What type of star is the Polaris?

Polaris: Getting to Know the Star That Guides Us

Polaris. You probably know it as the North Star, that trusty beacon in the night sky. But trust me, there’s way more to this star than just pointing north. It’s a cosmic oddity, a celestial yardstick, and a window into the wild lives of stars.

So, What Exactly Is Polaris?

Okay, so technically, Polaris is what astronomers call a Population I classical Cepheid variable star. Sounds like a mouthful, right? Basically, it’s a star that’s constantly pulsing – expanding and contracting – which makes it change in brightness. And get this: the speed of that pulse tells us how bright the star really is. This is super handy for measuring distances in space, like using Polaris as a cosmic mile marker. Plus, it’s the closest Cepheid variable to us, which is why scientists are so obsessed with it.

The main star, Polaris Aa, is a yellow supergiant. Think of it as a star that’s past its prime, puffed up like a cosmic marshmallow after it’s run out of fuel in its core. It’s officially classified as spectral type F7Ib, if you want to get technical.

More Than Meets the Eye

Here’s a fun fact: Polaris isn’t a solo act. It’s actually a triple star system! Imagine three suns hanging out together. The main star, Polaris Aa, has a buddy, Polaris Ab, that it dances around every 30 years or so. Then there’s Polaris B, hanging out further away, like the cool older brother. William Herschel, the same guy who discovered Uranus, spotted Polaris B way back in 1779.

And about that pulsing thing? Polaris Aa is a Cepheid variable, remember? That means it gets a little brighter and dimmer every four days. But here’s a weird twist: it’s not as dramatic as it used to be. The star’s putting on less of a show these days.

Polaris is also pretty old, cosmically speaking – somewhere between 45 and 67 million years old. It’s a hefty star, too, about five times the mass of our Sun. And if you could somehow put it next to our Sun, it would dwarf it – Polaris is almost 40 to 50 times bigger!

As for how far away it is, that’s a bit tricky. The latest measurements from the Gaia mission put it at around 448 light-years. But older measurements from the Hipparcos satellite say it’s closer, around 433 light-years. Space is big, and measuring it is hard!

The North Star: A Timeless Guide

Of course, the reason most people know Polaris is because it’s the North Star. It sits almost directly above Earth’s North Pole, so it barely seems to move as the Earth spins. That’s why it’s been used for navigation for centuries. You just find Polaris, and you know which way is north. Plus, the angle between Polaris and the horizon tells you roughly how far north you are. Pretty neat, huh?

But here’s a mind-blowing fact: Polaris hasn’t always been the North Star. The Earth wobbles like a top, and that changes which star lines up with the North Pole over thousands of years. Back in 3000 BCE, a star called Thuban was the North Star. Polaris only took over around 500 CE, and it’ll be at its closest to the pole around the year 2100. So, in a way, even the North Star changes!

What’s Next for Polaris?

Polaris will keep shining, guiding travelers and fascinating scientists for a long time to come. Even though it’ll eventually drift away from being perfectly aligned with the North Pole, its role as the brightest and closest Cepheid variable means it’ll always be a key player in our understanding of the universe. So, next time you see Polaris, remember it’s not just a point of light. It’s a pulsing, dancing, ancient giant with a fascinating story to tell.