exoplanet

a planet which is outside of Earth's solar system

'Is there life on other planets?' – It's one of the most intriguing questions of all time, and one that astronomers and scientists hope to be able to answer, one day. But during the last twenty years or so, it looks like we may in fact have begun to find that 'galaxy, far, far way' as explorations have gradually been moving to the next level with the identification of exoplanets – planets which exist outside of earth's solar system.

thanks to a new technique, candidate planets can now be verified in batches rather than one by one, which in recent weeks has abruptly increased the haul by a massive 715, the largest windfall of planets ever to be announced at once

Earth and the other seven planets we're familiar with form part of the solar system, or in other words, they orbit the sun. An exoplanet is a planet that orbits a star other than the sun and is hence alternatively known as an extrasolar planet, or an exosolar planet. Up until early 2014, just under 1000 of such planets had been discovered over two decades, but in late February the tally took a giant leap to around 1700. These phenomenal discoveries were made possible through use of NASA's Kepler space telescope, an observatory launched in 2009 to discover Earth-like planets orbiting other stars. When Kepler was first used, the number of confirmed planets came at a trickle. But thanks to a new technique, candidate planets can now be verified in batches rather than one by one, which in recent weeks has abruptly increased the haul by a massive 715, the largest windfall of planets ever to be announced at once.

Four of the new planets discovered orbit their host stars in what's technically referred to as a 'habitable zone', the region around a star where water can keep a liquid state (and therefore where life could, in principle, be sustained). Kepler's target planets are hundreds of light years away, however, so are much too distant for detailed observation. It seems then that this fantastic discovery hasn't quite yet brought us any closer to establishing whether there is, indeed, life out there …

Background – exoplanet

The word exoplanet first appeared in the mid-nineties, when initial discoveries of such planets were announced. It quickly became adopted as an abbreviation of the more formal expression extrasolar planet (extra- = 'outside' or 'beyond', compare e.g. extraterrestrial, extracurricular), but has still largely remained outside of public radar until the breakthrough discovery in February 2014 brought it more firmly into the mainstream spotlight. There's also some evidence for a derived adjective exoplanetary and related terms exocomet and exomoon.

These words incorporate the prefix -exo, which is of Greek origin and means 'external' or 'outside'. Other examples of the affix's use include the English adjective exogenous (relating to external factors), and noun exoskeleton (a hard outer covering on some insects and animals).

Another collision between the worlds of lexicography and astronomy occurred in the recent past when the American Dialect Society announced the verb pluto as its word of the year for 2006. Used to mean 'demote' or 'devalue', the word was inspired by a decision in the same year to officially demote Pluto from 'planet' to 'dwarf planet' status. The word turned out to be very much a flash in the pan however, and was in turn comprehensively plutoed from the lexicon within a relatively short time of its first appearance.