New exoplanet with Saturn mass discovered by astronomers

New exoplanet with Saturn mass discovered by astronomers

Target Pixel File (TPF) of TESS sector 5 with TIC-1167538 (=TOI-2447/NGTS-29) marked with a white cross. Other sources from Gaia DR3 are marked with red circles, ordered by scale relative to the target, ordered by distance. The aperture mask is indicated by the red outline. Credit: Gill et al., 2024.

Using NASA’s Transiting Exoplanet Survey Satellite (TESS), an international team of astronomers has discovered a new Saturn-mass planet orbiting a solar-type star known as TOI-2447. The finding was reported in a research paper published on the pre-print server on May 12 arXiv.

To date, TESS has identified more than 7,100 candidate exoplanets (TESS Objects of Interest, or TOI), of which 445 have been confirmed. Since its launch in April 2018, the satellite has surveyed about 200,000 of the brightest stars near the Sun with the aim of searching for transiting extrasolar planets, ranging from small, rocky worlds to gaseous giants.

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

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

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

The parent star TOI-2447 (also known as TIC-1167538) is a bright dwarf of spectral type G9V. It has a size and mass similar to that of the Sun, and its metallicity is at a level of 0.18 dex. The star is estimated to be 2.1 billion years old and has an effective temperature of about 5,730 K.

The researchers also gathered strong evidence for even more 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 suggesting the presence of an outer planet with an orbital period of about 150 days. However, additional 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 additional planets in the system,” the paper’s authors conclude.

More information:
Samuel Gill et al, TOI-2447 b/NGTS-29 b: a 69-day Saturn around a solar analog, arXiv (2024). DOI: 10.48550/arxiv.2405.07367

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