Physics 0625 · IGCSE · Stars and the Universe

Stars and the Universe — practice question

A galaxy at a distance of $3.1 \times 10^{21}\,\text{km}$ is receding from the Earth at a speed of $7000\,\text{km s}^{-1}$. What Hubble constant $H_0$ is obtained from this information, and what is the speed of a galaxy that lies $6.2 \times 10^{21}\,\text{km}$ from the Earth?

  • A$H_0 = 2.3 \times 10^{-18}\,\text{s}^{-1}$, speed $= 3500\,\text{km s}^{-1}$
  • B$H_0 = 2.3 \times 10^{-18}\,\text{s}^{-1}$, speed $= 14000\,\text{km s}^{-1}$
  • C$H_0 = 4.4 \times 10^{17}\,\text{s}^{-1}$, speed $= 3500\,\text{km s}^{-1}$
  • D$H_0 = 4.4 \times 10^{17}\,\text{s}^{-1}$, speed $= 14000\,\text{km s}^{-1}$

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