Lesson Worksheet: The Hubble Time Physics

In this worksheet, we will practice calculating the z-factor of distant galaxies and estimating the age of the universe from the Hubble constant.

Q1:

The Hubble constant is usually measured in units of km/s⋅Mpc, but in order to use the Hubble constant to calculate the Hubble time, it must be converted into units of s−1. What is 50.0 km/s⋅Mpc in units of s−1? Give your answer in scientific notation to two decimal places.

  • A1.62×10 s−1
  • B1.62×10 s−1
  • C1.62×10 s−1
  • D1.62×10 s−1
  • E1.62×10 s−1

Q2:

What is 65 km/s/Mpc in units of s−1? Give your answer in scientific notation to two decimal places.

  • A2.11×10 s−1
  • B2.11×10 s−1
  • C2.11×10 s−1
  • D2.11×10 s−1
  • E2.11×10 s−1

Q3:

Messier 60 is a galaxy in the constellation Virgo. It has a 𝑍-factor of 0.00373. How far away is Messier 60? Use a value of 74.0 km/s⋅Mpc for the Hubble constant. Give your answer to one decimal place.

Q4:

The Whirlpool Galaxy has a 𝑍-factor of 0.00154. What is its recessional velocity? Use a value of 3×10 m/s for the speed of light. Give your answer to the nearest kilometer per second.

Q5:

The Cartwheel Galaxy has a recession velocity of 9.05×10 m/s. What is the 𝑍-factor of the Cartwheel Galaxy? Give your answer to three decimal places.

Q6:

In March of 2019, the Hubble Space Telescope was used to measure the value of the Hubble constant. The value found was 2.40×10s. Use this value to estimate the age of the universe. Give your answer in scientific notation to two decimal places.

  • A4.17×10 years
  • B1.31×10 years
  • C2.40×10 years
  • D6.60×10 years
  • E1.32×10 years

Q7:

An astronomer observes the light coming from the Fireworks Galaxy and identifies the 410 nm hydrogen emission line in the spectrum. The emission line has been redshifted by 0.0545 nm. What is the recessional velocity of the galaxy? Give your answer to one decimal place.

Q8:

The Sunflower galaxy has a 𝑍-factor of 0.00161. By how much would the 486 nm hydrogen line be redshifted in light from the Sunflower galaxy? Answer in scientific notation to three decimal places.

Q9:

The Antennae galaxies are a pair of interacting galaxies that have a recessional velocity of 1,640 km/s. By how much would the 434 nm hydrogen line be redshifted in the light from these galaxies? Give your answer to two decimal places.

Q10:

An astronomer identifies a hydrogen emission line in the spectrum of light coming from a distant galaxy. The wavelength of the emitted light is 656 nm. The astronomer measures that the light has been redshifted by 9.54 nm. What is the 𝑍-factor of the distant galaxy? Give your answer to the nearest four decimal places.

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