Sodium (see left) in Earth’s air would not fly. It will rapidly combine with the oxygen. If caught in the rain, element number eleven will even turn violent.
At 1621 degrees F, it is gaseous, and is the first constituent of an extra-solar planetary atmosphere to be detected from Earth, thanks to clever work from UT-Austin astronomer Seth Redfield. Some planets pass between Earth and their home star during their orbit. We can detect these planets by the reduction in light coming from the star–a small percentage is blocked and astronomers can detect a dip of a few percent or less.
Redfield zeroed in on sodium emissions of the star HD189733 and compared this to the full spectrum of light.
The atmosphere of the planet will absorb more starlight at those wavelengths that correspond to specific transitions of the sodium atom.
“This causes the planet to appear larger, since we now ‘see’ the planet plus the atmosphere, and we measure more blocked light from the star,” Redfield said. When studying the planet at the particular wavelength of the sodium transition, the planet appears about 6 percent larger than at other wavelengths. The detection of sodium was possible because there’s a lot of it there, and the atomic transition is strong and falls within the visual range that ground-based telescopes can detect.
Sixty-three light years away and modern astronomers can detect sodium gas in a planet’s atmosphere. How cool is stuff like this?