Hubble has been in service for over 25 years and it continues to produce spectacular images of the universe. The latest release by NASA and ESA is a spectacular image of WR 31a, a large dying star, and its blue bubble nebula.
The nebula is made mostly of lighter elements like hydrogen and helium, and it was formed about 20,000 years ago when WR 31a stopped fusing hydrogen in its core. The object is propelled forward by intense stellar winds, which are expanding the nebula at a rate of over 60 kilometers (38 miles) per second.
WR 31a is located 30,000 light-years from Earth in the constellation of Carina, the Keel. It’s a Wolf-Rayet (WR) star, a special class of stellar objects that live fast and die young. WR stars are massive, at least 20 times the mass of the Sun, and they burn through their fusion fuel very quickly.
The intense stellar winds are not exclusive to WR 31a. In their final phases of their lives, all WR stars develop stellar winds that blow away their outer layer. In just 100,000 years they can lose half their mass. WR stars end in spectacular supernovae and their nebula goes into enriching the next generation of stars.
WR stars are some of the hottest, most massive, and most luminous stars we know. They have a surface temperature between 30,000 and 200,000 kelvins and they shine with several thousand times the luminosity of the Sun. The heaviest and most luminous observed star so far, R136a1, is a WR star. It has a mass of 256 solar masses and a luminosity of 8.7 million Suns.