An Etymological Dictionary of Astronomy and Astrophysics

A huge gaseous nebula (≥ 50 kpc) lying at high → redshifts
(z ~ 2-6) and strongly emitting radiation due to the
→ Lyman alpha line (luminosities of  ≥ 10⁴³ erg s^-1) of hydrogen gas.
Also called Lyman alpha blobs, they are thought to lie in massive (M ~ 10¹³ solar masses) → dark matter halos,
which would subsequently evolve into those typical of rich → galactic clusters.

See also: → Lyman; → nebula.