Scientists have made a groundbreaking discovery involving the exoplanet WASP-121 b, revealing that a vast cloud of helium gas is escaping from its atmosphere. This phenomenon was observed using the James Webb Space Telescope (JWST) and involves the helium forming long tails both in front of and behind the planet as it orbits its star. The findings, led by Professor Lisa Dang from the University of Waterloo’s physics and astronomy department, challenge existing atmospheric models and open new avenues for research.
WASP-121 b is categorized as an “ultra-hot Jupiter,” a type of massive exoplanet that orbits very close to its star, resulting in extremely high temperatures on its day side. The planet is tidally locked, meaning the same side always faces its star. Initially, the research team aimed to study the molecular differences between the planet’s day and night sides. However, their focus shifted upon discovering the distinct helium signature.
“There was a very apparent helium signature that stood out when looking at the data,” Professor Dang explained. “Normally, when we look at exoplanets, we search for tiny, tiny signals that are buried in the noise. This one was standing out of the noise, almost like it was waiting for us to find it.”
Unprecedented Atmospheric Loss
The helium signature revealed that WASP-121 b has a trail of helium covering 60% of its orbit, forming a stream in front of and behind the planet. This discovery marks the first time scientists have detected such significant atmospheric loss on a Jupiter-sized planet.
“Atmospheric loss of this nature is common for smaller Neptune-sized planets, but planets the size of WASP-121 b have a stronger gravitational pull and are usually very good at keeping their atmosphere intact,” Dang noted. “Until now, we didn’t know a hot Jupiter could lose its atmosphere at such a rate, so this is a surprising discovery.”
The team conducted simulations to understand the helium stream’s shape, providing insights into the planet’s atmospheric dynamics. These findings, published in Nature Communications, suggest that WASP-121 b’s atmospheric loss could be more common among ultra-hot Jupiters than previously thought.
Implications for Future Research
The discovery has inspired Dang and her colleagues to revisit other ultra-hot Jupiter-sized planets to determine if similar helium outputs exist or if WASP-121 b is unique. Observing these planets for a full rotation is necessary, requiring additional time on the JWST.
“To see whether any other ultra-hot Jupiters have the same helium outputs, we will have to observe them for a full rotation, which means requesting more time on the James Webb Space Telescope,” Dang stated. “Getting 40+ hours on the JWST aimed at one star is hard to get approved because the telescope is in such high demand, but I think there is the potential for meaningful science here that we would not be able to do without a long stare with JWST.”
As the research progresses, Dang will continue collaborating with her Waterloo co-op students to extract more information from the existing data set, potentially leading to further discoveries.
AI Forum and Faculty Retirements at the University of Waterloo
Faculty of Arts AI Forum
In other news, the Faculty of Arts at the University of Waterloo is hosting an AI Forum on Friday, December 19. Organized by the Faculty’s AI Task Force, the forum will address concerns related to Generative AI (GenAI), especially in writing, art, and design.
“When it comes to GenAI adoption, Arts has a specific set of concerns, especially regarding writing, art, and design,” writes Professor Marcel O’Gorman. “The task force is trying to address concerns from the Arts community while forging a path forward that leverages AI in critical and creative ways.”
The forum will feature presentations from faculty members and an open discussion on prioritizing AI strategies. It will take place in the Senate and Board chambers in NH 3407, with registration available online.
Celebrating Retirees from 2025’s Third Quarter
Additionally, the University of Waterloo is celebrating the retirement of several faculty and staff members who have contributed significantly to the institution. The retirees, who left between July and September 2025, include:
- July 2025: William Mark, Aida Martinez Casillas, Dolores Pereira, Mark Knight, Andrew Ecclestone, Susannah King.
- August 2025: Nancy Sej, Leslie Smith, Robyn Landers, Caroline Brookes, Susan Arruda, Liz Wehner, Sherri Anne Arsenault, Linda Bream.
- September 2025: Denise Hileeto, Robert Duniec, Shari Mann, David Rose, Douglas Cowan, Alfred Menezes, Erin Murphy, Shaun Frape, Bruce Wildfong, Catherine Wessels, Xianguo Li, Janusz Pawliszyn, Mungo Marsden.
The contributions of these individuals have been invaluable to the university’s growth and success, and their dedication is greatly appreciated.
