Comets have been caught battering an exoplanet for the first time, new observations suggest. If the existence of the planet is confirmed, the finding means that the impacts are bringing water and organic material – the essential ingredients for life – to a world that lies in the habitable zone around its star.
The cometary shower is taking place around a bright star about 60 light years away called Eta Corvi, which is visible to the naked eye in the northern sky.
The Spitzer Space Telescope spotted the infrared glow of a band of dust three times as far from Eta Corvi as Earth is from the sun. Carey Lisse of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, and his colleagues analysed the spectrum of light from this glow and found that it contains water, organics and rock.
The composition and amounts seen suggest that several small comets, or a single large one, crashed into a rocky world weighing up to a few times the mass of the Earth, creating a trail of debris behind the planet. For example, the dust seems to contain nanodiamonds, which form when organic materials smack into each other at ludicrous speeds, and bits of silica – essentially glass, which forms when rock melts and then quickly re-freezes.
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