About 880 light-years from Earth, scientists have made an exciting discovery: an exoplanet named WASP-121b, or Tylos, is leaking its atmosphere into space. This creates two gigantic tails of helium that stretch impressively around its star. This research marks the first time astronomers have continuously watched an exoplanet’s atmospheric escape throughout its full orbit.
Tylos is an extreme exoplanet, known for odd features like clouds of vaporized metal and rains of gemstones. This “hot Jupiter” is much closer to its star than our Jupiter is to the Sun, circling in just 30 hours. Because it’s so close, its atmosphere heats up to thousands of degrees, allowing lighter gases, like hydrogen and helium, to escape.
While gaseous leaks can occur rapidly, they often happen gradually. Even small losses over time can radically change an exoplanet’s size and makeup. Most of what we know about atmospheric escape comes from brief observations when planets cross in front of their stars, but this gives only a glimpse of the complete picture.
In this groundbreaking study, researchers used the James Webb Space Telescope (JWST) to observe Tylos for nearly 37 hours. They found that helium absorption extended significantly beyond the planet itself, covering almost 60% of its orbital path. This extended observation revealed “a persistent and large-scale outflow,” according to the study.
Interestingly, Tylos isn’t just expelling one stream of helium—it has two distinct tails. One trails behind the planet, while another stretches ahead. This finding surprised lead author Romain Allart, who noted that existing models only explain one tail, making the discovery of two a complex puzzle for scientists.
Understanding how radiation and stellar wind influence these helium tails could offer new insights into planetary atmospheres. Allart emphasized that this research reveals a deeper complexity in exoplanets and how they evolve.
This study not only helps explain Tylos’ unique behavior but also raises broader questions about how atmospheric loss affects various types of planets. For instance, can gas giants like Tylos transform into smaller, rocky planets over time?
With ongoing research, scientists aim to create better simulations to explore these atmospheric phenomena. This research was published in Nature Communications, highlighting a pivotal moment in understanding planetary evolution.
For more information, click here: NASA’s Exoplanet Catalog.
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