LTT 9779 b, an exoplanet 262 light years from Earth, always stares directly at the sun. With a surface of nearly 2000 degrees Celsius (about 3632 degrees Fahrenheit), the planet glows bright red while still reflecting starlight. Researchers have called it a rare ultra-hot Neptune.
Thanks to images from the James Webb Space Telescope (JWST) published in Nature Astronomy, researchers are now able to see and analyze extreme weather patterns on this intriguing exoplanet, which can help them better understand its unique atmospheric properties.
Understanding LTT 9779 b — The Hot Exoplanet
A 2020 study published in Nature Astronomy first identified LTT 9779 b. The study found that the exoplanet has been tidally locked — like Earth’s moon — meaning one side has continuously faced the sun, while the other side has been in constant darkness.
It’s nearly 30 times the size of Earth and is about 0.01679 astronomical units (AU) from its star. For reference, Earth is 1 AU from the sun, or about 93 million miles, and LTT 9779 b is about 15 million miles away from its sun.
The distance from its star is what makes LTT 9779 b so hot, but despite the extreme temperature, the new study used the JWST to identify reflective clouds on the western half of the exoplanet's dayside, which creates a major contrast to the hotter, eastern side.
“This planet provides a unique laboratory to understand how clouds and the transport of heat interact in the atmospheres of highly irradiated worlds,” said Louis-Philippe Coulombe, a graduate student at Université de Montréal's Trottier Institute for Research on Exoplanets (IREx), and lead author of the study, in a press release.
Read More: Exoplanet Winds Expose a World Out of Science Fiction
JWST and Reflective Clouds
Through the JWST, Coulombe and the research team noticed an asymmetry in LTT 9779 b’s dayside reflectivity. The team surmised that this unbalance may be due to strong eastward winds that distribute heat and clouds across the exoplanet’s surface. This new information redefines how heat can move across a planet and how clouds can form in an atmosphere.
For this study, the research team analyzed the exoplanet at different phases of its orbit, monitoring its properties at each phase. They found that reflective silicate clouds formed on the western side of the exoplanet, which is likely why it reflects so much of its star’s light.
The researchers then combined information from the reflective clouds and the exoplanet’s heat emissions to form a detailed model of LTT 9779 b’s atmosphere. According to a press release, the findings “reveal a delicate balance between intense heat from the star and the planet’s ability to redistribute energy.”
The research team also noted the presence of water vapor in the atmosphere, which helps give the team a better idea of the exoplanet’s composition.
"By modeling LTT 9779 b’s atmosphere in detail, we’re starting to unlock the processes driving its alien weather patterns," said Björn Benneke, Coulombe’s research advisor, an UdeM professor of astronomy, and co-author of the study, in a press release.
A Rare Ultra-Hot Neptune
Coulombe and the researcher team have intensified LTT 9779 b as an ultra-hot Neptune, meaning that the exoplanet is roughly the size of Neptune in our Solar System but is positioned much closer to its star. The team explains that the exoplanet resides in the “hot Neptune desert” and is extremely rare.
"Finding a planet of this size so close to its host star is like finding a snowball that hasn’t melted in a fire,” said Coulombe in a press release. “It’s a testament to the diversity of planetary systems and offers a window into how planets evolve under extreme conditions."
These findings can help researchers better understand the unique ways planets form and endure stellar forces.
“These findings give us a new lens for understanding atmospheric dynamics on smaller gas giants. This is just the beginning of what JWST will reveal about these fascinating worlds,” said Coulombe in a press release.
Read More: How the James Webb Space Telescope Takes Such Stunning Pictures
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Nature Communications. An ultrahot Neptune in the Neptune desert
Nature Communications. Highly reflective white clouds on the western dayside of an exo-Neptune
Space.com. 'Ultrahot Neptune' discovered around sunlike star
A graduate of UW-Whitewater, Monica Cull wrote for several organizations, including one that focused on bees and the natural world, before coming to Discover Magazine. Her current work also appears on her travel blog and Common State Magazine. Her love of science came from watching PBS shows as a kid with her mom and spending too much time binging Doctor Who.
