Cosmic star-formation history

Cosmic star-formation history traces how the universe’s total star-formation rate per unit comoving volume changes over time. It rises to a peak several billion years after the Big Bang, then declines.

Star-formation rate: The mass of gas converted into stars per unit time, usually measured for an individual galaxy. The cosmic history sums this quantity across galaxies per unit volume.
Madau plot: A graph of cosmic star-formation rate density as a function of redshift or cosmic time. It is the classic visualization of the history's overall shape.
Stellar mass density: The mass in stars per unit volume of the universe at a given epoch. Integrating the star-formation history predicts this accumulated quantity.
Dust attenuation: The reduction and reddening of light as dust absorbs and scatters radiation. Uncorrected attenuation makes ultraviolet surveys underestimate obscured star formation.
Cosmic star-formation rate density: The total stellar mass formed per unit time per unit comoving volume at a given cosmic epoch. This is the measured quantity whose evolution defines the history.
Cosmic noon: The era roughly two to three billion years after the Big Bang when cosmic star formation peaked. The history reaches its broad maximum during this epoch.
Galaxy evolution: The changes in galaxies' structures, contents, and activity over cosmic time. The global history provides a benchmark for models of evolving galaxies.
James Webb Space Telescope: A space observatory designed for infrared astronomy, launched in 2021. Its observations probe faint galaxies at epochs that test the early history.
H-alpha emission: Emission from hydrogen atoms that traces ionizing radiation produced by short-lived massive stars. Its luminosity estimates recent star formation in galaxies at accessible redshifts.
Reionization: The early-universe transition in which radiation from the first luminous sources ionized intergalactic hydrogen. Star formation during this era helped supply the photons that reionized the intergalactic medium.

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