Researchers study the atmosphere of distant “hot Neptune” planet

Shane McGlaun - Oct 26, 2020, 7:23am CDT
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Researchers study the atmosphere of distant “hot Neptune” planet

A team of astronomers has used data gathered from TESS and the Spitzer space telescope to investigate the atmosphere of a distant planet known as LTT 9779b. The planet is described as a “hot Neptune,” and the study marks the first time the atmosphere of this exoplanet was studied. Researchers performed the first spectral atmospheric characterization and global temperature map of any TESS planet that has an atmosphere and is classified as a hot Neptune.

The team found that the emission spectrum is fundamentally different from the larger “hot Jupiters” scientists have previously studied. Ian Crossfield, an assistant professor of physics and astronomy at the University of Kansas, says that the team, for the first time, measured light coming from a planet that shouldn’t exist. Crossfield says the planet is so intensely irradiated by its host star that its temperature is over 3000 degrees Fahrenheit. The planet’s atmosphere could have evaporated entirely due to the heat, but Spitzer observations show it has an atmosphere via infrared light emitted by the planet.

LTT 9779b doesn’t have a solid surface, thanks to surface temperatures much hotter than Mercury in our solar system. The surface temperatures are so hot that lead would melt in the atmosphere of the planet, as would platinum, chromium, and stainless steel. An entire year on the world spans less than 24 Earth hours.

LT9779b was discovered last year and was one of the first Neptune-sized planets discovered by the TESS all-sky planet-hunting mission. Researchers on the project used a technique called “phase curve” analysis to determine the atmosphere’s makeup. Crossfield says the team measured how much infrared light was emitted by the planet as it rotated 360 degrees on its axis.

Infrared light can tell you the temperature and where the hotter and colder parts of the planet are. The team found that the planet is hottest at just about noon and most infrared light comes from the part of the planet when the star is straight overhead with significantly less heat from other parts of the planet.


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