A small frozen world in the outer solar system has recently been discovered to possess an atmosphere, making it the second celestial body known to have one, after Pluto and ahead of Neptune.
This groundbreaking discovery in natural astronomy hints that such mini-worlds may be more active than planetary scientists previously believed.
The celestial object, designated 2002 XV93, is classified as an asteroid and a Trans-Neptune Object (TNO) that orbits the Sun in the Kuiper Belt region, beyond Neptune’s orbit.
Discovering Miniature Pluto
The atmosphere of 2002 XV93 is estimated to be around 5 to 10 million times thinner than Earth’s atmosphere—so thin that one cannot feel any wind at its surface.
To date, Pluto is the only other TNO confirmed to possess even trace amounts of an atmosphere, measuring 2,377 km (1,480 miles) in diameter, which is more than five times larger than 2002 XV93.
Given its small size, 2002 XV93 has very weak gravity, allowing its atmosphere to easily escape into space. Researchers predict that the atmosphere could completely vanish within the next 100 to 1,000 years.
This raises intriguing questions about how the atmosphere is being replenished, leading to two primary theories.
The first theory posits frigid volcanic activity. In extremely cold conditions, volatile substances—like water, methane, and ammonia—can behave similar to rock or magma.
According to Ko Arimatsu of the National Astronomical Observatory of Japan, who led the study, “Volatile substances may leak out from beneath the ice surface, perhaps due to activities such as polar volcanoes.” These gases can contribute to atmospheric formation.
However, polar volcanic activity has only been recorded on larger celestial bodies until now.
The second theory suggests a recent collisional event. Arimatsu noted, “A small icy object may have collided with 2002 XV93, possibly releasing gas or exposing volatile materials.”
Though such collisions are rare, they could lead to the transient appearance of an atmosphere at just the right time.
Observation During a Solar Eclipse
2002 XV93 takes approximately 247 years to complete one orbit around the Sun. While its position is similar to Pluto’s, its distance makes direct observation challenging.
Arimatsu’s team employed a technique known as “occultation,” where a planetary body passes in front of a distant star, temporarily obscuring its light.
If 2002 XV93 lacked an atmosphere, starlight would disappear abruptly. In contrast, the presence of an atmosphere causes the light to bend slightly, resulting in a gradual change.
On January 10, 2024, three Japanese observatories successfully observed the occultation of 2002 XV93.
Arimatsu remarked, “Our observations, particularly from Japan’s Kiso Observatory, show that the star’s light fades and then gradually recovers on the edge of the shadow. This gradual change is best explained by the bending of light due to the very thin atmosphere surrounding 2002 XV93.”
The research team plans to utilize the James Webb Space Telescope to analyze the atmospheric composition, but ongoing occultation observations are thought to provide the best insights.
“These observations can indicate whether the atmosphere is fading, stable, or evolving over time,” said Arimatsu.
The atmosphere’s gradual decline suggests it may be escaping without replenishment, supporting the impact theory, while a stable atmosphere could indicate ongoing volcanic activity.
However, precise alignment is crucial for occultation studies. “There are only a few (around 10) observatories with the right geometry and data quality needed to explore such a thin atmosphere surrounding an object of this size,” Arimatsu explained.
This suggests it may take time before we fully understand the atmospheric dynamics of 2002 XV93.
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Source: www.sciencefocus.com