Distant solar system pelted by comets
Eta Corvi is a bright star in the constellation Corvus (The Crow), and Spitzer recently observed that it had a bright ring of dust, at about the same distance as Earth is from the Sun. When infrared light from the ring was spectroscopically analysed, the dust was found to consist of rock, water ice and complex organic compounds – just like the comets we see in our own Solar System. The size and volume of the ring suggest that a truly massive comet may have smashed into a small rocky planet, and that what we are seeing is actually the resulting debris field.
The size of the collision, together with the Eta Corvi system’s youth (only a billion years – roughly a fifth of the age of our Solar system) has led researchers to speculate that we may be observing something similar to our own Late Heavy Bombardment, a turbulent period in the Solar System’s history when the slowly migrating orbits of the giant planets Jupiter and Saturn disturbed the Kuiper belt, throwing millions of comets out of their orbit. The results of this can be seen in the Moon’s scarred and cratered surface, testament to hundreds of thousands of collisions with massive objects (Earth would have been just as badly hit, but several billion years of tectonic activity and erosion from wind and water have erased all marks).
A paper describing the discovery and providing the details behind the speculation will be soon be published in the Astrophysical Journal.