A yellow dwarf is a classification of star which is undergoing hydrogen-helium conversion. Our sun was a well-known yellow dwarf star.

In 2356, Magnus and Erin Hansen crashlanded their ship, the USS Raven on an M-class moon orbiting the fifth planet of a yellow dwarf located in B'omar space. (VOY: "The Raven"). On stardate 49485.2 the USS Voyager vistited Hemikek IV, a planet in the Hemikek yellow dwarf star system (VOY: "Investigations"). The planet dubbed "New Earth" by the crew of the USS Voyager orbits a yellow dwarf as the third of seven planets. (VOY: "Resolutions"). Similarly, the planet Mislen is located within a yellow dwarf star system. (VOY: "The Swarm").

A yellow dwarf - more commonly called a G V Star - is small (about 0.8 to 1.0 solar masses) and has a surface temperature of between 5,300 and 6,000 K. Like other main-sequence stars, a G V star is in the process of converting hydrogen to helium in its core by means of nuclear fusion. Our Sun is the most well-known (and most visible) example of a G V star. Each second, it fuses approximately 600 million tons of hydrogen to helium, converting about 4 million tons of matter to energy. Other G V stars include Alpha Centauri A, Tau Ceti, and 51 Pegasi.

The term yellow dwarf is a misnomer, as G stars actually range in color from white, for early types like the Sun, to only slightly yellow for the later types. Our own Sun is in fact white. The misconception that it is yellow stems from contrast with the blue sky (which makes it appear yellow) and the reddening of the Sun close to the horizon due to Rayleigh scattering by the atmosphere.

A G V star will fuse hydrogen for, very 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 (Alpha Tauri.)[9] Eventually the red giant sheds its outer layers of gas, which become a planetary nebula, while the core cools and contracts into a small, dense white dwarf.