Comets orbiting a distant star have been found to contain water, marking the first time the ingredient considered key to life has been discovered in objects circling a star other than our sun, scientists announced Wednesday.
The discovery adds weight to the theory that other planetary systems may be similar to our own and may contain chemicals that are essential to the formation of life as we know it.
Scientists have no way of knowing whether life ever existed on any comets or planets orbiting this particular star, known as CW Leonis and located 3,000 trillion miles from Earth in the constellation Leo.
But they're certain that no life could exist there now. That's because, as it burns out the last of its nuclear fuel, the star has swelled and increased in luminosity, engulfing nearby objects and melting comets in orbits as distant as Neptune is from the sun, releasing the water that astronomers spotted using a radio telescope in outer space.
"Ironically, the existence of these bodies is measured through their destruction," said Gary Melnick, chief scientist on the project and an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
Melnick said the discovery is of particular importance because if there was a reservoir of water farther from the star, there could have been water closer to the star, bolstering the idea that life may have existed outside our solar system.
Comets are believed to have helped build life on Earth, Melnick and other scientists said. Besides bringing water to Earth's oceans, they are also thought to have transported important chemicals as they hurtled through Earth's atmosphere in past eons.
The researchers, who published their work in today's edition of the journal Nature, achieved the difficult task of testing the composition of an orbiting object in another planetary system. Until now, scientists knew mostly about the presence of large gaseous bodies orbiting other stars--but not what the objects contained. That's because the planets were detected only by measuring the effects of their gravity on the star.