Three "super-Earths" have been discovered in a star system 54 light-years away from our planet.

Astronomers located the super-Earths with a ground-based robotic telescope designed to locate planets beyond the Milky Way.

The team of scientists, assembled from the University of California, Berkeley; the University of Hawaii at Manoa; the University of California Observatories; and Tennessee State University have been working to find the planets for years. They made the discovery using the Automated Planet Finder (APF) Telescope at California's Lick Observatory and the W. M. Keck Observatory on Maunakea, Hawaii. They also deployed the Automatic Photometric Telescope (APT) at Arizona's Fairborn Observatory.

The researchers reveal that the three super-Earths orbit HD 7924  — their parent star. The orbiting distance of these exoplanets is closer than that of Mercury to our Sun. The super-Earths complete their orbitals in five, 15 and 24 days, respectively. The HD 7924 is located in the northern hemisphere and is visible from Earth at night.

"The three planets are unlike anything in our solar system, with masses seven to eight times the mass of Earth and orbits very close to their host star," revealed Lauren Weiss, leader of the UC Berkeley team.

The researchers at Lick Observatory deployed the APF, which is a relatively new robotic telescope. By using the Doppler method, the astronomers were able to measure the wobbles caused by the three super-Earths in orbit, which ultimately led to their discovery.

The APF was initially used by the astronomers like a regular telescope, but observation of the Milky Way shifted to a computer-based model for robotically hunting new planets.

 "We initially used APF like a regular telescope, staying up all night searching star to star. But the idea of letting a computer take the graveyard shift was more appealing after months of little sleep. So we wrote software to replace ourselves with a robot," said BJ Fulton, a graduate student from the University of Hawaii at Manoa.

This study was published in The Astrophysical Journal.

Karen Teramura and BJ Fulton | UH IfA 

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