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The Purple Earth Hypothesis (PEH) is an astrobiological hypothesis, first proposed by molecular biologist Shiladitya DasSarma in 2007, [1] that the earliest photosynthetic life forms of Early Earth were based on the simpler molecule retinal rather than the more complex porphyrin -based chlorophyll, making the surface biosphere appear purplish ...
Stellar classification. 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.
Shades of purple. There are numerous variations of the color purple, a sampling of which is shown below. In common English usage, purple is a range of hues of color occurring between red and blue. [1] However, the meaning of the term purple is not well defined. There is confusion about the meaning of the terms purple and violet even among ...
Celestial cartography, [1] uranography, [2] [3] astrography or star cartography[citation needed] is the aspect of astronomy and branch of cartography concerned with mapping stars, galaxies, and other astronomical objects on the celestial sphere. Measuring the position and light of charted objects requires a variety of instruments and techniques.
Hercules is a constellation named after Hercules, the Roman mythological hero adapted from the Greek hero Heracles. Hercules was one of the 48 constellations listed by the second-century astronomer Ptolemy, and it remains one of the 88 modern constellations today. It is the fifth-largest of the modern constellations and is the largest of the 50 ...
Color–color diagram. A color–color diagram is a means of comparing the colors of an astronomical object at different wavelengths. Astronomers typically observe at narrow bands around certain wavelengths, and objects observed will have different brightnesses in each band. The difference in brightness between two bands is referred to as color.
List of planet types. From top to bottom: Mercury, Venus without its atmosphere, Earth and the Moon, Mars, Jupiter, Saturn, Uranus, and Neptune in false colour (not to scale) The following is a list of planet types by their mass, orbit, physical and chemical composition, or by another classification. The IAU defines that a planet in the Solar ...
The so-called web color "violet" is in actuality not really a tint of violet, a spectral color, but is a non-spectral color. The web color violet is actually a rather pale tint of magenta because it has equal amounts of red and blue (the definition of magenta for computer display), and some of the green primary mixed in, unlike most other ...