While studying the unique class of ultra-hot exoplanets, NASA Hubble Space Telescope astronomers may be in the mood to dance to the Calypso Party song “Hot, Hot, Hot.” This is because these blooming Jupiter-shaped worlds are so uncertainly close to their original star that they are being burned at temperatures above 3,000 degrees Fahrenheit. It is hot enough to evaporate most metals, including titanium. They have the hottest planetary atmosphere ever seen.
In two new papers, a team of Hubble astronomers is reporting on strange weather conditions in these glowing worlds. The evaporative rock is raining down on one planet and the upper atmosphere of the other planet is getting warmer instead of getting colder because it is “sunburnt” due to the intense ultraviolet (UV) radiation of its star.
This research is beyond just finding strange and bizarre planetary atmospheres. By studying extreme weather, astronomers gain a better understanding of the diversity, complexity, and peculiar chemistry of our galaxy’s distant world.
“We still don’t have a good understanding of the atmospheres of different planets,” said David Singh of Johns Hopkins University in Baltimore, Maryland, co-author of the two studies. “When you look at the earth, all our weather forecasts are still in line with what we can measure. But when you go to a distant exoplanet, you have limited predictive powers because you have not developed a general theory of how everything in the atmosphere works together. Goes and responds to extreme situations. Even if you know the basic chemistry and physics, you don’t know how it will manifest in complex ways. “
In a paper in the April 7 issue of the journal Nature, astronomers described Hubble observations of WASP-178b about 1,300 light-years away. During the day the atmosphere is cloudless and it is enriched with silicon monoxide gas. Because one side of the planet is permanently close to its star, the tropical atmosphere rotates at night with a cyclone speed of more than 2,000 miles per hour. On the dark side, rainwater from silicon monoxide clouds can be cold enough to solidify, but even in the morning and evening, the planet is hot enough to evaporate the rock. “We know we’ve seen something really interesting with this silicon monoxide feature,” said Josh Lotharinger of the University of Utah in Orem, Utah.
In a paper published in the January 24 issue of the Astrophysical Journal Letters, University of Maryland, College Park’s Guangwei Fu reported on the superheated Jupiter KELT-20b, about 400 light-years away. The explosion of ultraviolet light from its original star on this planet is creating a thermal layer in the atmosphere like the Earth’s stratosphere. “Until now we did not know how the host star directly affects the planet’s atmosphere. There are many theories, but now we have the first observation data,” Fu said.
In comparison, on Earth, ozone in the atmosphere absorbs ultraviolet light and raises the temperature between 7 and 31 miles above the Earth’s surface. Ultraviolet radiation from the star on KELT-20b heats atmospheric metals, creating a very strong thermal inversion layer.
The discovery of Hubble’s water in near-infrared observations and the discovery of carbon monoxide from NASA’s Spitzer Space Telescope. They emit radiation from the warm, transparent upper atmosphere that is created by the turbulent layer. This signature is more unique than what astronomers see in the atmosphere of a hot-Jupiter orbiting cold stars like our Sun. “The emission spectrum for the KELT-20b is very different from other hot-Jupiters,” Fu said. “This is compelling evidence that planets do not live alone but are influenced by their host star.”
Although super-hot Jupiter is solitary, this type of research paves the way for a better understanding of the atmosphere of potentially inhabited terrestrial planets. “While we may not be able to detect what’s happening on the super-hot Jupiter with reliable solid observational data, we won’t have a chance to find out what’s happening in the weaker spectrum from observing Earth’s exoplanets,” Lothringer said. “It’s a test of our techniques that allows us to build a general understanding of physical properties, such as cloud formation and the composition of the atmosphere.”
The Hubble Space Telescope is an international collaboration project between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland conducts Hubble Science operations. STScI is run for NASA by the Association of Astronomical Research Universities in Washington, D.C.