Planets as small as Earth are hard to spot orbiting other stars; obtaining good data about their chemical composition is well beyond the abilities of our current instruments. However, a new study of four white dwarfs provides hints about the fate of planets like our own. It's not an especially happy one, as the astronomers found that the chemical composition of debris on the white dwarfs closely matches that of Earth.

These observations, which will be published in the Monthly Notices of the Royal Astronomical Society, focused on four "polluted" white dwarfs, which have traces of elements not usually seen in this type of star. B. T. Gänsicke et al. studied their ultraviolet spectrum using the Hubble Space Telescope, and determined they contained excessive amounts of silicon, aluminum, iron, and other elements, with abundances similar to those found on Earth. These results indicate that rocky debris has crashed onto the white dwarfs—debris that may possibly be from the destruction of a planet similar in composition to Earth.

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Astronomers have pulled off an interesting magic trick and made two planets appear. Since they appeared in a planetary system that already had seven, it gives that planetary system a total of nine, making it the most planet-rich system we're aware of (since our own has only eight). It may further its lead in the future, as well, as the authors conclude that there's not enough data yet to identify an Earth-sized planet.

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With better and better observations of exoplanets—planets orbiting other stars—the dream of discovering life on other worlds is much closer to reality than it has ever been before. However, in many ways we're still in the early days of exploration: despite the number of exoplanet discoveries, information about their surfaces and chemical compositions are still scanty.

A test run for inferring the presence of life on other planets would be to confirm the existence of life on Earth, using only astronomical measurements of some sort. Partly due to the lack of appropriate space-based instruments, nobody has made a successful observation of life on Earth using data that's as limited as what we'd get when studying another world. A new study by Michael F. Sterzik, Stefano Bagnulo, and Enric Palle attempts just that with an unusual source of light: Earthshine, or light from Earth reflected back to us by the Moon.

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