Supernova 1987a

The Tarantula Nebula before Supernova 1987a

The Tarantula Nebula after Supernova 1987a

Before (left) and after (right) images of the region near Supernova 1987a. The supernova glows bright in the lower right corner. The upper left region is the Tarantula nebula, a giant cloud of gas from which new stars are born. The stars in the nebula is what causes the gas to glow the reddish colour, a characteristic of hydrogen. Images: David Malin (AAO)

On February 23rd, 1987 Astronomers were alerted to a bright star suddenly appearing in the sky. It was named Supernova 1987a, since it was the first detected supernova of the year. Supernova 1987a was a core-collapse supernova that occurred in the Tarantula nebula, a stellar nursery located in one of our nearest neighbours, the Large Magellanic Cloud, which is only 160,000 light years away. Since it occurred at such a close proximity to the Earth, it was the brightest supernova observed since the telescope of invented, easily visible to the naked eye.

Supernovae only occur once every few hundreds of years in galaxies like the Milky Way and the Large Magellanic Cloud. Since galaxies are so distant, most supernovae are extremely faint and difficult to study.  However, due to its brightness, 1987a lead to a wealth of scientific study, and became one of the most important events in the history of astronomy. It may be centuries before we observe another supernova as bright as 1987a.

 The Anglo-Australian Telescope was used to make extensive measurements of Supernova 1987a using a large variety of techniques. The types of observations made by the AAT included:

  • Spectroscopy – To monitor changing conditions
  • Photography – To identify the precursor star and monitor the expanding light echoes.
  • Infrared Observations – To look at the dust around the system.
  • Speckle observations – Allows for a clearer view of the size and shape of the debris.
  • Polarimetry – Gives indirect indications of size and shape of the supernova.
  • Photometry – A measurement of brightness.

Similar to how water ripples can reflect off surfaces in a pond. Clouds of gas between us and the supernova can reflect the light from the supernova back towards us, arriving at a later time, just like an echo.

 An image showing the light echos from Supernova 1987a. 

The yellow rings are the light echoes. The dark spots are the stars that have been subtracted from the image.
Image: David Malin (AAO)