Since on January 5 Jupiter was at Opposition (Jupiter is opposite the sun in our sky) and 93 million miles closer to Earth than during the rest of its orbit I thought an article about the giant of our solar system was in order. For reference the Earth is approximately 93 million miles from the sun. Which is called an astronomical unit. So Jupiter is one AU closer to Earth than during the rest of its orbit this week. Now don’t get all excited about this, Jupiter’s average distance from the sun is 5.2 astronomical units. Yeah, our solar system is vast.
So what makes Jupiter so interesting? Well let’s take a look at some of the fascinating things scientists have discovered about the solar system’s big brother. Since we are all residents of Earth and are, therefore, most familiar with it I think a little comparison is in order just for the sake of understanding better what we are dealing with in Jupiter.
For starters the Earth is around 25,000 miles in circumference and takes 24 hours to complete a rotation. This makes the speed at which the Earth turns on it’s axis 25000miles/24hr or approximately 1000 miles/hour. (NASA)
Compare this with Jupiter which is around 272,942.9 miles in circumference. Now for the astonishing part: Jupiter’s day is only 10 hours long! Every time I think about that it boggles my mind. Jupiter is so large 1000 Earths could comfortably fit inside and it completes a full rotation in less than half an Earth day. (NASA Jupiter Factsheet)
Now unlike the Earth which has a solid surface Jupiter is a gas giant, so all we see is the gaseous upper cloud decks of the behemoth planet. Because of this the surface of the equator rotates more rapidly than the poles resulting in different lengths of the day depending on your latitude. The day varies from approximately 9 hours and 56 minutes at the poles to approximately 9 hours and 50 minutes at the equator. (Caltech)
Which brings us to composition. We know the Earth has a solid surface, we walk on it every day. Granted 70% of the Earth’s surface is covered by vast and life giving oceans but we have dry land to walk on. Also our atmosphere is mostly Nitrogen (N2) a whopping 78% with Oxygen comprising 21% and only traces of other gasses.
Jupiter’s atmosphere is Hydrogen and Heilium. NASA doesn’t even give percentages. The Earth has an iron nickel core. Jupiter’s core is predicted to either be a solid inner core about the size of earth or some speculate a ball of liquid hydrogen. Jupiter does, in fact, have a faint ring system discovered in 1971 by the Voyager 1 spacecraft. The only ring the Earth has is an artificial one made by satellites we’ve launched.
Speaking of satellites, the Earth has one, our Moon. Jupiter has over 50 moons and while Jupiter itself cannot support life as we know it some of its many moons have liquid oceans under the surface and may support alien life.
Hurricanes on Earth last for a few weeks. The great red spot on Jupiter is an enormous storm 3X the size of Earth that’s been raging for hundreds of years and shows no sign of slowing down. Pretty amazing, if you ask me.
On Earth the gravitational constant is 9.8 m/s^2. On Jupiter the gravitational constant is 24.79 m/s^2 wow. this makes the escape velocity of Jupiter 134,664 mph. Again, wow. By comparison the escape velocity of Earth is 25.031mph and look at the size of the rockets we have to build to get going just that fast.
Ok just one more fact comparison, because it’s fun and fascinating. The Earth’s revolves around the sun in 1 Earth year, which is 365 of our days. Our average orbital velocity is 66.622mph. Jupiter revolves around the sun in 1 Jovian year which is 12 Earth years. Compared to the Earth, Jupiter’s orbital velocity is a leisurely 29.205mph. The big planet is farther away from the sun and so doesn’t orbit the sun as quickly.
And one last fact about Jupiter, at 5.2 AU from the sun Jupiter radiates more energy than it receives from the sun. That is amazing! Not a star but an almost star. If it had been but 80X more massive it would have ignited fusion in its core. (NASA Solar System Exploration)
So since Jupiter is at Opposition this week it’ll be at it’s brightest for skywatchers. Go, take a look and marvel at the wonders of our universe. K.
(Originally published on M31 Publishing.com)