Alternate Names

V821 Ara

Type

Stellar mass

Location

In the constellation Ara, the altar

Distance

27,000 light-years

Mass

5.8 to 10 times the mass of the Sun

Size

Diameter 20-35 miles (31-60 km), equal to the size of a large city

Discovery Methods

• Detection of an accretion disk
• Measuring the motions of a companion star

This animation shows the link between the optical and X-ray light from GX 339-4. The inset shows optical images of the system, while the tracing shows changes in its infrared energy. They show that the visible light dims shortly before the X-ray energy spikes. The entire sequence covers less than 10 seconds. [ESO]

This document was last modified: January 13, 2011.