How old is the Epsilon star?

Answer 1

There is no such thing as an "epsilon star". There are several stars that have "epsilon" in their names; basically one for every constellation, so "Epsilon" followed by the genitive for example, Epsilon Eridani, Epsilon Crucis, Epsilon Canis Maioris, etc.

Answer 2

The stars in all constellations have a designation which comprises the name of the constellation followed by a letter of the Greek alphabet. In most cases the first few are named in descending order of visible brightness so any constellation with ten or so stars will have an epsilon star. For 88 constellations that makes 88 epsilon stars, and also makes a question which is impossible to answer.

Answer 3

There is an Epsilon in most of the constellations. It simply denotes the fifth brightest star. One example is Epsilon Eridani, which is thought to be less than a billion years old.