In deep space, far beyond our solar system, astronomers have spotted loads of super-Earths, mini-Neptunes, and hot Jupiters.
But only once have they found an "ultra-hot Neptune" — a Neptune-size world orbiting extremely close to its star. A year lasts under a day on this scorching planet, dubbed "LTT 9779 b." After discovering this curious world in 2020, scientists have now used the powerful James Webb Space Telescope to peer into the exoplanet's atmosphere and better grasp how such a world works.
"Finding a planet of this size so close to its host star is like finding a snowball that hasn't melted in a fire," Louis-Philippe Coulombe, a researcher at the Université de Montréal's Trottier Institute for Research on Exoplanets who led the study, said in a statement. "It's a testament to the diversity of planetary systems and offers a window into how planets evolve under extreme conditions."
LTT 9779 b, nearly 30 times Earth's mass, is certainly extreme. It's tidally locked to its star — like the moon is locked to Earth — meaning that one side of it incessantly seared by its star, while the other is dark and cooler. LTT 9779 b is nearly 3,630 degrees Fahrenheit (2,000 Celsius) on its dayside. That's hotter than lava.
The research team peered at LTT 9779 b for 22 hours, using an instrument on the Webb telescope called a spectrograph to reveal the composition of the planet's exotic atmosphere. (Similar to a prism, spectrographs spread an object's light into a spectrum of colors, revealing what's present or not in a far-off place.)
They found clouds very unlike ours (which are made of water vapor) composed of silicates, which are minerals that make up rocks on Earth. These clouds were on the planet's western dayside, as opposed to its hotter eastern hemisphere, suggesting that strong winds on LTT 9779 b transport atmospheric elements around the planet.
A conception of LTT 9779 b, located 262 light-years from Earth in the Milky Way galaxy, can be seen below. It depicts how highly reflective mineral clouds condense on the "slightly cooler" western dayside, but then evaporate when the planet's potent winds push these clouds to the hotter eastern dayside.
Scientific attempts to understand this profoundly rare — as far as we know — world are just beginning.
"We haven’t finished piecing together the information about this planet yet," Jake Taylor, a scientist in the Department of Physics at the University of Oxford who also worked on the study, explained. "We are currently using observations from the Hubble Space Telescope and the Very Large Telescope to study the dayside cloud structure in more detail to learn as much as possible."
To date, astronomers have confirmed 5,834 exoplanets, with thousands more awaiting confirmation.
The Webb telescope's powerful abilities
The Webb telescope — a scientific collaboration between NASA, ESA, and the Canadian Space Agency — is designed to peer into the deepest cosmos and reveal new insights about the early universe. It's also examining intriguing planets in our galaxy, along with the planets and moons in our solar system.
Here's how Webb is achieving unparalleled feats, and likely will for decades to come:
- Giant mirror: Webb's mirror, which captures light, is over 21 feet across. That's over two-and-a-half times larger than the Hubble Space Telescope's mirror, meaning Webb has six times the light-collecting area. Capturing more light allows Webb to see more distant, ancient objects. The telescope is peering at stars and galaxies that formed over 13 billion years ago, just a few hundred million years after the Big Bang. "We're going to see the very first stars and galaxies that ever formed," Jean Creighton, an astronomer and the director of the Manfred Olson Planetarium at the University of Wisconsin–Milwaukee, told Mashable in 2021.
- Infrared view: Unlike Hubble, which largely views light that's visible to us, Webb is primarily an infrared telescope, meaning it views light in the infrared spectrum. This allows us to see far more of the universe. Infrared has longer wavelengths than visible light, so the light waves more efficiently slip through cosmic clouds; the light doesn't as often collide with and get scattered by these densely packed particles. Ultimately, Webb's infrared eyesight can penetrate places Hubble can't.
"It lifts the veil," said Creighton.
- Peering into distant exoplanets: The Webb telescope carries specialized equipment called spectrographs that will revolutionize our understanding of these far-off worlds. The instruments can decipher what molecules (such as water, carbon dioxide, and methane) exist in the atmospheres of distant exoplanets — be they gas giants or smaller rocky worlds. Webb looks at exoplanets in the Milky Way galaxy. Who knows what we'll find?
"We might learn things we never thought about," Mercedes López-Morales, an exoplanet researcher and astrophysicist at the Center for Astrophysics-Harvard & Smithsonian, previously told Mashable.
