Stellar Evolution: Main Sequence to Giant, class notes, Astronomy 101, Valparaiso University, accessed on line June 19, 2007. Heintze, Astronomy and Astrophysics Supplement 46 (November 1981), pp. 130, ISBN 978-0199697144Įmpirical bolometric corrections for the main-sequence, G.
#NAME A RED MAIN SEQUENCE STAR SERIES#
Incoming Solar Radiation", Radiation and Climate: Atmospheric Energy Budget from Satellite Remote Sensing, International Series of Monographs on Physics, 138, OUP Oxford, p. The Sun is not in this class because even though it corresponds to the same mass, the Sun is slightly hotter than the typical temperature for a G4V star (at 5,778 K), so it is a G2V star, which is normally slightly more massive than the Sun Some of the nearest G-type stars known to have planets include the Sun, 61 Virginis, HD 102365, HD 147513, 47 Ursae Majoris, Mu Arae, and Tau Ceti. There are not yet any generally agreed upon G7V and G9V standards. The choices of G4 and G6 dwarf standards have changed slightly over the years among expert classifiers, but often-used examples include 70 Virginis (G4V) and 82 Eridani (G8V). Other primary MK standard stars include HD 115043 (G1V) and 16 Cygni B (G3V). those standard stars that have remained unchanged over years, are beta CVn (G0V), the Sun (G2V), Kappa1 Ceti (G5V), 61 Ursae Majoris (G8V). The "anchor points" of the MK spectral classification system among the G-type main-sequence dwarf stars, i.e. The revised Yerkes Atlas system (Johnson & Morgan 1953) listed 11 G-type dwarf spectral standard stars however, not all of these still conform to this designation. Eventually the red giant sheds its outer layers of gas, which become a planetary nebula, while the core rapidly cools and contracts into a compact, dense white dwarf. When this happens, the star expands to many times its previous size and becomes a red giant, such as Aldebaran (or Alpha Tauri). In addition, although the term "dwarf" is used to contrast yellow main-sequence stars with giant stars, yellow dwarfs like the Sun outshine 90% of the stars in the Milky Way (which are largely much dimmer orange dwarfs, red dwarfs, and white dwarfs, the last being a stellar remnant).Ī G-type main-sequence star will fuse hydrogen for approximately 10 billion years, until it is exhausted at the center of the star. The Sun is in fact white, but it can often appear yellow, orange or red through Earth's atmosphere due to atmospheric Rayleigh scattering, especially at sunrise and sunset. The term yellow dwarf is a misnomer, because G-type stars actually range in color from white, for more luminous types like the Sun, to only very slightly yellow for the less massive and luminous G-type main-sequence stars. Besides the Sun, other well-known examples of G-type main-sequence stars include Alpha Centauri A, Tau Ceti, and 51 Pegasi. Each second, the Sun fuses approximately 600 million tons of hydrogen into helium in a process known as the proton-proton chain (4 hydrogens form 1 helium), converting about 4 million tons of matter to energy. The Sun, the star to which the Earth is gravitationally bound in the Solar System, is an example of a G-type main-sequence star (G2V type). Like other main-sequence stars, a G-type main-sequence star is converting the element hydrogen to helium in its core by means of nuclear fusion. Such a star has about 0.84 to 1.15 solar masses and surface temperature of between 5,300 and 6,000 K., Tables VII, VIII. A G-type main-sequence star (Spectral type: G-V), often (and imprecisely) called a yellow dwarf, or G dwarf star, is a main-sequence star (luminosity class V) of spectral type G.
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