The first ELAN, discovered in 2014, was named the Slug Nebula, and scientists believe that it - as well as most other ELANs detected since then - is emitting Lyman-alpha radiation
as a result of being illuminated by intense radiation from quasars.
The name reflects the characteristic wavelength of ultraviolet light that they emit, known as Lyman-alpha radiation
Using the 10-meter Keck I telescope in Hawaii, the team detected Lyman-alpha radiation
emitted by cold hydrogen atoms spotlighted by the quasar's intense ultraviolet beam.
As observed from Earth, the ultraviolet Lyman-alpha radiation
is shifted to longer; or redder, wavelengths by the expansion of the universe.
The Lyman-alpha radiation
that Hu and her colleagues detected has a redshift of 6.
This is hardly surprising, though, since the redshifted Lyman-alpha radiation
occurs only fleetingly and brightens the Sun by a minuscule amount.
from the new object detected by Hu and McMahon has shifted to a near-infrared wavelength of 918 nm, revealing its extraordinary distance.
Dust readily absorbs ultraviolet light, including Lyman-alpha radiation
As a result, a typical quasar spectrum consists of a line of strong emission -- the Lyman-alpha radiation
shifted to visible light -- followed by a series of weak absorption lines at shorter wavelengths.