XMM-Newton image of pulsar

This XMM-Newton X-ray image shows the portion of the sky around the pulsar RX J0720.4-3125, which is the central bright object appearing in red.

This spinning star has been observed by XMM-Newton over a few years, and has shown an unexpected variation in the observed thermal emission. According to astronomers, this effect is not due to a real variation in temperature, but instead to a changing viewing geometry. The pulsar is most probably a slowly tumbling star, which exposes different areas of the surface over time.