The Crab nebula, and the pulsar at its center, is one of the most studied objects in astronomy. They are the remnants of a supernova that exploded in the year 1054. The Crab pulsar is one of few pulsars that is visible in optical and infrared light, making it important for our understanding of how pulsars emit such rediation. In a new article, Andreas Sandberg and Jesper Sollerman (Department of Astronomy, Stockholm University) have studied several aspects of the pulsar and its closest surroundings.

Previous studies have, among other things, suggested that the pulsar is rapidly becoming fainter in infrared, which is a sign of so called synchrotron self-absorption. Now it has been seen, however, that the pulsar shines brightly also in infrared. This gives important clues on how the pulses, which have a period time of only 33 milliseconds, arise. The results indicate that the pulses originate from a region that lies further away from the rotating neutron star than previously believed.

The study also shows that the pulsar is very slowly becoming fainter, something that is connected with its slowing rotation. The researchers have also investigated a "knot" of radiation, which lies very close to the pulsar, and which has proved able to change its brightness and very red colour dramatically over a few years.

The results are partly based on data from the VLT in Chile, taken with high resolution and the latest adaptive optics, as well as infrared data from the space telescope Spitzer.

Original article:
Optical and infrared observations of the Crab Pulsar and its nearby knot Contact:

Andreas Sandberg,
Jesper Sollerman, Tel: 08-5537 8554,