Astronomers say they've managed to make highly accurate measurements of the atmosphere of a distant planet, and "hot and dry" doesn't begin to describe it; how about 500-mph winds and temperatures of 5,400 degrees Fahrenheit?
Researchers are describing turbulent upper levels of the atmosphere of exoplanet HD 189733b as truly "infernal."
Astronomers from two Swiss universities in Geneva and Bern used a spectrometer to study spectrographic lines of sodium, an element in the exoplanet's atmosphere, to gather data on winds and temperatures, and also came up with theoretical models to support the observations.
The spectrograph, known as the HARPS instrument, has been mated to a relatively small telescope at the European Star Observatory in Chile.
Scientists had theorized in 2000 that sodium would be an ideal source of a clearly recognizable signal in any planet possessing an atmosphere, and the first observations confirming that in an exoplanet were made 2 years later by the Hubble Space Telescope.
Now the sodium data is helping astronomers study the gas giant planet HD189733b, located about 60 light years from Earth in the constellation Vulpecula, the "little fox."
The data gathered suggests the atmosphere's temperature changes with altitude, reaching temperatures in its upper levels high enough to melt iron, they say.
The results of the spectrographic observations are also supported by a theoretical study by University of Berne astrophysicist Kevin Heng, which produced a formula to estimate temperatures, pressures and densities in an exoplanet's atmosphere based on its size.
"Previous formulae assumed the atmosphere to have only a single temperature, but we know that this is probably too simplistic even for faraway exoplanets for which we have limited information," explains Heng.
"Our motivation was to derive new and simple formulae that took into account the changing temperatures and were specifically designed to interpret sodium lines," he says.
The HD 189733b observations along with Heng's theoretical work should lead to better methods of exploring exoplanet atmospheres, astronomers say, and a way to provide any question about such atmospheres with "a quick and relatively robust answer without crunching numbers in a computer," Heng says.
Even relatively small ground-based telescopes can provide characterizations of remote exoplanetary atmospheres using the new techniques and theoretical formulae, astronomers say.
Previously, detecting sodium in the atmospheres of exoplanets to make assumptions about conditions there required either the Hubble telescope or very large ground-based instruments in the 25- to 30-foot range.
"Sometimes, simple is better," Heng says.
Heng's theoretical study has been published in the Astrophysical Journal Letters, while the spectrographic study appears in the Astronomy & Astrophysics Journal.
