NASA has discovered the closest super-Earth exoplanet yet

Astronomers have found more than a thousand planets outside our solar system, but most of them are large compared to Earth. Of those thought to be small and rocky, they’ve all been incredibly far away, even by interstellar standards. Now NASA is reporting the discovery of a new exoplanet just several times larger than Earth (a so-called super Earth) that is only 21 light years away. This could make it a fantastic target for future study.
The alien planet is called HD 219134b and was detected by NASA’s Spitzer Space Telescope. The planet is roughly 4.5 times more massive than Earth, but only 1.6 times as wide. That means it’s most likely rocky. That’s what the “super Earth” distinction is based on, that it’s too small and dense to be a gas giant. We don’t know much else about the surface, though.
HD 219134b was detected via the transit method of exoplanet detection, which is the technique also used by NASA’s crippled Kepler telescope that regularly spots dozens of potential exoplanets. The transit method looks for small dips in the light output of a star, indicating that something is passing between it and our location on Earth. By watching for recurring dips, we can locate planets and partially characterize them.
It didn’t take long for Spitzer to confirm the existence of HD 219134b. It whips around its parent star once every three days. It also obits extremely closely to the star. This is a smaller, cooler Type K orange star, but the surface of HD 219134b is still far too hot for life as we know it to exist.

There are three other planets in the HD 219134 system, but we don’t know as much about them yet. There is one that is at least 2.7 times as massive as Earth, but it could be much larger. Its orbital period is 6.8 days. There’s also a Neptune-sized planet that orbits once every 47 days, and a planet 62 times larger than Earth that orbits once every 1190 days.
Astronomers are excited to find HD 219134b not only because it’s a super Earth, but because it’s the closest transiting world yet. The closest exoplanet we know of is about 14 light years away, but it doesn’t transit its star. We can learn much more about the nature of an exoplanet when it passes in front of a star like this one does.
The James Webb Space Telescope is currently scheduled to launch in 2018, and you can bet it’s going to be pointed at HD 219134b quickly. This instrument will be able to directly image some exoplanets and perform detailed spectroscopic analyses of their atmospheres.