Earth 2.0?

I recently have encountered a firestorm of people (friends and family, naturally) asking (or telling) me about the big news to recently come out of the astronomy newsletters. “Another Earth has been found,” I get told with much excitement. Yes, we have found a fascinating world, extremely close to home and which may be able to harbor life. But before we all jump the gun, the truth is that we MIGHT have discovered such a planet. Still, it’s a really interesting place worth noticing, so here’s a quick rundown of the discovery.

Earth 2.0 (as I like to call it), is orbiting around an M Dwarf star, which is astronomy’s way of saying a small, red, dim star that is much cooler than our sun. This star is called Gliese 581, and since this is the 6th planet around this star, the planet is called Gliese 581g (the first planet discovered is Gliese 581b, and it goes down the list alphabetically in order of discovery). Despite its bland name (I mean, it’s hard to compare to rock-solid names like Earth and Mars), Gliese 581g might be the coziest place for humans to go if we ever lost Earth. Orbiting at roughly 14 million miles away from its star (closer than Mercury is to our Sun), Gliese 581g is in what is referred to as the Habitable Zone, or “Goldilocks Zone”—not too cold, and not too hot. It is in this zone that liquid water is able to exist as its natural state. So far, only one planet has ever been confirmed to have this ability—Earth.

The Gliese 581 system, compared to the distances of our own inner solar system. Image courtesy of the National Science Foundation.

“But Dan, we orbit the sun at a distance of 93 million miles. How come the ‘Goldilocks Zone’ for our sun is so much farther than the zone for Gliese 581?” Great question, reader! The reason is actually very simple—our sun is hotter than Gliese 581, and so its Habitable Zone is much farther away than the one for Gliese 581. But being a cooler star is not a bad thing—stars such as Gliese 581 fuse hydrogen at a lower rate than other stars (they don’t run out of fuel as fast), allowing them to have extremely long life spans. In fact, no M Dwarf star has ever died out, and even after a trillion years (the Universe is only about 14 billion years old), they will still be alive and thriving! These stars have a soft spot in my heart, since I currently do research on them.

Why else does Gliese 581 excite us? It’s so close! Located in the constellation Libra, it is approximately 20 light years away. Of course, that’s 6 trillion miles away, but in our galaxy, whose diameter is 100,000 light years across, it’s literally our next door neighbor (ok, maybe about 2 or 3 houses away). At our current technological abilities, we will have no way of getting there. But who knows what the future holds.

Keep in mind, however, that Gliese 581g is still not confirmed to contain life, or even to contain liquid water at all. Scientists currently estimate an average temperature on this planet between 10 and -24 degrees fahrenheit, comparable to summer in Antarctica. Still, Gliese 581g is tidally locked to its star (the same side of the planet faces the star all the time, while the other side is permanently dark), so temperatures can vary wildly depending on what side you’re on. In fact, being 3 or 4 times the size of Earth, this planet may not be habitable at all. Indeed, conditions for life on a planet is complicated and based on many factors, so it’s very difficult at this time to really say what’s going on there.

Still, there’s a chance, and that’s exciting! In years to come, we should hopefully be able to find out more data about the planet (atmosphere, composition, density, etc.), as well as confirm the data we think we already know (size, temperature), and once we find out that data, we’ll be able to truly form a picture of what this planet may be like. Who knows…maybe this distant world is a kindred spirit to our own, blue paradise.