- One of the constellations representing technical and artistic apparatus introduced into the southern sky by the Frenchman Nicolas Louis de Lacaille after his observing expedition to the Cape of Good Hope in 1751–52. It lies under the keel of the now-dismembered Greek constellation Argo Navis, the ship of the Argonauts, next to the bright star Canopus. In fact the four brightest stars in Pictor, labelled α, β, γ, and δ by Lacaille, had been catalogued by the Dutch explorer Frederick de Houtman as part of Argo a century and half earlier.
- Stellar classification (Wikipedia)
In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The spectral class of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere’s temperature.