Did We Really Find an Earth-Like Planet?
Yup, we have all seen the headlines. Now it’s just a matter of time before the aliens descend upon us. Or is it?
Astronomers can actually tell if a planet is orbiting a star by looking at the light of the star itself. As the planet orbits, it tugs on the star ever-so-slightly. This causes the light emitted by the star to be doppler-shifted. Basically this means that the colour of the star changes as the planet orbits.
By looking at how much the colour of the star changes, and how often it changes, we can tell how big the planet is, and how far away from the parent star it is.
That’s pretty freakin’ amazing if you think about it. And now, astronomers have announced that there is a planet roughly 3 times the size of the Earth orbiting a star called Gliese 581, a red dwarf star roughly 20 light years away. The planet is called Gliese 581g.
What is making this headline news is that the planet is orbiting the star in the so-called “Goldilocks” zone. A distance which is just far enough from the star that liquid water could exist on the surface. Many scientists believe that liquid water is essential to the development of life. THAT’S whats gotten the media’s attention.
While I hate to cheapen the importance of this discovery, because it is important, we shouldn’t start panicking about a possible alien invasion just yet.
The only things we are sure of is that the planet is roughly 3 times the size of Earth, and orbits about 1/6 of the distance of the Earth from the Sun. That’s all. Yes, it is possible that liquid water could exist on the surface. This means that it is possible that life could develop on the planet, at some point. But we don’t know that, its just speculation.
Phil Plait also wrote about this on Bad Astronomy. It’s important to clarify what the scientists have actually discovered, and what the news outlets put into their articles. He also points out that perhaps the most important thing about this discovery is that 1) we can detect planets roughly the size of the Earth and 2) that if we can find Earth-size planets only 20 light years from Earth, it is very possible that our galaxy is teeming with planets. Very, very exciting.
For those interested, here is a link to the .pdf of the paper detailing the discovery of the planet. Like I said, it’s a pretty cool discovery, but we haven’t found the Klingon homeworld just yet.