Study says solar systems like ours may be common
Baku, October 30 (AZERTAC). Nearly one in four stars like the sun could have Earth-size planets, according to a University of California, Berkeley, study of nearby solar-mass stars.
UC Berkeley astronomers Andrew Howard and Geoffrey Marcy chose 166 G and K stars within 80 light years of Earth and observed them with the powerful Keck telescope for five years in order to determine the number, mass and orbital distance of any of the stars` planets. The sun is the best known of the G stars, which are yellow, while K-type dwarfs are slightly smaller, orange-red stars.
The researchers found increasing numbers of smaller planets, down to the smallest size detectable today - planets called super-Earths, about three times the mass of Earth.
`This is the first estimate based on actual measurements of the fraction of stars that have Earth-size planets,` said Marcy, UC Berkeley professor of astronomy. Previous studies have estimated the proportion of Jupiter and Saturn-size exoplanets, but never down to Neptunes and super-Earths, enabling an extrapolation to Earth-size planets.
Because the researchers detected only close-in planets, there could be even more Earth-size planets at greater distances, including within the habitable zone located at about the same distance as the earth is from our sun. The habitable, or `Goldilocks,` zone is the distance from a star neither two hot nor too cold to allow the presence of liquid water.
The researchers` results conflict with current models of planet formation and migration, Marcy noted. After their birth in a protoplanetary disk, planets had been thought to spiral inward because of interactions with the gas in the disk. Such models predict a `planet desert` in the inner region of solar systems.
The astronomers used the 10-metre Keck telescopes in Hawaii to measure the minute wobble of each star. Current techniques allow detection of planets massive enough and near enough to their stars to cause a wobble of about 1 metre per second. That means they saw only massive, Jupiter-like gas giants up to three times the mass of Jupiter (1,000 times Earth`s mass) orbiting as far as one-quarter of an astronomical unit (AU) from the star, or smaller, closer super-Earths and Neptune-like planets (15-30 times the mass of the earth). An AU is 93 million miles, the average distance between the earth and the sun.
Twelve possible planets also were detected, but they need further confirmation, Marcy said. If these candidate planets are included in the count, the team detected a total of 45 planets around 32 stars.
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