A blue bubble in space

The wolf-rayet star wr 31a.
The Wolf-Rayet star WR 31a.
ESA / Hubble / NASA / Judy Schmidt

The star at the centre of this image from the Hubble Space Telescope, known as WR 31a, is about 30,000 lightyears away from Earth in the constellation of Carina.

The distinctive blue bubble appearing to encircle WR 31a is a Wolf–Rayet nebula – an interstellar cloud of dust, hydrogen, helium and other gases. Created when speedy stellar winds interact with the outer layers of hydrogen ejected by Wolf–Rayet stars like WR 31a, these nebulae are frequently ring-shaped or spherical. The bubble – estimated to have formed around 20,000 years ago – is expanding at a rate of around 220,000 kilometres per hour.

The lifecycle of a Wolf–Rayet star only lasts a few hundred thousand years. Despite beginning life with a mass at least 20 times that of the Sun, these stars typically lose half their mass in less than 100,000 years. 

WR 31a is no exception. It will eventually end its life as a spectacular supernova, and the stellar material expelled from its explosion will later nourish a new generation of stars and planets.

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