Astronomy: The Size of Stuff

The vast majority of objects out there in the universe are pretty big…moons, planets, stars, galaxies, so it can be difficult sometimes to get your head round their actual size. Here you’ll see how some space stuff out there compares to Earth stuff down here…

Neutron Star

Neutron star size

How a neutron star compares to the North West of England, satellite image credit Nasa

This is how a typical neutron star would compare if it was on Earth, easily fitting right between Liverpool and Warrington in the north west of England. A star that is only around 20 kilometres across? Yes, but this is not any normal run of the mill star you’d see shining in the night sky, this thing is a weird and exotic object. A neutron star also crams in over 1.5 times the mass of the Sun into a tiny ball maybe not much bigger than your daily commute to work, and the Sun is huge (see the size of the Sun later). So this thing is incredibly dense, so dense in fact that just a tea spoon of it would weigh over a billion tonnes, and if you could stand on its surface you’d feel the gravitational pull of 200 billion times that of our planet…not that you’d ever survive it of course.

Of all the animals in the galactic zoo, neutron stars are amongst the strangest things out there. But these things do something else, they also spin. You probably own a kitchen blender, or you’ve seen one in action. Imagine a globe 20-30 kilometres across spinning faster than your kitchen blender, and the fastest known neutron star spins at 716 times a second. Their spin rates are extremely reliable, they are so accurate they even surpass an atomic clock, they’re natures most precise timepieces.

That’s a neutron star, an object not much bigger than a city, with the mass of 1.4 to 3.2 times the mass of our Sun, and spinning at a phenomenal rate.

Olympus Mons

Size of Olympus Mons

Martian volcano Olympus Mons would cover the state of Arizona

Mars is actually quite a small world but it does things on a big scale. Located in the Tharsis Montes region of Mars is a volcano, it’s the biggest volcano on Mars, bigger than any volcano on Earth, in fact it’s the biggest volcano in the whole solar system. The volcano in question is called Olympus Mons, an extinct shield volcano with a truly colossal size. See how it appears on Mars in this Nasa illustration (above centre). On the image above you can see how it would appear if it was in the state of Arizona. Taller than 3 Mount Everest’s above sea level, this monster volcano actually would be Arizona as it completely covers it.

It is 374 miles (624 km) across, it towers 16 miles into the martian sky, and is rimmed by a 4 mile high cliff. At the summit of this colossal structure is the caldera at 50 miles across, easily seen in the image above. Olympus Mons has other volcanic company, in the Tharsis Montes region are three other smaller volcanoes Arsia Mons, Pavonis Mons, and Ascraeus Mons that form a line to Olympus Mons’ south east.

Jupiter’s Moon Io

Size of Io

How Jupiter’s volcanic moon Io compares to North America

Jupiter’s moon Io is the solar system’s most volcanic body, looking like a cheese pizza it would fit between San Francisco and Detroit at 1,942 miles across or 3,636 kilometres. This moon of Jupiter is a similar size as Earth’s own Moon (2,160 miles), so you could do roughly the same size comparison above. Io is tiny compared to Jupiter though, this image shows Io floating above the gas giant’s raging storms far below…far far below in fact, Jupiter is actually 350,000 km away from Io, or roughly 2.5 Jupiters.

Io is the first of four main moons to Jupiter, and this is why it is covered in erupting volcanoes. Jupiter’s immense gravity pulls on and flexes Io as it travels around in its orbit. This gravitational influence from jupiter keeps the interior of Io molten and those volcanoes on its surface spewing lava on its surface, and covering its plains in yellow sulphur. Those volcanoes erupt high above the surface, so high that if they were on Earth their volcanic material would go past the International Space Station.


