December 30th, 2012 by James Ayre
2013 will be the year that the first extremely Earth-like exoplanet will be found, researchers in the field are predicting. Such a finding could uproot some entrenched ideas about the Earth, and the life on it, being unique.
There have been quite a few exoplanets discovered in the last couple of years that have some qualities in common with the Earth; size, inferred surface temperature, distance from their parent star, etc. But there has yet to be found a truly “alien Earth.” Many researchers in the field are confident predicting that that will change in 2013 though.
“I’m very positive that the first Earth twin will be discovered next year,” said Abel Mendez, who runs the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo.
The first exoplanet was discovered orbiting around a Sun-like star back in 1995. There have now been more than 800 exoplanets discovered. And considerably more ‘canidates’ that are awaiting confirmation.
“NASA’s prolific Kepler Space Telescope, for example, has flagged more than 2,300 potential planets since its March 2009 launch. Only 100 or so have been confirmed to date, but mission scientists estimate that at least 80 percent will end up being the real deal.”
“The first exoplanet finds were scorching-hot Jupiter-like worlds that orbit close to their parent stars, because they were the easiest to detect. But over time, new instruments came online and planet hunters honed their techniques, enabling the discovery of smaller and more distantly orbiting planets — places more like Earth. Last December, for instance, Kepler found a planet 2.4 times larger than Earth orbiting in its star’s habitable zone — that just-right range of distances where liquid water, and perhaps life as we know it, can exist.”
“The Kepler team and other research groups have detected several other worlds like that one (which is known as Kepler-22b), bringing the current tally of potentially habitable exoplanets to nine by Mendez’ reckoning. None of the worlds in Mendez’ Habitable Exoplanets Catalog are small enough to be true Earth twins. The handful of Earth-size planets spotted to date all orbit too close to their stars to be suitable for life.”
But it seems that such a planet being discovered is inevitable.
“The first planet with a measured size, orbit and incident stellar flux that is suitable for life is likely to be announced in 2013,” said Geoff Marcy, a veteran planet hunter at the University of California, Berkeley, and a member of the Kepler team.
“Mendez and Marcy both think this watershed find will be made by Kepler, which spots planets by flagging the telltale brightness dips caused when they pass in front of their parent stars from the instrument’s perspective.”
“Kepler needs to witness three of these ‘transits’ to detect a planet, so its early discoveries were tilted toward close-orbiting worlds (which transit more frequently). But over time, the telescope has been spotting more and more distantly orbiting planets — including some in the habitable zone.”
“An instrument called HARPS (short for High Accuracy Radial velocity Planet Searcher) is also a top contender, having already spotted a number of potentially habitable worlds. HARPS, which sits on the European Southern Observatory’s 3.6-meter telescope in Chile, allows researchers to detect the tiny gravitational wobbles that orbiting planets induce in their parent stars.”
“HARPS should be able to find the most interesting and closer Earth twins,” Mendez said, making a note of the fact that most Kepler exoplanets are located too far away to be characterized in detail. “A combination of its sensitivity and long-term observations is now paying off.”
“And there are probably many alien Earths out there to be found in our Milky Way galaxy, researchers say.”
“Estimating carefully, there are 200 billion stars that host at least 50 billion planets, if not more,” Mikko Tuomi, of the University of Hertfordshire in England, told SPACE.com via email.
“Assuming that 1:10,000 are similar to the Earth would give us 5,000,000 such planets,” added Tuomi, who led teams reporting the discovery of several potentially habitable planet candidates this year, including an exoplanet orbiting the star Tau Ceti just 11.9 light-years from Earth. “So I would say we are talking about at least thousands of such planets.”
Some more information on Exoplanets:
“An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of 854 such planets (in 673 planetary systems, including 126 multiple planetary systems) have been identified as of December 24, 2012. The Kepler mission has detected over 18,000 additional candidates. It is expected that there are many billions of planets in the Milky Way galaxy, not only occurring around stars but also as free-floating planetary-mass bodies The nearest known exoplanet is Alpha Centauri Bb. Almost all of the planets detected so far are within our home galaxy the Milky Way, however there have been a small number of possible detections of extragalactic planets.”
“For centuries, many philosophers and scientists supposed that extrasolar planets existed, but there was no way of knowing how common they were or how similar they might be to the planets of the Solar System. Various detection claims made starting in the nineteenth century were all eventually rejected by astronomers. The first confirmed detection came in 1992, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmed detection of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Due to improved observational techniques, the rate of detections has increased rapidly since then. Some exoplanets have been directly imaged by telescopes, but the vast majority have been detected through indirect methods such as radial velocity measurements.”
“Most known exoplanets are giant planets believed to resemble Jupiter or Neptune, but this reflects a sampling bias, as massive planets are more easily observed. Some relatively lightweight exoplanets, only a few times more massive than Earth (now known by the term Super-Earth), are known as well; statistical studies now indicate that they actually outnumber giant planets while recent discoveries have included Earth-sized and smaller planets and a handful that appear to exhibit other Earth-like properties. There also exist planetary-mass objects that orbit brown dwarfs and other bodies that ‘float free’ in space not bound to any star; however, the term ‘planet’ is not always applied to these objects.”
“The discovery of extrasolar planets, particularly those that orbit in the habitable zone where it is possible for liquid water to exist on the surface (and therefore also life), has intensified interest in the search for extraterrestrial life. Thus, the search for extrasolar planets also includes the study of planetary habitability, which considers a wide range of factors in determining an extrasolar planet’s suitability for hosting life.”
Image Credits: PHL @ UPR Arecibo, ESA/Hubble, NASA; NASA; Exoplanets via Wikimedia Commons
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