Field of Science

Pale Terraqueous Globes

Image credit: NASA Ames/JPL-Caltech/Tim Pyle
Imagine the closest star beyond the Sun has a planet orbiting it about the size of Earth. Visualize what your sunset would look like on this distant planet. Perhaps there would be two stars at the center of this solar system. Your sunset would be breathtaking. You could even visualize what the Sun would look like from this planet – just another unassuming star in the sky. You don't have to merely imagine that such a planet might exist. A planet like this really does exist – of course you'd still have to imagine the part where you are on the surface of this world. The Alpha Centauri star system, which is essentially a triple star system of Alpha Centauri A, Alpha Centauri B, and Proxima Centauri has just such a planet. There is a planet in the sky waiting for us at a distance that is just two hundred and seventy thousand times further than the Earth is from the Sun. This planet is near 1500 degrees on the surface, so we wouldn't want to be there, but nonetheless the fact is that astronomers are finding similar planets commonly. There may be a planet just the size of Earth at a nice temperature quite near us galactic speaking. We are searching.

Most planets don't seem to be much like Earth. In fact so far we haven't found a single planet that has a temperature and size similar to Earth, but part of the problem with finding planets is that finding big giant planets – like Jupiter is easy – while small rocky planets like Earth are elusive. But we are on the edge of discovery. All in all Earth-like planets likely abound. In fact with 95% confidence there is an Earth size planet in the habitable zone of a small star within 23 light years of us. The habitable zone is the place where a planet would not be too hot or too cold. A place where a planet wouldn't see its oceans boiled off or frozen into desolate ice tundra. Habitable planets are common in our galaxy and by galactic standards not very far apart. On average Earth-like planets are only 13 light-years apart.  

Continue reading my essay on planets over at 3 Quarks Daily...