Hubble views the colourful veil
Like living things, stars grow old and die. But heavyweight stars don’t fade away quietly. Instead, they go out with an enormous bang. All that remains after the brilliant light show of a supernova explosion is a hot, glowing shell of gas that flees the scene of the star’s death at high speed.
One of the most beautiful examples of a supernova remnant is the Veil Nebula, a faint ring of debris in the constellation of Cygnus. Pictures taken with the NASA-ESA Hubble Space Telescope show in remarkable detail the shattered remnants of a giant star. Smoke-like wisps of gas are all that remain.
The Hubble images show intertwined, rope-like streamers of gas in three different segments of the Veil Nebula. The colourful filaments result from the tremendous energy released when the fast-moving debris from the explosion ploughs into its surroundings. Shock waves, created by gas moving at 600,000 km per hour, heat the gas to millions of degrees.
Two distinctive features are visible in the Hubble images: sharp, linear filaments and broad clouds. This is because we see them from different angles. The filaments correspond to an edge-on view of a thin shock front, while the clouds correspond to a face-on view. The colours indicate light coming from different atoms excited by the shock waves: blue shows oxygen, green shows sulphur, and red shows hydrogen.
The supernova explosion occurred 5,000 to 10,000 years ago, when our ancestors would have seen a sudden increase in the star’s brightness until it matched the crescent Moon.