Little Big Earth and the Universe
Let’s talk about size… 😉 How big are the objects floating in our Universe and how big can they get? Starting with a “big” object, our very own Moon… Embark on a tour of space… A tour of our Universe…
The Moon is 3,500 km in diameter. That’s bigger than the ninth planet of our Solar System – Pluto is only 2,400 km.
Planets and their Approximate Sizes
The following are approximate diameters of some of the most familiar astronomical objects of the Solar System:
| Outer World | Diameter (km) |
|---|---|
| Mercury | 5,000 |
| Mars | 7,000 |
| Venus | 12,000 |
| Earth (You are Here!) | 13,000 |
| Neptune | 48,000 |
| Saturn | 120,000 |
| Jupiter | 140,000 |
“Big” Sun and Beyond
The Sun is 109 times the diameter of Earth.
We use a new unit here the solar radius, 1 R⊙ = 6.955 \times 105 km = 695,500 km.
| Stars | R⊙ |
|---|---|
| Sirius A (brightest star in the sky) | 1.711 |
| Pollux (giant orange star) | 8.8 |
| Arcturus (red giant star) | 25.4 |
| Aldebaran (red giant star) | 44.2 |
| Rigel (blue supergiant star) | 78.9 |
| Pistol Star (blue hypergiant star) | 306 |
| Antares A (red supergiant star) | 883 |
| Mu Cephei (red supergiant star) | 650-1,420 |
The largest known star, VY Canis Majoris red hypergiant 1420 ± 120 R⊙.
This star has a diameter of 2,800,000,000 kilometres.
Such a size is impossible to imagine…
A passenger plane flying at 900 km per hour over the surface of such a big object would take 1,100 years to circle around it once!
Not the Centre of the Universe…
Compared to it, Earth is tiny. The Sun’s bigger. And yet, it is merely a dot among several hundred billion stars that form our Galaxy.
And there are a hundred billion galaxies in the vast expanses of the Universe.
We are NOT the centre of the Universe. Far from it! We’re not even the centre of the Galaxy…
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