James Webb images ancient, cold super-Jupiter

Precise measurements of the star’s motion in the sky already showed in 2019 that a massive planet must orbit it. But new observations by the James Webb Space Telescope now show that the planet is much heavier and has a much wider orbit than expected, with an orbital period of about two hundred years.

Exoplanets (planets orbiting other stars) are usually detected indirectly: they reveal their presence by making their parent star wobble with its gravity, or by intercepting a small amount of light as it passes in front of its star.

However, the “giant Jupiter” orbiting Epsilon Indi has already been “seen”, as a rather bright point of light in infrared images from the Webb telescope. The brighter light from the star itself has been artificially masked.

Evolution of giant planets

Only about 25 exoplanets have been directly observed so far. In almost all cases, these are young gas giants that have not yet completely cooled after their birth. However, the newly discovered planet is about 3.5 billion years old and has a much lower temperature, close to the freezing point.

According to Elizabeth Matthews of the Max Planck Institute for Astronomy, this is the first time such an ancient, cold planet has been “imaged.” This is important for better understanding the evolution of these types of giant planets. Matthews and her colleagues published Webb’s new observations in late July. nature.

Spectroscopic measurements of the infrared light spot could provide further insight into the composition of the planet’s atmosphere. It appears to contain a relatively large amount of carbon, probably in the form of methane and carbon dioxide. Another explanation for the observations is that the planet’s atmosphere contains many clouds.