Distant Uranus-sized exoplanet discovered

With a technique called gravitational microlensing, scientists have discovered a Uranus-sized exoplanet orbiting far from its central star.

NASA's Hubble Space Telescope and the W.M. Keck Observatory in Hawaii have made independent confirmations of the discovery.

The planet orbits about 370 million miles from its parent star, slightly less than the distance between Jupiter and the Sun. The host star, however, is about 70 percent as massive as our Sun.

The large majority of exoplanets cataloged so far are very close to their host stars because several current planet-hunting techniques favour finding planets in short-period orbits.

But to fully understand the architecture of distant planetary systems, astronomers must map the entire distribution of planets around a star. Astronomers, therefore, need to look farther away from the star--from about the distance of Jupiter is from our sun, and beyond.

"It is important to understand how these systems compare with our solar system," said one of the researchers Jay Anderson of the Space Telescope Science Institute in Baltimore, Maryland, US.

"So we need a complete census of planets in these systems. Gravitational microlensing is critical in helping astronomers gain insights into planetary formation theories," Anderson said.

Microlensing technique can help find more distant and colder planets in long-period orbits that other methods cannot detect.

Microlensing occurs when a foreground star amplifies the light of a background star that momentarily aligns with it.

If the foreground star has planets, then the planets may also amplify the light of the background star, but for a much shorter period of time than their host star.

The exact timing and amount of light amplification can reveal clues to the nature of the foreground star and its accompanying planets.

The findings appeared in the Astrophysical Journal.