Polaris Star | Universe Today

Written by John Carl Villanueva

The Polaris Star or simply Polaris is the Earth's current North Star. That's right. Centuries from now, it will no longer hold that title. But that story belongs to another article here in Universe Today. For now, I'm here to talk about Polaris alone.

Try to walk out in an open field on a clear night and look for the Little Dipper (it's also known as Ursa Minor or Little Bear). At the tip of the dipper's handle, you'll find the Polaris star. Since Polaris is not a seasonal star, you'll get to see it on any day of the year. Also, you can't miss it because it's the brightest in that constellation.

Just be sure you live in the Northern hemisphere if you want to catch Polaris. While most stars are visible in both the Northern and Southern hemispheres, the North star can be seen in the Northern hemisphere alone since it's aligned right on top of the North Pole. As a matter of fact, if you were to stand on the North Pole and looked straight up to it, all stars would appear to rotate about it.

Polaris is actually a ternary system, made up of α UMi A, α UMi B, α UMi Ab. α UMi A is the heaviest, at 6 solar masses – 6 times heavier than out Sun!

Although this North Star is some 430 lightyears from Earth, you can easily see it in the night sky even with your naked eyes. Well, it wouldn't have earned the title, "North Star" had it been too faint.

You see, strictly speaking, for stars to be considered pole stars (i.e., either a North Star or South Star), they should be easily visible (aside from being as aligned to the poles as possible) since they are mostly used as references for navigation.

That's the reason why we don't have a TRUE south star. The Southern Cross simply points to what should be holding that title, Sigma Octantis. Unfortunately, Sigma Octantis is too faint to be considered a true pole star. Again, we'll have to wait for centuries before we get to have a true southern pole star.

The Polaris star is believed to be getting brighter. In fact, studies show that it is 2.5 times brighter now than it was when Ptolemy made observations of it some time in the 2nd Century. Ptolemy included Ursa Minor in his list of 48 constellations.

NASA has an article entitled "Planets around binary stars" that provides a more detailed discussion on certain types of stars. Other interesting questions regarding binary stars can be found in this link: Binary Star Systems.

Related articles can be found here in Universe Today:

Earliest Stars Came in Pairs, New Simulation Shows

Astronomers Catch Binary Star Explosion Inside a Nebula

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Moons and the Drake Equation, Stars in the Void, and Rings Around Stars
Stellar Roche Limits, Seeing Black Holes, and Water on Mars

Filed under: Astronomy