Extrasolar PlanetsMain article: Extrasolar planets See also: List of planetary systems
Astronomers search for extrasolar planets that may be conducive to life, such as Gliese 581 c, Gliese 581 g, Gliese 581 d and OGLE-2005-BLG-390Lb, which have been found to have few Earth-like qualities. Current radiodetection methods have been inadequate for such a search, since the resolution afforded by recent technology is inadequate for a detailed study of extrasolar planetary objects. Future telescopes should be able to image planets around nearby stars, which may reveal the presence of life – either directly or through spectrography – and would reveal key information, such as the presence of free oxygen in a planet's atmosphere:
- Darwin was a proposed ESA mission designed to find Earth-like planets and analyze their atmosphere.
- The COROT mission, initiated by the French Space Agency, was launched in 2006, and is currently looking for extrasolar planets; it is the first of its kind.
- The Terrestrial Planet Finder was supposed to have been launched by NASA, but as of 2011, budget cuts have caused it to be delayed indefinitely.
- The Kepler Mission, largely replacing the Terrestrial Planet Finder, was launched in March 2009.
It has been argued that Alpha Centauri, the closest star system to Earth, may contain planets which could be capable of sustaining life.
On April 24, 2007, scientists at the European Southern Observatory in La Silla, Chile said they had found the first Earth-like planet. The planet, known as Gliese 581 c, orbits within the habitable zone of its star Gliese 581, a red dwarf star which is 20.5 light years (194 trillion km) from the Earth. It was initially thought that this planet could contain liquid water, but recent computer simulations of the climate on Gliese 581 c by Werner von Bloh and his team at Germany's Institute for Climate Impact Research suggest that carbon dioxide and methane in the atmosphere would create a runaway greenhouse effect. This would warm the planet well above the boiling point of water (100 degrees Celsius/212 degrees Fahrenheit), thus dimming the hopes of finding life. As a result of greenhouse models, scientists are now turning their attention to Gliese 581 d, which lies just outside of the star's traditional habitable zone.
On May 29, 2007, the Associated Press released a report stating that scientists identified twenty-eight new extra-solar planetary bodies. One of these newly discovered planets is said to have many similarities to Neptune.
In May 2011, researchers predicted that Gliese 581 d, not only exists in the "Goldilocks zone" where water can be present in liquid form, but is big enough to have a stable carbon dioxide atmosphere and "warm enough to have oceans, clouds, and rainfall," according to France's National Centre for Scientific Research.
In December 2011, NASA confirmed that 600-light-year distant Kepler-22b, at 2.4 times the radius of Earth, is potentially the closest match to Earth in terms of both size and temperature.
Since 1992, hundreds of planets around other stars ("extrasolar planets" or "exoplanets") in the Milky Way Galaxy have been discovered. As of January 23, 2013, the Extrasolar Planets Encyclopaedia identified 859 extrasolar planets (in 676 planetary systems and 128 multiple planetary systems); the extrasolar planets range in size from that of terrestrial planets similar to Earth to that of gas giants larger than Jupiter. The number of observed exoplanets is expected to increase greatly in the coming years. Because the Kepler spacecraft must view three stellar transits by exoplanets before it identifies them as candidate planets, it has so far only been able to identify planets that orbit their star at a relatively quick rate. The mission is expected to continue until at least 2016, in which time many more exoplanet candidates are expected to be found.
Despite these successes, the transit method employed by the Kepler spacecraft requires that planetary orbits be at a small inclination to the line of sight of the observer. Due to this constraint, the probability of detecting a planet of Earth’s size and orbital radius around a distant star is just 0.47%. Thus, the number of planets we are currently able to detect is only a small fraction of the total number of planets present within the galaxy.
Other articles related to "extrasolar planets, planets, planet":
... The established convention for extrasolar planets is that the planets receive lower-case Roman letters starting from "b", in order of discovery ... proposed a modification of the designation system, where the planets are designated in order of characterization ... Since the parameters of the outermost planet were poorly constrained before the introduction of the 4-planet model of the system, this results in a different order of designations for the planets ...
... See also Super-Earth and Pulsar planet The majority of planets found outside the Solar System have been gas giants, since they produce more pronounced wobbles in the host stars and are thus more easily detectable ... However, a number of extrasolar planets are suspected to be terrestrial ... During the early 1990s, the first extrasolar planets were discovered orbiting the pulsar PSR B1257+12, with masses of 0.02, 4.3, and 3.9 times that of Earth's ...
... The planets of PSR B1257+12 are designated from A to D (ordered by increasing distance) ... The reason that these planets are not named the same as other extrasolar planets is mainly because of time ... Being the first ever extrasolar planets discovered, and being discovered around a pulsar, the planets were given the uppercase letters "B" and "C" (like other planets) ...
... Planets are extremely faint compared to their parent stars ... from the parent star in order to reduce the glare, while leaving the light from the planet detectable doing so is a major technical challenge ... radiation the images have then been made at infrared where the planet is brighter than it is at visible wavelengths ...
... Any planet is an extremely faint light source compared to its parent star ... For those reasons, fewer than 5% of the extrasolar planets known as of November 2011 have been observed directly ... astronomers have generally had to resort to indirect methods to detect extrasolar planets ...
Famous quotes containing the word planets:
“Perhaps when distant people on other planets pick up some wave-length of ours all they hear is a continuous scream.”
—Iris Murdoch (b. 1919)