Astronomers have discovered a distant planet similar to Jupiter that may be covered with thick clouds, offering new insights into how giant planets form and behave.
The planet, called Epsilon Indi Ab, lies just a few light-years away in the constellation Indus and is one of the closest known “exo-Jupiters”—planets outside our solar system that resemble Jupiter.
The discovery was led by Elisabeth Matthews and her team at the Max Planck Institute for Astronomy. Using the powerful James Webb Space Telescope (JWST), the researchers were able to directly image the planet and study its atmosphere in detail.
Their findings were published in The Astrophysical Journal Letters.
Over the past few decades, scientists have discovered thousands of exoplanets, mostly by observing how they affect the light of their host stars.
But studying the atmospheres of planets like Jupiter has been difficult.
Most of the gas giants observed so far are much hotter than Jupiter because they orbit very close to their stars. Epsilon Indi Ab is different. It orbits far from its star, making it much colder and more similar to the giant planets in our own solar system.
Epsilon Indi Ab is much more massive than Jupiter—about 7.6 times heavier—but its size is roughly the same. It orbits its star at a distance about four times greater than Jupiter’s distance from the sun.
Because of this, its temperature is quite low, ranging from about -70 to 20 degrees Celsius. Scientists believe the planet is still slightly warm because it retains heat from when it first formed, but it will continue to cool over billions of years.
To study the planet, the team used a special feature of JWST that blocks out the bright light of the host star, allowing the much fainter planet to be seen. They then observed the planet at specific wavelengths of infrared light that are linked to ammonia, a gas commonly found in the atmospheres of gas giants.
On Jupiter, ammonia gas and clouds are important parts of the upper atmosphere. Scientists expected Epsilon Indi Ab to have a lot of ammonia gas as well. However, the observations showed less ammonia than expected. This surprising result led researchers to a new explanation.
They believe the missing ammonia may be hidden by thick, patchy clouds made of water ice. These clouds could be similar to the thin, high-altitude cirrus clouds seen on Earth. If confirmed, this would be one of the first times scientists have found such clouds on a cold, Jupiter-like exoplanet.
This discovery also highlights a challenge in current scientific models. Many models of planetary atmospheres do not include clouds because they are difficult to simulate. The new findings suggest that clouds play a bigger role than previously thought, and scientists will need to update their models to better understand these distant worlds.
Future observations may help confirm the presence of these clouds. NASA’s upcoming Nancy Grace Roman Space Telescope, expected to launch in the next few years, will be able to detect reflected light from planets like Epsilon Indi Ab, making it easier to study cloud layers directly.
Beyond this single planet, the research represents an important step forward. By improving techniques for studying cold, distant gas giants, astronomers are building the tools they will eventually need to study Earth-like planets. One day, these methods could help scientists search for signs of life beyond our solar system.
For now, Epsilon Indi Ab offers a fascinating glimpse into the complexity of planetary atmospheres and reminds us that even familiar types of planets can still surprise us.
Source: Max Planck Society.
