Home » Astronomy

Look Again at the Big Dipper!

Submitted by admin on May 25, 2010 – 2:05 pmNo Comment

If there’s one constellation in the Northern Hemisphere that most living there learnt as a child, it’s The Plough, or Big Dipper. Truth be told, it’s not actually a constellation at all, it’s called an asterism — a pattern of stars seen in Earth’s sky which is not an official constellation. Like constellations, they are composed of stars which, while they are in the same general direction, are not physically related, often being at significantly different distances from Earth. The Big Dipper (named after the huge soup ladle farmers’ wives would use to serve up to the farm hands at the end of a busy day’s work), is actually part of a sprawling constellation called Ursa Major, home to wonders aplenty in terms of deep sky objects.

Here though, we’re going to just concentrate on the Big Dipper itself. To those in North America, Europe and Asia, both it, and indeed Ursa Major itself, is a circumpolar constellation, meaning it is visible every night throughout the year — its stars never set.

And so to a tour of the stars of this asterism, all visible with the naked eye, in all but the most appalling light pollution. Binoculars will start to reveal its true beauty, and a small telescope will give superb details of the multiple star members.

Starting in the top right hand corner of the bowl of the ladle, Dubhe (Alpha Ursae Majoris (α UMa / α Ursae Majoris)) is the second-brightest star in the constellation of Ursa Major, and is about 124 light years away. It is typical of a red giant, an evolved helium-burning star. It is also a multiple star, orbited by a main sequence companion, Dubhe B, at a distance of about 23 astronomical units (AU), as well as a close pair, Dubhe C, at a distance of about 8000 AU.

Journeying anticlockwise, we come to Merak (Beta Ursae Majoris (β UMa / β Ursae Majoris)). Both it and Dubhe are familiar to northern hemisphere observers as the “pointer stars” in the Big Dipper, and a line connecting them and moving north extends to Polaris, located at the north Celestial Pole in this epoch. Merak is fairly typical for a main sequence star of its type, although being slightly hotter and larger than our own Sun, it shines several times brighter. The star is surrounded by a cooling disk of dust, much like those discovered around Fomalhaut and most notably Vega. No planets have been discovered orbiting Merak, but the presence of the dust indicates they may exist or be in the process of forming.

Moving to the left of the bowl we come to Phad or Phecda (Gamma Ursae Majoris (γ UMa / γ Ursae Majoris)). It is an average main sequence star not unlike our Sun, although somewhat hotter, brighter and larger.

At the top left of the bowl is Megrez (Delta Ursae Majoris (δ UMa / δ Ursae Majoris)). Megrez has an apparent magnitude of +3.32 making it the dimmest of the seven stars in the Big Dipper. Located 81 light years away, it is a bluish-white main sequence star. It has two faint companions, the 11th magnitude Delta Ursae Majoris B, 190 arcseconds away, and the 10th magnitude Delta Ursae Majoris C, 186 arcseconds away.

Moving to the left, we first come to Alioth (Epsilon Ursae Majoris (ε UMa / ε Ursae Majoris)). It is the brightest star in the entire constellation of Ursa Major, at magnitude +1.76. It is the star in the tail of the bear closest to its body, and thus the star in the handle of the Big Dipper closest to the bowl. Historically, the star was frequently used in celestial navigation in the maritime trade, because it is listed as one of the 57 navigational stars.

Further out along the handle of the Big Dipper, we arrive at Mizar (ζ UMa / ζ Ursae Majoris), 78 light years away. It is a quadruplet system of two binary stars, with an apparent magnitude is +2.23. Its name comes from the Arabic m

Leave a comment!

Add your comment below, or trackback from your own site. You can also subscribe to these comments via RSS.

Be nice. Keep it clean. Stay on topic. No spam.

You can use these tags:
<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>

This is a Gravatar-enabled weblog. To get your own globally-recognized-avatar, please register at Gravatar.


Architecture »

Want Imperia 3 BHK apartments Dosti Group THANE MUMBAI

Affinity Solution Pvt. Ltd.
Presents
Dosti Imperia Thane Mumbai:
Dosti Group Imperia Thane ||91-9999684166|| Dosti Group Imperia Project Thane | Dosti Group Imperia Property Thane | Dosti Group Imperia Propeties Thane | Dosti Group Imperia Apartment Thane | …

Hi-Tech »

IT »

Benefits of Online Video on Demand Services for Individuals

Are you tired of waiting for your favorite programs or movies? On the other hand, do you have to wait restlessly in front of the idiot box and have to watch commercials in between your …

Medicine »

Bring your natural smile back by consulting Burbank cosmetic dentist

A beautiful and charming smile is all you need when you speak to somebody. Your smile can attract anyone and make an impressive impact to the listener. And a simple problem in your teeth and …

Press Releases »

Vashi Navi Mumbai New Booking Properties-09999684166 Sparsh Projects By Arihant Vashi Mumbai

Affinity Solution Pvt. Ltd.
Presents
Arihant Sparsh Vashi Navi Mumbai:
Arihant Sparsh | Arihant Sparsh Vashi | Arihant Sparsh Vashi Rates | Arihant Sparsh Vashi Navi Mumbai | Arihant Sparsh Vashi Location | Arihant Sparsh Project Vashi | …

Science »

Culinary Management Programs

There are many different culinary management programs throughout the country at various schools, but the most common type is the Bachelor of Culinary Management degree, which can be found at colleges, universities, technical institutions and …