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LONDON, England (CNN) -- British bookmakers have reduced the odds on finding extra-terrestrial intelligence after the discovery of a planet that may be able to sustain life.

William Hill lowered its odds on Wednesday -- from 1000/1 to 100/1 -- in the wake of the astronomical discovery, which was announced Tuesday.

The planet, which is 20.5 light years from Earth and orbits the star Gliese 581, is being described as "Earth-like" by NASA experts.

William Hill spokesman Graham Sharpe said the bookmakers could face a payout in the tens of millions of pounds if extra-terrestrial life was found.

"We felt we had to react to the news that an Earth-like planet, which could support intelligent life had been discovered," Sharpe said.

"After all, we don't know for sure that intelligent extra-terrestrial life has not already been discovered, but is being hushed up."

Scientists at the Search for Extra-Terrestrial Life Institute (SETI) plan to monitor the planet and its system for signs of intelligent life.

"The older the star is, maybe the greater the chance that it has produced something that's clever," SETI spokesman Dr Seth Shostak said.

William Hill has taken on many seemingly outlandish bets over past 50 years, some of which have resulted in big payouts.

In the early 1960s the bookmaker offered odds of 1000/1 that man would walk on the moon before 1970, and was forced to pay the equivalent of 1 million pounds ($2 million) to its customers.

Before the alien wager is paid out, the Prime Minister must officially confirm the existence of intelligent extra-terrestrial life within a year of the bet being placed.

With the discovery of the new planet, William Hill may still have to pay at the original 1000/1 odds if alien life is found by April 23, 2008.