For the first time, NASA's James Webb Space Telescope (JWST) has peered into the atmosphere of a distant planet and unambiguously confirmed the presence of water vapor there.
WASP-96 b is a hot, puffy gas giant orbiting a star about 1,150 light-years away. It's a little larger than Jupiter, but has less than half the mass of Jupiter. That makes it much puffier and less dense than any planet orbiting the sun.
Scientists previously doubted the planet could hold water, but NASA announced Tuesday that JWST had detected the clear chemical signature of water vapor in its atmosphere, along with evidence of haze and clouds.
Because the planet orbits so close to its star, at just one-ninth the distance between Mercury and the sun, its surface is about 1,000 degrees Fahrenheit. It's not a candidate for alien life.
However, scientists expect to refine JWST's observations over the coming years, until it can peer into the atmospheres of smaller planets orbiting at a greater distance from their stars.
"This is just the beginning. We're going to start pushing down to further, smaller planets," Knicole Colón, an exoplanet scientist, said in NASA's live broadcast revealing the new findings.
In the coming years, JWST is also expected to take direct images of planets orbiting other stars.
JWST can reveal new details about the atmospheres of distant planets
JWST, which launched into space in December, is now fully operational in its orbit around the sun, 1 million miles from Earth. NASA released its first full results and full-color images from the telescope on Tuesday. The imagery is jaw-dropping. It reveals distinct galaxies, exploding stars, and clouds of compressed gas birthing new stars, in a level of detail that astronomers only dreamed of until this week.
But most of JWST's science will come in the form of spectroscopy — the method it used to detect water vapor in this distant planet's atmosphere.
The telescope carries instruments that allow it to break down the infrared light from distant objects, analyzing where it falls across the spectrum of light. Basically, they break the light down into an infrared rainbow.
By assessing which spectra of light an object emits, scientists can determine which elements are present in that object, since different elements reflect distinct wavelengths of light.
That's how scientists identified the water vapor in WASP-96 b's atmosphere. JWST observed the planet for 6.4 hours as it passed in front of its star. The telescope analyzed starlight that passed through the planet's atmosphere and traveled to JWST's lens.
"This is exciting because it covers infrared wavelengths of light that we have not had access to before," Colón said. "We've been able to use other telescopes to explore exoplanet atmospheres in the infrared, but not to this level of detail. And this is just one sliver of data."
Scientists plan to run this analysis on many planets in the years to come.
"Spectra will be the bulk of the science," Antonella Nota, a JWST scientist who leads the office of the European Space Agency at the Space Telescope Science Institute, said in a briefing ahead of the telescope's launch.
"While an image, we say is worth 1,000 words, spectra for astronomers are just worth 1,000 images."
