Albert Einstein’s theory has been used to practically measure weight of a white dwarf – something that the great physicist had said might not be practical.
Published in journal Science is a study wherein astronomers have described how they managed to estimate the mass of a white dwarf by measuring the deflection of light rays as they passed near the star. To achieve this, astronomers first used the sharp vision of NASA’s Hubble Space Telescope to determine how much light from the background star is the white dwarf bending.
Hubble observed the white dwarf, Stein 2051B, as it passed in front of a background star. During the close alignment, the white dwarf’s gravity bent the light from the more distant star, making it appear offset by about 2 milliarcseconds from its actual position.
This observation is the first time Hubble has witnessed this type of effect created by a star. The data provide a solid estimate of the white dwarf’s mass and yield insights into theories of its structure and composition.
“This measurement is a triumph for the Hubble Space Telescope, a wonderful confirmation of theoretical predictions, and a beautiful reprise of the Einstein solar eclipse observations of a century ago,” said team member Howard Bond, Professor of Practice in the Department of Astronomy and Astrophysics at Penn State, and Astronomer Emeritus at NASA’s Space Telescope Science Institute, the science operations center for the Hubble Space Telescope.
Bond compared the mass that the Hubble team determined for the white dwarf — 68 percent of the mass of our Sun — with the theoretical predictions of its mass, based on the known radius of the star and the properties of the extremely dense matter that makes up a white dwarf. “The agreement of the theoretical prediction with the measurement we were able to make with Hubble was astonishingly good,” Bond said.
The researchers plan to use Hubble to conduct a similar microlensing study with Proxima Centauri, our solar system’s closest stellar neighbor.