What is the stellar halo?

Vast sparse spherical cloud of old stars and globular clusters surrounding the Milky Way’s disc.

Can you see it?

Not as one thing, no — the stellar halo is a place rather than a sight, and you are already inside it. What you go out and look at are the things in it, one at a time.

Worth knowing about the stellar halo

What it is: A vast, sparse, roughly spherical cloud of old stars and globular clusters surrounding the flat disc of the galaxy.; How we know: Halo stars are identified by odd orbits and spectroscopy showing far fewer heavy elements than disc stars. Rung 5 of the cosmic ladder — the distance to nearby stars
Arcturus, once counted among its stars: Arcturus, bright and fast-moving, was long counted as a halo star; its make-up says it belongs to the galaxy’s thick disc instead — an older, thicker layer of stars than the thin disc the Sun is in.

How anyone knows this

Things like it

The Orion Armpart of the galaxyBeyond a 150 mm telescope

The galactic bar and bulgepart of the galaxyNaked eye

The dark matter halopart of the galaxyBeyond a 150 mm telescope

Show the stellar halo in the model 📖 How the Milky Way fits together 🌙 Plan an evening outside