Using the Gemini South telescope, with an instrument called IGRINS, the team observed the planet's thermal glow as it orbited its host star. From this instrument they gathered information about the presence and relative amounts of various gases in its atmosphere
An international team of scientists, using the ground telescope of the Gemini Observatory in Chile, is the first to directly measure the amount of water and carbon monoxide in the atmosphere of a planet in another solar system some 340 light years away.
The team is headed by Senior Lecturer Michael Lane of Arizona State University's School of Earth and Space Studies, and the results were published today (October 27, 2021) in the journal Nature.
There are thousands of known planets outside our solar system (called exoplanets). Scientists use telescopes in space and on the ground to study how these exoplanets form and how they differ from the planets in our solar system.
In this study Lane and his team focused on the planet "WASP-77Ab", a planet of a type called "hot Jupiter" because they are like Jupiter in our solar system, but with a temperature exceeding one thousand degrees Kelvin.
They then focused on measuring the composition of its atmosphere to determine what elements are present, compared to the star it orbits.
"Because of their size and temperature, hot Jupiter-type planets are excellent laboratories for measuring atmospheric gases and testing our theories about planet formation," Lane said.
We can't yet send spacecraft to planets outside our solar system, but scientists can study the light coming from exoplanets using telescopes. The telescopes they use to observe this light can be in space, like the Hubble Space Telescope, or on the ground, like the telescopes at the Gemini Observatory.
Lane and his team have been busy measuring the atmospheric compositions of exoplanets using Hubble, but getting those measurements has been challenging. Not only is there fierce competition for telescope time, Hubble's instruments only measure water (or oxygen) and the team needed to collect measurements of carbon monoxide (or carbon) as well.
At this point the team turned to the Gemini South telescope.
"We had to try something different to answer our questions," Lane said. "And after we analyzed the capabilities of Gemini South, we saw that we could achieve very accurate atmospheric measurements."
Gemini South is an 8.1 meter diameter telescope located on a mountain in the Chilean Andes called Cerro Pachon, which is an excellent place for a telescope because of the very dry air and negligible cloud cover. It is operated by the National Science Foundation's National Optical-Infrared Astronomical Research Laboratory (NOIRLab).
Using the Gemini South telescope, with an instrument called IGRINS, the team observed the planet's thermal glow as it orbited its host star. From this instrument they gathered information about the presence and relative amounts of various gases in its atmosphere.
Similar to weather and climate satellites used to measure the amount of water vapor and carbon dioxide in the Earth's atmosphere, scientists can use spectrometers and telescopes, such as IGRINS in Gemini South, to measure the amounts of various gases on other planets.