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First exoplanet picture from James Webb Space Telescope revealed

For the first time, astronomers using the James Webb Space Telescope have captured an image of an exoplanet directly from space

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September 1, 2022

The exoplanet HIP 65426 b as seen by the NIRCam and MIRI instruments on the James Webb Space Telescope

NASA/ESA/CSA, A Carter (UCSC), ERS 1386 team, A. Pagan (STScI)

The James Webb Space Telescope (JWST) has captured its first images of an alien world — and because the telescope performs 10 times better than expected, we’re likely to see many more in the future.

Astronomers have captured direct images of only 20 exoplanets, all from telescopes on Earth. But because our planet’s atmosphere blocks much of the infrared range, it was difficult to detect features of these planets in detail.

“Being here on Earth makes the sensitivity really low for what we can detect, and to this day the lowest-mass planet we’ve been able to detect is about two Jupiter masses,” he says. Sasha Hinkley at the University of Exeter, UK.

Now, Hinkley and his colleagues have used JWST to directly image a so-called super-Jupiter exoplanet, HIP 65426 b, which has about seven Jupiter masses and orbits a star about 400 light-years from Earth. The team captured it in a range of infrared wavelengths and with a precision previously impossible.

“What we know from these observations is that JWST is going to break that sensitivity floor,” Hinkley says. Future observations should be able to go well below Jupiter’s mass, he says. “It allows us to go to planets that are analogs to ice giants in our own solar system. These could be things like Saturn, or possibly even Neptune if we’re lucky.”

HIP 65426 b is relatively young and hot, which means it is easier to shoot. It had previously been observed through ground-based telescopes, so the researchers used it to test JWST’s exoplanet imaging capabilities. They found that JWST performed 10 times better than expected and was much more sensitive than any previous telescope.

“We just get excellent sensitivity with JWST, so we can see very faint objects, especially if they’re a little further away from the star,” said team member Beth Biller at the University of Edinburgh, UK.

It was also particularly accurate in measuring changes in brightness for the exoplanet. “Brightness variability really means something like clouds, it means weather, on these exoplanets, so this probably means JWST will be sensitive enough to look for things like clouds,” Hinkley says.

The team captured the planet in a range of different infrared wavelengths, from the near-infrared used in previous images to mid-infrared wavelengths never used before. “By observing these planets over such a wide range of wavelengths, we just have more information,” Hinkley says. “We have more information about the chemical composition of their atmospheres and their chemical enrichment. This is very important because if we understand what these planets are made of and their chemical constituents, we could say something about their formation process.”

It is difficult to image HIP 65426 b because it orbits so close to its parent star, creating a high contrast in brightness. Hinkley and his team used a coronagraph to shut out the star’s light so they could see the image across a range of wavelengths. The planet looks a little different depending on which of JWST’s two infrared instruments, NIRCam and MIRI, were used, because of the way these devices process the images, Biller says — you can see some of these different images in the image. up here.

Because JWST is in so much demand to observe many different astronomical objects, it’s not really the optimal imaging device for exoplanets, says Michael Merrifield at the University of Nottingham, UK. “But it’s such a big leap forward in everything that I think it’s probably going to put us in regimes we’ve never been to before.”

That said, there are limits. Exoplanets are so far from Earth and so difficult to image that JWST can’t capture high-resolution images that look like planets in our own solar system. However, Hinkley hopes that the lessons learned from JWST will eventually lead to a telescope that can glimpse an Earth-sized planet orbiting another star.

“Eventually we want to get that image of an exo-Earth someday, and these observations are really the beginning of learning how to do coronagraphy in space,” he says.

Reference: arxiv.org/abs/2208.14990

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