So – you’re interested in Astronomy?
Here are 10 things you might want to know about our solar system
1. Our Solar System is over 4 ½ Billion years old.
How do scientists know? Easy…Meteorites!
Meteorites date back to the actual formation of our Solar System. Those that land on earth have all been tested, and guess what? They are all 4 ½ billion years old. So, that tells us everything in our solar system was formed at the same time.
2. The Solar System extends out into space for a distance of 2 light-years.
What is a Light-Year? It is the distance that light travels in space, in 1 year. Scientists have worked that out as equalling a distance of 10 trillion kilometres (6 trillion miles).
Why does it go so far? Because the Sun’s gravity overpowers everything else in that region of space. (Wow!) Did you know, that’s nearly half way to the nearest star to us?
3. Most of the mass of the Solar System is in the Sun.
But…how much is most?
The Sun contains 99.86% of all the mass in the solar system. Now, when you remember that 73% of our Sun is hydrogen, we can say that nearly everything in our Solar System is made of hydrogen. All the rest – the helium, oxygen and carbon. All the rocks and metals and other stuff – are just a tiny part of the mass of our Solar System. Incredible
4. The Sun is just one star in the Milky Way.
Our Sun isn’t really all that big. In fact, it’s classed as a yellow dwarf star. There are some stars out in space that are hundreds of times larger. The sun just looks big because it’s so close to us. In all, scientists believe there are over 200 billion other stars in the Milky Way.
5. The Moon isn’t as big as the sun.
It only looks like it, because the moon is so close to the Earth. In fact, the moon is only 384,000km (239,000 miles) away from the Earth. Spookily enough, because it’s only 3,474km (2,159 miles) in diameter, it looks exactly the same size as the sun from where we stand on the ground.
(And yet, the Sun has a diameter of 1.39 million kilometres/865 thousand miles).
6. Do you know how many planets we have in our Solar System?
If you said 9, I wouldn’t blame you, because people thought we had 9 planets for years and years. BUT, you’d be one away from the right answer. Why? In 2006, the International Astronomical Union reclassified Pluto as a dwarf planet. So, that means our Solar System has only 8 real planets.
7. What’s a Dwarf Planet?
Simply put, a dwarf planet is an object that has enough mass to form a sphere of material, and which orbits the sun. However, because it’s not strong/dense enough to clear other material away from its path, it has to share its orbit with other objects. But don’t be sad. We might have lost a planet because of the new qualifications, BUT, we gained something else.
8. The Solar System now has 4 dwarf planets.
That’s right! Although Pluto was downgraded to a dwarf planet, it also meant we gained three more! Ceres, Eris and Makemake. Now, the great thing about this is the fact that as our telescopes get ever more sensitive, we might discover even more dwarf planets than we have at the moment. So, our family of planets could get even bigger.
And talking of planets…
9. Did you know, everything orbits in the same direction?
Yes, everything orbits about the sun in a counter-clockwise direction. This would tend to confirm that all the things in our Solar System were formed at the same time from the same giant cloud of cooling material. As that original cloud of gas came together, it began to spin. The densest object was the Sun. So, it formed in the middle of that cloud. About it, a thing called an accretion disc formed. (That’s a spinning collection of lesser concentrations of gas and dust). A long time passed, and eventually, all the planets and dwarf planets and other things in the Solar System formed within the spinning cloud.
10. Now, scientists have sent spacecraft to all of the planets in our Solar System.
More are being made to ensure we also visit all the dwarf planets. We’ve also explored the Sun, the Moon, and lots of interesting things like asteroids and comets. And do you know what? The more we look, the more we keep finding. So, if you want to become interested in astronomy, you’ll never stop learning. Not even if you get to be 100 years old!
So – now we’ve had a little look at our Solar system. Let’s imagine what we can do next time. You might be feeling sad for poor old Pluto. After all, Pluto WAS a planet, but now, scientist say she’s only a dwarf planet. How about next time, we take a closer look at some interesting things about Pluto? You never know, YOU might discover something no one else has yet!
See you then