The star in question, WR 136, has been shedding successive layers of particles and gas as it readies itself for a possible supernova explosion. The Hubble image provides an unprecedented look into the interactions of these stellar cast-offs and, in the process, is offering new insights into the life cycle of stars and their impact on the evolution of our galaxy. The results of this study appear in the June issue of the Astronomical Journal.
WR 136 is surrounded by a bubble of gas dubbed the Crescent Nebula. Hubble's view covers a small region at the northeast tip of the structure, which is roughly three light-years across. A picture taken by a ground-based telescope at the lower right of the image shows almost the entire nebula.
WR 136 created this web of luminous material during the late stages of its life, when it gently puffed away some of its bulk. More recently, the star has developed a fierce wind — a stream of charged particles released from its surface. When the stellar wind collided with the material around the star, it swept it up into a thin shell. That shell broke apart into the network of bright clumps seen in the image.
As the stellar wind continues slamming into more material, it creates a kind of visual sonic boom. In the cosmic setting, though, this boom is visible as the thin blue skin surrounding the nebula.
As the stellar wind continues to muscle past the clumps of material, the surrounding pressure will drop, leading to a steady decline in brightness. Later, the shell may be compressed and begin glowing again, this time as the powerful blast wave of the star completely destroys itself in a powerful supernova explosion.
The nebula resides in the constellation Cygnus,
4,700 light-years from Earth. The observations were taken in June 1995 with
Hubble’s Wide Field and Planetary Camera 2, and released today.