Related topics: stars · planets · spacecraft · comet

Construction of Europe's exoplanet hunter PLATO begins

The construction of ESA's PLATO mission to find and study planets beyond our solar system will be led by Germany's OHB System AG as prime contractor, marking the start of the full industrial phase of the project.

Astronomers find a famous exoplanet's doppelgänger

When it comes to extrasolar planets, appearances can be deceiving. Astronomers have imaged a new planet, and it appears nearly identical to one of the best studied gas-giant planets. But this doppelgänger differs in one ...

How to find signs of life in space

Astrophysicists of the University of Bern, Switzerland, contributed to a series of NASA papers that lay out strategies to search for signs of life beyond our solar system. They assume that the detection of atmospheric signatures ...

Iron-rich stars host shorter-period planets

Astronomers with the Sloan Digital Sky Survey (SDSS) have learned that the chemical composition of a star can exert unexpected influence on its planetary system—a discovery made possible by an ongoing SDSS survey of stars ...

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Extrasolar planet

An extrasolar planet, or exoplanet, is a planet beyond our Solar System, orbiting a star other than our Sun. As of June 2009[update], 353 exoplanets are listed in the Extrasolar Planets Encyclopaedia. The vast majority have been detected through radial velocity observations and other indirect methods rather than actual imaging. Most announced exoplanets are massive gas giant planets thought to resemble Jupiter, but this is a selection effect (bias) due to limitations in detection technology. Projections based on recent detections of much smaller worlds suggest that lightweight, rocky planets will eventually be found to outnumber extrasolar gas giants.

Extrasolar planets became a subject of scientific investigation in the mid-19th century. Many astronomers supposed that such planets existed, but they had no way of knowing how common they were or how similar they might be to the planets of our Solar System. The first confirmed radial velocity detection was made in 1995, revealing a gas giant planet in a four-day orbit around the nearby G-type star 51 Pegasi. The frequency of detections has tended to increase on an annual basis since then. 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 fourth 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 that orbits within the habitable zone surrounding its star. Although initial measurements suggested that Gliese 581 d resided outside the so-called "Goldilocks Zone", additional measurements place it firmly within.

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