JWST captures frozen image of giant exoplanet 12 light-years away
The Jupiter-like world Epsilon Indi Ab is one of the coldest and closest exoplanets astronomers have ever seen.
Exoplanet Epsilon Indi Ab. Blue scaly features are seen in the background, and the light from the host star is blocked by a black circle in the center of the image, with dashed lines and a white star image overlaid on the image. The exoplanet is visible as a bright orange circle on the left.
ESA/Webb/NASA/CSA/STScI/E. Matthews/Max Planck Institute for Astronomy
Astronomers have captured a photo of a planet six times the mass of Jupiter orbiting one of the closest stars to the Sun, the first exoplanet discovered by direct imaging with the James Webb Space Telescope.
“This is a cold planet,” says Elizabeth Matthews, an astronomer at the Max Planck Institute for Astronomy in Heidelberg, Germany. Nature July 24th.
“If this is true, it would be by far the oldest and coldest planet ever imaged,” said astronomer Markus Jansson of Stockholm University.
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Researchers typically detect exoplanets by tracking them as they periodically cross Earth’s line of sight, temporarily dimming the light of their host star or causing measurable wobbles in the star itself due to their gravity. Only a few dozen exoplanets have been directly imaged so far, mainly because they are hot and bright enough to be detected despite the glare of their star.
Using “wobble” techniques, astronomers have already suggested the possibility of a massive object orbiting a sun-like star called ε Indi A in the southern constellation Indus, just 3.6 parsecs (12 light-years) from Earth.
To look for the planet, Matthews and his colleagues aimed the telescope so the star was exactly in the center of the field of view. They then used a “coronagraph” built into one of the Webb’s cameras, which can sample photons at slightly different times, or phases, in each of the frame’s four quadrants. That way, when the sensor data is combined, photons from ε Indi A itself (some of which are off-center) are largely canceled out, eliminating glare that would drown out other signals near the star.
The images showed a planet six times more massive than Jupiter, which means that like Jupiter, it must be a “gas giant” made mostly of hydrogen gas, Matthews says. The planet, named εIndy Ab, is about 15 times farther from its star than Earth is, and its temperature is just above 0 degrees Celsius.
Jansson cautions that there is still no “silver bullet that proves the source is definitely a planet” — later images that show the light particles moving — but he adds that “this work is very important because it’s a step toward possibly being able to image planets in mature systems.” Previous direct imaging efforts have been limited to observing young stellar systems, but εIndi A is about the same age as the Sun, he says.
Matthews says her team is planning follow-up observations to measure the spectrum of the planet’s light, which may also reveal some of the composition of its atmosphere, providing hints as to where in the protonebula where εIndi A formed, and how such a massive planet formed.
The star is part of a triple star system with two “brown dwarfs” (objects that never got large enough to produce hydrogen fusion reactions at their centers) that orbit the star more than 1,000 times farther away than a superjupiter. “This is a really rare type of system, and we’re really lucky to have it in our immediate vicinity,” Matthews says.
This article is reprinted with permission. First Edition July 24, 2024.
