The James Webb Space Telescope has again expanded humanity’s view of the universe, this time by capturing a rare and dramatic occurrence around a distant exoplanet. WASP-121b, referred to as an Ultrahot Jupiter is approximately 858 light-years from Earth and is already known to be a very extreme environment.
But James Webb has now revealed something even more peculiar the planet has two extended helium tails trailing behind it as it races around its star. This discovery marks the first time scientists have tracked atmospheric escape throughout an entire orbit, offering new insight into how giant planets transform over millions of years.
What JWST Found Around WASP-121b
WASP-121b orbits so close to its star that it completes one full loop in just 30 hours. The intense radiation heats the planet’s upper atmosphere to as high as 2,300 degrees Celsius, which energizes lighter gases and sends them flowing into space.
James Webb has observed those escaping gases for the first time and made a remarkable discovery of helium was not leaking in short bursts during transits but streamed out for over half of the planet’s orbit. That behavior uncovered two huge tails that extended far beyond the planet and were behaving almost like comet-like streams of gas.
Why Helium Escape Matters
Atmospheric escape plays a significant role in the shaping of planets, especially gas giants orbiting close to their stars. Lighter elements, when drifted away over long periods, can alter the planet’s size and structure.
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Till now, scientists believed they could detect this kind of loss during transits, when the planet crosses its star from our point of view. That understanding was completely changed by Webb’s continuous 37-hour observation. Now researchers know some exoplanets continue leaking gases at surprising rates even when they are not in front of their star.
How James Webb Observed the Tails
The data came from Webb’s NIRSpec instrument, which followed the planet long enough to see patterns that earlier telescopes had missed: The helium signal stretched far out from the planet to form the two long tails that make WASP-121b stand out among known hot Jupiters.
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According to study author Romain Allart of the University of Montreal, the length and duration of the helium escape were unlike anything previously recorded. The findings also point toward complex atmospheric physics that determine how planets interact with harsh stellar radiation.
What This Means for Future Exoplanet Studies
WASP-121b shows that ultrahot Jupiters are dynamic worlds-constantly reshaped by their environment. New observations provide a clear vision of how such planets evolve through time, progressively losing material and changing in composition.
The findings showcase the James Webb Telescope’s capability to observe exoplanets during full orbital cycles-a feat no mission has ever achieved. This breaks open the doors toward undertaking atmospheric escape studies in hundreds of other distant worlds and may alter how humanity understands the long-term life cycle of planets outside the Earth’s solar system.
Disclaimer: This article is based on current scientific findings and telescope data. Future research may refine or update the interpretations presented.
