Elnath has dual citizenship. Officially, it’s the second-brightest star of Taurus, so it’s known as Beta Tauri. It marks the tip of one of the bull’s horns. But it’s also known as Gamma Aurigae – one of the bright stars that outlines Auriga, the charioteer. That designation is un-official – it’s been considered defunct for almost a century.

The dual identity is a result of changes in how astronomers define the constellations. At first, the constellations were vaguely defined. Each one encompassed the connect-the-dots pattern that outlined the classical figure. But there weren’t hard borders.

In 1603, German astronomer Johannes Bayer published a new naming scheme for all the stars. In it, he assigned Elnath to both Taurus and Auriga. That worked fine for centuries. But in the early 20th century, astronomers decided to assign precise boundaries for each constellation – like the borders of states or nations. Elnath was just inside the border of Taurus. So, officially, Elnath belongs to the bull. But it still forms part of the classical outline of Auriga – giving Elnath a dual citizenship.

Elnath is about 130 light-years away. It’s about five times the size and mass of the Sun, and it’s hundreds of times brighter. It’s easy to pick out tonight because it’s close to the Moon. As night falls, they’re no more than one or two degrees apart – right along the border between the bull and the charioteer.

Script by Damond Benningfield

Just about every star is born in a cluster – a family of dozens to thousands of stars. Most of these families fall apart, with the individual stars going their own way. The Sun’s cluster, for example, dissipated billions of years ago.

One cluster that’s in the process of dissipating is the Hyades, which outlines the face of Taurus, the bull. It’s the nearest cluster, at a distance of about 150 light-years.

Today, the Hyades contains several hundred stars – probably less than half its original population. The other stars were pulled away by the gravitational tug of the rest of the galaxy.

The cluster’s heaviest stars reside in its tightly packed center. None of them is much more than about twice as massive as the Sun. That’s because of the cluster’s age – 625 million years. All of its heavier stars have already burned out. All that remains is their dead cores.

The least-massive stars have migrated to the outskirts of the cluster. Over the next few hundred million years, those stars will all drift away. That will leave only a sad little remnant of this impressive family of stars.

The Hyades stands to the lower left of the Moon this evening. Its stars form a “V” shape. The brightest star in the outline is bright orange Aldebaran, the bull’s eye. But it’s not a member of the cluster – it simply lines up in the same direction as the stars of the Hyades.

We’ll have more about the Moon and Taurus tomorrow.

Script by Damond Benningfield

For the kings of ancient Egypt, the Sun was much more than just a glowing orb in the daytime sky. It was the god Ra, one of the most important of all the gods. Ra was a creator of life, the king’s father, and a representation of the king as a god himself.

So the kings of the Fifth Kingdom, about 4500 years ago, built temples to honor the Sun. Archaeologists have recently excavated about half of the largest one yet discovered – a massive complex that might have been topped by a spot for watching the Sun and stars.

The temple is named “Joy of Ra” or “Joy of the Heart of Ra.” It’s at Abu Gorab, about 10 miles from Cairo, near the ancient capital, Memphis. It was built by King Nyuserre, who reigned for two or three decades. At the time, the kings identified themselves with Ra – as eternal gods. So the temple was a place to honor both Ra and the king.

Excavations have uncovered two large enclosures. The upper level was discovered 125 years ago, but the lower one was found just recently. The upper level included an altar for making offerings to Ra. And one end featured an obelisk that would have towered high above the courtyard and the surrounding landscape. It had a perfect east-west alignment – the directions of the rising and setting Sun.

The recent work also uncovered a stairway to the roof. The rooftop probably served as an observatory – helping Nyuserre follow his “father” across the sky.

Script by Damond Benningfield