Explore the Universe - Ursa Minor

Many people in the northern hemisphere have heard of the Big Dipper and the Little Dipper.  It is important to remember that neither of them are constellations.  They are both asterisms.  This is explained thoroughly in my blog post from January 14, 2017, see below.

http://simonjastronomy.blogspot.com/2017/01/what-are-constellations.html

The constellation of Ursa Minor is located around the North celestial pole and its brightest star is Polaris -- The North Star.  Polaris is not exactly on the North celestial pole but it is within a quarter of a degree of it.  This specificity is good enough for orienteering and navigation but not for polar aligning a mount.  Many mounts come with a polar scope that allows one to offset Polaris by the quarter degree in the correct direction.  I use a mobile application called Polaris View.  A screenshot of this application is shown below.

Polaris View

When looking through the polar alignment scope on you telescope mount you must place Polaris where indicated by the application.  This takes into account the quarter degree offset.

Ursa Minor has been known since the time of the civilizations in ancient Mesopotamia.  It was known as 'The Wagon of Heaven'.  This is likely due to its rotation around the celestial pole.  There are many Greek myths associated with Ursa Minor.  My favourite is the two bears that saved Zeus from his father by hiding him in the mountains.  Zeus rewarded them by grabbing them both by the tails and swinging them over his head to launch them into the sky.  This is the reason why Ursa Minor and Ursa Major (the two bears) have such long tails.

Another interesting fact is the Latin word for North is septentrio which is formed by combing 'septem' (seven) with 'trio' (plow ox).  This refers to the seven bright stars of Ursa Minor and the fact is looks like a plow.

Polaris, the North star, always occupies the same location in the sky throughout the year (within less than a degree).  If you measure the altitude of the star it will approximately equal your latitude.  Determining the longitude is a different beast altogether and is outside the scope of this entry.

Unfortunately, such a popular constellation is quite small and dim.  Only three stars are brighter than magnitude 4.0.  If you are looking for the constellation from the city you may only be able to see around 5 stars.  Since the city center is North of my home I was only able to see 4 stars with my naked eye at 1am.  If you look from a dark site away from light pollution you can easily make out the Little Dipper asterism.  Using binoculars I was able to find the Bayer classified stars throughout the constellation as shown below.

Ursa Minor Observation Record

Ursa Minor contains no Messier objects and has only a minor meteor shower that occurs a few days before Christmas known as the Ursids.  For a brief explanation of this shower please see the following link.

http://simonjastronomy.blogspot.com/2017/12/2017-week-51-december-17-23.html