14 DAY TRIAL // After discovering the smallest brown dwarf about to form a solar system, astronomers have succeeded to capture the closest white dwarf.
The image captured with the Hubble Space Telescope shows Sirius A, the brightest star in our nighttime sky, along with its faint, tiny stellar companion, Sirius B.
Astronomers overexposed the image of Sirius A [at centre] so that the dim Sirius B [tiny dot at lower left] could be seen.
The cross-shaped diffraction spikes and concentric rings around Sirius A, and the small ring around Sirius B, are artifacts produced within the telescope's imaging system.
At 8.6 light-years away, Sirius A is one of the nearest known stars to Earth.
White dwarfs are the leftover remnants of stars similar to our Sun. They have exhausted their nuclear fuel sources and have collapsed down to a very small size. Despite being the brightest white dwarf known, Sirius B is about 10,000 times fainter than Sirius itself, making it difficult to study with telescopes on Earth.
Although smaller than Earth, from the measurements made by the researchers, it resulted that Sirius B has 98% of the Sun's mass.
"Studying Sirius B has challenged astronomers for more than 140 years," said Martin Barstow of the University of Leicester, U.K., who is the leader of the observing team.
"Accurately determining the masses of white dwarfs is fundamentally important to understanding stellar evolution. Our Sun will eventually become a white dwarf. White dwarfs are also the source of Type Ia supernova explosions that are used to measure cosmological distances and the expansion rate of the universe. Measurements based on Type Ia supernovae are fundamental to understanding 'dark energy'," Martin Barstow added.
Sirius B has a diameter of 12,000 kilometers, less than the size of Earth, but is much denser. Its powerful gravitational field is 350,000 times greater than Earth's, meaning that a 68 kilogram person would weigh 25 million kilograms standing on its surface. Light from the surface of the hot white dwarf has to climb out of this gravitational field and is stretched to longer, redder wavelengths of light in the process.