levo
Log inStart

Astrophysics

Absolute magnitude, M

  • 4 things to know
  • Paper 3, section B

Overview

Absolute magnitude at 10 parsecs, and the distance modulus equation.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Numbers

What is the distance modulus equation, at what standard distance is absolute magnitude defined, and what three quantities does the equation relate?

Numbers

What is needed to find a star's absolute magnitude, and how is distance calculated?

Key term

What is (m − M) called, which two magnitudes give a star's distance, and what is needed to predict its apparent brightness?

Numbers

State the conversion factor between parsecs and light years

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define a parsec in terms of parallax angle.

    Model answer

    A parsec is the distance at which a star would have a parallax angle of one arcsecond.

  2. 2

    What is the approximate value of one parsec in light years?

    Model answer

    Approximately 3.26 light years.

  3. 3

    Express one parsec in metres.

    Model answer

    Approximately 3.09 × 10¹⁶ metres.

  4. 4

    Define a light year.

    Model answer

    A light year is the distance that light travels in one year through a vacuum.

  5. 5

    What is the approximate value of one light year in metres?

    Model answer

    Approximately 9.46 × 10¹⁵ metres.

  6. 6

    What is the definition of absolute magnitude M?

    Model answer

    Absolute magnitude M is the apparent magnitude a star would have if it were placed at a standard distance of 10 parsecs from Earth.

See the rest and revise

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book
2Open book
3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Measurements and Their Errors
Particles and Radiation
Waves
Mechanics and Materials

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

Q is .
positivenegativezero

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AP = 4πr²σT⁴.
BThe surface area of a spherical star is 4πr².
CP₁/P₂ = (r₁²/r₂²) × (T₁⁴/T₂⁴).

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

Speed means rate of change of distance.
TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Astrophysics, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Start revising, £5 a monthSee how the method works

Or £46 a year, about £3.83 a month. Cancel anytime.