We're clearing up the gossip around an important discovery that was made last week. You might have heard that the Kepler space telescope captured evidence of an Earth-like exoplanet 500 light-years away. Well, Kepler did something really important out there. But it was an Earth-size planet which is an important distinction and still looks exciting news.
The planet named Kepler-186F has a radius just 1.1 times the size of Earth's. That's a big deal because until now we have a hard time spotting exoplanets of this size. Using a technique called the Transit Method, Kepler watched for the minute dimming happens when a planet passes between us and its star, blocking at a tiny bit of its light. The smaller the planet the less light it blocks and the harder the dimming is to catch—that's why most other planets we've seen have been at least forty times larger than Earth. The discovery of Kepler-186F is heartening evidence that Earth-size exoplanets are out there.
The reason why this world has been described as Earth-like is just because being around the same size as Earth means it's likely to have some similar characteristics. For example, because of its size, astronomers think Kepler-186F may have gravitation similar as of Earth. They also say there's a very excellent chance that it has a rocky surface and it also may have water.
Like Earth, Kepler-186F is in a so-called habitable zone of its star. Meaning, it's just the right distance from its star that water could exist there in a liquid state. Not to say we know there's water there, let alone that it's liquid—as we talked about before, our own solar system proves that the habitable zone is just a big indicator about the possibility of water.
- Venus for instance is in the Sun's habitable zone but its atmosphere is too hot for liquid water.
- On Mars, weak magnetic fields allowed solar activity to strip away the atmosphere making it too cold for liquid water.
The other side, Kepler-186F is different from Earth in one very important way. Its parent star is different! Kepler-186F has a red dwarf, which means it’s much older than our Sun. On one hand, that could be promising because it means life would have had a much longer time to develop in its system. Furthermore, it's much smaller and cooler than our Sun. So, Kepler-186F probably only get about 30 percent as much energy from it as we get from our Sun.