A small exoplanet passing by Neptune has either a gaseous atmosphere, an ocean, or both

A small exoplanet passing by Neptune has either a gaseous atmosphere, an ocean, or both

TESS segment 13 HD target pixel file 207496 (white cross and #1) and main contaminant (#2) from the GAIA DR3 catalog. There are no other contaminants less than 9 orders of magnitude lighter than HD 207496 within the TESS aperture (shown as orange squares). The pixel scale is 21 pixels-1. credit: arXiv (2023). doi: 10.48550/arxiv.2303.03775

An international team of planetary scientists has identified some features of an exoplanet called HD-207496-b, which lies about 138 light-years from Earth. In their paper accepted for publication in the journal Astronomy and astrophysicsIt is currently posted on arXiv Preprint server, the group describes their study of the exoplanet and the two theories regarding its possible composition.

the exoplanet HD-207496-b was discovered as part of a larger effort to describe the naked fundamental planets. As such, the team has been analyzing HARPS Spectral notes from HD-207496 – a bright k dwarf. By adding TESS photometry data, the group was able to measure the stars’ brightness and wavelength, and by studying the properties of the exoplanet transits, the team was able to calculate the period, mass, radius, and density. This led them to a kind of puzzle – was the exoplanet gaseous or watery?

The researchers calculated that the exoplanet has a radius of 2.25 times that of Earth, and an orbit of 6.44 days. It had a mass approximately 6.1 times that of Earth. Simple math showed that the density of an exoplanet is 3.27 grams per cubic centimeter, which is less than that of planet Earth.

The research team concluded that this indicates that the planet has a rocky core that is mostly covered in water or gas. Intrigued by the possibilities, the group created a model to help them better appreciate the structure of an exoplanet. But the model wasn’t able to pinpoint its specific characteristics—it suggested it could be a water-rich, gas-rich exoplanet, or a combination of both.

The research team also discovered that modeling of evaporation showed that if exoplanets have atmospheres rich in helium and hydrogen, its current state is likely to be temporary. Gravity from its star will likely pull the atmosphere from an exoplanet within the next half-billion years. They also noted the possibility that these gases may have already evaporated, leaving the exoplanet with nothing but an ocean.

The team suggests that HD-207496-b likely contains a mixture of gas and water and also notes that future study of the planet is likely to lead to a better understanding of its composition.

more information:
SCC Barros et al, a Neptune HD 207496b microdevice that is either a bare core or about to become one, arXiv (2023). doi: 10.48550/arxiv.2303.03775

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the quote: Transiting a small exoplanet of Neptune that is characterized as having either a gaseous atmosphere, an ocean, or both (2023, March 14) Retrieved March 14, 2023 from https://phys.org/news/2023-03-transiting-mini- neptune-exoplanet-feature-gaseous.html

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