NASA's James Webb Telescope Discovers Giant Exoplanet Twice As Massive As Jupiter

A giant planet has been discovered hiding in one of the most closely studied planetary systems in the Milky Way. Astronomers using NASA's James Webb Space Telescope identified the new exoplanet, called Beta Pictoris d, through a unique chemical signal from its atmosphere, reported NASA.

The young and nearby star Beta Pictoris was already known to have two giant planets, Beta Pictoris b and Beta Pictoris c. Beta Pictoris b was one of the first exoplanets to be directly imaged. The discovery of Beta Pictoris d makes the system only the second known planetary system to contain at least three imaged planets.

Unlike the other two planets, Beta Pictoris d was not discovered by identifying a bright point of light. Instead, astronomers detected the unique chemical fingerprint of its atmosphere.

Aidan Gibbs, lead author of the new study published in the Astrophysical Journal Letters and a postdoctoral researcher at the University of California, San Diego, said this discovery adds another piece to an already fascinating planetary system. He said Beta Pictoris has long served as a laboratory for understanding how planetary systems form and evolve, and now another planet is helping tell that story.

Beta Pictoris is located 63 light-years from Earth and is about 23 million years old. 

The team estimates that Beta Pictoris d is likely at least two times the mass of Jupiter, making it the smallest of the three known giant planets in the system. Models suggest that it likely orbits its star at about 30 astronomical units, which is comparable to the region occupied by Neptune in our solar system.

It has the widest orbit among the three known planets, while still being inside the inner edge of the debris disk.

Astronomers were not searching for another planet with Webb. The discovery happened while the team was using the telescope's NIRSpec, or Near-Infrared Spectrograph, to study the atmosphere of Beta Pictoris b.

The team used NIRSpec's Integral Field Unit, which obtains both an image and a spectrum from each pixel in an image.

Gibbs said they were not looking for a new planet and were trying to understand one they already knew existed. He said a telltale signal then appeared in the data where they did not expect it.