Apparent magnitude is a measure of a star's what?

Answer 1

Apparent magnitude is the apparent brightness of a celestial body as seen from earth. The brighter the body is the lower its apparent magnitude (can be negative e.g. our sun has an apparent magnitude of -26.73).

Answer 2

The apparent magnitude is a measure of the brightness of the star to the naked eye on a clear, moonless night. The Ancient Greeks invented this concept, using a scale of 5 magnitudes, with the lowest number being the brightest and so on..1st magnitude stars were the brightest they could see and the decided upon 20 of them.
Of course, planets, the Sun and Moon were much brighter, so the concept was extended int negative magnitudes.Nowadays, astronomers quantify apparent magnitude by saying that each magnitude represents a brightness ratio of 2.512.
Apparent magnitude leads into Absolute Magnitude. Absolute magnitude is the apparent brightness of a celestial object if it were at some standard distance-------since the apparent magnitude is a function of both luminosity and distance.

As a standard distance, astronomers settled on a distance of 10 parsecs, where a parsec is approx. 3.26 light years. This is the distance where a star would have a parallax of one second of arc----PARallax /SECond.

Answer 3

Brightness when viewed with a naked eye.

Answer 4

luminosity as seen from earth.