Scientists using Chandra data have found evidence for an effect predicted by Einstein called gravitational redshift in a pair of orbiting stars across the Galaxy. Previously, astronomers found incontrovertible evidence for this phenomenon in our Solar System, but it has been challenging to observe it in more distant objects. The Chandra data show this effect in the spectra, or amounts of X-rays across wavelengths of 4U 1916-053. Shifts of the signatures of iron and silicon are seen. This system contains a neutron star and companion star in a remarkably close orbit.

The intriguing system known as 4U 1916-053 contains two stars in a remarkably close orbit. One is the core of a star that has had its outer layers stripped away, leaving a star that is much denser than the Sun. The other is a neutron star, an even denser object created when a massive star collapses in a supernova explosion. The neutron star (grey) is shown in this artist's impression at the center of a disk of hot gas pulled away from its companion (white star on left).