The lazily winding spiral arms of the spectacular galaxy NGC 976 fill the frame of this image from the NASA/ESA Hubble Space Telescope. This spiral galaxy lies around 150 million light-years from the Milky Way in the constellation Aries. Despite its calm appearance, NGC 976 was host to one the most dangerous astronomical phenomena ever recorded – a supernova blast. These violent and cataclysmic events occur at the end of the lives massive stars. They can even outshine whole galaxies in a very short time. Supernovae are responsible for the death of massive stars but they also create heavy elements that are incorporated in later generations of stars or planets.
Supernovae are also a useful aid for astronomers who measure the distances to faraway galaxies. Some supernova explosions release a lot of energy into space, which allows astronomers to calculate their distances based on how bright they are when seen from Earth. This image – which was created using data from Hubble’s Wide Field Camera 3 – comes from a large collection of Hubble observations of nearby galaxies which host supernovae as well as a pulsating class of stars known as Cepheid variables. Supernovae and Cepheids are both used to measure astronomical distances. Galaxies that contain both supernovae and Cepheids provide valuable natural laboratories for comparing the two methods.