What is the distance between Saturn and Neptune and Saturn and Jupiter?

Rob Thacker
23 January 2012

Above: Image © Public Domain

If we consider the exact distances today, then Saturn and Jupiter are about twice as close as Saturn and Neptune. However, if we just take the difference in average distances from the Sun, Saturn and Jupiter are about five times closer than Saturn and Neptune.

Did You Know? Saturn's average density is so low it would float, if you could find a big enough bath tub!

Let's sort out how we measure huge distances first. Astronomers use the Astronomical Unit or “AU” to measure distances in the Solar System. One AU is about 150,000,000 km and is set by the average distance between the Earth and Sun. That's still a long way — if you could walk to the Sun it would take 3,500 years to get there. Using the latest planetary data, the difference between the average distance of Saturn and Jupiter is 4.3 AU, while for Saturn and Neptune it is 20.5 AU. This is the distance we'd get if all the planets were in a straight line with the Sun — but they aren't. They're quite spread out.

Did You Know? The planets don't orbit in perfect circles, rather in very slightly flattened circles called ellipses.

Right now, both Jupiter and Neptune are on the opposite side of the Solar System to Saturn. A quick calculation shows that on March 1st 2010 the distance between Saturn and Jupiter is 14.5 AU, while the distance between Saturn and Neptune is 38.4 AU — about twice that of the distance from Saturn to Jupiter. So currently, these distances are almost the largest they could be. When we assumed the planets were lined up, we actually calculated the smallest distance they could be apart.

Did You Know? Each of the seasons lasts for 40 years on Neptune.

Believe it or not, part of this question could have been answered 400 years ago by the astronomer/mathematician Johannes Kepler. He was the first person to accurately figure out the orbits and positions of the planets. But he'd have had a tough time with Uranus and Neptune — they weren't discovered until much later!

This answer was written by Dr. Rob Thacker, Associate Professor at Saint Mary's University, a lead researcher in large scale structure and galaxy formation.

Related video:http://www.youtube.com/watch?feature=player_embedded&v=x1w8hKTJ2Co

Rob Thacker

I am a Professor of astronomy at Saint Mary's University in Halifax, Nova Scotia. I use supercomputers to answer questions about how galaxies form and evolve. As well as being interested in things in the sky, I am also passionate about our planet and take time to go backpacking or diving with my wife Linda whenever possible. English by birth, I still haven't quite gotten used to Canadian winters!

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