difference between absolute and apparent magnitudes?

Question

Explain the difference between the absolute and apparent magnitudes of stars using the Sun as an example.

Answer 1

Absolute magnitude is how bright the star would look if we could see it from a distance of 10 parsecs (which is 32.6 light years).

Apparent magnitude is how bright the star looks from _here_ (on earth).

A star's apparent magnitude depends not only on how bright the star "really" is (up close); but also how far away it is. Star "A" may be putting out 100 times as much light as Star "B"; yet B may look brighter to _us_ just becase B is so much closer. In that case we say the _apparent_ magnitude of B is brighter than the _apparent_ magnitude of A.

But suppose you could take a space ship so you were exactly 10 parsecs away from Star "A"; and then take another trip to 10 parsecs away from Star "B". In that case, you would definitely be able to tell that "A" was the brighter star, because you compared the two from the same distance. So we say the _absolute_ magnitude of A is brighter than the _absolute_ magnitude of B.

The absolute magnitude is one way of describing how much light a star actually puts out, rather than just how bright it happens to look from earth.

As relates to the sun: The _apparent_ magnitude of the sun is extremely bright (because we're so close to it). Its _absolute_ magnitude (how it would look from 10 parsecs away) would be much, much dimmer.

Answer 2

Apparent Magnitudes

Answer 3

Absolute Magnitude is how bright something actually is, apparent magnitude is how bright it is as viewed from Earth. After all, a dim star can appear much brighter in our sky than a star which is brighter but further away. things blocking the light like dust also come into play.


Think of absolute and apparent size - If you hold a quarter out at arms length, it's apparent size is the same as the sun or the moon. The Sun and the moon are obviously A LOT bigger, but the quarter is alot closer.

Answer 4

Everything that was already said is accurate. But I would add the physical interpretation of these quantities: Absolute magnitude is like the intrinsic flux (or luminosity) of an object. It's a measure of the objects brightness which does not depend on distance. So the sun has a fixed absolute magnitude, no matter where in the universe you happen to be observing it from. Apparent magnitude is the flux/brightness of the object based on your vantage point. If you get closer to the object, the brighter it will appear to you. It didn't get any more luminous, just closer.

Answer 5

Absolute magnitude is how bright the star would look if we could see it from a distance of 10 parsecs (which is 32.6 light years).

Apparent magnitude is how bright the star looks from _here_ (on earth).

A star's apparent magnitude depends not only on how bright the star "really" is (up close); but also how far away it is. Star "A" may be putting out 100 times as much light as Star "B"; yet B may look brighter to _us_ just becase B is so much closer. In that case we say the _apparent_ magnitude of B is brighter than the _apparent_ magnitude of A.

But suppose you could take a space ship so you were exactly 10 parsecs away from Star "A"; and then take another trip to 10 parsecs away from Star "B". In that case, you would definitely be able to tell that "A" was the brighter star, because you compared the two from the same distance. So we say the _absolute_ magnitude of A is brighter than the _absolute_ magnitude of B.

The absolute magnitude is one way of describing how much light a star actually puts out, rather than just how bright it happens to look from earth.

As relates to the sun: The _apparent_ magnitude of the sun is extremely bright (because we're so close to it). Its _absolute_ magnitude (how it would look from 10 parsecs away) would be much, much dimmer.

Answer 6

Absolute magnitude means just what its name implies... The intrinsic value of brightness of a star, viewed from any angle, with no dust or gas obstructions in the way.
Apparent magnitude describes the brightness of a particular object, or star, AS WE SEE IT, with all of the interfering gas and dust in the light path to our eyes.
Apparent magnitudinal values are always lower than absolute magnitudinal values, with the exception of near Earth objects (the Sun, the Moon, solar system planets, asteroids, etc.)
I'm pretty sure that's it.
Yeah, that's it.

Answer 7

Absolute magnitude is the same from wherever you view it.

Apparent magnitude takes account of what ever is between you and the thing you are viewing.

For instance, lots of gas, lots of distance, etc make a star appear "dimmer".