G band

G band (G for "green") is a designator sometimes given to visible light bands (roughly) corresponding to the color green, i.e., whose wavelengths are in the 510 nm region. This usage is not as common as use of R and B for red and blue, and most G bands likely do not imply green, such as those listed below. Sloan Digital Sky Survey (SDSS) data includes "G band" data, I presume from the SDSS/ugriz passband, g, that covers roughly 400 nm to 540 nm (which includes the color green but considerably more as well).

The term G band (more specifically, Fraunhofer's G band) is also commonly used to designate a (non-green) band covering the range of 430.40 nm to 430.61 nm, in which Sun light has a number of absorption lines which are among the Fraunhofer lines. Lines in Fraunhofer's G band include iron and methylidyne lines, which are prominent in G-type and K-type stars.

The term G band regarding Gaia data refers to a Gaia passband that allows all visible light, i.e., little or no filtering. In this case, "G" is clearly for Gaia, whose filtered passbands use G with a subscript, such as G_R for red.

The term G band is also used within radio communication for other, unrelated frequency-ranges.