Phosphor that includes cerium

A light emitting device comprising:

• an excitation light source that emits light at a wavelength of 600 nm or less;
• and
• a first phosphor that is irradiated with the light which is emitted by the excitation light source and that emits fluorescence at a longer wavelength than the light, wherein
• the first phosphor includes a crystal phase that has a chemical composition of (Y1-x-y,Cex,Lay)αSiβ-zAlzNγO, where
• the α satisfies 5.5≤α≤6.5,
• the β satisfies 9.5≤β≤12.5,
• the γ satisfies 17.5≤γ≤22.5,
• the x satisfies 0<x≤0.1,
• the y satisfies 0<y≤0.4, and
• the z satisfies 0≤z≤0.5, wherein
• a light emission spectrum of the first phosphor includes a peak within a wavelength range of not less than 600 nm and not more than 660 nm.