Newly Discovered Pink Exoplanet on the Lighter Side

Scientific Minds Want To Know

Researchers imaged this planet around a sun-like star, but its origins remain a mystery.

 by Jane J. Lee

There is a pink exoplanet circling a star very much like our own, 57 light-years away from Earth. But its origins are a mystery. 

In a new study announcing the magenta gas giant, researchers were able to directly image this exoplanet using the Subaru telescope on Hawaii. The color of this blushing body indicates it has less cloud cover than other observed exoplanets, meaning researchers can peer even deeper into its atmosphere to divine its components. (Related: "For First Time, Astronomers Read Exoplanet's Color.")

"If we could travel to this giant planet, we would see a world still glowing from the heat of its formation with a color reminiscent of a dark cherry blossom, a dull magenta," said Michael McElwain, an astrophysicist at NASA's Goddard Space Flight Facility in Maryland and a study co-author, in a statement.

It's one of only five or six exoplanets whose presence has been directly imaged by a telescope, rather than inferred from observing stars, said Markus Janson, an astrophysicist at Princeton University and a co-author of the new study.

Other planets that have been directly imaged orbit much more massive stars, he added. "In that sense, [the pink planet] feels a bit closer to home." (Related: "First Pictures of Alien Planet System Revealed.")

At about 460°F (237°C), this gas giant probably wouldn't be a very pleasant place to visit. But researchers are still interested in this lightweight—it's one of the lowest-mass exoplanets found around a sun-like star using direct detection methods. (Related: "Smallest Exoplanets Found—Each Tinier Than Earth.")

Ejected

It orbits about 43 astronomical units (AUs) away from its parent star, much farther out than Neptune's orbit (30 AUs) around the sun.

The wide gulf between this exoplanet and its star puts it outside the conventional area expected for planet formation.

In a mechanism called the core accretion model, bits of rock, dust, and ice in the disk of material around a young star collide and stick together until the solid lump grows to the size of a planet.

But this tends to happen close in to a star, said Janson. "Because [this planet] is so far out, it's very hard to see how it formed by core accretion."

The jostling amongst budding planets in a young solar system could have resulted in a collision that ejected the pink exoplanet out to its current orbit, said McElwain in an interview. (Related: "Youngest Planet Confirmed; Photos Show It Grew Up Fast.")

But planet formation is an evolving field, and this is just one possible explanation, he added.

So Far Away

McElwain and colleagues would also like a better sense of this magenta giant's orbit.

Something 43 AUs from its star would take more than a hundred years to complete an orbit, McElwain said.

But because of its orientation with respect to Earth, it's very possible this exoplanet is even farther away from its star.

The shape of the exoplanet's orbit would also lend further clues as to its formation. If it's on a very eccentric—or non-circular—orbit, that would support the scattering hypothesis, McElwain said.

A More Complete Picture

This is why it's important to get as complete a picture as possible on the types of exoplanets out there, said Adam Burrows, an astrophysicist at Princeton University and a study co-author.

And high-contrast imaging—the technique used to directly detect exoplanets—could really help with that. "[It] is starting to come into its own after being a secondary or tertiary means of discovering planets," he said.

Several telescopes coming online in the next year or two will be even better at picking up the faint glow given off by exoplanets, Burrows added.

Previous exoplanet-detection techniques work on bodies close in to their stars. But high-contrast imaging will tell us more about planets farther away from their parent stars, he said.