How NASA's Webb discovered giant new exoplanet near Beta Pictoris system

The James Webb Space Telescope discovered a giant planet outside our solar system, called an exoplanet, hiding within one of the most intensely studied planetary systems in our Milky Way galaxy, the National Aeronautics and Space Administration (NASA) said.

Beta Pictoris is a young nearby star, was already known to host two giant planets. One of them (“b”) is one of the first exoplanets ever directly imaged, and another is called Beta Pictoris c. The new planet (“d”) was discovered recently.

This makes Beta Pictoris only the second planetary system known to contain at least three imaged planets.

He added, "We were trying to understand one we already knew existed. Then, this telltale signal appeared in the data where we didn’t expect it."

This signal was a series of peaks and troughs within the spectroscopic data where the team expected to see a smooth spectrum from light bouncing off dust.

NASA said it was a distinctive pattern of carbon monoxide absorption lines, spread out like a barcode, "an expected feature in giant planet atmospheres."

"An unexpected blob was spotted in the IFU imaging - with the distinctive signature of carbon monoxide. Astronomers were able to figure out the object’s speed, position, and alignment with the debris disk of the star, making it clear that this object was orbiting Beta Pic and not just something in the background," NASA said.

Water vapor and methane detected during follow-up observations, further confirming the planet's identity while providing a richer look at the atmosphere of the planet.

A planet which remained hidden for years

According to NASA, Beta Pictoris d remained hidden for years because it lies within one of the brightest debris disks known.

Explaining why this exoplanet wasn't found sooner, NASA explained, “Beta Pic’s debris disk is really bright, and scatters light from the star, making it hard to tell planets from other structures. Webb effectively ignored the dust and was able to hone in on the signature of the planet.”

According to NASA, Beta Pic d is likely twice the mass of Jupiter, and the smallest of the three known giant planets in this system.

It orbits at a distance of about 30 astronomical units, putting it roughly where Neptune is in our own system.

How astronomers found Beta Pic d?

Unlike Beta Pictoris b and c, newfound Beta Pic d was discovered not by identifying a bright point of light - but by detecting its unique atmospheric chemical fingerprint.

Astronomers found Beta Pic d while studying the atmosphere of Beta Pic b with Webb’s Near-Infrared Spectrograph (NIRSpec).

NIRSpec has a special mode (using something called an Integral Field Unit) that returns not only spectral data but spatial data. This can give an image of the object being studied and also allows to map motion.

"We weren't looking for a new planet," said Aidan Gibbs, lead author of a new study published Wednesday in the Astrophysical Journal Letters.

It said that the discovery demonstrates a powerful new way to find exoplanets.

"This is the first directly imaged planet discovered primarily through moderate-resolution spectroscopy, showing that astronomers can identify worlds in complex environments through their atmospheric fingerprints rather than relying solely on traditional coronagraphic imaging," NASA explained.

What's next?

The researchers plan to continue analyzing Webb's observations to better determine the planet's temperature, atmospheric composition, and orbit, providing an even more detailed view of one of astronomy's most iconic planetary systems.