To understand the conditions of exoplanets, scientists at NASA are simulating atmospheres of special class exoplanets called "hot Jupiters" right here on Earth.
The objective of the research published in the Astrophysical Journal is to study carbon-rich exoplanet atmospheres at elevated temperatures. Also, it aims to know how light forming organic aerosols of gigantic gas planets hotter than Jupiter might develop in their respective atmospheres.
Studying 'Hot Jupiters'
There are nearly 2,000 exoplanets outside of Earth's solar system while over 5,000 candidate exoplanets have been identified. These exotic planets filled with gaseous elements are called "hot Jupiters."
Unlike planets in the solar system, these giant planets orbit closely to their stars. While it takes Earth 365 days and Mercury 88 days to orbit the sun, hot Jupiters orbit their stars in less than 10 days.
Hot Jupiters are described to have eccentric orbits similar to that of a comet. The very close proximity of hot Jupiters to a star produces very high temperatures ranging from 530 to 2,800 degrees Celsius or even hotter. The side of the planet facing its host star swiftly heats up to more than 1,100 degrees Celsius.
The planet's atmosphere becomes a "cauldron of chemical reactions" as it approaches the star and bursts with radiation and winds stronger than the force of a hurricane. Their color appears as opaque at high altitudes.
"Though it is impossible to exactly simulate in the laboratory these harsh exoplanet environments, we can come very close," said Murthy Gudipati, JPL principal scientist and leader of the study.
Baking Exoplanets In A Lab
NASA scientists used a high-temperature oven and mostly chemical mixtures to replicate the atmosphere of a hot exoplanet.
The special oven tightly seals in the gas to prevent leaks or contamination. It also allows the researchers to control the pressure of the gas as the temperature rises. This exoplanet furnace has allowed scientists to push boundaries while handling chemical processes inside a laboratory.
They combined hydrogen gas and 0.3 percent carbon monoxide and heated the mixture to 330-1,230 Celsius.
They also exposed the laboratory to a high dose of ultraviolet radiation generated by a hydrogen gas discharge lamp to simulate the bursting effect of an exoplanet near its host star. The lamps radiate a visible pink glow and UV light that enters the gas container inside the oven through a window.
The chemical reactions from the heated mixture produced significant amounts of carbon dioxide and water. The study also revealed that water can form when carbon and oxygen are present in equal amounts.
"We've assumed that temperature dominates the chemistry in these atmospheres, but this shows we need to look at how radiation plays a role," said Mark Swain, a JPL exoplanet scientist and co-author of the study.
The UV radiation is significant in accelerating the formation of carbon dioxide as subsequently revealed in the laboratory experiment.
The results of the study will be useful in interpreting hot Jupiters' atmospheres.