Hubble Discovers a Graveyard of Planets
The Hubble Space Telescope has discovered the rocky remains of planetary material scattered amongst the atmospheres of two white dwarfs in the Hyades star cluster. This suggests that these two stars may have once upon a time had their own planetary systems which at some point met with a dark fate.
Jay Farihi of the University of Cambridge and his team used Hubble’s Cosmic Origins Spectrograph (COS) to detect the faint signature of carbon and silicon in the two white dwarfs. The ratio of the two elements suggests that these “dead” stars are consuming rocky material of a similar chemical composition as Earth.
“The one thing the white dwarf pollution technique gives us that we won’t get with any other planet detection technique is the chemistry of solid planets,” said Farihi. “Based on the silicon-to-carbon ratio in our study, for example, we can actually say that this material is basically Earth-like.”
White dwarfs form after stars like our sun have used up all its fuel, expanded as a red giant and blown apart a planetary nebula. The white dwarf which is left behind can survive for billions more years. During the red giant stage, any planetary system that was once in orbit around the star will be severely disrupted. The extreme tidal stresses of the newly formed white dwarf will rip apart any orbiting body, grinding it to dust.
The significance of this latest finding is that by analyzing the light from white dwarfs, we aren’t only able to see evidence for planetary systems around stars in star clusters, we’re also looking into the future of our solar system. In a few billion years time, our own Sun will become a white dwarf, and Earth, as well as the other planets of our solar system, will join their own planetary graveyard.
