Astronomers Believe Sun-like Star Best Bet Yet for 'Earth's Twin'

The most Sun-like star ever found has some astronomers very excited. They say a planetary system around such a star would be the ideal place to find intelligent life.

HIP 56948 is a star that lies a little more than 200 light years from Earth. Everything about this star, including its size, mass, temperature, and chemical makeup, are all so similar to the Sun's that no measurable differences have yet been detected.

The analysis was carried out by Jorge Melendez of Mount Stromlo Observatory in Weston Creek, Australia, and Ivan Ramirez of the University of Texas in Austin using high-resolution observations made by the 2.7-meter telescope at the McDonald Observatory in Texas, US.

Other Sun-like stars have previously been identified, including 18 Scorpii, HD 98618, and HIP 100963. But all of these previously found stars have several times more lithium than the Sun, while HIP 56948 is a near perfect match to the Sun in this respect as well.

That particular similarity has led some researchers to be more hopeful about the possibility of alien life around HIP 56948, since studies have suggested that stars with less lithium, like the Sun, are “safer” or less active, which means there are fewer flares that can bombard planets with deadly radiation, says Ramirez. If this is the case, then this star would definitely have a higher chance of harboring life than other stars.

Stars that are very similar to the Sun are considered good hunting ground for the search for extraterrestrial intelligence (SETI), says Margaret Turnbull of the Space Telescope Science Institute in Baltimore, Maryland, US. Turnbull helped draw up an existing list of about 17,000 high-priority targets for SETI called HabCat.

"We don't know that Sun-like stars are necessarily the 'best' for intelligent life, but they are certainly a decent starting point given that we know of at least one civilization around such a star," she said.

Peter Backus of the SETI Institute in Mountain View, California, US, who is heading the institute's upcoming search for alien life with the new Allen Telescope Array, says the Sun's newly identified twin will be targeted in the search, and was already on the HabCat list. But he says for now it’s not receiving preferential treatment.

"It's still a matter of speculation on just what range of stars could host habitable planets. We will eventually get around to observing all of the stars [on the list]."

But astronomers at McDonald Observatory don’t plan on waiting. They have already started looking for planets around HIP 56948. They have already ruled out the possibility of any giant planets in tight orbits around the star, sometimes referred to as 'hot Jupiters' which would be the easiest planets to spot, but what they’re really looking for is planets that are not to hot and not too cold.

The star does have one main difference from the Sun in that it is probably about 1 billion years older. But that difference only makes it all the more attractive for SETI, Ramirez speculates, because older stars have had more time to produce intelligent civilizations.

"Assuming that these stars have planets and those planets have life, then you have given more time for that life to evolve," he points out.

Astronomers would be thrilled to observe a radio signal from a civilization around the star, but while it is possible for us to have received a signal at this point in time there is no way they could have received one of our radio signals. With a distance of over 200 light years from Earth, none of our radio or television signals would have had time to reach it yet, notes Ramirez. "If there is life there and intelligent life, then they haven't heard from us yet."

Posted by Rebecca Sato

SETI Radio: Extraterrestrial & Other Voices- How to Recognize a Message from E.T.
http://www.dailygalaxy.com/my_weblog/2007/09/seti-radio-on-e.html

Non-Carbon Lifeforms -Why We May Overlook Extra-terrestrial Life
http://www.dailygalaxy.com/my_weblog/2007/06/noncarbon_lifef.html

Cetacea: Mind-Bending Theories About the Planet's “Other” Intelligent Life
http://www.dailygalaxy.com/my_weblog/2007/06/cetacea-mind-be.html

source:
http://space.newscientist.com/article/dn12725-suns-twin-an-ideal-hunting-ground-for-alien-life.html