Astronomers using the NASA/ESA/CSA James Webb Space Telescope have captured compelling evidence of a planet with a mass similar to Saturn orbiting the young nearby star TWA 7. If confirmed, this would represent Webb’s first direct image discovery of a planet, and the lightest planet ever seen with this technique.
Using the coronagraph on Webb’s Mid-Infrared Instrument (MIRI) on 21 June 2024, the team carefully suppressed the bright glare of the host star to reveal faint nearby objects. This technique, called high-contrast imaging, enables astronomers to directly detect planets that would otherwise be lost in the overwhelming light from their host star. After subtracting residual starlight using advanced image processing, a faint infrared source was revealed near TWA 7, distinguishable from background galaxies or Solar System objects. The source is located in a gap in one of three dust rings that were discovered around TWA 7 by previous ground-based observations. Its brightness, colour, distance from the star, and position within the ring are consistent with theoretical predictions for a young, cold, Saturn-mass planet sculpting the surrounding debris disc.
Initial analysis suggests that the object – referred to as TWA 7b – could be a young, cold planet with a mass around 0.3 times that of Jupiter (~100 Earth masses) and a temperature near 320 Kelvin (roughly 47 degrees Celsius).
In this image from MIRI, light from the star TWA 7 has been subtracted. The location of the star is marked with a circle and a star symbol at the centre of the image. This leaves light from the debris disc around the star, as well as other infrared sources, visible. The bright spot to the upper right of the star is the source identified as TWA 7b, within the debris disc. The more distant orange spot visible in the left of the image is an unrelated background star.
Only a single MIRI band was used in this image (seen here in orange). The blue colour visible in the image results from an additional band taken by the SPHERE instrument of ESO’s Very Large Telescope (VLT), which showcases the location of the disc surrounding the host star and the exoplanet creating a gap within the disc that is revealed by MIRI.
[Image Description: An image of a nearby star and its vicinity. The star itself has been blocked out and its bright light has been removed. A dashed circle with a star symbol at the centre of the image marks the star’s location. A fuzzy blue disc surrounds the star. An orange spot, near to the star and inside this disc, is identified as a planet orbiting the star. A fainter orange spot far from the centre marks a distant star.]
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