Spinning Neutron Star
This XMM-Newton X-ray image shows the portion of the sky around the pulsar named '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.