An international group of astronomers has reported the discovery of a new exoplanet orbiting a solar-type star. The newly discovered alien world, called TOI-1135 b, is young, hot, and comparable in size to Saturn. The discovery was detailed in an article published on the preprocessing server on February 27. arXiv.

To date, NASA’s Transiting Exoplanet Search Satellite (TESS) has detected approximately 7,100 candidate exoplanets (TESS Objects of Interest, or TOIs), of which 420 have been confirmed. Equipped with wide-angle cameras, TESS has been surveying nearly 200,000 of the brightest stars near the Sun since its launch in April 2018, looking for transiting exoplanets, including giant extrasolar worlds.

A team of astronomers led by Manuel Mayorquin Díaz from Spain’s University of La Laguna confirmed another TOI observation of TESS. They identified a transition signal in the light curve of TOI-1135 (also known as HIP 62908 or TIC 154872375), a young solar-type star of spectral type G0, approximately 371 light-years away. The planetary nature of this signal was confirmed by further photometry and spectroscopy.

“This paper reports on the discovery and mass characterization of a nearby gas giant planet orbiting the young solar-type star TOI-1135,” the researchers write.

TOI-1135 b has a radius of about 0.8 Jupiter radii and a mass of about 0.062 Jupiter masses, giving a density of 0.16 g/cm³. The planet orbits its host at a distance of 0.082 AU every 8.02 days. The equilibrium temperature of TOI-1135 b is estimated to be approximately 950–1200 K.

The results thus indicate that TOI-1135 b is a bulging exoplanet similar in size to Saturn, but less massive than the two largest gas giants in the Solar System. The planet has a long atmosphere, most likely due to strong stellar radiation.

Astronomers suggest that TOI-1135 b may be in the process of losing its atmosphere through photoevaporation. They noted that the planet has a high mass loss rate of about 39 Earth masses per billion years, so it will eventually lose most of its atmosphere within a few hundred million years.

“Giant planets with less mass than Saturn tend to lose all or most of their atmospheres in the early stages if they receive sufficient radiation from the host star, which may be the case for TOI-1135 b,” the paper’s authors write.

The main star, TOI-1135, is slightly larger and more massive than the Sun, with a luminosity of 1.7 solar luminosities. The age of the star is estimated to be between 125 million and 1 billion years, and its effective temperature is around 6122 K.