Sky Watch: Star links two constellations

Constellations are like states.

Just as the continental U.S. is divided into 48 such states -- some large and some small -- the heavens are also divided into 88 constellations. And just as every city in the U.S. (except for the District of Columbia) is part of a unique state, every star is also part of a unique constellation.

Well, almost.

In the February evening sky, there's one star that officially belongs to two separate constellations -- a "linking" star, we call it. You can see its two star groupings this week and very high in the southeastern sky just after dark; their names are Auriga, the charioteer, and Taurus, the bull.

Interestingly, the star between Auriga and Taurus known as El Nath is one of only two stars that are shared with a neighboring constellation. Ancient Arabian astronomers once saw this star as part of Auriga, the charioteer, and called it the "Heel of the Rein Holder" but later officially assigned it to the tip of the bull's long, northernmost horn, in Taurus. In this new position, El Nath derived its name from the Arabic Al Natih, which means, in English, "the butting one."

El Nath is the 25th brightest star in the heavens and is located close to the anti-center of the Milky Way Galaxy -- the point directly opposite the galactic center, which lies in Sagittarius. At a distance of some 130 light years, this star is nearly five times larger and almost 700 times more luminous than our sun.

Bundle up this week and get outdoors to check out one of only two "linking" stars in the sky!