Polaris Star Facts: Getting to Know Our North Star
Similar to Hollywood, the night sky is loaded with stars. And, some stars are more famous than others. Polaris, known formally as Alpha Ursae Minoris, is possibly the most famous star. Now, you may know this star more commonly as the “north star.” But, you may not know all of the interesting facts this bright hydrogen factory has to offer!
Polaris Star Facts #10: It really is the north star!
Our Earth spins on an axis. And, Earth’s north axis points out, 2.5-quadrillion-miles away to Polaris. Because of this, Polaris always stays fixed directly to the North of our night sky. Actually, Polaris has been our north star, or “pole star,” for thousands of years.
Polaris Star Facts #9: It won’t always be the north star
Spin a toy top, and you will notice that it spins in a wobbling cone-like shape. Earth spins in a similar shape along its axis. But, Earth is huge! Due to its massive size, it takes nearly 26,000 years to complete one axis spin. So, Polaris is currently on a 26,000-year reign of the north star title.
Polaris Star Facts #8: Winner of best and brightest
Polaris is the brightest star in the constellation Ursa Minor, Latin for “lesser bear.” You might recognize Ursa Minor more easily as the little dipper! However, the little dipper, while quite recognizable, is not a true constellation. We call these almost-constellations, asterisms.
Polaris Star Facts #7: The THREE north stars?
Polaris is not simply a single star. Rather, it is a complex system, containing three stars! Brightest by far is Polaris A (alpha), circled by two smaller, dimmer companions locked in the massive star’s gravity.
Polaris Star Facts #6: Separated siblings
The Polaris system (mentioned above in #7) contains three stars, Polaris A, Polaris Ab and Polaris B. Now, when we hear “system,” we naturally think of close-knit objects. However, space is vast. Actually, Polaris A’s closest neighbor, Polaris Ab sits 2-billion-miles away! And, the third star, Polaris B orbits 240-billion-miles away!
Polaris Star Facts #5: Wait, the FIVE north stars!?
Mentioned in #7, our north star, Polaris is actually a three-star system. However, recent observations indicate that two more distant stars may be part of the Polaris system’s gravity. And, if confirmed, we technically have not one, but five north stars!
Polaris Star Facts #4: Before Google Maps, there was Polaris
Earth’s axis has been pointed directly at Polaris for around 2,000 years. Although, only seen from the northern hemisphere, the star has been a universal guide for centuries. Past civilizations have relied on- and survived because of its precise location. Thanks, Polaris!
Polaris Star Facts #3: There is no “south star”
Coincidentally, Earth is currently pointed directly at Polaris. Now, Earth, of course, does have a southern side to its axis. However, there are currently no stars in its crosshairs. But, one star, known as Sigma Octans, lies one degree from such a location. It is likely that in the future, a south star will emerge.
Polaris Star Facts #2: Far brighter than our Sun
Even at a staggering 433 light-years, Polaris shines bright in our sky at magnitude 1.97. Actually, the north star is 2,500 times brighter than our own star, the Sun! If Polaris were our solar system’s star, the radiation and brightness would be so intense that most complex life could not exist. Fortunately, its drastic distance makes it a brilliant compass, not a lethal weapon!
Polaris Star Facts #1: The closest Cepheid Variable to Earth
Cepheid variable stars pulsate at fixed rates. And, as they pulsate, their diameter changes, often by millions of miles! And, even at its extreme cosmic distance of 433 light-years, Polaris is currently the closest cepheid variable to Earth. Plus, this star type is commonly used to accurately calculate distances by observing their change in brightness. Once again, Polaris serves as a fantastic space navigator!
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Polaris’ location, as seen from Earth. Primarily, people wonder why Polaris is the “North Star,” yet, it tends to appear mid-sky, as opposed to directly above.This is a fantastic question. I, personally, long-pondered the very same thing.
You see, Polaris is precisely aligned with the northern point of Earth’s axis. Plus, Earth’s axis is not always directly “north” from where you are. This is very important to keep in mind! From the North Pole, Polaris would appear at a neck-straining 90º, because Earth’s axis points directly above. However, from lower longitudes, like the US, you are at different angles in relation to Earth’s axis. So, Polaris will actually appear at more mid-sky altitudes, usually between 30-40º.
When we are not directly aligned from the North Pole, Earth itself obstructs our view of Polaris. As shown in the diagram below, being at latitudes closer to the equator allow more shallow-angled views of the north star.
Polaris is over 2.5 quadrillion miles away, so moving mere thousands of miles on Earth should not make a difference, right? Actually, it makes a tremendous difference! Geometry does not change, nor care where we are!
Over all, viewing the north star from lower longitudes will always cause it to appear lower in the sky.