Editing 1517

#REDIRECT [[1517: Spectroscopy]]

{{comic
| number    = 1517
| date      = April 27, 2015
| title     = Spectroscopy
| image     = spectroscopy.png
| titletext = Although right now I'm more excited about ESPRESSO's radial velocity measurements, so I'm listening to This Kiss, her song about measuring "centrifugal motion" on "a rooftop under the sky".
}}

==Explanation==
Measuring the light output of stars (spectra) we are able to determine a number of details of the star, including rotation, relative radial velocity, chemical composition, temperature and to some degree, distance and size. As the planet pictured transitions between the star and the observer, and looking at the spectrum received, the viewer is able to determine that the planet is absorbing the specific wavelengths that molecular oxygen absorbs; a clear indication that the planet has large quantities of breathable oxygen. 

http://www.huffingtonpost.com/2015/04/23/nasa-nexss-search-for-life_n_7123788.html

This comic mixes this method of detection of oxygen on remote planets with the lyrics for the Faith Hill song "Breathe" 
"I see the sunlight" - examining the spectra of a remote star
"I dance across your face" - examining the transition of the planet across the star
"I can see you breathe" - determining that breathable oxygen exists.

The mouseover text refers to determining rotational velocity (based on emission line broadening) from another Faith Hill song, "This Kiss" referring to centrifugal motion.