New low-density super-Earth exoplanet discovered by TESS
Discovery of TOI-244 b
An international team of astronomers has discovered a new “super-Earth” exoplanet, designated TOI-244 b, using NASA’s Transiting Exoplanet Survey Satellite (TESS).
This newly discovered exoplanet is notable for its unusually low density.
TESS studies about 200,000 of the brightest stars near the Sun in search of passing exoplanets.
So far, nearly 6,600 possible exoplanets (TESS Objects of Interest, TOI for short) have been identified, of which 331 have been confirmed.
Astronomers led by Amadeo Castro-González of the Spanish Center for Astrobiology in Madrid, Spain, confirmed another TOI monitored by TESS.
A transit signal was detected in the lightcurve of TOI-244 (aka GJ 1018), a nearby bright early-type M2.5 V dwarf star nearly half the size and mass of the Sun.
The planetary nature of this signal was confirmed by radial velocity measurements made with the ESPRESSO spectrograph on the Very Large Telescope (VLT) of the European Southern Observatory in Chile.
Properties of TOI-244 b
TOI-244 b has a radius of 1.52 Earth radii and a mass of about 2.68 Earth masses, which corresponds to a density of 4.2 g/cm3.
The planet orbits its host every 7.4 days at a distance of about 0.056 AU and its equilibrium temperature is estimated to be about 458 K.
The term “super-Earth” is used to describe planets more massive than Earth but smaller than Neptune, as well as those larger than Earth but smaller than “mini-Neptune”. TOI-244 b conforms to these parameters.
The researchers suspect that TOI-244 b is made up of iron and silicates in a similar ratio to Earth.
However, its density is lower than most super-Earths of this size and below what one would expect for an Earth-like composition.
The low density of TOI-244 b may be due to the presence of a significant amount of volatile elements.
The researchers believe that atmospheric loss processes could have effectively removed a potential pristine hydrogen shell from TOI-244 b, but could have retained high-average molecular weight volatiles such as water.
They concluded that TOI-244 b is an excellent target for future atmospheric studies because of its unusual properties and the likely presence of an extended atmosphere.
The findings were published in a paper published on May 8 on the preprint server arXiv.
More about TESS
TESS, short for Transiting Exoplanet Survey Satellite, is a space telescope launched by NASA on April 18, 2018 with the specific mission of discovering exoplanets around the brightest stars in the sky.
Exoplanets are planets orbiting stars outside of our own solar system. TESS uses the transit method to find these exoplanets.
The transit method observes the tiny dip in a star’s brightness that occurs when an orbiting planet passes through, or “passes through” the star.
TESS is expected to scan an area of the sky 400 times larger than the area observed by the Kepler mission.
While Kepler focused on distant stars in a small patch of sky, TESS targets stars much closer to Earth, covering a much larger portion of the sky.
The main goal of TESS is to catalog thousands of exoplanet candidates for further study. The ultimate goal is to measure the masses, sizes and atmospheres of a large sample of small planets, including a sample of rocky planets in the habitable zones of their parent stars.
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