Size of Mars

How North America would measure up to Mars

Earth’s sister planet Mars boasts some huge structures such as Olympus Mons and Valles Marineris, but the planet isn’t actually that big. In the image above see how big the United States and Canada would be if it was on the red planet. So if you could take a plane from one side of Mars to the other, it would take probably around 8 hours or so. This rusty desert world orbiting between Earth and Jupiter is only 53% the size of our planet, measuring 4,220 miles (6,792 km) at its equator, band from pole to pole it is 25 miles (40 km) smaller. This is why when viewed in a telescope Mars is always pretty small compared to planets like Jupiter and Saturn for example, although that doesn’t mean you can’t see features on this mysterious world. Through a decent sizes telescope you can see the ice caps and dark and lighter land features.

Earth’s rusty neighbour in the solar system is the second smallest of the planets, Mercury being smallest. The actual dry land mass of Mars is around the same as Earth’s, because although Mars is much smaller it doesn’t of course have any seas, you’ll have to go back a few billion years to see cool blue water slopping about on Mars.


Earth compared to Saturn

Many Earth’s would fit across the width of Saturn’s rings, main Saturn image credit Nasa

Jupiter holds the title for being the biggest planet in the solar system, but Saturn is no tiddler. It can hold its own in the size stakes, being 14, 514 miles smaller than Jupiter across its disk, and it also sports those fabulous rings. You can see just how Saturn dwarfs Earth in the image above, with nearly 6 Earths lining up across the width of its rings. The main dark gap in its rings is called the Cassini Division, this alone could almost contain the whole United States. Across the main planet’s disk of Saturn you could fit nearly 10 Earths, and if you could fill the inside of Saturn with Earths it would hold 764.

Saturn’s Rings

Earth Saturn's rings compared

With Saturn replaced with Earth, this is how our planet would appear at the ring’s centre

We’ll stay with Saturn for the minute to emphasise just how gigantic the extent of Saturn’s rings are. The main disk of Saturn has been taken out and replaced with Earth on the same scale. Saturn’s icy rings are composed of billions of particles from tiny grains right up to mountain sized chunks. The ring’s thickness is 1 kilometre, and they span around 175,000 miles (282,000 km), that’s about three quarters the distance from the Earth to the Moon.



North America is dwarfed by the immensity of Jupiter, main Jupiter image credit Nasa

Jupiter is the king of the solar system, it has more mass than all the other planets and moons put together, and spans a whopping 88, 846 miles (142, 984 km) at the equator. It is over 11 times the diameter of our planet, with lightening bolts up to 1,000 times more powerful than Earth’s, and wind speeds in the upper atmosphere that can reach 100 metres per second. This planet races around in just 10 hours compared to Earth’s 24, making it the fastest rotating planet in the solar system. The image above shows the gas giant with how North America would appear to the same scale, it is completely dwarfed by Jupiter’s Great Red Spot, a storm that has been raging since possibly the year 1665.

The Sun

Sun compared to Earth

Earth compared to the Sun

The Sun has far more mass than everything else in the solar system put together, in fact it is 99.86% of it. Which means that us and the other planets and moons are really just the left over rubble from the formation of the Sun 4.5 billion years ago…the cosmic byproducts. At the Sun’s scale Earth is now really starting to look puny, in the image above solar prominences visible along its limb explode into space many times the height of the Earth. A typical sunspot usually visible on most days on the Sun (with only the right equipment and know how), could easily dwarf Earth.  Across the Sun’s disk you could fit 109 Earths side by side, and to fill the Sun’s volume would take 1,300,000 Earths. On closer inspection the Sun has a granular or cellular appearance, these granules on the photosphere are the tops of convective cells that are plasma rising up from below. The solar disk has up to 4 million of these granules across its disk at any one time, and are on average the size of Texas.

The Sun puts out more energy in 1 second than has ever been produced in all of human history, and loses 4 billion tonnes of material into space every second but has enough to last for another 5 billion years. A solar flare, an explosion from the Sun’s surface caused when hugely powerful magnetic fields break apart under stress, can have the power of a billion Hiroshima bombs.

The Sun is only one among hundreds of billions of other stars in our Galaxy The Milky Way, but is larger than the average star.

