Class G — G-type (Yellow)

G-type stars are yellow main-sequence stars with surface temperatures of 5,200 to 6,000 K. The Sun (G2V) is the most famous G-type star, making this class of particular importance for astrobiology. G-type stars comprise about 7.6% of main-sequence stars. Their spectra are dominated by calcium and iron absorption lines. Other notable G-type stars include Alpha Centauri A (G2V) and Tau Ceti (G8.5V). They have lifetimes of roughly 10 billion years.

G-type stars are yellow stars with surface temperatures between 5,200 and 6,000 K. They comprise about 7.6% of main-sequence stars, and their most famous member is our own Sun (G2V). G-type stars are central to the search for habitable exoplanets because they combine long lifetimes (7-15 billion years on the main sequence) with sufficient luminosity to maintain liquid water at moderate orbital distances — making them prime targets for missions like Kepler, TESS, and the upcoming PLATO.

Characteristics

G-type spectra are characterized by prominent ionized calcium (Ca II) H and K lines, neutral metal lines (especially iron), and the G-band — a molecular absorption feature near 430 nm caused by CH molecules that gives the spectral class its name. G stars have deep convective envelopes that drive magnetic dynamos, producing sunspot cycles, chromospheric activity, coronae, and stellar winds. Their masses range from 0.8 to 1.04 solar masses. G-type giants and supergiants exist at higher luminosities as evolved stars that have left the main sequence.

Notable Examples

The Sun (G2V) is the defining member, the only star whose surface features — granulation, sunspots, prominences — can be studied in exquisite detail. Alpha Centauri A (G2V) is a solar twin and the brightest component of our nearest stellar neighbor at 4.37 light-years. Tau Ceti (G8.5V) is one of the nearest Sun-like stars and has been a target of SETI programs since 1960's Project Ozma. Capella (Alpha Aurigae) is a binary of two G-type giants, the sixth-brightest star system in the sky.

3 Psc46Gam Hya52 Leo54 Per54Phi Boo56 Hya57 Gem58 Eri5Alp1Cap60 Peg60 Sgr61 CetHIP 6487868 Aqr6 CVn73Pi Tau79 Cnc7Kap Del80 Vir82 G. Eri86 Aqr86 Vir87 Peg88 Psc94 Aqr95 Her9Omi VirAlasiaAlshainAmadiohaAshleshaCastulaCervantesChalawanChi EriCocibolcaDel1GruDel PavDofidaEps SctEps TelFuniGakyidGam1OctHIP 100HIP 100018HIP 100031HIP 100053

Frequently Asked Questions

What is a class G star?
Class G (G-type (Yellow)) stars are yellow stars. G-type stars are yellow main-sequence stars with surface temperatures of 5,200 to 6,000 K. The Sun (G2V) is the most famous G-type star, making this class of particular importance for astrobiology. G-
How hot are class G stars?
Class G stars have surface temperatures between 5,200 K and 6,000 K.
What color are class G stars?
Class G stars appear yellow.
How many class G stars are in the StarFYI database?
StarFYI currently catalogs 22,793 class G stars.
How luminous are class G stars?
Solar-like, 0.6-1.5 solar luminosities