How Planet Hunting Works


Planet Hunting Milestones: Kepler, Corot and the First Thousand
An artist's take on the Kepler-11 planetary system and our solar system from a tilted perspective. That perspective helps to show that the orbits of each lie on similar planes.
An artist's take on the Kepler-11 planetary system and our solar system from a tilted perspective. That perspective helps to show that the orbits of each lie on similar planes.
Image courtesy NASA

In March 2010, researchers announced another milestone: a Jupiter-like planet 1,500 light-years from Earth that was relatively cool and that could be studied in detail. Because the COROT satellite discovered it, it was dubbed COROT-9b. Previous work had already found other cool planets, but COROT-9b was the first that transits between its star and Earth. This meant that scientists could study both its size (from the amount it diminished the light of its parent star) and its atmospheric composition (from the way starlight interacted with it as it passed through its atmosphere) [source: ESA].

COROT-9b lies in its star's habitable zone but, because it's a gaseous world, scientists don't consider it likely to be hospitable to life. Its atmosphere might contain water, however, and such a large planet could also sport a habitable moon [source: ESA].

In late September 2010, a group of astronomers in the United States using spectroscopic data from ground-based instruments announced the discovery of a potentially hospitable planet, Gliese 581g, orbiting the star Gliese 581 just 20 light-years away. The announcement sparked widespread excitement because the planet was found so close to Earth, and only 15 years after astronomers identified the first exoplanets. Soon after the announcement, however, scientific groups began raising doubts about the discovery [source: Wall].

Researchers had already found evidence for other planets in the same red dwarf system, two of which (Gliese 581d and Gliese 581e) orbited on the fringes of the habitable zone. So, which of Gliese 581's children would take the crown as the best candidate yet found for supporting life? The issue was too complicated to resolve easily. Detecting planets spectroscopically requires toning down the noise inherent in observational data and then determining which assumptions to use. The same data can argue for different numbers of planets depending on whether you assume eccentric (highly elliptical) orbits or nearly circular ones. Scientists had yet to reach a consensus at the time this article was written.

January 2011 saw the Kepler mission confirm finding its first rocky planet, estimated at 1.4 times the size of Earth. Located well outside the habitable zone, Kepler-10b stands out as the smallest planet discovered outside our solar system so far.

And in February 2011, Kepler scientists announced the discovery of five planets, each orbiting in the habitable zones of stars smaller and cooler than our sun. If confirmed, these will represent the first planets of Earthlike size found in habitable zones.That same month, Kepler located six confirmed planets orbiting a sunlike star, Kepler-11, 2,000 light-years from Earth. This constitutes the largest group of transiting planets orbiting a single star ever discovered outside our solar system [source: NASA].

While those discoveries have been momentous, it's important to remember that Kepler so far has only searched a small fraction of the known universe. It may well be that in the years ahead, scientists will make even more amazing finds -- including, perhaps, an Earthlike planet that's home to living things.

