May 9, 2013
Earth-Like Planets Discovered In Atmospheres Of Dead Stars
[ Watch the Video: Ring of Rocky Debris Around a White Dwarf Star ]
Lee Rannals for redOrbit.com - Your Universe Online
The Hubble Space Telescope has helped astronomers spot signs of Earth-like planets in an unlikely place.
Astronomers say they found the planets sitting in the atmospheres of a pair of burnt-out stars in a nearby star cluster. The white dwarf stars are being polluted by debris from asteroid-like objects falling onto them, and the researchers say this discovery suggests that rocky planet assembly may be common in such clusters.
Hubble's observations helped identify silicon in the atmospheres of two white dwarfs, which is a major ingredient in the rocky material that makes up a large part of Earth. This silicon could have come from asteroids that were torn apart by the white dwarfs' gravity, and asteroids are often the building blocks of rocky planets. The rocky debris likely formed a ring around the dead stars, which eventually funneled the material inwards. The scientists say the debris detected around the white dwarfs suggests that terrestrial planets formed when these stars were born.
“We have identified chemical evidence for the building blocks of rocky planets,” says Jay Farihi of the University of Cambridge, who led the study. “When these stars were born, they built planets, and there´s a good chance that they currently retain some of them. The signs of rocky debris we are seeing are evidence of this — it is at least as rocky as the most primitive terrestrial bodies in our Solar System.”
The space telescope also detected low levels of carbon in the Hyades stars' atmospheres, offering yet another sign of a rocky planet.
“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,” Farihi says. “Based on the silicon-to-carbon ratio in our study, for example, we can actually say that this material is basically Earth-like.”
The scientists say they want to analyze more white dwarfs using the same technique to identify not only the rocks' composition, but also their parent bodies.
“The beauty of this technique is that whatever the Universe is doing, we´ll be able to measure it,” Farihi said. “We have been using the Solar System as a kind of map, but we don´t know what the rest of the Universe does. Hopefully with Hubble and its powerful ultraviolet-light spectrograph COS, and with the upcoming ground-based 30- and 40-meter telescopes, we´ll be able to tell more of the story.”
Astronomers using the Kepler Space Telescope announced the discovery of another Earth-like planet last month. The team said they discovered a planet 1.4 times the size of Earth called Kepler 62f in the Lyra constellation. The planet is one of two "super-Earths" discovered in Kepler 62's habitable zone.