By John Brady

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  1. Great article John! I love the progression in size comparison, and the use of things familiar to us to compare the sizes of different objects in our solar system!

      • Actually, I’m laughing at you. It’s a legitimate correction. It was made twice, so it’s more than just a typo. This is an educational/informational piece, so a mistake like that should be corrected.

        • Actually, Snake, If you would actually look at the photos, (like the one of Mars) you will see Canada and Mexico are there too.

          So, you ARE “that guy” that we are all laughing at.

    • The authors apparently have no concept of geography or grammar. Indeed, they seem not to be aware that Canada is part of North America as are another 10 countries or more that they omitted.

    • Question: Where do Americans live?

      Answer: Anywhere in North, Central and South America. Residents of Center and South American also refer to themselves as Americans.

      What do you call someone who speaks only one language?

      Someone from the United States.

      • “What do you call someone who speaks only one language?

        Someone from the United States.”

        Guessing you have never been to the U.S.? One language? BWHAHAHAHAHA No, We are the melting pot.

        What do you call someone who speaks only one language?
        Anyone NOT from the U.S. but migrates here and refused to learn English.

      • As a bilingual U.S. citizen, I will kindly ask you not to generalize a nation of 300+ million people. It really does you no service and, in fact, makes you look like an asshole.

        Como un estadounidense bilingüe, te pido por favor que no generalices a una nación con más de 300 millones de habitantes. En verdad no te sirve nada y realmente hace que luzcas bien cabrón.

  2. >wind speeds in the upper atmosphere that can reach 100 miles per second.

    Jupiter’s escape velocity is just 37 miles per second. Could you clarify your statement?

    • Whoops, yes you’re right well spotted. It should be 100 metres per second.

      Thanks for pointing that mistake out.

  3. Come on, give other continents love as well instead of just focusing on North America

  4. Please, note that Mexico is there too. It’s part of NorthAmerica.

    Soooo in Jupiter’s photo caption should say: “North America is dwarfed by the immensity of Jupiter” OR “Canada, United States and Mexico are dwarfed by the immensity of Jupiter”.

    Thanks for the wonderful info anyway =)

  5. What is so awesome after viewing all of these great comparisons is that it was all created by GOD.

    • Way to shove your god down everyone’s throats! There was a time when I was still on the cusp with religious beliefs, and then you overbearing folks came and pushed me and all the other intelligent would-be Christians away by, say, finding it necessary to interject god into every interesting scientific article on the internet just for the sake of it. You were completely unprovoked; no one asserted any scientific superiority over religion, no one implied that there wasn’t a god. You just had to take it there because you people are a bunch of self righteous pricks with nothing better to do than nose around in what everyone else believes.
      The Pope came out the other day and said science and god can coexist, which is a big step for religion, and should finally help to quiet down the knuckle heads (I personally know a few) who don’t believe in dinosaurs. BTW I’ve always gotten a kick out of the irony of people who devote their lives to an invisible man in the sky yet believe dinosaurs are fictitious, imaginary things. What gets me about the whole thing is that anyone with a brain should already know that science and religion can coexist. But the religious folks had to hear the Pope say it first. Now it’s like they’ll all suddenly have this epiphany and they’ll all be quoting this new Vatican line, when the same people a few years ago would have been arguing till they were blue in the face that science is just a trick that god is testing us with. The most weak minded people in the world, religious fanatics are. When I saw how pushy and arrogant and downright ignorant “god’s people” are, I made sure to hop on the other side of the line. If you’re offended and think “how sad this guy is all worked up and angry and he went on this big rant over basically nothing”, well, what can I say? You folks made a militant out me. We’re all just flawed people in the end after all. But you know what’s so awesome about us human beings? We were all created by SCIENCE.

