Astronomers discover new exoplanet with the mass of Saturn

Using NASA’s Transiting Exoplanet Survey Satellite (TESS), an international team of astronomers has discovered a new Saturn-mass planet orbiting a sun-like star called TOI-2447. The discovery was published in a research paper posted on the preprint server on May 12. arXiv.

To date, TESS has identified more than 7,100 exoplanet candidates (TESS Objects of Interest or TOI), of which 445 have been confirmed. Since its launch in April 2018, the satellite has been conducting a survey of about 200,000 of the brightest stars near the Sun to search for transiting exoplanets – from small, rocky worlds to gas giants.

A group of astronomers led by Samuel Gill of the University of Warwick, UK, now reports confirmation of another TOI monitored by TESS. They discovered a transit signal on the light curve of TOI-2447, which turned out to be planetary in nature. The newly discovered exoplanet was named TOI-2447 b or NGTS-29 b, as data from the Next-Generation Transit Survey (NGTS) was also used to confirm its planetary status.

“TOI-2447 b was identified as a transiting exoplanet candidate based on a single transit event of 1.3 percent depth and 7.29 hours duration in TESS Sector 31 and an earlier transit event from 2017 in NGTS data,” the researchers explained.

The newly discovered exoplanet has a radius of 0.86 Jupiter radii and a mass of 0.39 Jupiter masses. It orbits its host every 69.34 days at a distance of 0.35 AU. The equilibrium temperature of TOI-2447 b was estimated to be 414 K, which is generally lower than most planets discovered by TESS.

The parent star TOI-2447 (also known as TIC-1167538) is a bright dwarf star of spectral type G9V. Its size and mass are comparable to the Sun, and its metallicity is 0.18 dex. The age of the star is estimated at 2.1 billion years, and its effective temperature is about 5,730 K.

The researchers also gathered strong evidence for additional planets orbiting TOI-2447. They identified a transit signal in the NGTS data that did not come from TOI-2447, but most likely from another transiting object. In addition, they found evidence in the radial velocity data from the CHIRON high-resolution echelle spectrometer that suggests the existence of an outer planet with an orbital period of about 150 days. However, further observations are needed to confirm the planetary nature of these signals.

“We continue to monitor TOI-2447 with photometry and spectroscopy to better characterize these signals and determine the properties of other planets in the system,” the authors of the paper conclude.