For the very first time, a group of astrophysicists have found evidence of a water-dense planetary body outside of our solar system, zipping round a white dwarf.
The study was performed by researchers working at the University of Cambridge and the University of Warwick, situated in the United Kingdom, with the findings subsequently published in the journal Science. The group conducted analysis of the dust particulate and shattered remains around a white dwarf star, some 170 light years away.
Lead author of the study, Jay Farihi, based at Cambridge University’s Institute of Astronomy, explained how these remnants provide chemical clues that they were once part of a larger, watery terrestrial body, before briefly talking about the implications of such a finding:
“Those two ingredients – a rocky surface and water – are key in the hunt for habitable planets outside our solar system so it’s very exciting to find them together for the first time outside our solar system.”
Using a combination of observations collected by the Hubble Space Telescope, as well as the large telescopes located at the W. M. Keck Observatory, the research team discovered large amounts of oxygen, inferring that the debris once belonged to a much larger body, consisting of approximately 26 percent of water by mass. Contrasting this with our planet, for example, water accounts for less than 0.1 percent of the Earth’s mass.
According to a recent press release posted by Warwick University, although water has indeed been known to exist as an atmospheric constituent of various gas giants outside of our solar system, they highlight that their research represents the first occasion it has been located in a rocky body.
GD 61 White Dwarf
GD 61 is located approximately 150 million light years away from Earth, believed to have been formed approximately 200 million years ago. White dwarfs are remarkably dense, compact stellar remains of low mass stars, comprising the burned-out cores of these collapsed cosmic beasts.
When stars expend all of their nuclear fuel, they become unstable. Massive stars, that have a high mass, will often explode producing either a black hole or a neutron star. Meanwhile, those stars that do not possess enough mass will gradually shed its outer layers, spending the remainder of its life as a white dwarf.
These white dwarfs are very dimly lit objects, perceived amongst the darkness of space, and contain incredibly dense degenerative matter. Eventually, it is hypothesized that the Sun will also end up as a white dwarf, just like GD 61.
Building Blocks of Habitable Planets
Farihi, alongside his fellow researchers, assimilated data from ultraviolet spectroscopy to perform further investigation of the atmosphere around GD 61; they employed the
Cosmic Origins Spectograph instrument, located aboard Hubble for their research observations. When exploring the white dwarf’s surrounding, the team were able to identify iron, oxygen, magnesium and silicon, evidence that infers GD 61 destroyed a massive rocky body and, subsequently, absorbed much of its constituents.
The team calculated the rocky body to comprise 26 percent water, after discovering the presence of huge amounts of oxygen. Furthermore, based upon the absence of carbon, it is likely that the body was an asteroid; comets contain large amounts of carbon, whereas asteroids do not.
The group’s preliminary data suggests the asteroid to have been around 56 miles in diameter. During the press release, Farihi suggests that a rock the size of Vesta – a protoplanet situated in our solar system – was spun towards GD 61, by neighboring planets that were in orbit father away.
Farihi ruminated over the implications of his team’s remarkable findings, explaining that the discovery of water in the remnants of the debris around GD 61 shows that the “building blocks of habitable planets,” at one time, existed in the GD 61 system. Farihi suggests that these building blocks may even still exist in the region.
The researchers posit that the asteroid that was ripped apart by GD 61 could have been the type of body that delivered water to Earth, whilst it remained relatively young and dry. Ultimately, however, the finding of both a rocky body and an abundance of water suggests, given the correct conditions, this region of space could have been home to habitable, Earth-like planets.
By: James Fenner