Though the search for planets around other stars, or exoplanets, is showing researchers that planets are abundant in our galaxy, it helps a great deal to have directions when searching for as-of-yet undiscovered exoplanets.
Lowell astronomer Evgenya Shkolnik and her collaborators have written such a set of directions, if you will.
Their paper, recently published in The Astrophysical Journal, examined new and existing data from stars and brown dwarfs that are less than 300 million years old, as determined from strong X-ray emission readings. In all, the authors identified 144 young targets for exoplanet searches, with 20 very strong candidates, according to Dr. Shkolnik. This candidate list is being searched for planets with Gemini's NICI Planet-Finding Campaign and the Planets Around Low-Mass Stars survey, led by astronomer Michael Liu and graduate student Brendan Bowler, respectively, both at the Institute for Astronomy, University of Hawai'i.
By looking for markers in spectroscopic data and measuring the motions of the stars, Shkolnik and her collaborators were able to carefully examine the age of each stars. Since low-mass stars are small and dim, they are good candidates for directly imaging planets around them. And young stars make it even easier since the young planet is still hot and bright. Plus, knowing the planetary system's age allows for the characterization of the planet itself beyond the initial detection.
The authors sifted through data of about 8,700 stars within 100 light years of the Sun to find these candidates. The spectra were collected using two Hawaiian Mauna Kea telescopes (Keck and the Canada-France-Hawaii telescopes), and distances to the stars were measured by Guillem Anglada-Escude (Universitaet Goettingen) using the du Pont telescope in Chile, operated by the Carnegie Institution for Science.
"Since low-mass stars are the most common type of star in our galaxy, most planets probably reside in these environments," says Mr. Bowler. "Finding young versions of these stars to search for planets is fundamental to understanding the galactic census of exoplanets."
"These young stars help point the way. And if the Jupiter-mass planets are there, we will find them," notes Dr. Shkolnik.
In this search, planet hunters are happy to have directions but they know the landscape of our understanding is subject to change.
The full list of authors is:
Evgenya L. Shkolnik(1), Guillem Anglada-Escude(2), Michael C. Liu(3), Brendan P. Bowler(3), Alycia J. Weinberger(4), Alan P. Boss(4), I. Neill Reid(5), and Motohide Tamura(6)
(1) Lowell Observatory, 1400 W. Mars Hill Road, Flagstaff, AZ 86001, USA
(2) Institut fuer Astrophysik, Universitaet Goettingen, Friedrich-Hund-Platz 1, D-37077 Goettingen, Germany
(3) Institute for Astronomy, University of Hawaii at Manoa 2680 Woodlawn Drive, Honolulu, HI 96822, USA
(4) Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road, NW, Washington, DC 20015, USA
(5) Space Telescope Science Institute, Baltimore, MD 21218, USA
(6) National Astronomical Observatory of Japan, Tokyo, Japan
Online release: http://www.lowell.edu/news/
About Lowell Observatory
Lowell Observatory is a private, non-profit research institution founded in 1894 by Percival Lowell. The Observatory has been the site of many important findings including the discovery of the large recessional velocities (redshift) of galaxies by V.M. Slipher in 1912-1914 (a result that led ultimately to the realization the universe is expanding), and the discovery of Pluto by Clyde Tombaugh in 1930. Today, Lowell's 20 astronomers use ground-based telescopes around the world, telescopes in space, and NASA planetary spacecraft to conduct research in diverse areas of astronomy and planetary science. The Observatory welcomes about 80,000 visitors each year to its Mars Hill campus in Flagstaff, Arizona for a variety of tours, telescope viewing, and special programs. Lowell Observatory currently has four research telescopes at its Anderson Mesa dark-sky site east of Flagstaff, and recently completed a four-meter class research telescope, the Discovery Channel Telescope. For more information, please visit www.lowell.edu.