Hubble detects nearest 'exoplanet'
Artist's impression of a Jupiter-mass planet orbiting the nearby star Epsilon Eridani
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Tuesday, 10, Oct 2006 01:03
Nasa's Hubble telescope and ground-based observatories have provided evidence for the existence of the nearest planet outside of our solar system.
Known as an exoplanet as it exists beyond the solar system, the Jupiter-sized world orbits a sun-like star known as Epsilon Eridani at 10.5 light years away from the Earth (approximately 63 trillion miles).
Although images of the planet have not been possible to obtain so far, observations are expected to be made by Hubble and ground-based telescopes in 2007 when the planet makes its closest approach to Epsilon Eridani during its 6.9-year orbit.
The images are expected to be possible when the planet is most bright due to reflected starlight.
The planet's existence, mass and orbit were determined by measurements of subtle changes ("wobbles") in Epsilon Eridani's location in the sky.
"You can't see the wobble induced by the planet with the naked eye," said George Fritz Benedict of the University of Texas, who led the study.
"But Hubble's fine guidance sensors are so precise that they can measure the wobble. We basically watched three years of a nearly seven-year-long dance of the star and its invisible partner, the planet, around their orbits.
"The fine guidance sensors measured a tiny change in the star's position, equivalent to the width of a quarter [small US coin] 750 miles away," he added.
Details of the exoplanet are published in the November issue of the Astronomical Journal.