Photographer: Greg ParkerSummary Author: Greg Parker
Featured here (top) is an image of the stars Castor and Pollux, the prominent stars in the constellation Gemini (The Twins). Below is their spectral comparison. As you will have noted if you've ever looked at this constellation, Castor and Pollux are quite close in brightness -- 1.93 magnitude and 1.14 magnitude, respectively. Blue-white Castor is part of a multiple star system, some 52 light years away. Pollux, an orange giant, is slightly brighter than Castor and is found approximately 34 light years away.
All stars emit light across a variety of spectral wavelengths or colors. The wavelength at which light output peaks provides information about a star's temperature. Pollux is classified as a K0 IIIb spectral-type star. It's actually cooler than our Sun, having an estimated surface temperature of 8,000 degrees Fahrenheit (4,400 degrees Celsius), compared with the Sun's surface temperature of 10,000 F (5,500 C). Castor is an A type Main Sequence star (A1V + dM1e), much more massive than the Sun and much hotter (between 8,000-10,000 C). This spectral comparison between Castor and Pollux was another collaborative effort with my spectroscopist friend George Roberts.
Note that the annual Geminid meteor shower peaks on December 13. Even though the waxing gibbous Moon will affect viewing, it's worth stepping outside to take a look.
Photo Details: Taken with the 200 mm lenses and M26C OSC CCDs on the MiniWASP array.
Spectroscopy Details: Data captured with a Meade 127mm apo-refractor, a 500 lines/mm transmission grating-3d printed spectrometer and a QHY5-11m camera. Spectral data processed using BASS Project (Basic Astronomical Spectroscopy Software).
New Forest Observatory, U.K. Coordinates: 50.819444, -1.59
The JPO, Suffolk, U.K. Coordinates: 52.483161, 1.702376
Related Links:
Castor and Pollux in GeminiThe Classification of Stellar Spectra
