What's the Deal with 'Super-Earth' Exoplanets?

The big news in the universe this week is that NASA’s Spitzer Space Telescope has managed to capture light from an exoplanet. An alien "super-Earth" to be exact, which makes this the first time astronomers have managed to detect light from a small, rocky body.

But don't let the name fool you. Super-Earths have very little in common with our own planet. That's not to say the discovery isn't fascinating, but it's more science as usual than the discovery of our next home.

There are many parts to this story, like the part about 55 Cancri e. It isn't a new find. Astronomers discovered it in 2005 and have since determined that it's one of five planets in a solar system orbiting the star 55 Cancri about 41 lightyears away in the constellation Cancer. They also know that 55 Cancri e orbits extremely close to its parent star and its star-facing side is heated and emits a thermal glow -- that's the infrared emission Spitzer picked up.

This isn't the first planet Spitzer has observed directly either -- usually astronomers "see" planets by a telltale dip in the brightness of the parent star as they pass in front of it (i.e. the "transit method"), or the "wobble" of a star as an exoplanet orbits it (i.e. the "radial velocity method"). But the $770 million telescope, which was launched in 2003, is searching for exoplanets directly by detecting their glow in the infrared spectrum.

Hot Jupiters are gas giants that orbit their parent stars closer than Mercury orbits our Sun. These are big planets with big surfaces that reflect a lot of light and generate a lot of heat making them easier for telescopes to find. That Spitzer measured 55 Cancri e directly is impressive since as a super-Earth, it's much smaller than a hot-Jupiter and gives off a lot less light.

It's 55 Cancri e's classification as a super-Earth that's a little problematic. The term may be intuitive to astronomers, but to the rest of us it's incredibly misleading.

With the familiar name "Earth," it's easy to see why people read "super Earth" and get really excited. Our home planet Earth is pretty super. We have a temperate climate, fresh water, ample sunlight, a protective magnetic field, and a balanced atmosphere. Earth has everything that makes life possible. By extension, and by linguistic convention, a super-Earth should be better -- a bigger Earth with more fresh water, beach weather year round, a thicker or richer atmosphere, and anything else that could improve our own planet.

In actuality, super Earths are quite different from our Earth. Super Earths have masses roughly 10 times greater than Earth's, but 55 Cancri e shares its rocky nature with Earth -- that’s where the similarities end, however. But that isn't to say it’s not a really neat planet.

Read more at Discovery News