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The Info List - G-type Main-sequence Star


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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. 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. Like other main-sequence stars, a G-type main-sequence star
G-type main-sequence star
is converting the element hydrogen to helium in its core by means of nuclear fusion . The Sun
Sun
, the star to which the Earth
Earth
is gravitationally bound in the Solar System
Solar System
and the object with the largest apparent magnitude , is an example of a G-type main-sequence star(G2V type). Each second, the Sun
Sun
fuses approximately 600 million tons of hydrogen to helium, converting about 4 million tons of matter to energy . Besides the Sun, other well-known examples of G-type main-sequence stars include Alpha Centauri A , Tau Ceti , and 51 Pegasi
51 Pegasi
.

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. The Sun
Sun
is in fact white, and its spectrum peaks in blue and green light, but it can often appear yellow, orange or red through Earth
Earth
's atmosphere due to atmospheric Rayleigh scattering , especially at sunrise and sunset. In addition, although the term "dwarf" is used to contrast yellow main-sequence stars from giant stars , yellow dwarfs like the Sun
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 ).

A G-type main-sequence star
G-type main-sequence star
will fuse hydrogen for approximately 10 billion years, until it is exhausted at the center of the star. When this happens, the star expands to many times its previous size and becomes a red giant , such as Aldebaran (or Alpha Tauri). 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.

CONTENTS

* 1 Spectral standard stars * 2 Planets * 3 See also * 4 Notes * 5 References * 6 External links

SPECTRAL STANDARD STARS

The revised Yerkes Atlas system (Johnson however, not all of these have survived to this day as standards.

The "anchor points" of the MK spectral classification system among the G-type main-sequence dwarf stars, i.e. those standard stars that have remained unchanged over years, are beta CVn (G0V), the Sun
Sun
(G2V), Kappa1 Ceti (G5V), 61 Ursae Majoris (G8V). Other primary MK standard stars include HD 115043 (G1V) and 16 Cygni B (G3V). 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). There are not yet any generally agreed upon G7V and G9V standards.

PLANETS

Some of the nearest G-type stars known to have planets include the Sun
Sun
, 61 Virginis , HD 102365 , HD 147513 , 47 Ursae Majoris , Mu Arae , Tau Ceti and possibly Alpha Centauri .

SEE ALSO

* Star
Star
portal * Astronomy portal

* Brown dwarf
Brown dwarf
* Hertzsprung–Russell diagram
Hertzsprung–Russell diagram
* K-type main-sequence star
K-type main-sequence star
* Red dwarf
Red dwarf
* Solar twin * Star
Star
count , survey of stars * Stellar classification , class G

NOTES

* ^ The Sun
Sun
is not in this class because even though it corresponds to the same mass, the Sun
Sun
is slightly hotter than the typical temperature for a G5V star (at 5,778 K), so it is a G2V star, which is normally slightly more massive than the Sun

REFERENCES

* ^ Vardavas, Ilias M.; et al. (2011), "Chapter 5. Incoming Solar Radiation", Radiation and Climate: Atmospheric Energy
Energy
Budget from Satellite Remote Sensing, International Series of Monographs on Physics, 138, OUP Oxford
OUP Oxford
, p. 130, ISBN 0199697140 * ^ Empirical bolometric corrections for the main-sequence, G. M. H. J. Habets and J. R. W. Heintze, Astronomy and Astrophysics Supplement 46 (November 1981), pp. 193–237. * ^ A B Stellar Evolution: Main Sequence to Giant, class notes, Astronomy 101, Valparaiso University , accessed on line June 19, 2007. * ^ Why Does The Sun
Sun
Shine?, lecture, Barbara Ryden, Astronomy 162, Ohio State University , accessed on line June 19, 2007. * ^ Sun
Sun
Archived 2007-06-16 at the Wayback Machine ., entry at ARICNS , accessed June 19, 2007. * ^ Alpha Centauri A, SIMBAD
SIMBAD
query result. Accessed on line December 4, 2007. * ^ Tau Ceti, SIMBAD
SIMBAD
query result. Accessed on line December 4, 2007. * ^ 51 Pegasi, SIMBAD
SIMBAD
query result. Accessed on line December 4, 2007. * ^ What Color Are the Stars?, Mitchell N. Charity's webpage, accessed November 25, 2007 * ^ Cain, Frazer. "WHAT COLOR IS THE SUN?". Universe Today . * ^ "What Color is the Sun?". Stanford University . * ^ Dissanaike, George (19 October 1991). "Painting the sky red". New Scientist . 132 (1791): 31–33. * ^ SIMBAD
SIMBAD
, entry for Aldebaran , accessed on line June 19, 2007. * ^ Fundamental stellar photometry for standards of spectral type on the revised system of the Yerkes spectral atlas H.L. Johnson & W.W. Morgan, 1953, Astrophysical Journal, 117, 313 * ^ MK ANCHOR POINTS, Robert F. Garrison * ^ The Perkins Catalog of Revised MK Types for the Cooler Stars, P.C. Keenan ">

