Hubble Telescope Could Now Determine the Mass of White Dwarf

For the first time ever, a team of astronomers used the sharp vision of NASA's Hubble Space Telescope to measure the mass of a dead star known as "white dwarfs."

Their measurements, published in the journal Science, utilized a novel method based on the bending of light near massive objects, or the deflection of light rays as they pass near the white dwarf.

"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, in a press release.

To test out their new method, the researchers observed the white dwarf Stein 2051B using the Hubble Space Telescope. The observation was conducted as the white dwarf passes in front of a background star. When the white dwarf and the background star aligned, the researchers observed that the white dwarf's gravity bent the light from the distant star, causing it to appear offset by about 2 milliarcseconds from its actual position.

The new method using the Hubble Telescope estimated the mass of Stein 2051B to be around 68 percent of the mass of our sun. The researchers compared this estimate with the theoretical prediction of the white dwarf's mass. The theoretical prediction was based on the known radius of Stein 2051B and the properties of the extremely dense matter that makes up the white dwarf.

Surprisingly, the estimate produced using the Hubble Space Telescope agrees with the theoretical prediction. The result of their observations also helped verify the theory of how a white dwarf's mass can be determined by its radius. Additionally, the new method also confirms that the internal composition of white dwarf is made mostly of carbon and oxygen.

With the positive results of the new method, astronomers plan to use the similar microlensing technique to Proxima Centauri, the nearest stellar neighbor of our solar system.