Nasa's Kepler space telescope, launched in March 2009, has discovered its first five planets.
The five planets, named Kepler 4b, 5b, 6b, 7b and 8b, are all "very hot, inhospitable worlds", Nasa said in a statement on Monday.
The Kepler telescope is designed to look for Earth-sized planets in habitable zones around sun-like stars. It continously conducts observations of more than 150,000 stars at the same time, looking for tiny periodic variations in brightness caused by planets passing between their host stars and the telescope.
"These observations contribute to our understanding of how planetary systems form and evolve from the gas and dust disks that give rise to both the stars and their planets," said William Borucki, the Kepler mission's principal investigator, in the statement. "The discoveries also show that our science instrument is working well. Indications are that Kepler will meet all its science goals."
The planets are known as 'hot Jupiters', said Nasa, due to their high masses and extreme temperatures. The space agency estimates the temperatures of the planets to be between between 2,200°F to 3,000°F (1,200°C to 1,650°C). This class of planet is easier to detect than cooler, smaller planets further away from the host star, and thus was expected to be the first detected as Kepler began its observation. Large planets orbiting close to stars create a much larger variation in observed light.
Ground observations to confirm the discoveries were conducted at: the Keck I telescope in Hawaii; Hobby-Ebberly and Harlan J Smith 2.7m in Texas; Hale and Shane in California; WIYN, MMT and Tillinghast in Arizona; and Nordic Optical in the Canary Islands.
The mission is named after Johannes Kepler, a German astronomer, mathematician and philosopher who first deduced the laws of planetary orbits in his book, Astronomia Nova, published in 1609, 400 years before the launch of the space telescope.