UK (BBN)-Several dying stars in our galaxy contain the obliterated remains of asteroids. These hunks of rock must have fallen into the stars and been ripped to smithereens.
While the asteroids were mostly made of rock, they also contained a lot of water, according to scientists that have peered into the stars' atmospheres, reports BBC.
The finding could help explain how Earth got its water. It suggests there are many water-rich asteroids in the galaxy, which could supply water to planets and help nurture life.
“Our research has found that, rather than being unique, water-rich asteroids similar to those found in our Solar System appear to be frequent", says lead author Roberto Raddi of the University of Warwick in the UK.
The big question the team ultimately want to answer is where the Earth got its water from.
In its early days Earth may well have been a dry, barren place. A collision with a massive water-rich asteroid or comet could have supplied the water for the oceans.
To support that, Raddi needed to find evidence that water-rich asteroids are common, and for that he needed elderly stars.
When a star reaches the end of its life, it becomes a tiny "white dwarf". While it is small, its gravitational field is still strong enough to tear apart any asteroids or comets that fall into its atmosphere.
These collisions reveal what the rocks are made of. Each chemical element, like oxygen and hydrogen, absorbs light in slightly different ways. The team managed to detect these patterns in the light from white dwarfs, using the William Herschel Telescope in the Canary Islands.
By peering into dying stars as far as 500 light-years away, Raddi and his colleagues measured the chemical composition of the shattered asteroids. They were mostly made out of rock and water.
The fact that so many asteroids contain water "strongly supports the view" that the oceans we have today were created by asteroid impacts, says Raddi.
In recent years astronomers have found many planets outside our Solar System. The Kepler telescope alone has discovered over 1,000.
These exoplanets could possibly host life if they are roughly Earth-sized and located in the "Goldilocks zone" around their stars, where the temperature is neither too hot nor too cold for life.
Co-author Boris Gansicke, also of the University of Warwick, says water-filled asteroids could have delivered water to some of these alien planets.
That water would be essential for life as we know it to exist. But even if they do host life, Gansicke says, it will be very difficult for us to spot it.