A recent discovery has unveiled an intriguing feature of the exoplanet WASP-69 b: a “tail” of gas trailing behind it.
WASP-69 b is an example of what astronomers refer to as a “hot Jupiter”—a type of exoplanet characterized by its size and close proximity to its host star. In this case, WASP-69 b orbits its star so closely that intense radiation heats its outer atmosphere, causing the phenomenon known as photoevaporation.
During photoevaporation, lightweight gases such as hydrogen and helium are pushed outward into space. However, the star’s stellar wind, a steady stream of charged particles, shapes these gases into a visible tail, similar to the tail of a comet. “Strong stellar winds can sculpt that outflow in tails that trail behind the planet,” explained Dakotah Tyler, an astrophysicist from the University of California, Los Angeles.
The dynamics of the stellar wind play a pivotal role in the formation and variability of the tail. If the stellar wind decreases, although the planet would continue losing gas, it wouldn’t form a tail. On the other hand, an increase in the wind results in a more pronounced tail. Tyler likened this to a windsock filling with air, forming a structured shape as the wind intensifies.
The observed tail of WASP-69 b extends more than 7.5 times the radius of the planet, over 350,000 miles. This is a minimum estimate, as the research team had to conclude their observations before the tail’s termination was detected. Notably, the length and shape of the tail can fluctuate with changes in the stellar wind, providing a dynamic canvas for further astrophysical studies.
These fluctuations make exoplanetary tails quite fascinating. They could provide insights into the interactions between stellar and planetary atmospheres, potentially acting as indicators of stellar behavior. This is particularly significant as understanding these interactions can deepen our knowledge of stars beyond our own Sun.
The planet’s current rate of gas loss is staggering, at approximately 200,000 tons per second. Yet, despite this rapid loss, there is no imminent threat of WASP-69 b being stripped of its atmosphere entirely. Over billions of years, the planet has lost an amount of gas equivalent to the mass of seven Earths, indicating a slow and steady depletion.
The discovery was spearheaded by Dakotah Tyler and his team, utilizing observations from Keck/NIRSPEC. Their work, published in “The Astrophysical Journal,” offers a glimpse into the complex dynamics at play in planetary systems, expanding our understanding of such phenomena.
The study of WASP-69 b’s atmospheric tail opens new avenues for research into the link between stellar activity and planetary atmospheres. Such insights could enhance our understanding of both planetary evolution and stellar behavior in distant systems.
Source: Science.nasa
