A robotic telescope working the late shift at the Lick Observatory has discovered three “super Earths” orbiting a nearby star. Originally human astronomers manned the Automated Planet Finder, a new telescope on Mount Hamilton outside San Jose, California but ultimately decided to replace themselves with a computer for the late night shifts.
“We initially used the 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 Benjamin “BJ” Fulton a graduate student at the University of Hawaii in a statement.
The new planets, invisible to the naked eye, are rocky but much larger and closer to their host star than planets like the Earth and Mars.
“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,” said Lauren Weiss.
Weiss is a UC Berkeley graduate student and leader of the Berkeley branch of the team that found the planets.
Most of the exoplanets discovered to date have been gas giants ranging from Neptune size (17 times Earth’s mass) to Jupiter size (several hundred times the mass of Earth). The AFP is designed to find smaller planets which could theoretically support life as we know it.
“The discovery demonstrates the APF’s ability to find low-mass planets around nearby stars. Robotic telescopes are going to be the way we find planets in the future,” said Weiss.
The planets were detected by a slight wobble in the visible light from the planets host star. The first evidence of planets orbiting HD 7924 came from the W.M Keck Observatory in Hawaii in 2009. It took five additional years of research from the Keck and a year and a half with the APF Telescope, with assistance from the Automatic Photometric Telescope at Fairborn Observatory in Arizona, to identify the three planets.
All three of the planets, located 54 light years from Earth, orbit HD 7924 more closely than Mercury orbits our sun. The complete orbits of the planets, or the years on those planets, are five, 15 and 24 days long.
The observations are detailed in a paper that has been accepted for publication by the Astrophysical Journal and is currently available on the open site Arxiv.
The robotic observations for the APF are just getting started. The telescope will now begin a two year survey of nearby stars in an attempt to find more super-Earths.
“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.
The completion of that survey should almost coincide with the launch of the James Webb Space Telescope (JWST), scheduled for 2018. The JWST, the successor to the Hubble Space Telescope, is expected to aid in the discovery of exoplanets and will be able to analyze the atmospheres of those planets better than any instrument to date. That analysis will be key in determining which planets might support forms of life familiar to us.
