مبحث سيارات فراخورشيدي نخستين بار در سال 1990 و با کشف اولين سياره خارج از منظومه شمسي مطرح شد. گرچه آن سياره به دور ستارهاي در حال زوال پيدا شد، اما به شدت کنجکاوي منجمان را براي کشف سيارات فراخورشيدي برانگيخت. از سوي ديگر، از آنجا که در آن زمان اميدها براي کشف حيات در منظومه شمسي به خصوص سياره مريخ روز به روز کمتر ميشد و مطالعات بر اقمار مشتري و زحل هنوز در حد گستردهاي شروع نشده بود، امکان کشف سيارهاي با شرايط شكلگيري حيات خارج از منظومه شمسي، ايدهاي بس مهيج مينمود.جستجو براي يافتن سيارات فراخورشيدي آغاز شد و ديري نپاييد تا نخستين سياره فراخورشيدي که به دور ستارهاي مانند خورشيد در حال گردش بود در سال 1995 کشف شد.
An extrasolar planet, or exoplanet, is a planet beyond the Solar System. As of December 2007, the count of known exoplanet candidates has reached 268.[1] The vast majority have been detected through various indirect methods rather than actual imaging.[1] Most of them are massive giant planets likely to resemble Jupiter.According to the International Astronomical Union's working definition of "planet," a planet must orbit a star.[2] There have also been reports of free-floating planetary-mass objects (sometimes called "rogue planets" or "interstellar planets"): that is, ones not orbiting any star. Since such objects are outside the working definition of "planet," they are not discussed in this article. For more information, see rogue planet.Extrasolar planets became a subject of scientific investigation in the mid-nineteenth century. Astronomers generally supposed that some existed, but how common they were and how similar they were to the planets of the Solar System remained mysteries. The first confirmed detections were finally made in the 1990s; since 2000, more than fifteen have been discovered every year with 2007 so far the most. It is now estimated that at least 10% of sunlike stars have planets, and the true proportion may be much higher.[3] The discovery of extrasolar planets further raises the question of whether some might support extraterrestrial life.[4]Currently Gliese 581 d, the third planet of the red dwarf star Gliese 581 (approximately 20 light years from the 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 of the "Goldilocks Zone", but the greenhouse effect may raise the planet's surface temperature to that which would support liquid water.Unconfirmed until 1988, extrasolar planets have long been assumed as plausible, and speculation on planets circling around the fixed stars dates to at least the early 18th century, with Isaac Newton's General Scholium (1713), which has "And if the fixed Stars are the centers of other like systems, these, being form'd by the like wise counsel, must be all subject to the dominion of One" (trans. Motte 1729).Claims about detection of exoplanets have been made from the 19th century. Some of the earliest involve the binary star 70 Ophiuchi. In 1855, Capt. W. S. Jacob at the East India Company's Madras Observatory reported that orbital anomalies made it "highly probable" that there was a "planetary body" in this system.[5] In the 1890s, Thomas J. J. See of the University of Chicago and the United States Naval Observatory stated that the orbital anomalies proved the existence of a dark body in the 70 Ophiuchi system with a 36-year period around one of the stars.[6] However, Forest Ray Moulton soon published a paper proving that a three-body system with those orbital parameters would be highly unstable.[7] During the 1950s and 1960s, Peter van de Kamp of Swarthmore College made another prominent series of detection claims, this time for planets orbiting Barnard's Star.[8] Astronomers now generally regard all the early reports of detection as erroneous.
