Moon and Elnath

The Moon butts up against the tip of one of the horns of Taurus early tomorrow. They’ll appear to almost touch as they climb into good view, around 2:30 or 3 a.m. They’ll be closest as viewed from the East Coast, especially the northeast.

The tip of the horn is represented by Elnath. It’s the second-brightest star in the constellation. It’s outranked only by Aldebaran, the bull’s eye.

Based on the calendar alone, Elnath is a youngster – roughly 100 million years old. That’s only about two percent the age of the Sun. But the star is well into middle age. That’s because it’s about five times the mass of the Sun. Heavier stars “burn” through their nuclear fuel much faster than lighter stars. So Elnath probably is about halfway through its prime phase of life.

Right now, it’s fusing hydrogen to make helium. So is the Sun. The process is more complicated for heavier stars. But the result is the same: the nuclei of four hydrogen atoms fuse together to make one helium atom. Almost one percent of the mass of the hydrogen is converted to energy, making the star shine.

The Sun converts more than four million tons of mass to energy every second. Elnath fuses its hydrogen at a much faster rate, and it has a lot more hydrogen to start with. So it converts hundreds of millions of tons of matter to energy per second – making “the butting one” almost 600 times brighter than the Sun.

Script by Damond Benningfield