Hubble measures deflection of starlight by a foreground Object

This illustration reveals how the gravity of a white dwarf warps space and bends the light of a distant star behind it.

White dwarfs are the burned-out remnants of normal stars. The NASA/ESA Hubble Space Telescope captured images of the dead star, called Stein 2051 B, as it passed in front of a background star. During the close alignment, Stein 2051 B deflected the starlight, which appeared offset by about 2 milliarcseconds from its actual position. This deviation is so small that it is equivalent to observing an ant crawl across the surface of a 1€ coin from 2300 kilometres away. From this measurement, astronomers calculated that the white dwarf's mass is roughly 68 percent of the sun's mass.

Stein 2051 B resides 17 light-years from Earth. The background star is about 5000 light-years away. The white dwarf is named for its discoverer, Dutch Roman Catholic priest and astronomer Johan Stein.