Astronomers have found the broken leftovers of an asteroid holding large quantities of water circling a white dwarf star, known as GD 61. The astronomers think that the GD 61 planetary system may have once played host to habitable exoplanets. The planetary system resides 150 light-years from Earth.

According to a news release from the University of Cambridge, this is the first time in which both water and a rocky surface have been discovered together outside of our solar system. It is widely known that water and a rocky surface are key ingredients for habitable planets.

The finding of this watery asteroid supports the theory that our planet’s water came from water-rich asteroids smashing into Earth’s surface, and that a similar delivery system could have taken place in the GD 61 planetary system. The asteroid examined holds 26 percent water mass, which is similar to that of Ceres, the biggest asteroid in the primary belt of our solar system. According to astronomers, both asteroids are considerably more water-rich compared to our planet.

The astronomers contend that this is the first “reliable evidence” for water-rich, rocky planetary material in any extrasolar planetary system.

“The finding of water in a large asteroid means the building blocks of habitable planets existed – and maybe still exist – in the GD 61 system, and likely also around substantial number of similar parent stars,” said Jay Farihi, from Cambridge’s Institute of Astronomy.  “These water-rich building blocks, and the terrestrial planets they build, may in fact be common – a system cannot create things as big as asteroids and avoid building planets, and GD 61 had the ingredients to deliver lots of water to their surfaces.  Our results demonstrate that there was definitely potential for habitable planets in this exoplanetary system.”

The astronomers conclude that the water discovered likely originated from a planet at least 90 kilometers in diameter that once orbited the GD 61 star before it became a white dwarf approximately 200 million years ago. Astronomers have determined the size and density of exoplanets, but have not measured their composition.

The only technique to determine what a distant planet is composed of is to shred it into pieces, and nature does this for astronomers in the GD 61 planetary system. The astronomers utilized the Hubble Space Telescope’s Cosmic Origins Spectrograph to gather data on the broken leftovers of the water-rich asteroid. Detlev Koester, from the University of Kiel, then determined the chemical makeup of the watery asteroid using chemical analysis.

“These asteroids tell us that the GD 61 system had – or still has – rocky, terrestrial planets, and the way they pollute the white dwarf tells us that giant planets probably still exist there,” Farihi said. “This supports the idea that the star originally had a full complement of terrestrial planets, and probably gas giant planets, orbiting it – a complex system similar to our own.”