For the first time, NASA’s James Webb Space Telescope (JWST) has peered into the atmosphere of a distant planet and unequivocally confirmed the presence of water vapour.
WASP-96 b is a hot, puffy gas giant orbiting a star about 1,150 light-years away. It’s a little bigger than Jupiter, but it has less than half the mass of Jupiter. This makes it much puffier and less dense than any planet orbiting the sun.
Scientists previously doubted the planet could hold water, but NASA announced on 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, just one-ninth the distance between Mercury and the sun, its surface is around 1,000 degrees Fahrenheit. It’s not a candidate for extraterrestrial life.
However, scientists expect to refine JWST’s observations over the next few years, until it can peer into the atmospheres of smaller planets orbiting at greater distances from their stars.
“This is just the beginning. We’re going to start pushing towards other smaller planets,” exoplanetary scientist Knicole Colón said during a NASA live broadcast revealing the new findings.
In the coming years, JWST should also take direct images of planets orbiting other stars.
JWST may reveal new details about the atmospheres of distant planets
JWST, which was launched into space in December, is now fully operational in its orbit around the sun, 1 million kilometers from Earth. NASA released its first full results and color images of the telescope on Tuesday. The imagery is breathtaking. It reveals distinct galaxies, exploding stars and clouds of compressed gas giving rise to new stars, in a level of detail astronomers only dreamed of this week.
But most of the JWST’s science will take the form of spectroscopy – the method used to detect water vapor in the atmosphere of this distant planet.
The telescope carries instruments that allow it to break down infrared light from distant objects, analyzing where it falls across the spectrum of light. Basically, they break up light into an infrared rainbow.
By evaluating the spectra of light emitted by an object, scientists can determine which elements are present in that object, since different elements reflect distinct wavelengths of light.
This is how scientists identified water vapor in the atmosphere of WASP-96 b. 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 objective.
“It’s exciting because it covers infrared wavelengths of light that we didn’t have access to before,” Colón said. “We’ve been able to use other telescopes to explore exoplanet atmospheres in the infrared, but not at this level of detail. And that’s just a fragment of data.”
Scientists plan to perform this analysis on many planets in the coming years.
“The spectra will be the bulk of the science,” said Antonella Nota, a JWST scientist who heads the European Space Agency’s office at the Space Telescope Science Institute, during a pre-launch briefing for the telescope.
“While a picture, we say, is worth 1,000 words, spectra for astronomers are only worth 1,000 pictures.”