A nearby star system is currently going through hell, as hinted at by NASA's Spitzer Space Telescope. Through its infrared eye, Spitzer has detected the dusty remains of comet impacts around the star Eta Corvi -- reminding us what it must have been like during the early evolution of our own solar system.
During our solar system's "Late Heavy Bombardment" (LHB) some four billion years ago, the inner planets were constantly peppered with massive comets impacting their surfaces. Earth would have been unrecognizable -- the planet's surface was a burning, molten mess; young atmosphere constantly punctuated by incoming cometary fragments.
Devoid of any eroding atmosphere, the moon's surface bears the scars of this epic cometary onslaught -- huge impact craters providing a reminder of how violent the "early years" of our solar system really was.
Despite the continuous cycle of cataclysmic impact events generating a hellish cauldron on Earth, the LHB has been linked with the genesis of life -- evidence points to a cometary source for the organic ingredients. Needless to say, the growing pains inflicted by the LHB on our planet is of huge importance to scientists.
Therefore, to spot the signs of similar cometary bombardments in other star systems would be pretty awesome. Not only would that help us understand the evolution of planetary systems orbiting other stars, it would provide a "time capsule" for us to have a glimpse of the early life of our own solar system. Of course, it would also give us an idea of how many other stars could be "ripe" for life (as we know it).
Now, scientists using observations by Spitzer have detected cometary Armageddon around Eta Corvi, a star some 50 light-years away in the constellation Corvus.
A ring of warm dust closely surrounds Eta Corvi, and after analysis of the dust, it appears to have the same chemistry as pulverized comets -- water ice, rock and organics. This provides the hint that the star may be going through a similar phase as the early solar system -- comets are careening inward, colliding with as-yet to be detected planetary bodies.
The star is approximately a billion years old, an age that scientists estimate is "just right" for a cometary hailstorm to occur.
"We believe we have direct evidence for an ongoing Late Heavy Bombardment in the nearby star system Eta Corvi, occurring about the same time as in our solar system," said Carey Lisse, senior research scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
Not only does the chemical fingerprint of the debris surrounding Eta Corvi demonstrate active impacts from a huge reservoir of comets, the dust's chemistry resembles that of the Almahata Sitta meteorite, fragments of which fell to Earth in Sudan in 2008. This suggests ancient material floating around in the solar system may have a common formation process as the material getting bashed up in Eta Corvi.
The similarities don't end there. There is evidence of another, cooler dusty ring further away from the star than the cometary impact debris, approximately 150 AU (150 times the Earth-sun distance) from Eta Corvi. The ring was detected in 2005 and could be the location of cometary nuclei, asteroids and other debris. The solar system has a region at roughly the same distance -- the Kuiper Belt.
Could this outer, cool ring be the source of the comets currently smashing through the inner Eta Corvi system? Possibly.
This is a fascinating study as Spitzer has gleaned an insight to the nature of a star system, possibly containing several planetary bodies -- after all, it was the migration of Jupiter and Saturn in the early history of the solar system that kick-started the LHB in the first place. Perhaps Eta Corvi is currently undergoing a similar process.
"We think the Eta Corvi system should be studied in detail to learn more about the rain of impacting comets and other objects that may have started life on our own planet," said Lisse.These findings have been accepted for publication in The Astrophysical Journal and were presented at the Signposts of Planets meeting at NASA's Goddard Space Flight Center in Greenbelt, Md.
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