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Size comparisons, take two August 14, 2009

Posted by Jorge Candeias in Ceres, Mercury, Neptune.
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I’ve already shown you a comparison between the largest Solar System planets in each category, and then I thought, heck, for the sake of completeness let’s do the same with the smallest ones, also with the help of Celestia. So here you go:

Size comparison between Neptune and Mercury

Size comparison between Neptune and Mercury

Size comparison between Mercury and Ceres

Size comparison between Mercury and Ceres

Isn’t this cute? The proportions look very much like those of the largest planets in each group, and if you prefer some numbers here they are: Neptune is 10 times larger than Mercury, wereas Mercury is nearly 5 times larger than Ceres. If you go check the masses, you’ll find that Neptune is almost 290 times heavier that Mercury, and Mercury 375 times heavier than Ceres. Everything very similar to the proportions between the biggest planets in each class. It should be noted, though, that Neptune may be the smallest of the giants but is not the lightest; that is Uranus’ claim to fame. Or one of them, anyway.

And, again, there isn’t much of a point in this. It’s just a visual reminder that if you look at the objects without taking into consideration their positions relative to eachother, the differences between giant and terrestrial planets tend to be larger than the difference between the terrestrials and the dwarfs.

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Some size comparisons August 7, 2009

Posted by Jorge Candeias in Earth, Eris, Jupiter.
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Well, I think it’s about time this blog includes a few pictures. And, since posts with pictures tend to require less words, it’s also a great way to give it content without spending in it too much time. So here are two quick renditions I made with Celestia, showing side by side the largest of the Solar System’s giant, terrestrial and dwarf planets:

Size comparison of Jupiter and the Earth

Size comparison of Jupiter and the Earth

Size comparison of the Earth and Eris

Size comparison of the Earth and Eris

The Earth in the bottom image is slightly larger than Jupiter in the top image (it isn’t easy to get this just right in Celestia without doing some math, which I didn’t), but I think the comparisons are effective even so. Eris (which doesn’t look like that, by the way; since we’ve never seen its surface, Celestia uses by default a generic texture, the same for all bodies in the same situation) is closer to the size of the Earth than the Earth is to the size of Jupiter. If you need numbers, then they are approximately as follows: the diameter of Jupiter is 11 times that of Earth. The diamater of the Earth is 5 times that of Eris (and no, the rather large uncertainties in Eris data don’t change this by much; at most they may drop that number to 4). More interestingly, if you compare not sizes but masses, which are actually more relevant, you get a couple of very similar numbers: Jupiter is about 320 times more massive than the Earth; the Earth is approximately 360 times more massive than Eris.

And the point is?

There isn’t much of a point, really. This just goes to show you that when it comes to compare sizes we’re not all that gifted. The big boys in the block are really big. And if you look at them from this perspective, the dwarfs don’t seem all that insignificant anymore.

And remember: if you look beyond the Solar System you’ll find other big boys that are even bigger than the big boy from our own neighbourhood, making our planet seem even more puny and helpless. HD 139357 b, for instance, is a behemoth 9.76 times more massive than Jupiter, which is to say 3100 times more massive than the Earth. Yes, that’s three thousand Earths needed to make only one gas giant.

Good thing that it strolls around almost 400 light years away, huh?