RX J0822−4300, often referred to as a "Cosmic Cannonball", is a radio-quiet neutron star currently moving away from the center of the Puppis A supernova remnant at 672±115 km/s, making it one of the fastest moving stars ever found.

Astronomers used NASA's Chandra X-ray Observatory to observe the star over a period of 11 years to determine its speed.

[3] Although the cosmic cannonball is not the only hypervelocity star discovered, it is unique in the apparent origin of its speed.

Others may have derived theirs from a gravitational slingshot around the Milky Way's suspected supermassive black hole, Sagittarius A*.

Current theories fail to explain how such speeds can be attained from a supernova explosion.