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  2. Galaxy color–magnitude diagram - Wikipedia

    en.wikipedia.org/wiki/Galaxy_color–magnitude...

    The diagram has three main features: the red sequence, the green valley, and the blue cloud. The red sequence includes most red galaxies, which are generally elliptical galaxies. The blue cloud includes most blue galaxies, which are generally spirals. In between the two distributions is an underpopulated space known as the green valley which ...

  3. Stellar classification - Wikipedia

    en.wikipedia.org/wiki/Stellar_classification

    Class G main-sequence stars make up about 7.5%, nearly one in thirteen, of the main-sequence stars in the solar neighborhood. There are 21 G-type stars within 10pc. [c] [11] Class G contains the "Yellow Evolutionary Void". [84] Supergiant stars often swing between O or B (blue) and K or M (red).

  4. Redshift - Wikipedia

    en.wikipedia.org/wiki/Redshift

    For example, if a Sun-like spectrum had a redshift of z = 1, it would be brightest in the infrared(1000nm) rather than at the blue-green(500nm) color associated with the peak of its blackbody spectrum, and the light intensity will be reduced in the filter by a factor of four, (1 + z) 2. Both the photon count rate and the photon energy are ...

  5. Main sequence - Wikipedia

    en.wikipedia.org/wiki/Main_sequence

    For the cooler stars, dwarfs such as red dwarfs, orange dwarfs, and yellow dwarfs are indeed much smaller and dimmer than other stars of those colors. However, for hotter blue and white stars, the difference in size and brightness between so-called "dwarf" stars that are on the main sequence and so-called "giant" stars that are not, becomes ...

  6. Stellar evolution - Wikipedia

    en.wikipedia.org/wiki/Stellar_evolution

    These stars are often observed as a red clump of stars in the colour-magnitude diagram of a cluster, hotter and less luminous than the red giants. Higher-mass stars with larger helium cores move along the horizontal branch to higher temperatures, some becoming unstable pulsating stars in the yellow instability strip (RR Lyrae variables ...

  7. Giant star - Wikipedia

    en.wikipedia.org/wiki/Giant_star

    Main-sequence stars with masses above about 12 M ☉ are already very luminous and they move horizontally across the HR diagram when they leave the main sequence, briefly becoming blue giants before they expand further into blue supergiants. They start core-helium burning before the core becomes degenerate and develop smoothly into red ...

  8. Why Red and Green Became the Shades of the Holiday Season

    www.aol.com/why-red-green-became-shades...

    According to NPR, in the Victorian era, Christmas had a much wider and varied palette, which featured combinations of red and green, red and blue, blue and green, or blue and white—and that ...

  9. Red-giant branch - Wikipedia

    en.wikipedia.org/wiki/Red-giant_branch

    The red-giant branch runs from the thin horizontal subgiant branch to the top right, with a number of the more luminous RGB stars marked in red. The red-giant branch (RGB), sometimes called the first giant branch, is the portion of the giant branch before helium ignition occurs in the course of stellar evolution.