Radcliffe wave

The Radcliffe wave is a neighbouring coherent gaseous structure in the Milky Way, dotted with a related high concentration of interconnected stellar nurseries.

It has been suggested that it could be a result of a much smaller galaxy colliding with the Milky Way, leaving behind "ripples", or could be related to dark matter.

[1] Many of the star-forming regions found in the Radcliffe wave were thought to be part of a similar-sized but somewhat helio-centric ring which contained the Solar System, the "Gould Belt".

It is now understood the nearest discrete relative concentration of sparse interstellar matter instead forms a massive wave.

[8][4] It was announced by co-author Alyssa A. Goodman at the 235th meeting of the American Astronomical Society, held at Honolulu[9] and published in the journal Nature on 7 January 2020.

The latter is more dispersed as to its interstellar medium than the wave and has further large star-forming regions such as Monoceros OB1, California Nebula, Cepheus Far, and Rho Ophiuchi.