The atmosphere of the faraway gas giant HR8799c gives us clues about how it formed and perhaps how our own solar system began.
The exoplanet, which orbits the star HR8799, has seven times as much mass as Jupiter. Unlike most exoplanets, it’s big enough and far enough from its star to be detected directly, separately from the star.
This turned out to be valuable for scientists studying its atmosphere. Astronomers from Canada and the United States found that the young exoplanet’s atmosphere contains water and carbon monoxide, but no methane.
“The fact that we don’t see methane tells us a lot about the chemical processes at work in the atmosphere of this young gas giant,” Quinn Konopacky, an astronomer from the University of Toronto, said in a press release.
With this information, the researchers can guess that the planet formed through a process called core accretion, the same process that probably formed our solar system. Core accretion means that the planet’s core formed first, and then the atmosphere slowly formed around it.
“By studying the HR8799 system, we can get a peek at how Jupiter-like planets look very shortly after they form,” said Konopacky.
When the planet’s host star was young, it was surrounded by a disk of gas and dust that would later become planets. The scientists suspect that this disk contained bits of water ice.
“These ice grains stuck together to make bigger ice chunks, a few kilometers across, that kept colliding and building up the planet’s solid core,” said Konopacky.
“The atmosphere came later—from gas that the planet attracted after it got big enough. By the time that happened, some of the ice grains were gone and the gas didn’t have as much water in it.”
The research was published in the March 14 issue of the journal Science Express.