First Ever 'Earth-Sized' Alien Planets Discovered - orbiting a star 950 light-years from Earth -
Two planets orbiting a star 950 light-years from Earth are the smallest, most Earth-size alien worlds known, astronomers announced Tues., Dec. 20. One of the planets is actually smaller than Earth, scientists say.
These planets, while roughly the size of our planet Earth, are circling very close to their star, giving them fiery temperatures that are most likely too hot to support life, researchers said. The discovery, however, brings scientists one step closer to finding a true twin of Earth that may be habitable.
"We've crossed a threshold: For the first time, we've been able to detect planets smaller than the Earth around another star," lead researcher François Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., told SPACE.com. "We proved that Earth-size planets exist around other stars like the sun, and most importantly, we proved that humanity is able to detect them. It's the beginning of an era."
To discover the new planets, Fressin and his colleagues used NASA's Kepler space telescope, which noticed the tiny dips in the parent star's brightness when the planets passed in front of it, blocking some of its light (this is called the transit method). The researchers then used ground-based observatories to confirm that the planets actually exist by measuring minute wobbles in the star's position caused by gravitational tugs from its planets.
"These two new planets are the first genuinely Earth-sized worlds that have been found orbiting a sunlike star," University of California, Santa Cruz astronomer Greg Laughlin, who was not involved in the new study, said in an email to SPACE.com. "For the past two decades, it has been clear that astronomers would eventually reach this goal, and so it's fantastic to learn that the detection has now been achieved."
Chances for life
The two Earth-size planets are among five alien worlds orbiting a star called Kepler-20 that is of the same class (G-type) as our sun, and is slightly cooler.
Two of the star system's planets, Kepler-20e and Kepler-20f, are 0.87 times and 1.03 times the width of Earth, respectively, making them the smallest exoplanets yet known. They also appear to be rocky, and have masses less than 1.7 and 3 times Earth's mass, respectively.
Kepler-20e makes a circle around its star once every 6.1 days at a distance of 4.7 million miles (7.6 million kilometers) — almost 20 times closer than Earth, which orbits the sun at around 93 million miles (150 million km).
The planet's sibling, Kepler-20f, makes a full orbit every 19.6 days, at a distance of 10.3 million miles (16.6 million km). Both planets circle closer to their star than Mercury does to the sun. [Infographic: Earth-Size Alien Planets Explained]
These snuggly orbits around their star give the newfound planets steamy temperatures of about 1,400 degrees Fahrenheit (760 degrees Celsius) and 800 degrees Fahrenheit (430 degrees Celsius) — way too warm to support liquid water, and probably life, researchers said.
Fressin said the chance of life on either of these planets is "negligible," though the researchers can't exclude the possibility that they used to be habitable in the past, when they might have been farther from their star. There is also a slim chance that there are habitable regions on the planets in spots between their day and night sides (the planets orbit with one half constantly facing their star and the other half always in dark). But astronomers aren't holding out hope.
"The chances of liquid water and life as we know it on Kepler-20e and f are zero," Laughlin said.
Read more: http://www.foxnews.com/scitech/2011/12/20/first-ever-earth-sized-alien-planets-discovered/
Two planets orbiting a star 950 light-years from Earth are the smallest, most Earth-size alien worlds known, astronomers announced Tues., Dec. 20. One of the planets is actually smaller than Earth, scientists say.
These planets, while roughly the size of our planet Earth, are circling very close to their star, giving them fiery temperatures that are most likely too hot to support life, researchers said. The discovery, however, brings scientists one step closer to finding a true twin of Earth that may be habitable.
"We've crossed a threshold: For the first time, we've been able to detect planets smaller than the Earth around another star," lead researcher François Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., told SPACE.com. "We proved that Earth-size planets exist around other stars like the sun, and most importantly, we proved that humanity is able to detect them. It's the beginning of an era."
To discover the new planets, Fressin and his colleagues used NASA's Kepler space telescope, which noticed the tiny dips in the parent star's brightness when the planets passed in front of it, blocking some of its light (this is called the transit method). The researchers then used ground-based observatories to confirm that the planets actually exist by measuring minute wobbles in the star's position caused by gravitational tugs from its planets.
"These two new planets are the first genuinely Earth-sized worlds that have been found orbiting a sunlike star," University of California, Santa Cruz astronomer Greg Laughlin, who was not involved in the new study, said in an email to SPACE.com. "For the past two decades, it has been clear that astronomers would eventually reach this goal, and so it's fantastic to learn that the detection has now been achieved."
Chances for life
The two Earth-size planets are among five alien worlds orbiting a star called Kepler-20 that is of the same class (G-type) as our sun, and is slightly cooler.
Two of the star system's planets, Kepler-20e and Kepler-20f, are 0.87 times and 1.03 times the width of Earth, respectively, making them the smallest exoplanets yet known. They also appear to be rocky, and have masses less than 1.7 and 3 times Earth's mass, respectively.
Kepler-20e makes a circle around its star once every 6.1 days at a distance of 4.7 million miles (7.6 million kilometers) — almost 20 times closer than Earth, which orbits the sun at around 93 million miles (150 million km).
The planet's sibling, Kepler-20f, makes a full orbit every 19.6 days, at a distance of 10.3 million miles (16.6 million km). Both planets circle closer to their star than Mercury does to the sun. [Infographic: Earth-Size Alien Planets Explained]
These snuggly orbits around their star give the newfound planets steamy temperatures of about 1,400 degrees Fahrenheit (760 degrees Celsius) and 800 degrees Fahrenheit (430 degrees Celsius) — way too warm to support liquid water, and probably life, researchers said.
Fressin said the chance of life on either of these planets is "negligible," though the researchers can't exclude the possibility that they used to be habitable in the past, when they might have been farther from their star. There is also a slim chance that there are habitable regions on the planets in spots between their day and night sides (the planets orbit with one half constantly facing their star and the other half always in dark). But astronomers aren't holding out hope.
"The chances of liquid water and life as we know it on Kepler-20e and f are zero," Laughlin said.
Read more: http://www.foxnews.com/scitech/2011/12/20/first-ever-earth-sized-alien-planets-discovered/
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