Worksheet: Brightness Magnitude

In this worksheet, we will practice calculating the absolute magnitude of a star given its apparent magnitude and the distance to the star from Earth.

Q1:

Gliese 832 is a star with an absolute magnitude of 10.2. The star is located 16.2 light-years away from Earth. What is the apparent magnitude of Gliese 832? Give your answer to 3 significant figures.

Q2:

Alpha Centauri B is a star with an apparent magnitude of 1.34, as viewed from Earth. Epsilon Eridani is a star with an apparent magnitude of 3.73, as viewed from Earth. Which star appears brighter as viewed by an astronomer on Earth?

  • AAlpha Centauri B
  • BEpsilon Eridani

Q3:

Luyten 726-8 B is a star located 2.70 pc away from Earth with an apparent magnitude of 13.0. What would the star’s apparent magnitude be if it were located 5.00 pc away? Give your answer to 3 significant figures.

Q4:

Teegarden’s Star has an apparent magnitude of 15.1 and an absolute magnitude of 17.2. How far away from Earth is Teegarden’s Star? Give your answer in kilometers to 3 significant figures.

  • A4.46×10 km
  • B1.17×10 km
  • C2.13×10 km
  • D8.12×10 km
  • E7.33×10 km

Q5:

If a star had an absolute magnitude of 3.44 and were located at a distance of 28.9 parsecs from Earth, what would its apparent magnitude be? Give your answer to 3 significant figures.

Q6:

The table shows the apparent magnitudes of several nearby stars and how far each star is away from Earth.

StarApparent MagnitudeDistance (pc)
Kruger 60 A9.794.02
Luyten 726-8 A12.52.70
Lacaille 8,7606.673.99

Which star would appear the brightest if they were all viewed from the same distance?

  • AKruger 60 A
  • BLuyten 726-8 A
  • CLacaille 8760

Q7:

The table gives the apparent magnitudes of several nearby stars.

StarEpsilon IndiGliese 1Procyon ARoss 154Sirius B
Apparent Magnitude4.698.550.3810.438.44

Which star appears dimmest as viewed from Earth?

  • AEpsilon Indi
  • BSirius B
  • CProcyon A
  • DGliese 1
  • ERoss 154

Q8:

A star located 8.2 light-years away from Earth has an apparent magnitude of 3.09. What is the absolute magnitude of the star? Give your answer to 3 significant figures.

Q9:

61 Cygni A is a star with an apparent magnitude of 5.21. The star is 3.50 parsecs from Earth. What is the absolute magnitude of 61 Cygni A? Give your answer to 3 significant figures.

Q10:

The graph shows how the apparent magnitude of six stars varies with distance away from Earth. The apparent magnitude of each star as measured from Earth, as well as its distance away from Earth, is marked on each line. Which star would appear dimmest when viewed from a distance of 14 ly?

  • AProcyon A
  • BAlpha Centauri A
  • CGliese 412 A
  • DEpsilon Eridani
  • ESirius A

Q11:

A star observed from Earth has an apparent magnitude of 15.5. Its absolute magnitude is found to be 2.70. What is the distance between Earth and the star? Give your answer in parsecs to 3 significant figures.

Q12:

The table shows the period and mean apparent magnitude of three Cepheid variable stars. Use the formula 𝑀=2.4((𝑃)1)4.1log, where 𝑀 is the mean absolute magnitude of a Cepheid variable star and 𝑃 is its period, to work out which of the stars is furthest away.

StarPeriod (Days)Mean Apparent Magnitude
Star A12.313.1
Star B55.913.1
Star C40.113.1
  • AStar A
  • BStar C
  • CStar B

Q13:

The graph shows the apparent magnitudes of several nearby stars against their distance away from Earth in light-years. The red line shows what the apparent magnitude of the Sun would be if it were at a given distance from Earth. Which of the stars shown on the graph would be brighter than the Sun if viewed from the same distance as the Sun?

  • AAlpha Centauri A, Sirius A, and Procyon A
  • BAlpha Centauri B and Epsilon Eridani

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