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.

HIP 17029HIP 17063HIP 17083HIP 17092HIP 17100HIP 17151HIP 17155HIP 20478HIP 20504HIP 20517HIP 20524HIP 20552HIP 20602HIP 20608HIP 20622HIP 20632HIP 20639HIP 20659HIP 20666HIP 20672HIP 20690HIP 20722HIP 2074HIP 20740HIP 20753HIP 20776HIP 20782HIP 20802HIP 20822HIP 20899HIP 17327HIP 17334HIP 17336HIP 17338HIP 17343HIP 17377HIP 17385HIP 17393HIP 17409HIP 1742HIP 1746HIP 1747HIP 17472HIP 17478HIP 1760HIP 17650HIP 20964HIP 20982

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