      • the devils greats accomplishment was to make himself not to be real,, after all he deceived eve and she was perfect,,so in our limited copacetic as humans its no wonder to jump at a theory to have something to believe in,,the devil all so has made so many believe god doesn’t exist either …

      • Hi Quark, I think it’s important to note that many of the leaders of scientific discovery were faithful Christians. What the Pope says today is nothing new. Copernicus, Bacon, Kepler, Galileo, Descartes, Newton and many more… Even the theorist of the Big Bang Theory, George’s Lemaitre had a personal devotion to God. For many their passion for discovery was inspired by reading the Bible and contemplating Gods magnificent creation.

        There is room for everyone in this grand old universe! Faith is a journey not a destination. Hope you enjoy the ride!

      • Faith and reason are not in conflict. In particular, Christianity and science are not in conflict. Whoever thinks they are probably doesn’t understand Christianity, or doesn’t understand science, or both.

        In any case, surely there are fundamentalists on both sides who create a conflict where there need be none. But there are also reasonable folks, on both sides, who see that there is no conflict. In fact, there are many scientists who are people of faith, and there are many people of faith who are scientists.

        If there is any conflict, it is philosophical.

        Here are some books that attempt to explain these ideas. One author, in particular, is quite interesting, considering that he has double doctorates in physics and theology: Stanley Jaki. It would behoove anyone interested in having a rational discussion (instead of resorting to name-calling) to read some of these books. Borrow them from your library, if you don’t want to buy them:

      • Popes and Christian theologians have been saying pretty much since the get-go that faith and science are not opposed. Those who’re so uninformed and critically unequipped to discuss religion that they can’t resist recourse to stupid caricatures should probably stay out of the discussion.

      • Well said. How I wish I can write the same presentation the way you presented it here.

        • God is real, and he made the universe. But not everyone who believes in Him tries to force everybody to be a Christian. And how can you prove that the Big Bang and evolution is real? You can’t do that, either. None of us were alive back then. Think about it…

          • Evolution has mountains of evidence. The Big Bang theory has mountains of evidence. God? None. Just a made up book written hundreds of years after the bullshit was supposedly spewed. It’s a ridiculous argument to ask somebody to disprove some gray haired imaginary man in the sky. That, as you should know, is not science.

    • no frank, it isn’t.

      what is awesome, and i mean the original meaning of the word, is that you need pictures of astounding beauty and dimensions beyond your frame of mind, to be reminded of your creator.



    • It’s funny, because I looked at the immensity of our solar system here and thought how immensely limited religion is to think that it’s all about us.

      When you look at the beauty of the reality, it really seems so mentally restricted to try and reduce it to the mistranslated fables of ignorant, underdeveloped people long ago, who had no knowledge of germs, tectonic plates, a solar system revolving around a sun, galaxies, gravity, etc., and attributed it all to an invisibe man in the sky who could read their minds and was obsessed about punishing them for not praising him enough.

      It’s so obviously utter twaddle, but what makes it even more ridiculous is that even with our discoveries and knowledge showing it to be nonsense, so many people still can’t see it for what it is.

      Worst of all is their uncontrolled desire to not only demand that their nonsense is respected, but that they can thrust it in your face with impunity, ignoring all facts, and denounce you as immoral for not buying into their fantasy.

      Their self-righteousness hitting its zenith in stating with certainty that you are not only temporarily misguided, but will ultimately have a deathbed conversion before you die.

      I find this all so bloody offensive.

      I’d rather marvel at the scientific beauty of the reality without the Holy Joe’s ruining the view with talk of their imaginary friends.

      • We are on just 1 planet, going around 1 star, amongst hundreds of billions of others orbiting around just 1 galaxy the Milky Way. Out there beyond our own galaxy are hundreds of billions of other galaxies, and in each one of those hundreds of billions of galaxies, are hundreds of billions of stars, with their trillions upon trillions of planets and moons. Is it a bit arrogant to think that a god made the whole thing just for us? What a waste of space. For those who believe, God is getting increasingly getting squeezed out the picture as science continues to explain the universe.

        The Sun god, the moon god, the volcano god, earthquakes happen because the gods are angry. The crops have failed, we must give a sacrifice to the sun god. Gods were invented to explain nature when we had no proper understanding, now we do.

