February 7th, 2013 by James Ayre
Earth-like planets may be as close as just 13 light-years away, orbiting around red dwarf stars, new research suggests. By utilizing data that was obtained by NASA’s Kepler space telescope, researchers at the Harvard-Smithsonian Center for Astrophysics (CfA), have discovered that about 6% of red dwarf stars have ‘habitable’ Earth-size planets.
“We thought we would have to search vast distances to find an Earth-like planet. Now we realize another Earth is probably in our own backyard, waiting to be spotted,” said Harvard researcher/primary author Courtney Dressing (CfA).
Red dwarf stars are quite a bit diffrent than our own Sun, but certainly capable of supporting life. They are, essentially, the fainter, smaller, and cooler, versions of our Sun. On average, they are about 1/3 as large as the Sun, and 1/1000 as bright. Because of their faintness, there are none that are visible with the naked eye from the Earth, even though some are rather close to us.
“Despite their dimness, these stars are good places to look for Earth-like planets. Red dwarfs make up three out of every four stars in our galaxy for a total of at least 75 billion. The signal of a transiting planet is larger since the star itself is smaller, so an Earth-sized world blocks more of the star’s disk. And since a planet has to orbit a cool star closer in order to be in the habitable zone, it’s more likely to transit from our point of view.”
For the new research, the Kepler catalog of 158,000 target stars was analyzed to determine all of the red dwarfs. These stars were then reanalyzed to more accurately determine their qualities, such as size and temperature. The researchers discovered that nearly all “of those stars were smaller and cooler than previously thought.”
“Since the size of a transiting planet is determined relative to the star size, based on how much of the star’s disk the planet covers, shrinking the star shrinks the planet. And a cooler star will have a tighter habitable zone.”
In total, 95 planetary candidates orbiting red dwarf stars were identified. “This implied that at least 60 percent of such stars have planets smaller than Neptune. However, most weren’t quite the right size or temperature to be considered truly Earth-like. Three planetary candidates were both warm and approximately Earth-sized. Statistically, this means that six percent of all red dwarf stars should have an Earth-like planet.”
“We now know the rate of occurrence of habitable planets around the most common stars in our galaxy,” said co-author David Charbonneau (CfA). “That rate implies that it will be significantly easier to search for life beyond the solar system than we previously thought.”
“Our Sun is surrounded by a swarm of red dwarf stars. About 75 percent of the closest stars are red dwarfs. Since 6 percent of those should host habitable planets, the closest Earth-like world is likely to be just 13 light-years away.”
“Locating nearby, Earth-like worlds may require a dedicated small space telescope, or a large network of ground-based telescopes. Follow-up studies with instruments like the Giant Magellan Telescope and James Webb Space Telescope could tell us whether any warm, transiting planets have an atmosphere and further probe its chemistry.”
Because these planets orbit red dwarfs though, they would be very different worlds. Because thy orbit so close to their Sun, it would be very likely for them to be tidally locked to their stars. “However, that doesn’t prohibit life since a reasonably thick atmosphere or deep ocean could transport heat around the planet. And while young red dwarf stars emit strong flares of ultraviolet light, an atmosphere could protect life on the planet’s surface. In fact, such stresses could help life to evolve.”
“You don’t need an Earth clone to have life,” said Dressing.
“Since red dwarf stars live much longer than Sun-like stars, this discovery raises the interesting possibility that life on such a planet could be much older than life on Earth.”
“We might find an Earth that’s 10 billion years old,” speculated Charbonneau.
“The three habitable-zone planetary candidates identified in this study are Kepler Object of Interest (KOI) 1422.02, which is 90 percent the size of Earth in a 20-day orbit; KOI 2626.01, 1.4 times the size of Earth in a 38-day orbit; and KOI 854.01, 1.7 times the size of Earth in a 56-day orbit. All three are located about 300 to 600 light-years away and orbit stars with temperatures between 5,700 and 5,900 degrees Fahrenheit. (For comparison, our Sun’s surface is 10,000 degrees F.)”
The new research is set to be published in The Astrophysical Journal.
In order to journey to a planet 13 light-years away there would need to be a revolution in our current space travel technologies though. New communication and/or artificial intelligence technologies/capabilities would also be needed, as the distances involved are too vast for our current communication technologies to function as remote control. Artificial intelligence could possibly address this, as could quantum communication though.
At any rate, it is interesting to consider that Earth-like planets could be so close. And especially since the parent stars of these planets aren’t even visible to the naked eye.
Image Credits: David A. Aguilar (CfA)
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