A team of astronomers used data collected 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 that the atmosphere of this exoplanet has been studied. The researchers carried out the first spectral atmospheric characterization and the 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 largest “hot Jupiters” that scientists previously studied. Ian Crossfield, assistant professor of physics and astronomy at the University of Kansas, says the team, for the first time, measured light from a planet that shouldn’t have existed. Crossfield says the planet is so intensely irradiated by its host star that its temperature is over 3,000 degrees Fahrenheit. The planet’s atmosphere could have completely evaporated due to the heat, but Spitzer’s observations show that he has an atmosphere through infrared light emitted by the planet.
LTT 9779b does not have a solid surface, thanks to surface temperatures much higher than that of Mercury in our solar system. The surface temperatures are so high that lead would melt in the planet’s atmosphere, as well as platinum, chromium and stainless steel. A whole year in the world covers less than 24 hours on land.
LT9779b was discovered last year and was one of the first Neptune-sized planets discovered by the TESS planet-hunting mission in the sky. The project researchers used a technique called “phase curve” analysis to determine the composition of the atmosphere. Crossfield said the team measured how much infrared light was emitted by the planet as it rotated 360 degrees on its axis.
Infrared light can tell the temperature and where the hottest and coldest parts of the planet are. The team found that the planet gets hotter around noon and most of the infrared light comes from the part of the planet where the star is high above with significantly less heat from other parts of the planet.