This Week's Amazing Sky: Other Earths

Researchers have already found thousands of exoplanets.  So what was special about discovering yet another one? In fact, this is a planet that's less Earthlike than others we've found.

Packaging, that's what.  The Kepler team issued a press release calling their newly found world Earth 2.0. This catchy phrasing got media coverage and brought it global headlines.

An artist's depiction of Kepler 452b. Credit: NASA.

In truth, this exoplanet, named Kepler 452b, has five times the mass of Earth, a 50% larger diameter, and twice our gravity. Not remotely an Earth-twin. It's a coin toss whether it even has a rocky surface as opposed to being a gas world like Neptune. It probably didn't deserve the front page.

An artist compares Earth to this new planet (called Kepler 452b). Source: NASA

Another Earth?

The public adores the notion of “another Earth,” and the hope of finding ET life is the engine driving that train. The honest-to-goodness major discoveries in that area were:

1. The first exoplanet, found orbiting a star in Pegasus two decades ago, and 
2. Discovering thousands more of all kinds, letting us know our galaxy has at least 20 billion Earth-sized planets in comfortable regions.

Those are the important take-aways. The next potentially big news would be discovering either radio signals signifying intelligence, or else free oxygen in a planet's atmosphere which would indicate plant life. Nothing else matters very much. Having Earth-size and a comfortable orbit isn't enough to draw any conclusions about life.

So now we know that our galaxy is brimming with planets. As for life, perhaps we needn't travel very far. We might want to fast-track a mission to Jupiter's moons. At least two of them have warm, life-friendly, salt water oceans!