Science & Technology (Commonwealth Union) – The fascination with outer space has existed throughout the ages. The possibility of finding a planet similar to earth has always been in high demand.
An exoplanet the size of the Saturn with temperatures similar to those found on Earth has been found to possess a methane-rich atmosphere, according to new research conducted using NASA’s James Webb Space Telescope (JWST). This discovery contrasts sharply with planets in our own solar system, such as Jupiter and Saturn, which are distant from the Sun and therefore extremely cold, as well as with “hot Jupiters” outside the solar system that experience extreme heat due to orbiting very close to their host stars. The newly studied world is among a very small number of known temperate giant exoplanets and marks the first time the atmosphere of such a planet has been examined in detail. Researchers say these findings will help refine models of how planets form and evolve, while also offering potential insights into the workings of Earth’s own atmosphere.
The study, published in The Astronomical Journal on May 20, was carried out by a team led by astronomers from Penn State and NASA’s Jet Propulsion Laboratory (JPL) at the California Institute of Technology.
According to Renyu Hu, associate professor of astronomy and astrophysics at Penn State and lead researcher of the study, exoplanet research provides a unique opportunity to examine a wide variety of planetary types, especially those not found in our own solar system. Since the first exoplanet discovery in 1992 by a team that included Penn State astronomer Aleksander Wolszczan, thousands of such worlds have been identified. However, only a few giant planets with temperate conditions are known, and this represents the first detailed.
The planet, known as TOI-199b, orbits a star located more than 330 light-years away from Earth, completing one revolution roughly every 100 days. It has an estimated temperature of about 175°F (around 80°C), which is still extremely hot by human standards, though not far above Earth’s record highs of approximately 134°F. Such temperatures can even be reached in everyday situations, such as inside cars left in direct sunlight. This makes it far more moderate compared with “hot Jupiters,” which can reach thousands of degrees, and also warmer than the frigid gas giants in our own solar system that sit hundreds of degrees below freezing.
To study the atmosphere of an exoplanet like this, scientists use a method called transmission spectroscopy. This involves examining starlight that filters through the planet’s atmosphere as it passes in front of its host star from our point of view. For this technique to work, the planet’s orbit must be precisely aligned so that it transits between its star and the observing telescope. The James Webb Space Telescope (JWST) then splits the incoming starlight into different wavelengths, much like a prism disperses white light into a spectrum of colors.
“As a planet passes in front of its star, some of the star’s light passes through the planet’s atmosphere where it interacts with the elements and molecules in the atmosphere,” explained Aaron Bello-Arufe, a postdoctoral researcher at JPL and the first author of the paper. “Specific elements will absorb specific wavelengths of light, creating a fingerprint in the spectrum of light that JWST detects that reflects the atmosphere’s composition.”
The spectrum recorded during the transit is compared with baseline observations of the star’s light, which were built up over roughly 20 continuous hours of monitoring by JWST. The transit event itself lasts around seven hours—significantly longer than that of hot Jupiters, whose transits can take an hour or even less. By comparing the baseline and transit spectra, scientists can determine which wavelengths of starlight are being absorbed by the planet’s atmosphere. This allows researchers to identify the elements and molecules present in the atmosphere.
