The oldest star clusters form
Half a billion years in, stars begin binding into the dense spheres that still orbit galaxies today.
- When
- Known to
- ± 100 million years
- Era
- Reionisation, Stelliferous
Globular clusters — tightly bound swarms of hundreds of thousands of stars — begin forming alongside the first galaxies. JWST's first deep image found clusters whose stars may have formed barely 500 million years after the Big Bang. Those in the Milky Way's halo are among the oldest objects that can be dated directly, and for decades their ages set a hard lower bound on the age of the universe itself.