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Gould's Belt (or the Gould Belt) is a mass of visible stars including many nearby early stars (O-type stars and B-type stars), roughly forming a great circle around the celestial sphere as seen from Earth. It is 20 degrees tilted from the apparent Milky Way, tilted "up" (galactic north) in the direction toward the galactic center. It also includes the nearest star-forming regions, including Rho Ophiuchi Cloud Complex and Taurus-Auriga Complex. As such, it is the target of much of the study of early stars and star formation.
Its appearance suggests an Earth-encircling ring, but it has been revealed to be a disk, on the order of 1000 pc in diameter, the Sun within it, about 12 pc above its midplane. This is small enough that it represents a relatively small feature on a Milky Way spiral arm. It is expanding, and a maximum age based upon the time to reach its present size (from the point from which it expands) suggests an age of less than 50 million years, much younger than the solar system. The bright stars are necessarily young, and the SF regions include YSOs.
There are theories as to its formation, one of which is that it stems from an HI region that was moving through the galactic halo colliding with the galactic disk. Recent research suggests most of it is actually a portion of a larger structure named the Radcliffe wave, i.e., what has been called Gould's Belt is not a unified structure.