What is the faintest magnitude visible to the naked eye?

About +6.0 under perfect dark-sky conditions.

Can apparent magnitude be negative?

Yes. Very bright objects have negative magnitudes: Sirius is -1.46, the full Moon is -12.7, and the Sun is -26.7.

It accounts for radiation across all wavelengths, not just visible light. Visual magnitude (V) only measures one band.

Determine a star's apparent magnitude from its absolute magnitude and distance using the distance modulus: m = M + 5 log10(d/10).

Absolute Magnitude (M)

Distance

Apparent Magnitude

4.83 mag

Distance Modulus0.00 mag

Apparent Magnitude vs Absolute Magnitude (M)

Apparent magnitude (m) is how bright a star appears from Earth.

m = M + 5 log10(d / 10)

*M* = absolute magnitude (brightness at 10 pc)

*d* = distance in parsecs

Lower magnitudes are brighter. Each magnitude step is a factor of ≈2.512 in brightness.

The Sun has M = 4.83. How bright would it be at 10 pc?

Find intrinsic brightness from apparent magnitude and distance.

Find distance from the magnitude difference.

Calculate total power output of a star.