I fell way behind on my science and space exploration research last year. I now have a tall pile of to-be-read books and papers in my reading room. But I’m now starting to catch up, beginning with this paper on the atmospheres of Earth-like planets.
As explained in this article from the Planetary Society, the goal of this paper is to start creating a guidebook for finding planets that might be home to alien life. And based on what the paper says early on, it sounds like there are plenty of “habitable Earth-like planets” out there to be found!
If we’re looking only at red dwarf stars, which are the smallest and most common of stars, about 30% of them should have a habitable Earth-like planet orbiting them. And between 5 and 20% of orange, yellow, and yellow-white dwarf stars should have habitable Earth-like planets too. Our own Sun, by the way, is a yellow dwarf star.
Statistically speaking, this means we should find another Earth orbiting a red dwarf within only 2 parsecs of us. And there should be another another Earth orbiting an orange, yellow, or yellow-white dwarf within 6 parsecs. I feel like that’s surprisingly close, at least in the grand scheme of our universe.
Except when astronomers talk about Earth-like planets, what they’re actually describing does not necessarily sound much like Earth. Any planet that’s about the same size and mass as Earth can be called Earth-like, and by that standard Venus is about as Earth-like as any planet can be, aside from Earth itself.
And when this paper talks about habitable Earth-like planets, I’m pretty sure all the authors mean are planets within the habitable zones of their parent stars. But just because a planet orbits within a habitable zone does not mean that planet is truly habitable. Again, look at Venus.
So when we do find a “habitable Earth-like planet” within 2 or 6 parsecs of us, how will we know we’re looking at another Earth and not another Venus? That’s a tricky question. Maybe it would help to think about the problem from a different perspective. You see, while we humans are having a really difficult time finding alien life, the aliens may also be having a very difficult time finding us.
More on that in the next post!