        • who says He made it all for just us on this earth? Has it ever occurred to you that in all those billions of stars and galaxies and such that there are billions of earth like planets with people on them too? The universe is for *us*, as in all the innumerable inhabitants across its span, not just one little planet.

          the more I learn about science the more apparent the reality of God becomes.

        • Arrogant asses, all of you. Science does not disprove God and God does not invalidate science. None of us really know shit….Except what we insist we know. Lol….fools.

    • Yes, of course it was Frankenfurter. hahahahahaha But, let’s look at 1 problem at a time here (none others need to be looked-at.) Counting the generations from “adam and eve” to jeeeeesus, we come-up with about 4,000 years; add to that, the time from jeeeesus to now…about 2,000 years, and we get 6,000 years since the “creation” of the Universe. (It’s hard for me to stop laughing long enough to write more here). The little, itty-bitty problem here is that if this is correct, we should not be able to see any other galaxies in the universe; or even the majority of stars in our own Milky Way galaxy! See: and But, of course, none of these observable facts will stop the right-wing nutcases from simply saying “god can do anything.” How so? “My book of fairy tales tells me so!” (sing this verse to the music of “jeeeesus loves me, this I know, cuz my bibble tells me so…..) hahahahaha Absurdity at its’ best!!!!!!

  6. Your earth/saturn rings picture. It would be nice to also show the moon in relative size and position. Improving the sense of scale :-)

  7. Awesome article. I thought the red spot was the size of earths in diameter. Given that scale, wouldn’t North america appear to be smaller than what you have shown?

    • The Great Red Spot was about 3-Earths across when first discovered, though it has gotten smaller over time. It’s about 2-Earths now. It may actually disappear entirely in the future!

  8. Love this! Haha I thought the comparison of North America to Jupiter was great. Also seeing Saturn’s rings around Earth really made me appreciate how big Saturn is. Awesome job!

  9. Another cool pic: Compare the thickness of Saturn’s rings to something terrestrial. Considering the map-scale of the other objects, a 10 meter building would be a very interesting contrast.

  10. Thanks, Mr. Brady. And great work with your links in addition to writing an eye-opening article. I was blown away by take image of Io floating above Jupiter. That is one awe-inspiring pic.

  11. Hey guys, there’s enough room on earth, not to mention the solar system or our galaxy, for everybody to believe in whatever they please. The man with the beard up there, a volcano god, a rain god, Wotan, Ishtar, astrology or science, you name it. As long as they don’t bother you, why not just let them be? After all, we’re all in this together.
    And thanks Mr Brody for fantastic images.

  12. I loved this. Everything about it. The photos, the comparisons, the information on mass (neutron stars are baddasses!) and all the debate too. Science is fantastic and I’m so humbled by all these gorgeous images.

    Being an American, I always feel a little self-conscious about things like this when they show just Earth’s western hemisphere, and more precisely more of the US in the North America shots, and we don’t see Asia or Africa or Australia. I brace at the concept that the USA is often the most-used image in maps, or the like. I share the planet (and the sun, moon, and the rest) with everyone else.

    Be that as it may, this was a wonderful treat for me. I remember being a little girl and lying on my belly pouring over my mother’s seemingly huge (probably just a regular-sized book in reality) books on astronomy and the planets. I often would fall asleep on them.

    Thanks for doing such a great job.

    • Hi Molly,

      Thanks for the comment and you bring up an interesting point, why do we always use the western hemisphere? Maybe that needs to change.

  13. Beautiful photos and impressive comparisons. I note, however, that, in your comparing North American to the size of Jupiter, you mistakenly call it “United States and Canada” even though your photo clearly includes Mexico.

  14. Would like to point out a glaring mistake that distracts from an otherwise impressive page. Three countries make up North America; Canada, USA and Mexico. There’s no need to mention Canada separately. Hope you have a chance to correct that, otherwise thanks for the interesting article!!

