First evidence of rocky planet formation in a Tatooine-like system

Tatooine system

A disc of rocky debris from a disrupted planetesimal surrounds white dwarf plus brown dwarf binary star. The white dwarf is the burn-out core of a star that was probably similar to the Sun, the brown dwarf is only ~60 times heavier than Jupiter, and the two stars go around each other in only a bit over two hours.
(Credit: Mark Garlick, UCL, University of Warwick and University of Sheffield.)

28 February 2017

Evidence of planetary debris surrounding a double sun, ‘Tatooine-like’ system, has been found for the first time by a UK-led team of researchers.

The research was funded by STFC and the European Research Council and the study reports on the remains of shattered asteroids orbiting a double sun consisting of a white dwarf and a brown dwarf roughly 1000 light years away in a system called SDSS 1557.

The discovery is remarkable because the debris appears to be rocky and suggests that terrestrial planets like Tatooine – Luke Skywalker’s home world in Star Wars – 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.

Lead author, Dr Jay Farihi of UCL Physics and Astronomy, said: “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. 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." 

In the Solar System, the asteroid belt contains the leftover building blocks for the terrestrial planets Mercury, Venus, Earth, and Mars, so planetary scientists study the asteroids to gain a better understanding of how rocky and potentially habitable planets are formed. The same approach was used by the team to study the SDSS 1557 system as any planets within it cannot yet be detected directly but the debris is spread in a large belt around the double stars, which is a much larger target for analysis.

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. 

More details can be found here.

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