On February 8, the fully automatic telescope KAIT in California discovered a new bright spot in the outskirts of the spiral galaxy UGC 2998, 150 million light years away. It was likely a supernova, a star that had exploded and whose light now had reached the Earth. However, bad weather made it impossible for KAIT to confirm that the new object was not just an asteroid or an instrumental error. The astronomers at KAIT requested observations from other telescopes around the world, and the first to successfully take images and confirm the new supernova was the AlbaNova telescope.

Magnus Persson and Robert Cumming at the Department of Astronomy observed the supernova in different filters only about one day after the first observations and could establish that the new light source showed all the signs of being a supernova. The supernova lies approximately at the same distance from the center of the galaxy UGC 2998 as the Sun from the center of the Milky Way. The supernova shines in a blue colour, in contrast to the stars in the galaxy which are generally old and red, and the other stars in the image which lie in our galaxy. Shortly after the explosion, such a supernova emits as much energy as the entire host galaxy.

One day later, astronomers on the Canary Islands took a spectrum using the considerably bigger Telescopio Nationale Galileo and concluded that the supernova was of type Ia, that is a white dwarf star which had exploded in a binary system. As Magnus' and Robert's confirmation was published in an astronomical telegram, the new supernova was named SN 2009ab, this year's 28th supernova. Last year a total of 278 supernovae were discovered, most of them even further away than SN 2009ab.

The Department of Astronomy uses the AlbaNova telescope mainly for education and instrumental development. This discovery shows that it is also possible to do scientifically interesting observations with the telescope, despite the limitations from Stockholm's bad weather and light pollution.
- It is exciting that the telescope is in full use. If we can do observations like these, we can do much more, says Robert Cumming.

Contact:

Robert Cumming, Tel: 08-5537 8542, robert@astro.su.se
Magnus Persson, magnusp@astro.su.se