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False-color infrared image of the brown dwarf 2M1207 (blue) and its planetary companion 2M1207b (red), as viewed by the Very Large Telescope. As of September 2006 this is the only confirmed extrasolar planet to have been directly imaged.

The smallest planet outside the Solar System was discovered by Spanish astronomers, led by Ribas and named “GJ 436T”. It is located 30 light years^[1] from Earth and was detected using a new technique. According to Ignasi Ribas of Spain’s CSIC scientific research institute, this technique “will allow us to discover in less than 10 years the first planet resembling Earth in terms of mass and orbit”.

The astronomers discovered it through their gravitational pull on other planets already discovered around the same star in the constellation of Leo. It is the smallest extrasolar planet^[2] among the about 300 identified so far, because the mass of the planet is five time the size of Earth. The distance between the new planet and its stars is far less than that between the Earth and the and that is why “GJ 436T” is uninhabitable. For a planet to be habitable it must have an atmosphere, a similar orbital distance from its stars, liquid waters on its surface and a mass similar to that of Earth.

After some calculations it was concluded that the new planet rotates in 4.2 Earth days and orbits its star every 5.2 days.

NOTES: 1) A light-year or light year (symbol: ly) is a unit of measurement of length, specifically the distance that light travels in a vacuum in one year. While there is no authoritative decision on which year is used, the International Astronomical Union (IAU) recommends the Julian year.

The exact length of the light-year depends on the length of the reference year used in the calculation, and there is no wide consensus on the reference to be used. The figures above are based on a Julian year (not Gregorian year) of exactly 365.25 days (each of exactly 86,400 SI seconds, totaling 31,557,600 seconds) as recommended by the IAU.[1] However, the 1900.0 mean tropical year is often used, thus the light-year is not an appropriate unit to use when extremely high precision is required.

The light-year is often used to measure distances to stars. In astronomy, the preferred unit of measurement for such distances is the parsec, which is defined as the distance at which an object will appear to move one arcsecond of parallax when the observer moves one astronomical unit perpendicular to the line of sight to the observer. This is equal to approximately 3.26 light-years. The parsec is preferred because it can be more easily derived from, and compared with, observational data. However, outside scientific circles, the term light-year is more widely used.

Other light years are listed below:

2) An extrasolar planet, or exoplanet, is a planet beyond the Solar System. As of April 2008, 287 exoplanets have been detected. The vast majority were detected through various indirect methods rather than actual imaging. Most of them are massive giant planets likely to resemble Jupiter.

Extrasolar planets became a subject of scientific investigation in the mid-19th century. Astronomers generally supposed that some existed, it was not known how common they were and how similar they were to the planets of the Solar System. The first confirmed detections were made in the 1990s; since 2000, more than 15 have been discovered every year. The frequency of detection is increasing with 61 planets detected in 2007. It is estimated that at least 10% of sun-like stars have planets, and the true proportion may be much higher. The discovery of extrasolar planets sharpens the question of whether some might support extraterrestrial life.

Currently Gliese 581 d, the third planet of the red dwarf star Gliese 581 (approximately 20 light years from Earth), appears to be the best example yet discovered of a possible terrestrial exoplanet which orbits close to the habitable zone of space surrounding its star. Going by strict terms, it appears to reside outside the "Goldilocks Zone", but the greenhouse effect may raise the planet's surface temperature to that which would support liquid water.