Webb Telescope Captures 4 Distant Worlds in a Single Direct Image

Yahoo

21-03-2025

NASA's James Webb Space Telescope has done it again. Though it's notoriously difficult to snap direct images of distant planets, the overachieving observatory has managed to capture four of them in a single image. Located 130 light-years from Earth, the exoplanets orbit the young main-sequence star HR 8799, around which they're thought to have formed roughly 30 million years ago.
Far-away exoplanets are tricky to photograph due to their host stars' luminosity, which outshines the target object and renders the image unviable. (Think about trying to spot an airplane in a sunlit sky—if the plane appears too close to the Sun, your eyes will be too overwhelmed by light to find what they're looking for.) Instead, astronomers tend to resort to indirect imaging techniques, like measuring the "wobble" of a star being tugged on by a planet's gravity, or tracking how much a star's light dims as its planet transits, or passes in front of it.
But if you hold up your hand to block the Sun, the plane might be easier to see. Some traveling space observatories can do this, too, using a tool called a coronagraph. Attached to Webb's Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI) are a total of nine coronagraphic masks, which conveniently block the light from a distant star while allowing the faint light from an exoplanet to shine through.
Researchers in the United States, Germany, and Spain used the NIRCam coronagraphs to train Webb's eye on HR 8799, a stable star system whose planets were first discovered in 1998. Thanks to infrared data from Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS), scientists could tell back then that a handful of planets orbited the star, but the star's light obscured its planetary companions. Webb's image, released by NASA on Monday and described in The Astronomical Journal the same day, picks up where Hubble left off.
Credit: NASA, ESA, CSA, STScI, W. Balmer (JHU), L. Pueyo (STScI), M. Perrin (STScI)
Each of the image's four fuzzy balls of light is an exoplanet named after its star. (In the above image, NASA has placed a star-shaped icon where HR 8799 hid behind NIRCam's coronagraph.) HR 8799 b, depicted in dark blue on the image's left side, orbits HR 8799 from a shy 6.3 billion miles away—more than 68 times further than Earth orbits the Sun. It's a gas giant with an estimated mass that sits somewhere between 4 and 7 Jupiter masses, and thanks to its distant orbit, a year on HR 8799 b takes approximately 460 Earth years. The gas giant HR 8799 e, by contrast, has 10 times Jupiter's mass and orbits its star relatively closely at 1.5 billion miles, making its year just 57 Earth years.
HR 8799 c and HR 8799 d sit somewhere in the middle. Both are gas giants with 7 times Jupiter's mass, and while a year on HR 8799 c takes about 200 Earth years, HR 8799 d's year is closer to 110 Earth years. Like their siblings HR 8799 b and HR 8799 e, they're thought to have formed like Jupiter and Saturn likely did: through core accretion, in which a solid core attracts and accumulates gas.
Beyond capturing all four exoplanets in one direct image, Webb's coronagraphic imaging technique allowed the researchers to infer the exoplanets' atmospheric composition. By examining signs of infrared light in wavelengths absorbed by certain gases, they found carbon dioxide and carbon monoxide on HR 8799 e. Now they hope to use Webb to image and examine other exoplanets in a similar manner.
"Our hope with this kind of research is to understand our own solar system, life, and ourselves in comparison to other exoplanetary systems, so we can contextualize our existence," said Johns Hopkins University astronomer and study author William Balmer. "We want to take pictures of other solar systems and see how they're similar or different when compared with ours. From there, we can try to get a sense of how weird our solar system really is—or how normal."