  15. There is a reason why mars and earth have the same dry land mass, and why mars is smaller without oceans and earth is larger with oceans. You just need to look at nasa’s crustal age of the sea floor and you’ll see exactly what is going on!

  16. FYI, the comparison of Olympus Mons to Arizona is wrong. That is not Olympus Mons. Look at the picture of N. America over Mars; the really really big volcano off the Pacific northwest coast… That is Olympus Mons. Notice at this scaling, the central caldera is as big as Arizona! :)

    • Hi Adam,

      I can see what you mean, but what looks like the central caldera off the Pacific NW is actually the whole volcano. But yes it does actually look like the area surrounding it is part of the volcano. Hope this helps.

      John Brady

  17. The artist needs to go back to school and take a geography lesson…being from nova scotia ..i ask why several Canadian east coast provinces and islands are missing ..makes me wonder how he can even scale comparison to mars when he cant even draw a proper map of north America …missing are the four Atlantic provinces of Canada including islands of cape Breton and prince Edward island..Newfoundland isn’t joined to Labrador and several arctic islands are missing as well….please draw it properly..or use the Google maps that are used in most …really a scientist drew that?? wtf?

  18. You stated that the distance from inner to outer ring of Saturn is roughly 3 quarters (3/4) of the distance between the Earth and Moon. You also stated that you could fit a little less than 6 Earths across the rings. Earth’s diameter is about 7,918 miles. This would mean Saturn’s rings are roughly 47,000 miles across from inner to outer ring. The average distance between Earth and Moon is about 238,900 miles. 47,000 isn’t even 1/5 of 238,900, let alone 3/4. Your claims and the math don’t match. Unless of course you were referring to the distance between opposite sides of the outer ring, that distance is roughly 175,000 miles.

    • Entirely correct. The idea of this article is interesting, but the execution is dreadful. So many errors, and not even proof-read well. “North America and Canada” – what continent does the author think Canada is on?

    • Hi Smitty Wesson,

      Yes you are right.

      Many thanks for pointing that out. What was meant was the diameter of the rings, from outer ring to outer ring. Which is as you rightly said is roughly 175,000 miles, 3/4 of the distance between the Earth and Moon. Noted and corrected.

      John Brady

  19. The coolest thing would to gather/create more of these illustrations, and publish them in a book that I could have in my classroom for kids to see… (hint, hint)

  20. Thank you for sharing these data. It’s amazing to see the comparison of some of the objects in our Universe relative to Earth.

  21. Like canada, god is a figment of someone’s imagination. Science has proven both do not exist.

  22. wonderful article with a lovely perspective – thoroughlky enjoyed it – thank you John

    • God… So obvious that it can be passed in silence. Fish don’t discuss the water which encompasses them.
      Yet the water is there… So is God.

      • Fish don’t discuss the magic elves that rearrange our furniture when we’re not looking either. We don’t need to discuss God for the same reasons

  23. Hello, John,
    I have just discovered your site, thanks to a French newspaper (to-day’s issue of Ouest-France). It is very well done, very appealing. Makes astronomy what it really is: a fascinating subject.


  24. I’m an engineer and have always been interested in astronomy. The biggest surprise I found in this article is that Saturn’s rings are only 1km thick?!? That means that if you were on the surface (ok top of the clouds) directly under the rings, you could not see them! You would have to be many degrees out of the ring plane (or in latitude assuming the rings orbit the equator as physics would indicate), and have the light at the right angle before you would ever even notice they were there…

    So I guess if the rings were around Earth, the poor peoples of Mexico and Central America wouldn’t get to enjoy them, that is until they illegally immigrated to the USA (or Canada)…

  25. The comparison of North America and Jupiter’s Red spot is completely inaccurate. NA is roughly 3,000 miles across. Nasa states the spot is roughly 10,000 miles across (shrunk from 14,500 in 1979). You state the red spot is 88,000 miles across. If you were right, the spot would be 30x as wide as NA.

  26. great pictures. i teach a Bible study. always interested in signs and wonders in the sky..

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