# Free Astrophysics Notes (1 Viewer)

#### mreditor16

##### Well-Known Member
what does bump mean
Just a way to get the thread back in the limelight

BUMP!

#### Drsoccerball

##### Well-Known Member
Is this statement true? i thought it was the other way around ?

"In general, stars with a negative B-V colour index will appear more blue and stars with a positive B-V colour index will appear more yellow, orange or red"
EDIT: My bad its magnitude ahahahaha

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bump!

#### Drsoccerball

##### Well-Known Member
"Therefore, if two stars have the same apparent magnitude but are different distances away from Earth, the closer star will have an absolute magnitude smaller than that of the star further away."

Smaller absolute magnitude = Brighter
Doesn't make sense that the closer one is brighter...?

#### InteGrand

##### Well-Known Member
"Therefore, if two stars have the same apparent magnitude but are different distances away from Earth, the closer star will have an absolute magnitude smaller than that of the star further away."

Smaller absolute magnitude = Brighter
Doesn't make sense that the closer one is brighter...?
No, absolute magnitude is the intrinsic brightness of the star, apparent magnitude is the perceived brightness by an observer on Earth. So when we see a star as being "bright" from Earth, we are referring to its apparent magnitude.

Obviously intuitively if two stars appear equally bright (apparent brightness) but are difference distance away, the one that is further away is more "powerful" (i.e. higher absolute magnitude, more intrinsically bright) than the closer one.

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#### Drsoccerball

##### Well-Known Member
No, absolute magnitude is the intrinsic brightness of the star, apparent magnitude is the perceived brightness by an observer on Earth. So when we see a star as being "bright" from Earth, we are referring to its apparent magnitude.
Absolute magnitude is the brightness perceived if the star was at a distance of 10 Pc... The lower the magnitude the brighter the star. So if something was -2 in apparent magnitude it outshines another star of apparent magnitude of X $\bg_white Where x > -2$ So it would make logical sense that the one further away assuming both appear the same in brightness has a lower absolute magnitude.

#### Drsoccerball

##### Well-Known Member
Obviously intuitively if two stars appear equally bright (apparent brightness) but are difference distance away, the one that is further away is more "powerful" (i.e. higher absolute magnitude, more intrinsically bright) than the closer one.
But magnitude is different to brightness. The lower the magnitude the brighter it is.

#### InteGrand

##### Well-Known Member
But magnitude is different to brightness. The lower the magnitude the brighter it is.
By "smaller" in the notes, maybe it meant smaller as in smaller absolute value, e.g. -1 is smaller than -4, in the sense than |-1| < |-4|.

#### Drsoccerball

##### Well-Known Member
By "smaller" in the notes, maybe it meant smaller as in smaller absolute value, e.g. -1 is smaller than -4, in the sense than |-1| < |-4|.
Lol i thinks its just a mistake

#### leehuan

##### Well-Known Member
The less positive magnitude is brighter. There.

Bump

#### leehuan

##### Well-Known Member
What the hell. I just realised you were another astrophysicist who became an actuary