A spacecraft the size of a cereal box has collected precise measurements of the atmospheres of large, puffy planets known as "hot Jupiters." The findings, led by a team of researchers at the University of California, Berkeley, Boulder, help reveal how the atmospheres around these planets and many other worlds escape into space.
Despite its small size, NASA's CUTE spacecraft has significantly advanced our understanding of "hot Jupiters," revealing a variety of atmospheric behaviors that help us understand planetary evolution while also providing students with hands-on experience.
These observations are the first results from a hard-working NASA spacecraft called the Colorado Ultraviolet Transit Experiment (CUTE).
Kevin Francisco, the mission's principal investigator, presented the team's findings at the American Geophysical Union's 2023 meeting in San Francisco.
This 14-inch-long gadget may be cute, but it's packed with scientific discoveries. Since its launch in September 2021, CUTE has pointed its single ultraviolet telescope at a series of hot Jupiters approximately hundreds of light-years away from Earth.
Hot Jupiters are among the hottest and angriest planets in the Milky Way. As their name suggests, they are gas giants like our own Jupiter. However, these planets are much closer to their parent stars, completing their orbits approximately every few Earth days. In the process, stellar radiation bakes hot Jupiters to thousands of degrees Fahrenheit, and their atmospheres expand to very large sizes, a bit like bread heating up in an oven.
Researchers have long suspected that this constant onslaught of stellar radiation could strip away the atmospheres around some exoplanets over millions to billions of years, and data from CUTE suggests that the process may not be that simple.
The CUTE team, which includes several undergraduate and graduate students, has observed seven hot Jupiters to date, with more to come. Some of them appear to be losing their atmosphere, but others are not.
"The planets seem to come in all shapes and sizes," said French, an associate professor in the Laboratory of Atmospheric and Space Physics (LASP) and the Department of Astrophysics and Planetary Sciences. He added that CUTE is helping scientists compile a field guide to the many types of planets that exist in the Milky Way — including ones that look nothing like Earth's closest neighbors.
"We want to understand how our solar system fits into the family of solar systems in the universe," Francisco said. "That means understanding the big planets, the small planets, the planets that might have life and the planets that definitely don't, and all the important physical processes that operate on those planets."
CUTE’s road to scientific research success has not been smooth sailing. When the spacecraft first entered orbit around Earth, Francisco and his colleagues quickly noticed that it seemed to be experiencing some glitches -- a normal problem with many small satellites, or CubeSats. On one occasion, the shutter protecting the CUTE telescope kept closing suddenly when it shouldn't.
The research team, which includes several undergraduate and graduate students, isn't giving up. The researchers commanded the spacecraft to open its shutter and then drained the battery that powered it, preventing the instrument from shutting down again.
"CUTE is still working and collecting data today," France said. "It's really exciting when we get the first real scientific results."
CUTE observes distant planets as they pass in front of their parent stars, dimming the ultraviolet light emitted by these stars in the process. In some cases, the spacecraft's observations are so precise that they can detect when starlight dims by as little as 1%.
In a paper published in September, researchers described their observations of a world called WASP-189b. The planet orbits a star in the constellation Libra, more than 300 light-years, or quadrillion miles, from Earth. The planet is also incredibly hot, with its atmosphere reaching about 15,000 degrees Fahrenheit, according to the team's findings. This is thousands of degrees hotter than the surface of the sun.
CUTE's observations also show that gas is escaping from around WASP-189b at a similarly alarming rate, about 400 million kilograms (nearly 900 million pounds) per second.
Not all the planets studied by CUTE in its first two years are so exciting. In unpublished findings, the team observed a second planet, called MASCARA-4b, which did not appear to have lost much gas. Other planets like KELT-9b are somewhere in the middle.
Francisco and his colleagues hope their findings will help shed light on why some planets lose chunks of their atmospheres while others remain largely unchanged. He suspects it has something to do with a combination of the planets themselves (larger planets have stronger gravitational pulls) and the dynamics of the stars (more active stars can cause more damage to planets than quiet stars).
Over time, these same processes could have potential effects on planets in Earth's solar system and beyond. For example, scientists speculate that Mars once had a thicker atmosphere, but that it was lost through billions of years of solar erosion.
Atmospheric escape could also explain the origin of a class of planets called "super-Earths," which are slightly larger than our world.
"Much evidence suggests that super-Earths started out as Neptune-sized planets with large, fluffy atmospheres, then plummeted in mass, leaving only rocky cores and possibly thin atmospheres," Francisco said.
He said CUTE's greatest legacy may be its impact on students. The small team of about 20 people is involved in nearly every aspect of the spacecraft's life - from building the satellite to launching it and sending commands to downloading and analyzing scientific data. CUTE is currently orbiting about 326 miles (525 kilometers) above the Earth's surface and is expected to re-enter the atmosphere in 2027.
"All of these things are happening on NASA's big missions, just on a much larger scale, and our students and early career scientists are getting the full experience from the proposal stage all the way to launched science products."
Compiled source: ScitechDaily