What is true of alpha star in a constellation?

Answer 1

The standard designations of stars within a constellation is a Greek letter followed by the Latin name of the constellation. This is called the "Bayer designation".

In general - but not in EVERY case - the stars were lettered in order by brightness. Please remember that this was done a few hundred years ago, before the invention of detailed electronic instruments. And over the centuries, in a few cases the stars themselves have varied in brightness. For example, in the constellation of Orion, the star Betelgeuse is "Alpha Orionis", even though it is the SECOND-brightest star in Orion.

Why the discrepancy? A couple of reasons, perhaps. Rigel, the brightest star in Orion, isn't all THAT much brighter; both are "first magnitude" stars. Second, Betelgeuse is known to be a variable star, and 300 years ago we believe that Betelgeuse was actually brighter than Rigel is.

Answer 2

The alpha star is the brightest star in a constellation. This is because "alpha" is first in the Greek alphabet, so beta (the second) is the second brightest star. One example is the Centaurus constellation, alpha centauri, the brightest star, then beta centauri and so on.

Answer 3

Generally, true, but there are rare exceptions. For example, Betelgeuse is "Alpha Orionis" while Rigel, generally brighter then Betelgeuse, is "Beta Orionis". Betelgeuse is a somewhat variable star, and when the Bayer designations were assigned, Betelgeuse was the brighter star.

Answer 4

Within a constellation, the stars are tagged with Greek letters in the order of their brightness. The "alpha" is the brightest star in that constellation.

Note: The "constellations" aren't only the familiar stick-figures in the sky any more. Nowadays the astronomical catalogs have split the sky up into regions, just like the nations on a map. The regions generally are named for the ancient constellation contained in that region.