NASA Astronomers Discover a Planet With a Tail Over 350,000 Miles Long

Astronomers have discovered a breathtaking phenomenon that challenges our understanding of planetary dynamics. WASP-69 b, a distant gas giant located 163 light-years from Earth, has been observed with a striking comet-like tail composed of escaping gases. This extraordinary feature is not just an aesthetic wonder; it is shaped by the powerful stellar winds emanating from the planet’s host star. The findings offer scientists a unique opportunity to study the intricate relationship between planets and their stars, revealing how these celestial bodies evolve under the influence of external forces. This discovery marks a new chapter in the study of exoplanets and their interactions with their cosmic environments.

Wasp-69 b: A Planet Under Stellar Influence

WASP-69 b belongs to a class of exoplanets known as hot Jupiters, which are gas giants that orbit their stars at close range. This proximity exposes the planet to intense stellar radiation, leading to a process called photoevaporation, where the planet’s outer atmosphere heats up and lightweight elements like hydrogen and helium escape into space. But what sets WASP-69 b apart is the interaction between these escaping gases and the stellar wind—a continuous stream of charged particles emitted by the host star.

These stellar winds shape the escaping gases into a tail that stretches at least 350,000 miles—more than seven times the radius of the planet. Lead researcher Dakotah Tyler, an astrophysicist at the University of California, Los Angeles, explains, “Strong stellar winds can sculpt that outflow in tails that trail behind the planet.” Tyler compares this phenomenon to the tail of a comet, highlighting the transformative effects of stellar forces on planetary atmospheres.

The Dynamic Nature of a Stellar Tail

The tail of WASP-69 b is not a static feature; its size and shape are determined by the strength and variability of the stellar wind. When the stellar wind intensifies, the escaping gas is swept into a well-defined, elongated tail. Conversely, when the stellar wind weakens, the escaping gas disperses symmetrically around the planet, losing its distinctive shape.

“If the stellar wind were to taper down, then you could imagine that the planet is still losing some of its atmosphere, but it just isn’t getting shaped into the tail,” Tyler notes. “Without the stellar wind, that gas escaping on all sides of the planet would be spherical and symmetrical. But if you crank up the stellar wind, that atmosphere then gets sculpted into a tail.”

Tyler likens this process to a windsock fluttering in the breeze—the stronger the wind, the more pronounced and structured the windsock becomes. Similarly, the tail of WASP-69 b reacts dynamically to changes in the stellar wind, providing scientists with a real-time demonstration of atmospheric escape and stellar influence in action.

The Gradual Loss of Atmospheric Mass

WASP-69 b is losing approximately 200,000 tons of atmospheric gas every second. While this figure may seem dramatic, the process occurs over such an extended timescale that the planet remains intact. Over its estimated 7-billion-year lifespan, WASP-69 b has lost an amount of atmospheric material equivalent to seven Earths in mass. Despite this significant loss, the planet continues to maintain its core structure, demonstrating the resilience of gas giants under extreme conditions.

The gradual erosion of WASP-69 b’s atmosphere serves as a vivid example of how external forces can slowly transform a planet over billions of years. This ongoing interaction between the planet and its host star not only highlights the influence of stellar forces but also underscores the delicate balance that defines the evolution of planetary systems.

Insights into Stellar and Planetary Dynamics

The discovery of WASP-69 b’s tail provides a rare glimpse into the interplay between stars and their planetary companions. The tail, illuminated by the star’s light, serves as a natural tracer for studying stellar winds and their effects on planetary systems. This unique feature allows astronomers to observe and analyze the behavior of stellar winds in distant star systems, contributing to a broader understanding of how stars influence the worlds that orbit them.

Moreover, the study of exoplanetary tails like that of WASP-69 b could inform future research on planetary habitability. By examining how stellar activity shapes planetary atmospheres, scientists can refine models of atmospheric retention and loss, offering valuable insights into the potential for life on exoplanets in different stellar environments.

A Milestone in Exoplanet Research

The groundbreaking findings on WASP-69 b were published earlier this year in The Astrophysical Journal by a team led by Dakotah Tyler. Using advanced spectroscopic observations from Keck/NIRSPEC, the researchers documented the planet’s tail in unprecedented detail. Their work not only advances our understanding of exoplanetary atmospheres but also sets the stage for future explorations into the dynamic relationships between planets and their host stars.

“This discovery is a vivid example of how the forces in space can transform worlds in unexpected ways,” Tyler remarked. “WASP-69 b shows us that even far-off planets have stories to tell, shaped by the powerful and ever-changing winds of their stars.”