Discovery of a new super-Neptune exoplanet

An international team of astronomers reports the discovery of a new super-Neptune exoplanet orbiting a solar-like star. The newly detected alien world, which was given the designation TOI-5005 b, is approximately six times larger and more than 30 times more massive than Earth. The discovery was detailed in a paper published September 26 on the preprint server. arXiv.

NASA’s Transiting Exoplanets Survey Satellite (TESS) is conducting a survey of about 200,000 of the brightest stars near the sun in an effort to search for transiting exoplanets. So far, it has identified more than 7,200 candidate exoplanets (TESS Objects of Interest, or TOI), of which 557 have been confirmed so far.

Recently, a group of astronomers led by Amadeo Castro-González of the Astrobiology Center in Madrid, Spain, confirmed another TOI monitored by TESS. They found a transit signal on the light curve of TOI-5005, a moderately bright solar-like star of spectral type G2V, located about 685 light-years away. The planetary nature of this signal was confirmed by follow-up observations made using ground-based installations.

“In this work, we used TESS, HARPS, PEST and TRAPPIST-South data to confirm the planetary nature of TOI-5005 b and characterize its orbital and physical properties,” the researchers wrote in the paper.

The new planet has a radius of 6.25 Earth radii and a mass of 32.7 Earth masses, giving a density of 0.74 g/cm.³. It orbits its host every 6.31 days, at a distance of approximately 0.066 AU from it. The planet’s equilibrium temperature has been estimated at 1040 K.

By studying the internal structure of TOI-5005 b, astronomers estimated that its core mass fraction and shell metal mass fraction are approximately 0.74 and 0.08, respectively. In total, the overall mass fraction of metals on this exoplanet was calculated at 0.76, therefore slightly lower than that of Uranus and Neptune. These results suggest that TOI-5005 b formed by central accretion.

Based on the data obtained, the authors of the article classified TOI-5005 b as a super-Neptune near the crest of the “Neptunian savannah”. The so-called Neptunian desert and savannah mark the dearth of Neptune-like exoplanets in the shorter orbits and their modest presence at greater orbital distances. They are separated by a recently identified Neptune overdensity (ridge) in the 3-5 day orbital period range.

The researchers noted that TOI-5005 b became a new member of a generally rare population of low-density Neptunes in the Neptunian savannah, unlike ridge planets, which typically have higher densities, greater than 1.0 g/cm.³.

In their concluding remarks, the scientists added that the brightness of TOI-5005 makes the newly detected planetary system a key target for observations of atmospheric and orbital architecture.

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