Star Wars-like planetary system discovered

Scientists have for the first time found evidence of a Tatooine-like rocky planetary system - Luke Skywalker's home world in the Star Wars series - about 1,000 light-years away.
The system called SDSS 1557 consists of the remains of shattered asteroids orbiting a double sun consisting of a white dwarf and a brown dwarf, researchers said.
The discovery led by researchers at University College London (UCL) in the UK is remarkable because the debris appears to be rocky and suggests that terrestrial planets like Tatooine might exist in the system.
To date, all exoplanets discovered in orbit around double stars are gas giants, similar to Jupiter, and are thought to form in the icy regions of their systems.

In contrast to the carbon-rich icy material found in other double star systems, the planetary material identified in the SDSS 1557 system has a high metal content, including silicon and magnesium.
These elements were identified as the debris flowed from its orbit onto the surface of the star, polluting it temporarily with at least 1.1 trillion tonnes of matter, equating it to an asteroid at least four kilometres in size.

"Building rocky planets around two suns is a challenge because the gravity of both stars can push and pull tremendously, preventing bits of rock and dust from sticking together and growing into full-fledged planets," lead author Jay Farihi from UCL said.

"With the discovery of asteroid debris in the SDSS 1557 system, we see clear signatures of rocky planet assembly via large asteroids that formed, helping us understand how rocky exoplanets are made in double star systems," said Farihi.
The discovery came as a complete surprise as the team assumed the dusty white dwarf was a single star but Steven Parsons from University of Sheffield in the UK, an expert in double star (or binary) systems noticed the tell-tale signs.
"We know of thousands of binaries similar to SDSS 1557 but this is the first time we have seen asteroid debris and pollution.

"The brown dwarf was effectively hidden by the dust until we looked with the right instrument, but when we observed SDSS 1557 in detail we recognised the brown dwarf's subtle gravitational pull on the white dwarf," said Parsons.
The team studied the binary system and the chemical composition of the debris by measuring the absorption of different wavelengths of light or 'spectra', using the Gemini Observatory South telescope and the European Southern Observatory Very Large Telescope, both located in Chile.
"Any metals we see in the white dwarf will disappear within a few weeks, and sink down into the interior, unless the debris is continuously flowing onto the star. We will be looking at SDSS 1557 next with Hubble, to conclusively show the dust is made of rock rather than ice," said Professor Boris Gansicke from University of Warwick in the UK.

The study was published in the journal Nature Astronomy.