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Astronomical question and answer 253

 

Frank L. Preuss

 

Why is Sirius the brightest star in the starry sky?

 

Because it is so close by.

And also, because it is a relative large star, relative to the sun.

Sirius is 1.7 times bigger than the sun.

Sirius, in the constellation Canis Major, is the sixth closest star.

The closest star is Proxima Centauri, in the constellation Centaur. It is only 0.14 times as big as the sun.

Proxima Centauri is 4.2 light years away. Sirius 8.6 light years.

Procyon, in the constellation Canis Minor and the eighth brightest star, is 11.3 light years away, but two times as big as the sun.

Betelgeuse, in the constellation Orion, is 400 times as big as the sun, but 270 light years away.

When one therefore has a look at the constellation Orion, then Sirius is not far away from it, the Belt of Orion, the three stars in the middle of Orion, point directly in the direction of Sirius, then is Betelgeuse more than 200 times as big as Sirius, but not as bright as Sirius, because it is far more away.

That the distance of a star is an important factor, determining the brightness, one can also see on it that the planets are often brighter than Sirius, a fixed star.

 

This is the end of "Astronomical question and answer 253"
To the German version of this chapter: Astronomische Frage und Antwort 253

 

 

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