You know how, in August, we look toward the center of our Milky Way galaxy? Well, in January and February, we do the opposite. In the evening, we look opposite the galaxy’s center, toward the galactic anticenter and the galaxy’s nearest outer edge. The star Elnath (sometimes also called Alnath) in the constellation Taurus the Bull is the closest bright star on our sky’s dome to the galactic anticenter. Follow the links below to learn more about the star Elnath, and about looking toward the anticenter of the Milky Way.
How to locate the star Elnath. Elnath is easy to find, if you learn to recognize the Face of the Bull in the constellation Taurus. The Face of the Bull in Taurus is shaped like the letter V. You can actually see that V-shape on the sky’s dome.
If you extend one end of the V, you come to the star Elnath. Elnath represents the Northern Horn of Taurus the Bull. It’s also called Beta Tauri, because it’s the second-brightest star in Taurus, after Aldebaran, the reddish star that depicts the Bull’s Eye.
Elnath isn’t quite as bright as Aldebaran. But it’s also part of a noticeable pattern, and it’s blue-white in color.
Can’t find the Face of the Bull? Try finding Orion the Hunter first, an extremely prominent constellation. You can recognize Orion for its Belt – a short straight row of three medium-bright stars.
Draw a line upward through Orion’s Belt to find Aldebaran and the V-shape group of stars outlining the Bull’s Face. Extend this V-shape face outward to locate the two stars marking the tips of the Bull’s horns. The northern and brighter horn star is Elnath.
In the Northern Hemisphere, we see Taurus and its stars on winter evenings. Elnath stands opposite the sun around mid-December, at which time this star rises around sunset and sets around sunrise. In January and February, Elnath is already up in the east to south at sunset. By June, Elnath will be lost to the sun’s glare and won’t be seen at all. Excepting June, however, Elnath can be seen for at least part of the night throughout the year.
Elnath stands a bit north of the ecliptic – the annual pathway of the sun in front of the background stars. Because the moon’s path is always near the ecliptic, the moon swings close to Elnath every month. Generally, the moon swings to the south of Elnath. On occasion, the moon swings far enough north so that it occults – covers over – Elnath. This won’t happen again until September 7, 2023, the occultation marking the first of a series of monthly occultations that will last until April 11, 2027.
How to locate the Milky Way’s anticenter. The galactic anticenter lies about 3 degrees to the east of the star Elnath. Three degrees is about the width of your thumb at an arm’s length away. We are not talking about a place here – but just a direction in the sky. Elnath is about 130 light-years away. The outskirts of our galaxy’s disk are many thousands of light-years away.
The galactic anticenter doesn’t actually lie in Elnath’s constellation, Taurus the Bull. Instead, it lies in a neighboring constellation Auriga the Charioteer.
Still, Elnath is the nearest bright star to this point.
Science of the star Elnath. Elnath sparkles white, and is tinged in blue. This star’s color indicates that it has a hot surface temperature of about 13,600 Kelvin (24,000 Fahrenheit). Contrast this to the surface temperature of our yellowed-colored sun, which is 5800 Kelvin (10,000 Fahrenheit).
According to the star expert Jim Kaler, Elnath has 4.5 times the sun’s mass, and shines with the firepower of 700 suns.
Elnath’s position is RA: 5h 26m 17.5s, dec: +28° 36′ 27″
Bottom line: Elnath, sometimes called Alnath, is the second-brightest star in the constellation Taurus the Bull. It marks the Northern Horn of the Bull. It lies just three degrees from the galactic anticenter in our sky. It is larger than our sun and shines blue-white in color.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.