Astronomy

One galaxy, several distances

Move a galaxy to higher redshift. Compare comoving, luminosity and angular-diameter distance, and see why more distant galaxies can look larger.

Actual application image

The model and its limits

Flat matter–Λ cosmology; radiation is neglected for z ≤ 8. Standard candles and rulers are ideal, without lensing, dust or selection effects.

Equations used in the module

Equations
D_C = (c/H₀)∫₀ᶻ dz/E(z); D_L=(1+z)D_C; D_A=D_C/(1+z)

Astronomy

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.

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.