Astronomers find exoplanet twice the mass of Jupiter hiding in plain sight

The planet is only a few million years old and may be responsible for a spiral 'arm' in its surrounding protoplanetary disk.
Chris Young
An artist's impression of an exoplanet.
An artist's impression of an exoplanet.

Дмитрий Ларичев / iStock 

Scientists discovered a giant exoplanet, MWC 758c, that they believe might be responsible for generating spiral "arm" patterns in protoplanetary disks extending from the Milky Way's center.

These spiraling arms of gas are filled with stars, and they are thought to be the birthplace for planetary systems.

At the same time, scientists have theorized that interactions with nascent planets may cause the spiraling patterns themselves. Now, scientists believe they may have the first direct evidence that this is, in fact, the case.

Unearthing a nearby exoplanet

The scientists, who detailed their new findings in a paper in the journal Nature Astronomy, believe the planet MWC 758c may be generating the spiral arms in its infant planetary system.

"Our study puts forward a solid piece of evidence that these spiral arms are caused by giant planets," Kevin Wagner, lead author of the paper and a postdoctoral researcher at the UArizona Steward Observatory, explained in a press statement.

"And with the new James Webb Space Telescope, we will be able to further test and support this idea by searching for more planets like MWC 758c," Wagner added.

The planet's star is roughly 500 light-years away from Earth and is only a few million years old. Typically, a protoplanetary disk takes about 10 million years to disappear from a system.

The spiral pattern surrounding the planet was first discovered in 2013. Scientists quickly pointed out that it may be representative of findings connected to theoretical simulations showing the formation of giant planets.

"I think of this system as an analogy for how our solar system would have appeared less than 1 percent into its lifetime," Wagner explained. "Jupiter, being a giant planet, also likely interacted with and gravitationally sculpted our disk billions of years ago, which eventually led to the formation of Earth."

"Spiral arms can provide feedback on the planet formation process itself," Wagner continued. "Our observation of this new planet further supports the idea that giant planets form early on, accreting mass from their birth environment, and then gravitationally alter the subsequent environment for other, smaller planets to form."

Why haven't we detected more planets like MWC 758c?

Scientists don't fully understand why we have only detected a planet within a spiral arm for the first time. Their models suggest that these planets should be very bright when they are newly formed. However, the discovery of MWC 758c may explain why these newly-formed giants are so elusive.

The UArizona researchers used an instrument at the Large Binocular Telescope Interferometer or LBTI, which has a similar capacity to the James Webb Space Telescope for detecting infrared light. Without it, they say they wouldn't have been able to detect the planet, despite it being at least twice Jupiter's mass.

Though they don't fully understand why, MWC 758c has a red hue, meaning its longer, red wavelengths are harder to detect when passing through the thermal glow of Earth's atmosphere.