April 4, 2013
New Method Could Help Find 100 Billion Earth-Like Planets
Lee Rannals for redOrbit.com - Your Universe Online
Researchers at The University of Auckland wrote in the Monthly Notices of the Royal Astronomical Society that they have a new method that could lead to the discovery of 100 billion earth-like planets.The new strategy, called gravitational microlensing, requires a combination of data from microlensing and the NASA Kepler space telescope.
“Kepler finds Earth-sized planets that are quite close to parent stars, and it estimates that there are 17 billion such planets in the Milky Way," said Lead author Dr. Phil Yock from the University of Auckland´s Department of Physics. "These planets are generally hotter than Earth, although some could be of a similar temperature (and therefore habitable) if they´re orbiting a cool star called a red dwarf."
He said their proposal is to measure the number of Earth-mass planets orbiting stars at distances typically twice the Sun-Earth distance.
"Our planets will therefore be cooler than the Earth. By interpolating between the Kepler and MOA results, we should get a good estimate of the number of Earth-like, habitable planets in the galaxy. We anticipate a number in the order of 100 billion," Yock added. "Of course, it will be a long way from measuring this number to actually finding inhabited planets, but it will be a step along the way.”
Yock says this reflects the difficulty of detecting from a distance of a tiny non-luminous object like Earth orbiting a bright object like the Sun. The planet gets lost in the glare of the star, so indirect methods of detection must be used.
Kepler measures the loss of light from a star when a planet orbits between us and its host star, and microlensing measures the deflection of light from a distant star that passes through a planetary system en route to Earth.
Researchers have used microlensing to detect several planets as large as Neptune in recent years, and the team hopes this new strategy for detecting the tiny deflection caused by an Earth-sized planet will work. Simulations carried out by Yock and colleagues showed that Earth-sized planets could be detected more easily if a worldwide network of moderately sized, robotic telescopes was available to monitor them. A network like this is being developed by Las Cumbres Observatory Global Telescope Network (LCOGT) that will be used to study microlensing events.
Scientists from Penn State's Department of Geosciences said in March that earth-like planets could be more common than previously thought. The team wrote in the Astrophysical Journal Letters that earth-like planets might be as common as four in 10 of the nearest small stars as a conservative estimate.
“I used our new habitable zone calculations and found that there are nearly three times as many Earth-sized planets in the habitable zones around these low mass stars as in previous estimates,” said Ravi Kopparapu, a post-doctoral researcher in geosciences. “This means Earth-sized planets are more common than we thought, and that is a good sign for detecting extraterrestrial life.”