Strange X-ray source is the brightest pulsar ever observed

A composite image of the galaxy M82, composed of x-ray images from the NuSTAR telescope (seen in purple) and the Chandra X-ray Observatory (blue), and optical images from the NOAO 2.1 meter telescope (gold).

X-ray: NASA/CXC/Univ. of Toulouse/M.Bachetti et al, Optical: NOAO/AURA/NSF

A new observation of the M82 galaxy has turned up a surprise—a previously undiscovered, incredibly bright object. The object, called M82 X-2, is bright enough to be classified as an ultra-luminous X-ray source, or ULX. It sits close to its previously discovered sibling, M82 X-1, near the core of M82. The discovery, which was made by NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array) and the Chandra X-ray Observatory, has provided new clues about the nature of that mysterious class of objects.

X-2 turns out to be the brightest pulsar ever discovered—so bright that it challenges current models of how pulsars work.

NuSTAR had initially been pointed toward M82 in the hope of observing a new supernova, and the team of researchers had no idea that they would happen upon a new ULX. They were surprised to discover a pulsating ULX amid a group of bright X-ray sources. To clarify which source was producing the pulsations, the Chandra X-ray Observatory observed the region, successfully separating X-2 from the noise.