A “wobble” in measured gravity of a nearby solar system has allowed NASA astronomers to identify “earth’s bigger cousin” hanging out in the Aquarius constellation.
The rocky planet orbits the star Gliese 876, which centers a solar system just 15 light-years away (an astronomically modest 90 trillion miles from Earth), and is around seven times the size of Earth. Of the 155 identified “extra-solar” planets, NASA scientists say this planet is the most Earth-like so far.
“It’s like Earth’s bigger cousin,” Paul Butler of the Carnegie Institution of Washington and NASA team member who helped identify the planet.
What makes it so earthlike is that the planet is rocky with a metal core, as opposed to Jupiter- or Neptune-like gassy and/or icy planets that inhabit the same solar system. Earth’s cousin takes just 2 days to orbit its star, resting just 2 million miles away from it. Earth is 93 million miles from the sun.
The planet’s proximity to its star makes it far too hot to support any type of life similar to Earth’s, however, raising its temperature to between 400 and 700 degrees F (204-371 C).
“It’s a very unearthly world,” said Jack Lissauer of NASA’s Ames Research Center. “It’s likely to be the first rocky planet orbiting a star like our sun.”
Three other rocky planets have been discovered prior to this one, but all three orbit a pulsar, or the remnant of an exploded star.
Finding the planet wasn’t easy.
“It took 150 observations of this star to glean the existence of this Earth-like planet,” said planet hunter Geoffrey Marcy of the University of California, Berkeley. “This will definitely be one of our favorite stars from now on.”
And still, astronomers have no direct proof of the planet’s rocky makeup. The low mass is thought to indicate that the planet is not a gas giant like Jupiter.