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Sources

  • Ames Research Center. " Frequently Asked Questions from the Public." (Feb. 21, 2011) http://kepler.nasa.gov/Mission/QuickGuide/faq/
  • Ames Research Center. "NASA Finds Earth-size Planet Candidates in Habitable Zone, Six Planet System." Feb. 1, 2011. (Feb. 21, 2011) http://kepler.nasa.gov/news/index.cfm?FuseAction=ShowNews&NewsID=98
  • Bean, Jacob, et. al. "The Proposed Giant Planet Orbiting VB 10 Does Not Exist." The Astrophysical Journal Letters. Vol. 711, no. 1. Page L19. 2010.
  • Borucki, W.J. "A Brief History of the Kepler Mission." Kepler.nasa.gov. May 22, 2010. (Feb. 14, 2012) http://kepler.nasa.gov/Mission/QuickGuide/history/
  • Brumfiel, Geoffrey. "Kepler Uncovers Planetary Menagerie." Nature. Jan. 27, 2012. http://blogs.nature.com/news/2012/01/kepler-uncovers-planetary-menagerie.html
  • Choi, Charles Q. "New Estimate for Alien Earths: 2 Billion in Our Galaxy Alone." Space.com. March 21, 2011. (Feb. 14, 2012) http://www.space.com/11188-alien-earths-planets-sun-stars.html
  • Cowen, Ron. "Existence of Habitable Exoplanet Questioned." Science News. Nov. 6, 2010
  • Cowen, Ron. "Astrometry nabs an exoplanet." Science News. July 4, 2009.
  • Cowen, Ron. "First Detection of Carbon Dioxide in an Exoplanet." Science News. Jan. 3, 2009.
  • Cowen, Ron. "Smallest Exoplanet Yet is Found." Science News. May 23, 2009.
  • Cowen, Ron. "This Exoplanet is So Cool." Science News. March 17, 2010.
  • Encyclopedia Britannica. "Somnium." Encyclopedia Britannica, 2011.
  • Grossman, Lisa. "Super-Earth Found Close By, May Host Water." Science News. Jan. 16, 2010.
  • Harwood, William. "Kepler Spacecraft Detects More Than 1,200 Possible Planets Orbiting Distant Suns." CBS News. Feb. 2, 2011. (Feb. 21, 2011) http://www.cbsnews.com/network/news/space/home/spacenews/files/54c081c636823e0dbaf8eb95d6fbb3ef-155.html
  • Jet Propulsion Laboratory. "Planet-Hunting Method Succeeds at Last." May 28, 2009. (Feb. 24, 2011) http://www.jpl.nasa.gov/news/news.cfm?release=2009-090
  • Keim, Brandon. "Most Earth-Like Extrasolar Planet Found Right Next Door." Wired. Dec. 16, 2009. (Feb. 23, 2011)
  • Klotz, Irene. "Earth-Like Planet Can Sustain Life." Discovery News. Sept. 29, 2010. (Feb. 22, 2011) http://news.discovery.com/space/earth-like-planet-life.html
  • Lissauer, Jack and David Stevenson. "Formation of Giant Planets." (Feb. 24, 2011) http://www.astrosmo.unam.mx/esp/PPV/7%20%20PLANET%20FORMATION%20AND%20EXTRASOLAR%20PLANETS/sec7-1.pdf.
  • Matson, John. "A Warm Jupiter: A Newfound Exoplanet Bears a Resemblance to the Solar System's Own Worlds." Scientific American. March 17, 2010. (Feb. 23, 2011) http://www.scientificamerican.com/article.cfm?id=corot-9b-extrasolar
  • Mayor, Michel, and Queloz, Didier. "A Jupiter-mass companion to a solar-type star." Nature. Nov. 23, 1995. (Feb. 14, 2012) http://www.nature.com/nature/journal/v378/n6555/abs/378355a0.html
  • "NASA's Kepler Announces 11 Planetary Systems Hosting 26 Planets." Nasa.gov. Jan. 26, 2012. (Feb. 14, 2012) http://www.nasa.gov/mission_pages/kepler/news/new-multi-systems.html
  • "NASA's Kepler Spacecraft Discovers Extraordinary New Planetary System." Nasa.gov. Feb. 2, 2011. (Feb. 14, 2012.) http://www.nasa.gov/mission_pages/kepler/news/new_planetary_system.html
  • National Science Foundation. "Small Planet, Small Star." (Feb. 22, 2011)http://www.nsf.gov/news/news_summ.jsp?cntn_id=111642
  • "Newly discovered planet could hold water." ESA.int. March 18, 2010. (Feb. 14, 2012) http://www.esa.int/esaMI/COROT/SEMJOMCKP6G_0.html
  • O'Neill, Ian. "Milky Way stuffed with 50 billion alien worlds." Discovery News. Feb. 19, 2011. (Feb. 14, 2012) http://news.discovery.com/space/milky-way-stuffed-with-50-billion-alien-worlds.html
  • "Planet Candidates." Kepler.nasa.gov. (Feb. 14, 2012) http://kepler.nasa.gov/Mission/discoveries/candidates/
  • Rincon, Paul and Jonathan Amos "'Lightest' Exoplanet Discovered." BBC News. April 21, 2009. (Feb. 25, 2011) http://news.bbc.co.uk/2/hi/8008683.stm
  • Sagan, Carl. "Cosmos: Johannes Kepler." (Feb. 25, 2011) http://www.youtube.com/watch?v=lAVeTFin0mU
  • Sanders, Laura. "Distant World Could Support Life." Science News. Oct. 23, 2010.
  • "Table of Confirmed Planets." Kepler.nasa.gov. (Feb. 14, 2012) http://kepler.nasa.gov/Mission/discoveries/
  • University College London. "First Organic Molecule on Extra-Solar Planet Found." March 19, 2008. (Feb. 21, 2011) http://www.ucl.ac.uk/news/news-articles/0803/08031902
  • Wall, Mike. "R.I.P. Possibly Habitable Planet Gliese 581g? Not So Fast, Co-Discoverer Says." Space.com. Feb. 19, 2011. (Feb. 14, 2012) http://www.space.com/10897-alien-planet-gliese-581g-great-debate.html

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