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The James Webb Space Telescope (JWST) has taken the first direct picture of a recently found exoplanet. Astronomers have revealed that Webb discovered a Saturn-mass planet around the neighboring young star TWA 7. TWA 7 b is the smallest planet yet discovered by direct imaging, with a mass around 0.3 times that of Jupiter, or roughly Saturn's mass. Most of the almost 6,000 known exoplanets have been discovered indirectly. The JWST team detected TWA 7 b by blocking the star's light using a coronagraph, similar to a solar eclipse.
Detecting A Hidden World
According to a research published in the journal Nature, Webb's team chose TWA 7 because its dusty disk is almost face-on, displaying visible ring structures. To reduce the glare from the star, they employed Webb's MIRI equipment in conjunction with a coronagraph. After analyzing the data, a weak infrared point source revealed 1.5 arcseconds away from TWA 7 (approximately 50 times the Earth-Sun distance).
This source is located in a gap in the star's second dust ring. Its brightness and hue correspond to what theoretical models anticipate for a young, frigid planet of Saturn's mass. The object appears to be carving out the ring gap in the same way as an orbiting planet does. Astronomers ruled out alternative theories (such as a background star) to conclude that the signal is best explained by a planet.
A step toward smaller worlds
TWA 7 b's Saturn-like mass makes it ten times less massive than any other exoplanet seen in a direct view. Its finding demonstrates that Webb can now image worlds far smaller than the previously observed large exoplanets. Scientists believe the telescope will someday identify planets as light as 10% of Jupiter's mass, bringing them closer to Earth's size.
This accomplishment "paves the way" for picturing fully terrestrial planets in the future. Astronomers even believe that new observatories will significantly increase the number of Earth-sized planets seen through direct imaging. Next-generation telescopes, both on the ground and in space, are being designed with even more powerful coronagraphs to search for the first directly imaged Earth analogues.
