North Star Or Pole Star
They're Both Polaris 

Polaris A and Polaris Ab
Source: Hubblesite.org

One of the most important stars in the night sky is Polaris, the North Star.

Resting , it seems, on top of the world, Polaris is the star that acts like the anchor of the sky.

All the northern stars seem to revolve around this point as the Earth rotates.

People are often surprised to learn that this 2nd magnitude star is only about the 50th brightest star in the sky.

Sirius is the night's brightest star and Arcturus is the brightest star in the northern sky.

Polaris is the alpha star in the constellation Ursa Minor and is the last star in the handle of the “Little Dipper” asterism.

LOCATING THE POLE STAR

Right Ascension: 2 Hours 31 minutes

Declination: +89 degrees

Visible between latitudes: -1 and +90 degrees

apparent Magnitude: 2

Visible to every place from the equator going north, Polaris is easy to spot.

By finding the “Big Dipper” you can always find the North Star.

From the two front stars of the dipper bowl you simply follow a line about 5 times the distance between the 2 stars to Polaris.

The farther north you are the higher in the sky the star will be.

MULTIPLE STAR SYSTEM

Artist
Source: Hubblesite.org

Like many stars Polaris is part of a multiple star system.

There are 3 stars in the main grouping and 2 more distant stars believed to be a part of the system.

The main star Polaris A is a yellow supergiant star about 4.5 times the size of the Sun. It is a variable star and its brightness changes very slightly from time to time.

It has a dwarf companion about 1.25 times the size of the Sun.

Polaris B is the companion visible in telescopes(the faint star near the top in the above photo and lower right in the below pic). It has an apparent magnitude of 8.7.

William Herschel discovered it in 1780 using a reflector telescope.

Polaris C and Polaris D are faint distant stars and not available to the backyard stargazer.

NAVIGATIONAL AID

Polaris A and Polaris B
Source: Hubblesite.org

Used by ancient sailors and travelers to find their way. Knowing where the North Star was meant you always knew what direction you were heading.

 

American slaves used it as a guide to lead them towards freedom in the north and Canada.

CHANGING POLES

The celestial pole will begin to move away from Polaris by the end of the 21st century. Due to precession the poles are always changing, though it takes an incredible length of time to us humans and its always the same during an individual's lifetime.

The south pole has a pole star as well. Sigma Octantis is the current South Star, sometimes known as Polaris Australis. Sigma Octantis isn't very bright(about 6th magnitude), so southern travelers use the "Southern Cross", the constellation Crux to find south.

North Star to Little Dipper

› North Star

photographs courtesy NASA and STSCI from the Hubble Telescope.

Please enable JAVATM to use the Mini-AstroViewer night sky map.

Use the mini astroviewer to see your night sky.

This app requires the use of a Java enabled browser.

Site Search Site Search
Enter Your E-mail Address
Enter Your First Name (optional)
Then

Don't worry — your e-mail address is totally secure.
I promise to use it only to send you The Celestial Solar System.
SBI Video Tour!
Stargazing For Beginners E-book!
Secrets Of The Deep-sky!

promo code 260826