University of Georgia

Far out!

artists' rendering of new plant, 51 Eridani b, by Danielle Futselaar and Franck Marchis, SETI Institute

A team of astronomers has discovered a Jupiter-like planet within a young star system about 96 light years from Earth that could serve as a decoder ring for understanding how planets formed in our own solar system.

The new planet, 51 Eridani b, is the first exoplanet discovered by the Gemini Planet Imager (GPI), a new instrument operated by an international collaboration headed by Bruce Macintosh, a professor of physics in the Kavli Institute at Stanford University.

The GPI was designed specifically for discovering and analyzing faint, young planets orbiting stars. After GPI was installed on the 26-foot Gemini South Telescope in Chile, the team set out to look for planets orbiting young stars. They’ve looked at almost a hundred stars so far.

“This discovery is one of many imaging detections of exoplanets to come in the next few years,” said Inseok Song, an associate professor in the department of physics and astronomy in the UGA Franklin College of Arts and Sciences and co-principal investigator on the GPI exoplanet survey team. “Unlike most of the currently known confirmed exoplanets, these GPI images of exoplanets allow us to examine planetary atmospheric information, which will eventually allow astronomers to examine biosignatures from mature planets during the next decade.”

Once the astronomers zeroed in on the star, they blocked its light and spotted 51 Eridani b orbiting a little farther away from its parent star than Saturn does from the Sun.

Even though the light from the planet is very faint—nearly a million times fainter than its star—subsequent observations revealed that it is roughly twice the mass of Jupiter.

In addition to being the faintest planet ever imaged, it’s also the coldest—800 degrees Fahrenheit, whereas others are around 1,200 degrees—and features the strongest atmospheric methane signal on record. Previous Jupiter-like exoplanets have shown only faint traces of methane, far different from the heavy methane atmospheres of the gas giants in this solar system.

All of these characteristics point to a planet that is very much what models suggest Jupiter was like in its infancy.

UGA research scientist
Inseok Song is an associate professor of physics and astronomy in UGA’s Franklin College of Arts and Sciences.