Webb telescope detects thickest atmospheric haze ever seen on exoplanet

Yesterday 15:20

By: Dakir Madiha

Webb telescope detects thickest atmospheric haze ever seen on exoplanet

Astronomers using the James Webb Space Telescope have identified an exceptionally dense atmospheric haze surrounding the exoplanet Kepler-51d, blocking efforts to determine its chemical composition and origin, according to a study published in the Astronomical Journal.

An international team led by researchers at Penn State examined the planet, located about 2,615 light-years from Earth in the Cygnus constellation. Despite the telescope’s advanced near-infrared spectrograph, which extends observations to wavelengths up to 5 microns, scientists found no clear chemical signatures in the planet’s atmosphere.

Kepler-51d belongs to a rare class of so-called “super-puffy” planets. These worlds are roughly the size of Saturn but have only a few times Earth’s mass, resulting in extremely low densities comparable to cotton candy. The planet orbits a relatively young star, about 500 million years old, at a distance similar to that between Venus and the Sun. Under such conditions, stellar radiation would normally strip away atmospheric gases, making its current structure difficult to explain.

Researchers attribute the featureless spectrum to an unusually thick haze layer with a radius comparable to Earth. This haze absorbs and scatters light across all observed wavelengths, concealing any molecular signatures beneath it. Scientists say the phenomenon resembles the haze observed on Titan, Saturn’s largest moon, which contains hydrocarbon compounds such as methane, but on a much larger scale.

The team also considered whether a tilted ring system could explain the observations by making the planet appear larger and less dense. However, the data showed a steady increase in light absorption at longer wavelengths, a pattern more consistent with a dense haze than with rings, which would require highly precise conditions to match the findings.

Future observations using Webb’s mid-infrared instrument could help penetrate the haze or identify possible ring material. Scientists are also analyzing data from another planet in the same system, Kepler-51b, to determine whether such dense atmospheres are common among super-puffy planets or unique to Kepler-51d.