White Dwarf Star Stein 2051 B

Stellar Alignment Yields White Dwarf's Mass

Looks can be deceiving. In this Hubble Space Telescope image, the white dwarf star Stein 2051 B and the smaller star below it appear to be close neighbors. The stars, however, reside far away from each other. Stein 2051 B is 17 light-years from Earth; the other star is about 5,000 light-years away.

Astronomers made the Hubble observations of the white dwarf, the burned-out core of a normal star, and the faint background star over a two-year period. Hubble observed the dead star passing in front of the background star, deflecting its light. During the close alignment, the distant starlight 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 quarter from 1,500 miles away. From this measurement, astronomers calculated that the white dwarf's mass is roughly 68 percent of the sun's mass.

Stein 2051 B is named for its discoverer, Dutch Roman Catholic priest and astronomer Johan Stein.

About the colours

This image is a composite of separate exposures acquired by the WFC3/UVIS instrument on the Hubble Space Telescope. Two filters were used to sample different wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are: cyan F606W and orange F814W.

About the data

The image was created from Hubble data from proposals 13457 and 13850 P.I. K. Sahu (STScI).