suddenly plunges into the black hole; in the moment before it crosses the event horizon, it shines brightest of all. This "big gulp" produces an outburst of energy not just in X-rays, but in radio waves and other forms of energy.

The accretion disk's magnetic field funnels some of the superhot gas, known as plasma, into "jets" of charged particles that shoot into space from the black hole's north and south poles. The jets from 4U 1543-47 are shorter and weaker than those produced by many other erupting black holes, however.

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This document was last modified: March 14, 2012.