Size Does Matter!

October 12, 2020

When it comes to Space Size Matters!!!

Only last week, whilst on the Star Safari someone asked me a question and I wasn’t sure of the answer.  They asked how big in KM is our Sun?  They also said what about in comparison to the Earth and our Moon!  So guy today I thought we should talk about size!

I suggested that our Sun’s diameter was over 1 million km but I wasn’t entirely sure so the next morning I looked it up and realised just how big it really was at a staggering diameter of 1.3927 Million KM

That’s a wow right there.  So I decided to look at other sizes of our solar system.  I started with The Earth and our Moon.  The Earth is 12,742KM in diameter, making the suns diameter about 109 times larger than the Earth.  In-fact you could fit 1.3 million Earths inside our sun!!!!


So if thats the sun to the Earth what about the Moon to the Earth? Well our Moon has a diameter of 3474.20 Km.  WOW, that means the moon is about a quarter of the size of the Earth.  I already knew that our Moon was the fifth largest satellite in the solar system but this would make it by far the largest satellite relative to the size of the Planet it orbits in the whole solar system.

This got me wondering what about some of our other planets and their moons!  Lately, we have been seeing Mars rise during our tour.  We know Mars is the 4th Planet from the sun and the furthest out of our terrestrial (rocky) planets at a size of only 6787km (only about twice the size of our) and on average 53 million miles away from teh Earth.  Mars has two moons, Phobos and Deimos.  These two moons are in somewhat of an identity crisis, as they resemble asteroids compared to the size of Earths Moon.  Both of them are tiny, the largest, Phobos is only 22km wide while the smaller Deimos is only 13km!  This makes them some of the smallest moons in our solar system.


We have been viewing Jupiter all summer.  We call Jupiter the God Father of planets.  The oldest and largest in our solar system.  Jupiter comes in as the fifth planet from the Sun and has a whooping diameter of  around 140000 kilometres.  Now Jupiter has 79 moons that we know of, the largest of these being the Galilean Moons.   The Galilean moons are by far the largest and most massive objects to orbit Jupiter, with the remaining 75 known moons and the rings together composing just 0.003% of the total orbiting mass.  From nearest to Jupiter to furthest the Galilean moons are Io at 3660km diameter, Europa 3121.6km diameter, Ganymede 5268.2km and Callisto at 4820.6 km diameter.  WOW! That means Ganymede is the ninth (9th) largest object in our Solar system after the Sun and seven of the planets coming in at larger than Mercury who’s diameter is just 4879.4 km and who has no moons!

What about my favourite planet to view in summer Saturn?  Saturn lies at twice the distance as Jupiter at an average of 1 Billion miles away.  It is the fifth planet from the sun and the second largest in the soar system some 95 times more massive than the Earth!  Until recently we believed Jupiter to have the most moons with 79.  However, Saturn now has 82 moons. Fifty-three moons are confirmed and named and another 29 moons are awaiting confirmation of discovery and official naming. Saturn’s moons range in size from larger than the planet Mercury — the giant moon Titan — to as small as a sports arena.  Titan is almost as big as Ganymede with a diameter of 5150 Km.

So as you can see within our solar system size does matter.  Next time when we talk about sizes, we will compare the suns of our galaxy, and the wider universe itself.  When we do, you will see that outside of our solar system, Size is relative!  Until next time this is Kieran saying by to you all, unless you are a member of our new Moon Light Members Club  and have access to exclusive content and our incredible members offers then please keep reading….

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