Some stars are noteworthy for themselves — for their size, temperature, or composition. Others, though, are noteworthy for factors that have nothing to do with the stars themselves. An example is El Nath, the second-brightest star of Taurus, the bull. It’s in the western sky at nightfall right now. Tonight, it’s not far to the lower right of Venus, the “evening star.” One thing that makes the star noteworthy is its name. “El Nath” comes from an Arabic phrase that means “the butting one.” It refers to the star’s position at the tip of one of the bull’s horns. And that’s a second noteworthy item about the star — its position in the patterns that make up the ancient constellations. Not only is El Nath an important member of Taurus, it also forms part of the adjoining constellation Auriga, the charioteer. When these constellations were first drawn, there were no boundaries between them. So El Nath was incorporated into two pictures. Today, though, astronomers have established borders betwe
