NASA's James Webb Space Telescope Discovers New Giant Planet Hidden In Nearby Star System

Astronomers have found a new giant planet in a nearby star system using NASA's James Webb Space Telescope. The discovery was made while researchers were studying another known planet, making it an unexpected finding in one of the most closely studied planetary systems in the Milky Way galaxy, reported NASA.

The newly discovered planet, called Beta Pictoris d, is an exoplanet located outside our solar system. The young 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 ever directly imaged.

With the discovery of Beta Pictoris d, Beta Pictoris has become only the second known planetary system with at least three directly imaged planets.

Unlike Beta Pictoris b and c, the new planet was not discovered by identifying a bright point of light. Instead, astronomers detected the unique chemical fingerprint of its atmosphere, a method that could change the way scientists search for planets around other stars.

Lead author Aidan Gibbs, a postdoctoral researcher at the University of California, San Diego, said that this discovery adds another piece to an already fascinating planetary system.

He said that Beta Pictoris has long served as a laboratory for understanding how planetary systems form and evolve, and now another planet is helping scientists tell that story. The study was published in the Astrophysical Journal Letters.

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

The research 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 the planet orbits its star at about 30 astronomical units, similar to the region where Neptune orbits in our solar system. It has the widest orbit among the three known planets but still remains inside the inner edge of the debris disk.

Astronomers were not searching for another planet when they made the discovery. The team was using Webb's Near-Infrared Spectrograph (NIRSpec) to study the atmosphere of Beta Pictoris b. 

The signal appeared as a series of peaks and troughs in the spectroscopic data where the team expected to see a smooth spectrum from light reflecting off dust. It showed a distinctive pattern of carbon monoxide absorption lines, which is an expected feature in the atmospheres of giant planets.

Using spectroscopy, the researchers also measured the planet's motion. They found that the planet's speed, position and alignment with the debris disk matched an object orbiting Beta Pictoris rather than a background star or a brown dwarf with carbon monoxide in its atmosphere.

Follow-up observations using Webb's Mid-Infrared Instrument (MIRI) through a Director's Discretionary Time request detected water vapour and methane. These observations further confirmed the planet's identity and provided a more detailed view of its atmosphere.

A separate imaging study led by Ben Sutlieff of the University of Edinburgh and Markus Bonse of the European Southern Observatory supported the findings. Using data from the European Southern Observatory's Very Large Telescope and Webb's Near-Infrared Camera (NIRCam), the study independently confirmed the existence of Beta Pictoris d.