NSEA · Elementary Astronomy

Galaxies and Cosmology

Milky Way structure, galaxy types, redshift, Hubble's law and basic cosmological ideas.

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  • Q1 · Galaxies and Cosmology · HARD

    A galaxy shows a redshift z = 0.05. Assuming Hubble's constant H₀ = 70 km/s/Mpc, what is the approximate recession velocity of this galaxy in km/s?

  • Q2 · Galaxies and Cosmology · HARD

    A galaxy is observed to have a recessional velocity of 15,000 km/s. Using a Hubble constant of 70 km/s/Mpc, approximately how far is this galaxy from Earth?

  • Q3 · Galaxies and Cosmology · MEDIUM

    According to the Friedmann equation for a flat universe, if the current Hubble constant is H₀ = 70 km/s/Mpc and the universe is matter-dominated, what is the approximate age of the universe in billion years?

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