Free Astronomy Magazine July-August 2015

SPACE CHRONICLES I telescope. This same combination was also used to find other super- Earths orbiting nearby stars in plan- et searches led by UH astronomer Andrew Howard and UC Berkeley Professor Geoffrey Marcy. It took five years of additional observations at Keck Observatory and the year- and-a-half campaign by the APF Telescope to find the two additional planets orbiting HD 7924. The new APF facility offers a way to speed up the planet search. Planets can be discovered and their orbits traced Robot discovers two new neighbors by Keck Observatory A team of astronomers using ground-based telescopes in Hawaii, California, and Ari- zona recently discovered a plane- tary system orbiting a nearby star that is only 54 light-years away. All three planets orbit their star at a distance closer than Mercury orbits the sun, completing their orbits in just 5, 15, and 24 days. Astronomers from the University of Hawaii at Manoa, the University of California, Berkeley, the University of California Observatories, and Tennessee State University found the planets using measurements from the W. M. Keck Observatory on Maunakea, Hawaii, the Automated Planet Finder (APF) Telescope at Lick Observatory in California and the Automatic Photometric Telescope (APT) at Fairborn Observatory in Ari- zona. The team discovered the new planets by detecting the wobble of the star HD 7924 as the planets or- bited and pulled on the star gravita- tionally. APF and Keck Observatory traced out the planets’ orbits over many years using the Doppler tech- nique that has successfully found hundreds of mostly larger planets orbiting nearby stars. APT made cru- cial measurements of the brightness of HD 7924 to assure the validity of the planet discoveries. The Keck Observatory found the first evidence of planets orbiting HD 7924, discovering the innermost plan- et in 2009 using the HIRES instru- ment installed on the 10-meter Keck