Deneb Algedi 
Every star tells a tale. It tells us how big it is, how hot it is, how it’s moving through space, and even what stage of life it’s in.
The story is told in the star’s spectrum — the rainbow of colors that’s produced when you split starlight into its individual wavelengths. But sometimes, the story is difficult to decipher.
Consider Deneb Algedi, a star whose name means “tail of the kid” — a reference to its position at the tail of Capricornus, the sea-goat. The constellation is in the south at nightfall. Its brightest stars form an outline that looks like the bottom of a bikini bathing suit, with Deneb Algedi at the left point.
We do know that the star is bigger, hotter, and brighter than the Sun, and that it’s about 40 light-years away. But the rest of the story is unclear.
Astronomers are sure that the star is around the end of its “normal” lifetime — the long stretch when it burns the hydrogen in its core to produce helium. But they’re not quite sure just where the star is in this process.
It could be in the final days of its hydrogen-burning phase. Or it could have completed that phase and moved into the next phase, where it begins burning the helium to make heavier elements, and puffs up to become a giant. Or it could be in the transition stage between those phases — basically marking time until the core triggers the process of helium fusion. The answer is yet to be deciphered — hidden in the star’s light.
Script by Damond Benningfield, Copyright 2012