Giant Stars

Many of the stars that populate space are smaller than the Sun, and certain exotic kinds are smaller than Mercury or the Moon. But others are incredibly large.
Your teacher has a movie to help you see these different sizes.
Thus a "giant" star such as Arcturus which is about 25 times wider than the Sun, would have to be represented in our One Km Walk model by a ball 5 metres across. Rigel, a "super- giant" 50 times wider that the Sun, would be a ball 10 metres across - the size of a whole classroom. If we stood it in place of the Sun, it would reach most of the way out to the first planet, Mercury. Red supergiants are larger still: Antares, 700 times wider that the Sun, would be about 160 metres across, so that Mercury, Venus, Earth, and Mars would be orbiting deep inside it! Betelgeuse is thought to vary from about 550 to 1000 times the width of the Sun, so that if substituted for the Sun it would be a colossal ball of 260 metres with Jupiter barely clearing its surface. (One more, the dark companion of the star Epsilon Aurigae, used to be regarded as the largest star known, 2800 times wider than the Sun, large enough to swallow the solar system to well beyond Saturn. But it is more likely some kind of cloud.)

Yet these monsters, like all stars, are so far away that they appear to us as points with no width at all.

(The Sun itself, in its "red giant" phase, will swell up like this and put an end to us about 4,000,000,000 years from now.)

View the movie Solar System Comparison

Write your wonderings.
After you have viewed the Solar System Compared movie and done any other research around questions that came up, write up your notes and paste them here. Keep thinking about the size of the Earth

Dan (4r]1$]3

........ AAAAAAAAHHHHHHHHHHH WERE ALL GONNA DIE, those things are so unnaturally large they are giantgantically hugenourmus I can't even explain it!!!! THERE ISN'T A WORD TO DESCRIBE IT, THATS WHY I HAD TO MAKE UP THOSE AAAAAAAAAAAAHHHHHHHHHHHHH!!!!!

Matthew, Greytown

The planets and stars all around us are huge. The star W Cephei is 3,676,200,000 km across, thats 288,194 times the size of the earth!!!!!!! *


Man alive those stars are sooooooooooooooooooo big imagine sailing around that worlds ocean.If it had one.that Epsilon Aurigae.


It would take 2,200,000 years traveling at the speed of light to get to the Andromeda galaxy

Sophie, Greytown

Wow. I'm scared. I had no idea we were so small. I couldn't help but laugh at how tiny our 'huge' sun is. I agree, how could one man think he was superior.
VV Cephei, the largest star known, is 1900 times the size of our sun. But compared to the Milky Way, our galaxy, VV Cephei would be the size of a single pixel. Just imagine what is out there that we haven't discovered?

Here's a question - what are stars even for?
Here's a question - what are stars even for?

Emma, Greytown

Yeah, for some reason I always thought stars were small, but that 'Betelgeuse' gives the sun a run for it's money! So obviously the sun isn't as big as I thought it was... Sophie - that comment you said bout one man being superior - I wasn't sure who you meant? Possibly Maui? Didn't he conchor the sun once? I wonder how big black holes are comparatively... I think I'll go find out.

Tig (Greytown)

I see now why they are called solar giants. You look up in the sky and want to see those sparkling pinpricks of light more closely, But if you got close enough to examine them properly, you'd be vapourised.
Emma, you were wondering how big a black hole is.. it's about the size of an atom, it just looks big cos of all the stuff getting sucked into it

Just For Interest

Globular Clusters

Globular clusters are awesome balls of up to a million stars, in a space perhaps 150 light-years across. In photographs such a cluster looks like a swarm of luminous bees, ever thicker toward the core, which appears a solid unresolved white. It seems as if the stars must be almost touching and the space among them must be white hot, burning with light. And in fact these stars are 25,000 times more densely packed than normal. Yet this means that they still average about a tenth of a light-year apart - in our model a mere 200 kilometres (about Masterton to Napier with our little 20 centimetre suns!) from each other instead of 7000.

Even these densest collections of stars are mostly empty space.

Even though there are heaps of stars in each of them, none of these clusters can be seen with the naked eye from Earth – you need telescopes!

A few sites you might like to visit to find out more.

Order of magnitude - details units of measurement with some useful examples.
Orders of size
Windows on the Universe – a comprehensive site
Distance between Earth and other planets – at light speed!!

For other pictures of things in our universe go to