Double Horn

The Moon pays a call on one of the horns of the bull tonight. As night falls, the star Zeta Tauri is quite close to the right or upper right of the Moon. It’s so close that you might need to blot out the Moon with your hand to see it.
Zeta Tauri represents the tip of one of the horns of Taurus, the bull — at least in western mythology. In China, it was known as Tianguan — the “celestial gate.” A couple of years ago, the International Astronomical Union adopted that as the star’s official name.
Actually, the system consists of two stars, but the proper name applies only to the brighter one. The second star is Zeta Tauri B.
We can’t see star “B,” even through the biggest telescopes. That’s because it’s much fainter than Tianguan, and the stars are quite close together — they’re only about as far apart as Earth is from the Sun.
Astronomers discovered the companion by breaking the light from the system into its individual wavelengths or colors. That revealed two patterns of light. They shi