More Lepus

Our Sun is a sedate middle-aged star. It’s been shining for about four and a half billion years, and it’s expected to keep shining for billions of years more.
But some stars that are well into the final stages of life are only a fraction of the Sun’s age. These stars are much heavier than the Sun, and it’s a star’s mass that determines its timeline.
An example is Arneb, the leading light of Lepus, the rabbit. The constellation stands below the feet of Orion, the hunter, which is in the southeast at nightfall.
Arneb is only about 13 million years old, yet it’s well into old age. In fact, it’s likely to expire within the next million years or so.
That’s because Arneb is about 14 times as massive as the Sun. Its gravity squeezes its core tightly. That makes the core extremely hot, which revs up the nuclear reactions that power the star.
The extreme radiation from the core pushes outward on the surrounding layers of gas, making the star puff up like a balloon. So Arneb is more than a hundr