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The world's first robotic planet finder is expected to boost the search for Earth-like planets that might support life in other solar systems.

Now scientists have proven its capabilities by using the telescope to find a unique a planetary system orbiting a nearby star 54 light-years away.

All three planets in the system orbit the star, HD 7924, at a distance closer than Mercury orbits the sun, completing their orbits in just 5, 15 and 24 days.

The Automated Planet Finder (APF) consists of a 2.4-metre automated telescope and enclosure, and a high-resolution spectrograph. The spectrograph takes starlight from the telescope and spreads it into a rainbow of colours, splitting the light into a spectrum of thousands of different wavelengths that can be measured

'The three planets are unlike anything in our solar system, with masses 7-8 times the mass of Earth and orbits that take them very close to their host star,' explains UC Berkeley graduate student Lauren Weiss.

While the planets are likely to be too hot to support life, their discovery reveals the powerful capabilities of the Automated Planet Finder (APF) in California.

'This level of automation is a game-changer in astronomy,' said Andrew Howard, an astronomers UC Berkeley. 'It's a bit like owning a driverless car that goes planet shopping.'

AFP found the star system by tracing out the planets' orbits over many years using the Doppler technique to see shifts in the star's light.

The planet system was also spotted by the Keck Observatory and the Automatic Photometric Telescope (APT) at Fairborn Observatory in Arizona.

But unlike other telescope, the new APF facility offers a way to speed up the planet search as it robotically searches for planets every clear night.

Training computers to run the observatory all night, without human oversight, took years of effort by the University of California Observatories staff team.

'We initially used APF like a regular telescope, staying up all night searching star to star,' said University of Hawaii graduate student BJ Fulton.

'But the idea of letting a computer take the graveyard shift was more appealing after months of little sleep.'

The Kepler Space Telescope has discovered thousands of extrasolar planets and demonstrated that they are common in our Milky Way galaxy.

Scientists have proven the APF's capabilities by using the telescope to find a unique a planetary system orbiting a nearby star 54 light-years away. All three planets in the system orbit the star, HD 7924, at a distance closer than Mercury orbits the sun, completing their orbits in just 5, 15 and 24 days

AFP found the star system by tracing out the planets' orbits over many years using the Doppler technique to see shifts in the star's light. The planet system was also spotted by the Keck Observatory and the Automatic Photometric Telescope (APT) at Fairborn Observatory in Arizona.

However, nearly all of these planets are far from our solar system. Most nearby stars have not been searched for the small 'super-Earth' planets that Kepler found in great abundance.

This discovery shows the type of planetary system that astronomers expect to find around many nearby stars in the coming years.

'Starspots, like sunspots on the sun, can momentarily mimic the signatures of small planets.

'Repeated observations over many years allowed us to separate the starspot signals from the signatures of these new planets,' explains Evan Sinukoff, a UH graduate student who contributed to the discovery.

The robotic observations of HD 7924 are the start of a systematic survey for super-Earth planets orbiting nearby stars.

Fulton will lead this two-year search with the APF as part of his research for his doctoral dissertation.

'When the survey is complete we will have a census of small planets orbiting sun-like stars within approximately 100 light-years of Earth,' says Fulton.

Pictured is the Keck Observatory in Hawaii and on the right, which also helped find the planets. The robotic observations of HD 7924 are the start of a systematic survey for super-Earth planets orbiting nearby stars