NASA's Webb Discovers Its First Alien Planet And It's Hiding A Trojan Disk Surprise

This week NASA's James Webb Space Telescope (JWST) provided the first direct image of a planet with a mass similar to Saturn's, orbiting the young star TWA 7. This landmark observation, detailed in the Nature journal, not only marks Webb's inaugural planet discovery but also unveils the lightest exoplanet ever seen.

Astronomers utilizing Webb's Mid-Infrared Instrument (MIRI) detected a faint infrared source nestled within the debris disk surrounding TWA 7, a red dwarf star approximately 6.4 million years old and located about 34 light-years away in the TW Hydrae association. The newly identified object, designated TWA 7 b, is estimated to be roughly 50 times the Earth-Sun distance from its host star, a position that aligns with expected features observed within the debris disk.

What makes this discovery particularly special is the planet's role as a "shepherd," actively sculpting the surrounding disk of dust and rocky material. For years, scientists have theorized that gaps and rings within these debris disks are carved out by nascent planets, yet direct observational evidence of such an interaction has remained elusive until now. TWA 7 b resides within a distinct gap in one of TWA 7's three concentric dust rings, providing the first clear detection of a planet creating such a void. This observation also offers the first potential hint of a "trojan disk"—a collection of dust trapped in the planet's orbit.

Anne-Marie Lagrange, French National Center for Scientific Research researcher and lead author of the study stated, "Our observations reveal a strong candidate for a planet shaping the structure of the TWA 7 debris disk, and its position is exactly where we expected to find a planet of this mass." Lagrange further emphasized the observatory's capability to image planets akin to those in our own solar system, marking a significant stride in understanding planetary systems.

Initial analyses suggest TWA 7 b is a young, relatively cold planet, with a mass around 0.3 times that of Jupiter (equivalent to one Saturn mass or approximately 100 Earth masses) and a temperature of about 120 degrees Fahrenheit (47 degrees Celsius).

The imaging technique employed by Webb's MIRI, known as high-contrast imaging, involves suppressing the glare of the host star to reveal faint, nearby objects. This allowed researchers to pinpoint TWA 7 b, ruling out background galaxies or foreground solar system objects as alternative explanations.