This is the first image of an exoplanet from the James Webb Space Telescope.
“We’re actually measuring photons from the atmosphere of the planet itself,” says astronomer Sasha Hinkley of the University of Exeter in England. Seeing those light particles, “to me, that’s very exciting.”
The planet is about seven times the mass of Jupiter and more than 100 times farther from its star than Earth is from the sun. direct observations of the exoplanet HIP 65426 b to show. It’s also young, about 10 to 20 million years old, compared to Earth’s more than 4 billion years old, Hinkley and his colleagues report in a study published August 31 on arXiv.org.
Those three characteristics (size, distance, and youth) made HIP 65426 b relatively easy to see, and therefore a good planet to test JWST’s observing capabilities. And the telescope has once again exceeded the expectations of astronomers (Serial number: 7/11/22).
“We’ve really shown how powerful the JWST is as an instrument for direct imaging of exoplanets,” says exoplanet astronomer and co-author Aarynn Carter of the University of California, Santa Cruz.
astronomers have found over 5,000 planets orbiting other stars (Serial number: 03/22/22). But nearly all of those planets were detected indirectly, either because the planets pulled on stars with their gravity or blocked starlight as it crossed between the star and a telescope’s view.
To see a planet directly, astronomers have to block the light from its star and let the planet’s own light shine through, a complicated process. It is condition done prior tobut only for about 20 planets in total (D.N.: 11/13/08; Serial Number: 03/14/13; Serial Number: 7/22/20).
“In all areas of exoplanet discovery, nature has been very generous,” says MIT astrophysicist Sara Seager, who was not involved in the JWST discovery. “This is the one area where nature didn’t really show up.”
In 2017, astronomers discovered HIP 65426 b and took a direct image of it using an instrument on Chile’s Very Large Telescope. But because that telescope is on the ground, it can’t see all of the light coming from the exoplanet. Earth’s atmosphere absorbs many of the planet’s infrared wavelengths, exactly the wavelengths that JWST highlights in the observation. The space telescope observed the planet on July 17 and 30, capturing its brightness in four different infrared wavelengths.
“These are wavelengths of light where we’ve never seen exoplanets before,” says Hinkley. “I have literally been waiting for this day for six years. It feels amazing.”
Images at these wavelengths will help reveal how planets formed and what their atmospheres are made of.
“Direct imaging is our future,” says Seager. “It’s amazing to see the Webb work so well.”
While the team hasn’t yet studied HIP 65426 b’s atmosphere in detail, it has. report the first spectrum — a measure of light over a range of wavelengths — from an object orbiting a different star. The spectrum allows a deeper look into the object’s chemistry and atmosphere, astronomer Brittany Miles of UC Santa Cruz and her colleagues reported Sept. 1 on arXiv.org.
That object is called VHS 1256 b. It is as heavy as 20 Jupiters, so it may look more like a transitional object between a planet and a star, called a brown dwarf, than a giant planet. JWST found evidence that the amounts of carbon monoxide and methane in the orb’s atmosphere are out of balance. That means the atmosphere is mixing, with winds or currents pulling molecules from the lower depths to the top and vice versa. The telescope also saw signs of sand cloudsa common feature in the atmospheres of brown dwarfs (Serial number: 7/8/22).
“This is probably a violent, turbulent atmosphere that is full of clouds,” says Hinkley.
HIP 65426 by VHS 1256 b are unlike anything we see in our solar system. They are more than three times the distance of Uranus from their stars, suggesting that they formed in an entirely different way than the more familiar planets. In future work, astronomers hope to use JWST to image smaller planets that are closer to their stars.
“What we would like to do is study the Earths, right? We’d really like to get that first image of an Earth orbiting another star,” says Hinkley. That’s probably out of the scope of JWST: Earth-size planets are still too small. But a Saturn? That may be something JWST could focus on.