The European Space Agency (ESA)’s Gaia space telescope has discovered two surprising streams of stars that formed and wove together over 12 billion years ago.

• The two streams, named Shakti and Shiva, helped form the infant Milky Way.
• Both are so ancient that they likely formed before even the oldest parts of our present-day galaxy’s spiral arms and disc.
• Each stream contains the mass of about 10 million Suns, with stars of 12 to 13 billion years in age, all moving in very similar orbits with similar compositions. 

Gaia is a space observatory of the European Space Agency (ESA), launched in 2013 and expected to operate until 2025. The spacecraft is designed for astrometry: measuring the positions, distances and motions of stars with unprecedented precision, and the positions of exoplanets by measuring attributes about the stars they orbit such as their apparent magnitude and color.

The mission aims to construct by far the largest and most precise 3D space catalog ever made, totalling approximately 1 billion astronomical objects, mainly stars, but also planets, comets, asteroids and quasars, among others.