(ORDO NEWS) — The team, led by an astronomer from the University of Kansas, collected data from NASA’s TESS and Spitzer space telescopes to display the atmosphere of a highly unusual exoplanet dubbed “hot Neptune” for the first time.
The results concerning the recently discovered planet LTT 9779b were published in the Astrophysical Journal Letters. The article details the first spectral signature of any planet’s atmosphere discovered by TESS, the first global temperature map of any planet TESS with an atmosphere and hot Neptune, whose emission spectrum is fundamentally different from many of the larger “hot Jupiters” previously studied.
“This is the first time we’ve measured the light emanating from this planet, which shouldn’t be,” said Ian Crossfield, assistant professor of physics and astronomy at the University of California and lead author of the paper. “This planet is so intensely irradiated by a star that its temperature is over 3000 degrees Fahrenheit, and its atmosphere should have completely evaporated. However, our Spitzer observations show its atmosphere through the infrared light that the planet emits.”
While the LTT 9779b is unusual, one thing is for sure: people won’t like it there.
“This planet does not have a solid surface, and it is much hotter than even Mercury in our solar system – there is not only molten lead in the planet’s atmosphere, but also platinum, chromium and stainless steel,” said Crossfield. “A year on this planet is less than 24 hours – so quickly it revolves around its star. It’s a pretty extreme system. ”
Hot Neptune LTT 9779b was discovered last year and was one of the first Neptune-sized planets discovered by NASA’s TESS planetary search mission. Crossfield and his co-authors used a technique called “phase curve analysis” to analyze the atmospheric composition of an exoplanet.
“We measure how much infrared light a planet emits when it rotates 360 degrees on its axis,” he said. “Infrared light tells the temperature of something and where the hotter and colder parts of this planet are – it’s not the hottest day on Earth; the hottest time is a couple of hours in the afternoon. But this planet is actually hottest around noon. We see most of the infrared light coming from the part of the planet where its star is directly overhead, and much less from other parts of the planet.”
A planet’s temperature readings are viewed as a way to characterize its atmosphere.
“The planet is much colder than we expected, which suggests that it reflects most of the starlight falling on it, presumably due to daytime clouds,” said co-author Nicholas Cowen of the Institute for Exoplanet Research (iREx), who helped with the analysis. and interpreting the temperature phase curve measurements. “The planet also does not carry much heat to the night side, but we think that the absorbed starlight is absorbed high in the atmosphere, from where the energy is quickly radiated back into space.”
According to Crossfield, the results are just the first step towards a new phase in exoplanet exploration, as the study of exoplanet atmospheres advances steadily towards smaller and smaller planets.
“I would not say that now we understand everything about this planet, but we have measured enough to understand that this will be a really fruitful subject for future research,” he said. “It is already targeted for observation with the James Webb Space Telescope. Our measurements so far show what we call absorption spectral characteristics – and its spectrum indicates carbon monoxide and / or carbon dioxide in the atmosphere. We begin to understand what molecules make up its atmosphere. What the global temperature map looks like tells us something about how the winds spread energy and materials through the atmosphere of this miniature gas planet.”
“We think the rarity of finding hot Neptune is because they are not massive enough to avoid significant atmospheric evaporation and mass loss,” Crossfield said. “The closest hot exoplanets are either massive hot Jupiters or rocky planets that have long since lost much of their atmosphere.”
While LTT 9779b is not suitable for colonization by humans or other known life forms, assessing its atmosphere will hone methods that could one day be used to find better planets for life.
“Big and hot planets like LTT 9779b help with learning and show that we really know what we are doing and can do everything right.”
Crossfield said there is still a lot of work to be done to better understand LTT 9779b and similar hot Neptunes not yet discovered.
“We want to continue observing with other telescopes so that we can answer other questions,” he said. “How can this planet maintain its atmosphere? How did it form? Was it originally larger, but lost some of its original vibe? If so, why is its atmosphere not just a scaled down version of the atmosphere of superhot large exoplanets? What else might be hiding in its atmosphere?”
“We found carbon monoxide in its atmosphere and that the constant day side is very hot, while very little heat is transferred to the night side,” said Bjorn Bennecke of iREx and the University of Montreal. “Both discoveries make the planet a very interesting target for future performance detailing with JWST. We are now also planning much more detailed NIRISS observations of the phase curve at JWST.”
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