The National Optical Astronomy Observatory announced on Wednesday the discovery of Kepler-21b, a new planet that’s close to the size of earth and is only about 352 light years away. Right next door in astronomical standards.
Astronomers frequently discover new planets (according to Time magazine, we’re up to over 2,000), but what’s exciting about Kepler 21-b is that the planet is nearly Earth-sized. While its mass is about 10 times the size of our planet, its radius is only 1.6 times the size of Earth’s.
Until a few years ago, the smallest extra-solar planet that we had discovered were the size of Jupiter or Saturn, which are about ten times bigger than Earth. Now we’re getting down to something almost the size of the Earth, showing that we now have the technology to find the earth-size planets.
The new planet has a star that’s a bit bigger and hotter than Sol, although it’s substantially younger. But because the planet is so close to its star, it’s far too hot to have liquid water, the base for life as we know it. At only 6 million kilometers (about 3.7 million miles) away from the star, Kepler-21b’s temperature is a blistering 2,960 degrees Fahrenheit.
By contrast, Earth is about 150,000,000 km (93 million miles) from our sun.