What is the size of Procyon star?

Procyon: Getting to Know the “Before the Dog” Star a Little Better

Ever heard of Procyon? Probably not as often as Sirius, but this star is definitely worth knowing. Officially called Alpha Canis Minoris (α CMi), it’s a binary star system hanging out pretty close to us – just a tad over 11 light-years away in the constellation Canis Minor. That makes it one of our stellar next-door neighbors, and bright enough to snag the eighth spot on the list of brightest stars we can see at night. Its name, “Procyon,” is kind of cool too, coming from the Greek for “before the dog.” Why? Because it pops up in the sky just before Sirius, the “Dog Star” in Canis Major. Clever, right?

Procyon Not Quite a Main Sequence Star Anymore

The main star in this duo, Procyon A, shines with a crisp white light. Astronomers classify it as an F-type star, but here’s where it gets interesting. It’s not quite a “main sequence” star anymore. Think of it like a star going through a mid-life crisis. It’s starting to run out of hydrogen fuel in its core and is transitioning into what’s called a subgiant.

So, how big are we talking?

• Radius: Procyon A is about twice the size of our Sun. To be exact, it’s around 2.048 times the Sun’s radius.
• Diameter: Picture this: if our Sun stretched about 1.39 million kilometers across, Procyon A would be roughly 2.08 million kilometers wide. That’s a hefty star!
• Mass: It’s got some weight to it as well, clocking in at 1.4 to 1.5 times the mass of the Sun.

Compared to our own star, Procyon A is bigger, brighter, and a bit hotter. It shines with about 7 times the Sun’s luminosity. And with a surface temperature of around 6,530 Kelvin, it’s definitely got some heat!

Now, in the grand scheme of the universe, Procyon A isn’t a giant monster star or anything. But it’s still pretty impressive. I always like to imagine it this way: if Earth were a marble, Procyon A would be about the size of a car. Puts things in perspective, doesn’t it?

Procyon B: The Tiny, Fading Sibling

Then there’s Procyon B, the quieter, less flashy member of the pair. This one’s a white dwarf – basically, the stellar equivalent of a retired star.

Let’s break down its size:

• Radius: Procyon B is tiny compared to its big brother. We’re talking about a radius of just 0.012 times the Sun’s. That’s only about 1.35 times the radius of the Earth!
• Mass: Don’t let the size fool you. It still packs a punch, with a mass of about 0.6 times the Sun’s.

White dwarfs are seriously weird. They cram a mass similar to the Sun into a space roughly the size of Earth. Procyon B is scorching hot, with a surface temperature around 7,740 Kelvin. But because it’s so small, it barely puts out any light – only about 0.00049 times the Sun’s luminosity. It’s like a tiny ember glowing faintly in the dark.

Their Cosmic Dance

Procyon A and B are locked in a celestial waltz, orbiting each other every 40.84 years. Their orbit isn’t a perfect circle; it’s more of an oval, or ellipse, which astronomers call eccentricity. This means the distance between the two stars changes as they go around each other, ranging from about 9 to 21 astronomical units (AU). On average, they’re about 15 AU apart, roughly the same distance as Uranus is from our Sun.

What’s Next for Procyon?

So, what does the future hold for these two stars? Well, Procyon A is going to keep evolving. Eventually, it’ll puff up into a red giant, ballooning to maybe 80 to 150 times its current size. That’s expected to happen in the next 10 to 100 million years. After that, it’ll eventually become a white dwarf itself, joining its companion in stellar retirement. It’s a long, slow process, but it’s a reminder that even stars have a life cycle, just like us.