Supernova 2011Fe was discovered on 24 August 2011 by the Palomar Transient Factory. It occurred in the spiral galaxy Messier 101, and was of Type Ia. This was a very important supernova discovery, as it allowed scientists to calibrate Type Ia supernovae and use them as standard candles. This calibration is essential for determining the distances to galaxies and the expansion rate of the Universe.
The light curve of SN 2011Fe showed that it peaked at about 15 days after explosion, with a maximum apparent magnitude of 11.9 (about 10 times fainter than what can be seen with the naked eye). After peak brightness, the light curve declined steadily over the next few months. By January 2012, SN 2011Fe had faded to mag 16.4, making it too faint to be seen without a large telescope.
Scientists were able to study SN 2011Fe in great detail because it happened relatively closeby (only 21 million light years away) and also because it was discovered very soon after explosion. High-resolution spectra taken with Keck/LRIS showed that SN 2011Fe had unusually low velocity ejecta for a Type Ia supernova – only 5500 km/s compared to typical velocities of around 10000 km/s . This suggested that SN 2011Fn could be used as a “low-velocity outlier” when studying other Type Ia supernovae .
SN 2011Fn is therefore an important event for our understanding of how stars explode and how we can use them to measure cosmological parameters such as the age and size of the Universe.