What happens when a white dwarf—the zombie remnants of a small star—meets an asteroid?
Well, it’s bad news for the asteroid. The rock is ripped apart, and the star’s gravity pulls the remaining gaseous debris and dust particles into a ring around its body, forming a stellar counterpart to planets like Saturn. Ultraviolet rays from the hot, dense zombie star illuminate the gas in the surrounding band, giving off a dark red glow.
According to the European Southern Observatory (ESO), only seven white dwarfs with orbiting disks have been found. And thanks to the ESO’s Very Large Telescope and other observatories, a group of researchers has obtained the first image of such a body, SDSS J1228+1040.
“When we discovered this debris disk orbiting the white dwarf back in 2006, we could not have imagined the exquisite details that are now visible in this image, constructed from twelve years of data—it was definitely worth the wait,” said Boris Gänsicke, of the Univ. of Warwick.
Between 2003 and 2015, the researchers observed changes in the light from the white dwarf and its surrounding material. Several instruments, including the Ultraviolet and Visual Echelle Spectrograph, were used. And a technique called Doppler tomography, which operates on principles similar to medical tomography used in hospitals, allowed the team to map the white dwarf’s orbiting disk.
“The image we get from the processed data shows us that these systems are truly disk-like, and reveal many structures that we cannot detect in a single snapshot,” said Christopher Manser, of the Univ. of Warwick’s Astrophysics Group. “The image shows a spiral-like structure which we think is related to collisions between dust grains and the debris disk.”
Manser noted the astronomy world has known about disks orbiting white dwarfs for over 20 years, but this marks the first instance of visualizing the phenomenon.
The researchers concluded from observations that the disk was lopsided and not yet circular.
“The diameter of the gap inside of the debris is 700,000 km, approximately half the size of the sun and the same space could fit both Saturn and its rings, which are only around 270,000 km across,” said Manser. “At the same time, the white dwarf is seven times small than Saturn but weighs 2,500 times more.”
Astronomers believe studying white dwarfs, such as J1228+1040, may provide clues to the future environment of the solar system. After all, the sun is slated to burn out in 7 billion years.
