Astronomy

The first stars clear the fog

Switch on an ionizing source and follow the growing H II region. Increase gas density and see recombination limit the size of the ionized bubble.

Actual application image

The model and its limits

One Strömgren sphere in static uniform hydrogen, with case-B recombination at 10,000 K. cosmological expansion and overlap are not solved.

Equations used in the module

Equations
R_S=[3Q/(4πα_Bn²)]^(1/3); R(t)=R_S[1-exp(-t/t_rec)]^(1/3); t_rec=1/(α_Bn)

Astronomy

Advance the scale factor and compare the Hubble sphere, particle horizon and event horizon. They answer three different questions about light.

Astronomy

Send identical light pulses from a compact star. Increase compactness and compare the emitter’s clock with a distant observer’s clock.

Astronomy

Approach the final contact of two compact stars. Compare gravitational-wave frequency and inspiral time as their masses change.