Astronomers discover an unusually low-density super-Earth


Astronomers discover an unusually low-density super-Earth

TESS target pixel file from TOI-244. Credit: Castro-González et al, 2023

An international team of astronomers has reported the discovery of a new “super-Earth” exoplanet using NASA’s Transiting Exoplanet Survey Satellite (TESS). The newly discovered alien world, called TOI-244 b, turns out to have an unusually low density. The finding was reported in a paper published May 8 on arXiv Prepress server.

TESS is surveying about 200,000 of the brightest stars near the sun with the goal of searching for transiting exoplanets. To date, it has identified nearly 6,600 exoplanet candidates (TESS Objects of Interest, or TOI), of which 331 have been confirmed so far.

Now, a group of astronomers led by Amadeo Castro-González of the Spanish Center for Astrobiology in Madrid, Spain, has confirmed another TOI observed by TESS. They report that a transit signal has been detected in the light curve of TOI-244 (aka GJ 1018) – a close M-dwarf star of spectral type M2.5 V, approximately half the size and sun block. The planetary nature of this signal was confirmed by radial velocity measurements made with the ESPRESSO spectrometer installed on the European Southern Observatory’s Very Large Telescope (VLT) in Chile.

Based on the transit signal detected from the TESS data, we conducted an intense radial velocity campaign with ESPRESSO to confirm its planetary nature, obtain an accurate mass measurement, and also to search for more planetsthe researchers wrote.

According to the study, TOI-244 b has a radius of 1.52 Earth-masses, while its mass is about 2.68 Earth-masses, resulting in a density at a level of 4.2 g/cm.3. The planet orbits its host every 7.4 days, at a distance of about 0.056 astronomical units from it, and its equilibrium temperature is estimated at about 458 K.

Based on the results, the Castro-González team classified TOI-244 b as a “super-Earth.” These planets are more massive than Earth but do not exceed the mass of Neptune. Although the term “super-Earth” refers only to a planet’s mass, it is also used by astronomers to describe planets larger than Earth but smaller than the so-called “mini-Neptunes” (with radii ranging from two to four radii). to Earth).

The results indicate that TOI-244 b is composed of iron and silicates in a ratio similar to that of Earth. However, the planet is less dense than the majority of superplanets of its size. The TOI-244 b intensity is also lower than what would be expected for an Earth-like composition.

The researchers hypothesize that the low density of TOI-244 b is related to the presence of a large amount of volatile elements.

“In this sense, we found that atmospheric loss processes may have been very effective for removing a possible primordial hydrogen shell, but higher molecular weight volatiles such as water could have been retained,” the paper’s authors concluded.

The astronomers added that TOI-244 b is an excellent target for future atmospheric studies, due to its unusual properties and potential for an extended atmosphere.

more information:
Castro-González et al, An unusually low-density super-Earth passing through an early-type M-dwarf GJ 1018 (TOI-244), arXiv (2023). doi: 10.48550/arxiv.2305.04922

Journal information:

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