* v * t * e

Star
Star

FORMATION

* Accretion * Molecular cloud * Bok globule * Young stellar object * Protostar

* Pre-main-sequence star
Pre-main-sequence star

* Herbig Ae/Be

* Orion

* T Tauri * FU Orionis

* Herbig–Haro object * Hayashi track * Henyey track

EVOLUTION

* Main sequence
Main sequence
* Red giant
Red giant
branch

* Horizontal branch
Horizontal branch

* Red clump
Red clump

* Asymptotic giant branch
Asymptotic giant branch
* Protoplanetary nebula * Planetary nebula * PG1159 star * Dredge-up * Instability strip * Luminous blue variable * Blue straggler
Blue straggler
* Stellar population
Stellar population
* Supernova
Supernova
* Supernova
Supernova
impostor * Hypernova
Hypernova
* Hertzsprung–Russell diagram
Hertzsprung–Russell diagram
* Color–color diagram
Color–color diagram

LUMINOSITY CLASS

* Subdwarf
Subdwarf

* Dwarf

* Blue * Red * White * Yellow * Brown

* Subgiant

* Giant

* Blue * Red

* Bright giant
Bright giant

* Supergiant
Supergiant

* Blue * Red * Yellow

* Hypergiant
Hypergiant

* Yellow

Spectral classification

* O * B * A * F * G * K * M * WR * Be * OB * Subdwarf
Subdwarf
O * Subdwarf
Subdwarf
B * Late-type

* Chemically peculiar

* Am * Ap/Bp * Barium * Carbon * CH * CN * Extreme helium * Lambda Boötis * Lead * HgMn * S * Technetium

* Shell

REMNANTS

* White dwarf
White dwarf

* Helium
Helium
planet

* Neutron star
Neutron star

* Radio-quiet

* Pulsar
Pulsar

* Binary * X-ray

* Magnetar
Magnetar

* Stellar black hole

* X-ray binary
X-ray binary

* Burster

THEORETICAL STARS

* Black dwarf

* Exotic

* Quark * Strange * Preon * Planck * Electroweak star

* Dark-matter star * Dark-energy star * Black star * Gravastar * Frozen star * Q star * Quasi-star * Thorne–Żytkow object * Iron star * Blitzar

NUCLEOSYNTHESIS

* Deuterium burning * Lithium burning * Proton–proton chain * CNO cycle
CNO cycle
* Helium
Helium
flash * Triple-alpha process
Triple-alpha process
* Alpha process * Carbon burning * Neon burning * Oxygen burning * Silicon burning * S-process
S-process
* R-process * Fusor

* Nova
Nova

* Symbiotic * Remnant * Luminous red nova

STRUCTURE

* Core

* Convection zone

* Microturbulence * Oscillations

* Radiation zone

* Atmosphere

* Photosphere
Photosphere
* Starspot * Chromosphere * Corona
Corona

* Stellar wind
Stellar wind

* Bubble * Bipolar outflow

* Accretion disk
Accretion disk

* Asteroseismology

* Helioseismology
Helioseismology

* Eddington luminosity * Kelvin–Helmholtz mechanism
Kelvin–Helmholtz mechanism

PROPERTIES

* Designation * Dynamics * Effective temperature * Kinematics * Magnetic field * Absolute magnitude * Mass * Metallicity * Rotation * UBV color

* Variable star

* Mira variable
Mira variable

STAR SYSTEMS

* Binary

* Contact * Common envelope * Eclipsing

* Multiple

* Star
Star
cluster

* Open cluster * Globular cluster
Globular cluster
* Super star cluster

* Planetary system * Earth\'s Solar System
Solar System

Earth-centric observation of

* Pole star * Circumpolar star * Constellation * Asterism

* Magnitude

* Apparent * Extinction * Photographic

* Radial velocity * Proper motion
Proper motion
* Parallax * Photometric-standard star

LISTS

* Star
Star
names

* Arabic * Chinese

* Extremes * Most massive * Highest temperature * Largest volume * Smallest volume

* Brightest

* Historical

* Most luminous

* Nearest

* Nearest bright

* Stars with exoplanets * Brown dwarfs * White dwarfs *