Compass and scale image of WR 122 (NaSt1)

This visible-light image taken by NASA's Hubble Space Telescope reveals a pancake-shaped disk of gas around an extremely bright star in our Milky Way galaxy. The disk glows brightly in the light of ionized nitrogen.

The central star is nicknamed "Nasty 1," derived from its catalogue name of NaSt1. Nasty 1 is thought to be a Wolf-Rayet star, a massive, rapidly evolving star weighing well over 10 times the mass of our Sun. The star is losing its hydrogen-filled outer layers quickly, exposing its super-hot and extremely bright helium-burning core.

Nasty 1 is thought to have a companion, and gravitational interactions between them may have created the gas disk. Both stars are heavily obscured by gas and dust in the disk. Hubble observations suggest that as Nasty 1 sheds its weight, some of the mass is falling onto a companion star and some is leaking into space, forming the disk. The vast structure is nearly 2 trillion miles wide. The disk is clumpy because astronomers think the outbursts occur sporadically. The knot at left of center is an unusually bright clump of gas. The image is tinted blue to bring out details in the disk.

Astronomers were surprised to find the disk-like structure, which has never been seen before around a Wolf-Rayet star in our galaxy. The star may represent a brief transitory stage in the evolution of massive stars.

The Nasty 1 system may be as close as 3,000 light-years from Earth.

The observations were taken in April 2013 with the Wide Field Camera 3.