cosmic engine (shadwick) (1 Viewer)

[jnney]

"Stars Procyon and Betelgeuse are almost equal brightness as observed from Earth. However, Betelgeuse is more than 100 times more luminous than Procyon. Account for these differences.

There are several possibilities. If their distances are the same, their either Betelgeuse is much larger than Procyon or its surface temperature is higher, or a combination of both. Or, if their size and temperature are similar, then Betelgeuse must be significantly further from earth."




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[Aykay]

What don't you understand?

If Betelgeuse is, in reality, 100 times more luminous than Procyon, and they are, from earth seen at the same luminousity, obviously Betelgeuse has to be further from the earth to account for the seemingly equal luminousity from Earth.

Think about it in-terms of the inverse-square law.

 

[jnney]

Oh! right

 

[SpiralFlex]

Don't you mean 1000 times luminous?

Definition: Luminosity is a measure of the rate at which a star emits energy, it is a measure of the total power emitted by a star. It depends on two factors.

If the distances are equal, then there are two factors that will influence its luminosity are:

• The size of the star: The larger the star, the more surface area it has, the more luminous it is.

• The surface temperature of the star: The hotter the star, the higher output of power.

OR

• It could be their distances apart. The light radiated from the star may appear to be dimmer at a distance.