There are over 5,000 known exoplanets, but the vast majority of them have been detected using techniques such as the transit method, in which the light from a host star dips slightly when a planet passes in front of it, or radial velocity, in which a star is slightly dragged by the gravity of a planet. In these methods, the existence of a planet is inferred because of an observable effect on a star, so the planet itself is not directly observed. In rare cases, however, an exoplanet can be observed directly, particularly if it is a large planet that is relatively close. This image shows the exoplanet HIP 65426 b in different bands of infrared light, as seen by the James Webb Space Telescope: purple shows the NIRCam instrument view at 3.00 micrometers, blue shows the NIRCam instrument view at 4.44 micrometers, yellow shows the MIRI instrument view at 11.4 micrometers, and red shows the MIRI instrument view at 15.5 micrometers. These images look different because of the ways the different Webb instruments capture light. NASA/ESA/CSA, A Carter (UCSC), the ERS 1386 team and A. Pagan (STScI) Webb made one such direct observation of the exoplanet HIP 65426 b and was able to capture an image of the planet using four different filters. Each of these filters corresponds to a different wavelength of light, capturing different features of the planet and its environment. The planet is large with a mass between six and 12 times that of Jupiter, and is relatively young at just 15 to 20 million years old. “This is a transformative moment, not just for Webb but for astronomy in general,” head of observations Sasha Hinckley said in a statement. To observe the planet, the researchers had to block out the light coming from the planet’s host star. As the star is much brighter than the planet, this light must be blocked in order to see the planet. This is done with an instrument called a coronagraph, which is a mask that blocks light from a light source. “It was really impressive how well the Webb coronagraphs worked to suppress the starlight,” Hinckley said. “Getting this image was like hunting for space treasure,” said another of the researchers, Aarynn Carter. “At first all I could see was light from the star, but with careful image processing I was able to remove that light and reveal the planet.” This finding demonstrates some of Webb’s ability to find and investigate exoplanets. “I think the most exciting thing is that we’re just getting started,” Carter said. “There are many more images of exoplanets to come that will shape our overall understanding of their physics, chemistry and formation. We may even discover previously unknown planets.”
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