Hubble resolves the White Dwarf trivia
Unraveling the mysteries of the brightest star in the nighttime sky Sirius also known as the Dog Star, in unique details, an international lineup of astronomers has used the Hubble Space Telescope to isolate light from the white dwarf called Sirius B.
The burned-out astral is located in the winter constellation Canis Major and the trace is a distant yet faint companion of the luminous blue-white Dog Star, Sirius.
The research confirms that the stellar spark is about as massive as the sun but smaller than the Earth. The study should help astronomers to measure precisely the white dwarf’s mass based on how its strong gravitational field alters the wavelengths of light emitted by the star and how stars evolve.
The small star has a surface temperature of about 25,200 °C - hotter than Sirius, which is about 10,500 °C. It is also so dense that its gravity slows down the light leaving its surface, stretching it into longer, redder wavelengths. Space Telescope Imaging Spectrograph (STIS) measured this "gravitational red shift" to calculate the white dwarf’s mass, which is about the same as the Sun’s.
Studying Sirius B has challenged astronomers for more than 140 years," said Martin Barstow of England’s University of Leicester, leader of the observing team. "Only with Hubble have we at last been able to obtain the observations we need, uncontaminated by the light from Sirius, in order to measure its change in wavelengths.
"Accurately determining the masses of white dwarfs is fundamentally important to understanding stellar evolution," said Barstow.
At 8.6 light-years away, Sirius is one of the nearest known stars to Earth. Stargazers have watched Sirius since antiquity. Its little companion, however, was not discovered until 1862, when it was first glimpsed by astronomers probing Sirius through one of the most powerful telescopes of that time.
Details of the work were reported in the October 2005 issue of the Monthly Notices of the Royal Astronomical Society.
