Wednesday, May 17, 2006

The Night Of The Gas Giants

They may be giants...
Actually, they are, four of them in fact. These are the Gas Giants, the four largest bodies in our Solar System. This month, and through most of June, our night skies will be blessed with not one, but two of them, Jupiter and Saturn. To be honest, these two are the easiest to see from Earth, if only due to their size (however, they're also much closer than the outer two); Jupiter is around 11 times the size of our humble planet, while Saturn is roughly 9 times our diameter. In short, these are big worlds.
Both planets have numerous, notable features. Jupiter, the larger (and brighter) of the two is noted for the Great Red Spot, a huge storm that revolves around the planet just south of Jupiter's equator. The Great Red Spot is so large that you can drop the Earth through it and not even touch its edges. This storm has raged for centuries, and may continue to do so for many more.
Another, easily noticeable feature of Jupiter are its four largest moons. Ganymede, Io, Europa and Callisto; these are the so called "Galilean Satellites", named for their discoverer, Galileo Galilei. These were in fact the first moons found to orbit another world, and were first seen in January of 1610. And they are big. Ganymede is the largest satellite in our Solar System, easily larger than the planet Mercury. In total, Jupiter has over 60 moons; another notable feature indeed!
Not to be outdone, Saturn is also very lovely to look at due to its huge ring system. To be fair, all four Gas Giants have rings, but Saturn's are the only ones truly visible from Earth (unless, of course, you have a 6 meter telescope and really good imaging equipment). These rings are possibly the remains of a moon that broke up, no doubt due to Saturn's gravitational force. On the subject of moons, Saturn has over 40, the largest of which, Titan, is truly unique. It has an atmosphere that is composed primarily of nitrogen but which also has a methane "smog" that blankets the moon. There is a very real possibility that hydrocarbons actually rain down onto its surface. It is in many ways Earth-like, except many times colder. So cold, in fact, that frozen water behaves much as rock does here on Earth, even breaking up into frozen water "sand".
To find these worlds this month and through June, one doesn't have to look too hard. Jupiter simply can't be missed, rising high into the eastern skies after sunset, and by far the brightest "star" in the sky. Saturn is a bit dimmer and lies more to the west. By mid-June, Saturn will begin disappearing into the western twilight.

Not too long ago, Saturn appeared much brighter. Amazingly, it's still bright, but when you realize that Saturn is right now over 877 million miles (1.416 billion kilometers) away, its size and majesty truly hit home. Jupiter is only 409 million miles (660 million kilometers) away, less than half the distance, but of course its also 20% larger than Saturn. Below is a chart showing their relative position (though obviously not to scale) for the night of 19 May 2006, courtesy of Fourmilab's Solar System Live.

For this session of the Vagabond Astronomer, I'll be set up in the parking lot of Books-A-Million on Friday, 19th May 2006 after 8:30pm (See Platial link on the right). Hopefully you can come out and visit as we take in these two majestic wonders and really enjoy the Night of the Gas Giants. Looking forward to seeing you there!


deisnor said...

If I were anywhere near St. Augustine I would be there- sounds fantastic.

Robert said...

Thanks for the comment... and the reminder that I had to update my profile! Much as I love St. Augustine, I now live in Jacksonville. If you think you'll ever be in the area, just check the blog... never know where I might be!

The Vagabond