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How big is Sirius A?

Sirius A is 2,300,000 kilometres

An Introduction to Sirius A

Have you ever looked up at the night sky and wondered about the stars? If so, you might have noticed one star shining brighter than the others. That star is Sirius, also known as the Dog Star. It is the brightest star that we can see from Earth. But did you know that Sirius is not just one star, but two? The main star, Sirius A, is accompanied by a smaller companion, Sirius B. Let’s unravel the mysteries and explore the incredible size of Sirius A, our sky’s shining superstar!

Size of Sirius A

Sirius A is really big! It’s about 1.71 times the size of our Sun. That might be hard to imagine, so let’s compare it to something a bit more familiar.

  • If Sirius A were a beach ball that is 5 feet wide, our Sun would be a slightly smaller beach ball that is about 3 feet wide.
  • If Sirius A were the size of a basketball, our Sun would be about the size of a soccer ball. Isn’t that amazing? Sirius A is a giant compared to our Sun!

Comparing Sirius A to Other Stars

Even though Sirius A is huge compared to our Sun, it is not the biggest star in the universe. There are other stars out there that are much, much bigger. For example:

  • Betelgeuse, a star in the constellation Orion, is about 700 times bigger than Sirius A!
  • VY Canis Majoris, one of the largest stars ever discovered, is so big that it could hold 1 billion Sirius As inside of it! However, despite not being the biggest, Sirius A is still very special because it is the brightest star that we can see from Earth.

Sirius A: A Close Neighbor

One reason Sirius A appears so bright to us is because it is relatively close to our Solar System. It’s only about 8.6 light-years away. This might sound like a lot, but in the grand scale of the universe, it’s like a neighbor living down the street!

  • To put it in perspective, if the distance between the Earth and the Sun (which is about 93 million miles) was just one inch, then the distance to Sirius A would be about 9 miles. That’s about the distance of a short car ride!

Conclusion: The Glowing Giant

So next time you gaze up at the night sky and spot the brightest star, remember that’s Sirius A. It’s a glowing giant, much larger than our Sun and one of the closest stars to us. Even though there are stars out there that are bigger, none shine brighter in our sky than Sirius A. Its size and brightness make it a truly fascinating part of our universe! Isn’t it amazing what you can discover when you look up at the sky?

Smaller By Category
Alpha Centauri A
Alpha Centauri A is the largest star of the Alpha Centauri star system (composed of three stars), which is the closest star system to us. It is also the fourth brightest star in the night sky.
Sun
Also known as Sol, the Sun is what gives Earth the energy that makes it able to have life. The Sun is over 100 times larger in diameter than Earth! 20,000 times more solar energy hits the Earth than the human race uses.
Alpha Centauri B
Alpha Centauri B is the second largest star in the Alpha Centauri star system. Its diameter is approximately 1.25 million kilometers, so it is slightly smaller than the Sun. Alpha Centauri A & B are so close they appear as a single star to us Earthlings.
Larger By Category
Pollux
In Greek mythology, Pollux's twin is Castor. They are also stars in the constellation Gemini, meaning "twins". However, in reality, Pollux is a single star, while Castor is three binary stars, for a total of six stars. Castor is a set of sextuplets!
Altair
Altair is one of the three stars in the Summer Triangle. The Summer Triangle is an acute triangle, which means that all the angles are less than 90°! The other two are Vega and Deneb. Like many other stars, Altair spins very quickly, bulging at the center!
Procyon
Did you know that over the next 10 million years, Procyon will grow to 100 times its current diameter and become red? This is because Procyon's hydrogen is now all helium. The Sun will do the same thing in a couple billion years.