Hubble Targets Super-Earth Exoplanet to Study its Alien Atmosphere

Astronomers are peering further and further afield, thanks in part to NASA's Kepler spacecraft. Now, scientists are using Hubble in order to study the exoplanets that Kepler identified, which could eventually lead to the discovery of life on other planets.

After NASA's Kepler spacecraft was launched on a planet-hunting mission in 2009, it eventually went on to identify more than 4,000 candidate exoplanets, where are planets outside of our solar system. Surprisingly, Kepler showed that smaller planets are much more common than big ones, and the most common are those that are just a bit larger than Earth, dubbed super-Earths. Despite being common, though, there are no examples of super-Earths in our corner of the galaxy.

"We are left with this situation where super-Earths appear to be the most common kind of exoplanet in the galaxy, but we don't know what they're made of," said Heather Knutson, one of the researchers, in a news release. "It's really interesting to think about these planets because they could have so many different compositions, and knowing their composition will tell us a lot about how planets form."

In order to learn a bit more about these super-Earths, the scientists are using Hubble and Spitzer Space Telescopes. In this case, the researchers have focused on the super-Earth called HD 97658b in the constellation Leo. They used Hubble to measure the decrease in light when the planet passed in front of its parent star over a range of infrared wavelengths in order to detect small changes caused by water vapor in the planet's atmosphere.

That said, the data came back featureless. It's likely that the super-Earth is enveloped by clouds, or has an atmosphere that's lacking hydrogen. Because such an atmosphere could be very compact, it would make the telltale fingerprints of water vapor and other molecules very small and hard to detect.

"Our data are not precise enough to tell whether it's clouds or the absence of hydrogen in the atmosphere that's causing the spectrum to be flat," said Knutson. "This was just a quick first look to give us a rough idea of what the atmosphere looked like. Over the next year, we will use Hubble to observe this planet again in more detail. We hope those observations will provide a clear answer to the current mystery."

The findings reveal some challenges that the researchers will face as they continue to study exoplanets. This, in turn, will help them better target their studies in order to make more precise findings in the future.

The findings are published in The Astrophysical Journal.