14-inch spacecraft provides new details on ‘hot Jupiters’

A spacecraft the size of a cereal box has collected precise measurements of the atmospheres of large, puffy planets called “hot Jupiters.” The results, led by a team at the University of Colorado Boulder, could help reveal how atmospheres around these and many other worlds escape into space.

These observations are the first results coming from a NASA spacecraft, known as the Colorado Ultraviolet Transit Experiment (CUTE).

Kevin France, principal investigator of the mission, will present the group’s results during a press briefing on Monday, December 11 at 4:30 p.m. during the 2023 meeting of the American Geophysical Union in San Francisco.

The little spacecraft, which measures just 14 inches in length, may be cute, but its scientific findings, published in The astronomical journal, are anything but. Since its launch in September 2021, CUTE has aimed its unique ultraviolet telescope towards a series of hot Jupiters, a few hundred light years from Earth.

Hot Jupiters are among the hottest and angriest planets in the galaxy. As their name suggests, they are gas giants like our own Jupiter. These planets, however, come much closer to their home stars, completing an orbit approximately every several Earth days. In the process, stellar radiation cooks the hot Jupiters to thousands of degrees Fahrenheit, and their atmospheres swell to enormous sizes, much like bread rising in an oven.

Researchers have long suspected that these constant bursts of stellar radiation could destroy the atmosphere around some exoplanets over millions or even billions of years. CUTE’s data suggests the process may not be so simple.

The CUTE team, which includes several undergraduate and graduate students, has observed seven hot Jupiters so far, with more on the way. Some of them seem to lose their atmosphere, but others don’t.

“Planets seem to come in all shapes and sizes,” said France, an associate professor in the Laboratory for Atmospheric and Space Physics (LASP) and the Department of Astrophysical and Planetary Sciences.

He added that CUTE is helping scientists develop their field guide to the many types of planets that exist in the Milky Way, including those that look nothing like Earth’s close neighbors.

“We want to understand how our solar system fits into the family of solar systems in the universe,” France said. “That means understanding the big planets, the small planets, those that have life and those that definitely don’t, and all the important physical processes that take place on those planets.”

It’s hot in here

CUTE’s path to scientific success has not been easy.

When the spacecraft first entered orbit around Earth, France and his colleagues quickly noticed that it seemed to have some problems, a normal problem for many small satellites, or CubeSats, which often test technology that had never been sent into space before. In one case, the shutter that protected CUTE’s telescope kept closing when it wasn’t supposed to.

The team, made up of several undergraduate and graduate students, did not give up. The researchers ordered the spacecraft to open its shutter, then drained the battery that powered it, preventing the device from closing again.

“CUTE continues to work and collect data today,” France said. “When we got our first real scientific results, it was really exciting.”

CUTE observes distant planets as they pass in front of their home stars, causing the ultraviolet light from those stars to dim. In some cases, the spacecraft is so precise that it can detect when starlight dims by just 1%.

In an article published in September in Letters from the astrophysical journal, researchers described their observations of a world called WASP-189b. This planet orbits a star in the constellation Libra located more than 300 light years, or trillions of kilometers, from Earth. It’s also incredibly hot, with the atmosphere reaching temperatures of around 15,000 degrees Fahrenheit, according to the team’s results. That’s thousands of degrees warmer than the surface of the sun.

CUTE observations also suggest that gas is escaping around WASP-189b at an equally staggering rate of about 400 million kilograms (nearly 900 million pounds) per second.

The planets evolve

Not all of the planets CUTE studied in its first two years were as exciting. In unpublished results, the team observed a second planet called MASCARA-4b that didn’t appear to be losing much gas. Others, like KELT-9b, fall somewhere in the middle.

France and his colleagues hope their results could help uncover why some planets lose large parts of their atmosphere, while others remain virtually unchanged. He suspects this is due to a combination of the planets themselves (larger planets generate a stronger gravitational pull) and the dynamics of their stars (more active stars likely wreak more havoc on planets than quiet stars ).

These same processes can potentially sculpt planets, both in and out of Earth’s solar system, over time. Scientists, for example, hypothesize that Mars once had a much thicker atmosphere, but that the sun eroded it over billions of years.

Atmospheric escape may also explain the origin of a class of planets known as “super Earths”, slightly larger than our own world.

“Much evidence suggests that super-Earths originated as Neptune-sized planets with large, inflated atmospheres, which then lost so much mass that only the rocky core and possibly a thin atmosphere remained,” France said.

CUTE’s greatest legacy may be its impact on students, he said. The small mission team of about 20 people was involved in almost every aspect of the spacecraft’s life: from building the satellite to launching it, sending commands, and then downloading it. and analysis of scientific data. CUTE is currently orbiting approximately 525 kilometers above the Earth’s surface and is expected to re-enter the atmosphere by 2027.

“All of these things happen on big NASA missions, but on a much larger scale,” France said. “Our students and early career scientists benefit from a comprehensive experience from the proposal stage to the release of the scientific product.”