Astronomers from the European Southern Observatory (ESO) announced today the discovery of an exoplanet only 5.5 times the mass of the Earth orbiting a red dwarf star located near the center of the Milky Way galaxy, some 20,000 light years away from our own solar system. The discovery could indicate that rocky planets like the Earth are common throughout the universe.
The discovery of the exoplanet is only the third using a technique called gravitational microlensing. Microlensing is a faint but detectable brightening of light from a more distant object caused by gravitational lensing by a nearer object passing directly in front of it as seen from the Earth. Microlensing does not provide a direct visual observation of intervening bodies but instead indicates their presence indirectly.
A network of robotic telescopes monitors the galaxy 24 hours a day, 7 days a week, looking for microlensing events. Using the Danish 1.54m telescope at ESO La Silla, Chile, astronomers detected a microlensing event on July 11, 2005 by an intervening star less massive than our own Sun. Immediately after the event was detected, notification went out across the network to provide constant coverage of the phenomena. Ten days later, an anomaly in the wanning microlensing effect indicated the presence of a planet.
The planet has been labeled OGLE-2005-BLG-390Lb after the designation for the microlensing event. Astronomers speculate that the planet is cold and probably contains a significant amount of ice in its composition due to its location approximately three times as far from its parent star as the Earth is from the Sun. Its size is sufficient to hold a substantial atmosphere but such an environment may not be hospitable to life as we know it.
According to NASA’s “Planet Quest” site, 159 exoplanets have been detected to date, although other sources give a number closer to 170. Only one other rocky exoplanet candidate has been discovered and only one exoplanet has been directly imaged. Space agencies and astronomers are developing improved telescopes, spacecraft, and techniques to accelerate the detection and direct imaging of Earth-sized exoplanets over the next decade. The improved technologies may also allow scientists to look for evidence of biological markers in the atmospheres of exoplanets to determine the extent of life in our galaxy.
- Scientific Paper: Nature Letter, J.-P. Beaulieu, et. al., “Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing“, Nature 439, 437-440 (26 January 2006) | doi:10.1038/nature04441
- European Southern Observatory (ESO)
- Press Release – January 25, 2006 – “It’s Far, It’s Small, It’s Cool: It’s an Icy Exoplanet!“
- Video: ESO PR Video 03a/06
- United States National Science Foundation
- Technology – Microlensing events are rare and last only a short time (generally days.) Therefore, networks of robotic telescopes have been set up to automate observation and provide continuous coverage during an event.
- Planet Quest – the search for another Earth