Looking Up column: Get to know the Big Dipper’s seven stars
With the Big Dipper as high as it can be in the early evening sky, let’s take a closer look at its seven stars.
Before I do, if you haven’t had the pleasure of being acquainted with the Big Dipper, allow me. Some of you may be from below the equator or, understandably, have been more focused on life here on planet Earth, as we all should. Nonetheless, as anyone who enjoys the starry heavens can tell you, looking up can do wonders for you inside as you look outward at the meaning and mystery of it all.
The seven stars of the Big Dipper are for most the first star pattern they are taught. It is so easily recognized, actually looking like a kitchen utensil for spooning soup from a kettle, or water from a bucket. It’s technically not a constellation, but part of a large constellation known as Ursa Major the Big Bear. The Dipper’s stars are the Bear’s brightest and best seen.
The Dipper is also always with us; unless you live in the southern states or further down, the stars of the Dipper never dip below the flat, northern horizon. They are among other star patterns in the north that remain circumpolar, circling the point on the northern sky where our planet’s axis of rotation seems to point. That imaginary point on the sky, the North Celestial Pole, is very close to the star Polaris, the North Star.
The Big Dipper, of course, is at its highest every 24 hours, as the Earth spins. This time of year, mid-spring, it is high up around 8 to 9 p.m. The Dipper shape is oriented so it appears upside down, the handle to the right.
Pardon me if this seems very basic. It is, but I never tire of such a simple pleasure of appreciating the stars as we see them with the naked eye, even as I look forward to bringing out the telescope and hunt down dim galaxies or details on planets. The hope of this column is to inspire more people to simply “look up” and appreciate the heavens, perhaps enough to make it a hobby and take a closer gander. For all of us, the stars and the constellation patterns they make, seem like friends for life, a constant in a world changing too fast.
The stars marking the front of the Big Dipper’s bowl are Dubhe and Merak. These stars serve as pointers, leading you straight down (in this orientation on a spring evening) to the North Star.
Dubhe is the one at the tip, at lower left when the Dipper is at its highest. Otherwise known as Alpha Ursae Majoris, this star has a marvelous yellow-orange shade, best seen in binoculars or a telescope. Dubhe shines at magnitude +1.79 and is 123 light-years away. It is a very close double star, detectable by spectroscope. It is the official star of the State of Utah, and was a U.S. Navy ship was dubbed Dubhe.
Merak is magnitude 2.4 and is 79 light-years away. Two Navy ships were named for Merak.
The two stars in the back of the bowl are Phecda and Megrez. Phecda is on the bottom of the bowl across from Merak (remember, the bowl is upside down on spring evenings). Phecda is magnitude 2.4 and 84 light-years from us. It has a close companion star.
Megrez is right across from Dubhe. The 2.1-magnitude star is 78 light-years away. There are two faint companion stars in the system. The Navy named a ship after Megrez.
The three stars marking the Big Dipper’s handle, in order from the bowl, are Alioth (mag. 1.8, 81 light-years away); Mizar (mag. 2.1, 78 light-years away) and Alkaid (mag. 1.9, 101 light-years distant).
These stars all have had Navy ships named for them, and all have companion stars.
Take a close look at Mizar with naked eyes. There is a dimmer star right next to it, named Alcor; together their nicknames are the “Horse and the Rider.” Binoculars show them very well. A small telescope will show that Mizar is a double star, easily resolved with medium magnification.
Five of the Big Dipper’s stars are part of the “Ursa Major Moving Group,” a nearby stellar association traveling space together. They are believed to have arisen from a common nebula where stars are formed. In all, 14 stars are identified as part of this association. The only ones of the Dipper not part of it are Dubhe and Alkaid. Maybe they didn’t pay their dues?
The Big Dipper pattern is imagined as a plow in Great Britain. The North Star, by the way, marks the end of the handle of the Little Dipper, which is part of Ursa Minor the Little Bear. Most of the Little Dipper’s stars are relatively dim, and require a dark, moonless night without excessive light pollution to easily see them.
Users of telescopes, with a lens or mirror as small as 3 inches and equipped with some experience and a good star atlas, enjoy looking up fairly bright galaxies in the neighborhood of the Big Dipper, especially the Whirlpool Galaxy M51, and the M81/M82 pair.
Full moon is on May 7.
Keep looking up at the sky!
Peter Becker is managing editor at The News Eagle in Hawley, Pennsylvania. Notes are welcome at email@example.com. Please mention in what newspaper or website you read this column.