Question

A star with an apparent magnitude of +1.0 is located at a distance of 40 pc. What is its absolute magnitude M? What is its distance modulus?

Answer 1

Answer on Question #54916, Physics / Astronomy | Astrophysics

We know magnitude (m) = +1, and D = 40 pc. Then, from the distance modulus, the absolute magnitude M can be calculated:

$$M = m + 5 - (5 \log D)$$ $$M = + 1 + 5 - (5 \log 40)$$ $$M = + 6 - (5 \log 40)$$

So the absolute magnitude M can be calculated:

$$M = + 6 - (5 \times 1.602) = -2.01$$

Then the distance modulus is:

$$(m - M) = + 1 - (-2.01) = 3.01$$

Answer: m-M = 3.01

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