Magnitudes—how astronomers express brightnesses of stars—are confusing to those unfamiliar with them, to say the least. They use a modified version of base-10 logarithms. The smaller—or more negative—the magnitude, the brighter the object. An object with a magnitude of zero is not an object with no brightness but instead is rather bright.

1.
C.
Sirola
, “
I love my baffling, backward, counterintuitive, overly complicated magnitudes
,”
Phys. Teach.
55
,
124
115
(
2017
).
2.
A.
Pringle-Pattison
, “Weber's law,” in
Encyclopædia Britannica
, edited by
Hugh
Chisholm
(
Cambridge University Press
,
1911
),
11th ed
., Vol.
28
, pp.
458
459
.
3.
Astronomical Magnitude Systems
,” https://lweb.cfa.harvard.edu/∼dfabricant/huchra/ay145/mags.html, accessed Jul. 4,
2022
.
4.
“Flux” as used in astronomy is defined as power per unit area, more commonly referred to as “intensity” in physics and not related to the physics usage of the term flux.
5.
Vega—one of the brightest stars in the night sky—was once used as the reference for zero magnitude. Vega is now known to rotate extremely rapidly for a star, meaning its surface temperature changes significantly across its surface, making it a poor choice of standard. Astronomers no longer depend on one individual star to set magnitude standards.
6.
Readers can access the supplemental material at TPT Online at https://doi.org/10.1119/5.0146515, under the Supplemental tab.

Supplementary Material

AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.