New tool refines exoplanet search

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Washington, DC– Planet-hunting is an ongoing process that's resulting in the discovery of more and more planets orbiting distant stars. But as the hunters learn more about the variety among the tremendous number of predicted planets out there, it's important to refine their techniques. New work led by Carnegie's Jonathan Gagné, Caltech's Peter Gao, and Peter Plavchan from Missouri State University reports on a technological upgrade for one method of finding planets or confirming other planetary detections. The result is published by The Astrophysical Journal.

One of the most-popular and successful techniques for finding and confirming planets is called the radial velocity method. A planet is obviously influenced by the gravity of the star it orbits; that's what keeps it in orbit. This technique takes advantage of the fact that the planet's gravity also affects the star in return. As a result, astronomers are able to detect the tiny wobbles the planet induces as its gravity tugs on the star. Using this method, astronomers have detected hundreds of exoplanets.

For certain kinds of low-mass stars, however, there are limitations to the standard radial velocity method, which can cause false positives — in other words, find something that looks like a planet, but isn't.

To address this issue, Gagné, Gao, and Plavchan decided to use the radial velocity technique, but they examined a different, longer wavelength of light.

"Switching from the visible spectrum to the near-infrared, the wobble effect caused by an orbiting planet will remain the same regardless of wavelength," Gagné explained. "But looking in the near-infrared will allow us to reject false positives caused by sunspots and other phenomena that will not look the same in near-infrared as they do in visible light,"

Radial velocity work in the near-infrared wavelengths has been conducted before, but it has trailed behind planet hunting in the visible spectrum, partially due to technical challenges. The research team was able to develop a better calibration tool to improve the overall technology for near-infrared radial velocity work, which should make it a better option going forward.

They examined 32 low-mass stars using this technological upgrade atthe NASA Infrared Telescope Facility atop Mauna Kea, Hawaii. Their findings confirmed several known planets and binary systems, and also identified a few new planetary candidates.

"Our results indicate that this planet-hunting tool is precise and should be a part of the mix of approaches used by astronomers going forward," Gao said. "It's amazing to think that two decades ago we'd only just confirmed exoplanets actually existed and now we're able to refine and improve those methods for further discoveries."

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Other members of the team were: Guillem Anglada-Escude of University of London and the Centre for Astrophysics Research; Elise Furlan, Carolyn Brinkworth, Chas Beichman, and David Ciardi of the NASA Exoplanet Science Institute (Brinkworth also of the National Center for Atmospheric Research); Cassy Davison, Todd Henry, and Russel White of Georgia State University; Angelle Tanner of Mississippi State University; Adric Riedel and Michael Bottom of the California Institute of Technology; David Latham and John Johnson of the Harvard-Smithsonian Center for Astrophysics; Sean Mills of University of Chicago; Kent Wallace, Bertrand Mennesson, Gautam Vasisht, and Timothy Crawford of the Jet Propulsion Laboratory; Kaspar Von Braun and Lisa Prato of Lowell Observatory; Stephen Kane of San Francisco State University; Eric Mamajek of University of Rochester; Bernie Walp of the NASA Dryden Flight Research Center; Raphael Rougeot of the Euroopean Space Research and Technology Centre; Claire Geneser of Missouri State; and Joseph Catanzarite of NASA Ames Research Center.

This work was supported by an Infrared Processing and Analysis Center (IPAC) fellowship, a grant from the Fond de Recherche Québécois – Nature et Technologie and the Natural Science, a grant from the Engineering Research Council of Canada, an iREx postdoctoral Fellowship, and a JPL Research and Technology Development Grant. This work was performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by the National Aeronautics and Space Administration (NASA) through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute.

The Carnegie Institution for Science (carnegiescience.edu) is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.

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