A Guide to the Night Sky by Tre Gibbs, LAAS - May 2017

Jupiter, The Roman King of the Gods, is back and putting on a brilliant show for observers here on planet Earth, rising in the east about the same time the sun is setting in the west. So much to say about this amazing world, it’s hard to know where to begin…

Jupiter is a giant ball of gas. When you see Jupiter’s surface in pictures or through a telescope, you are looking at the tops of clouds. In fact, the famous Great Red Spot is a huge, 350 year old storm, roughly the size of Earth.

Jupiter has about 67 moons, four of which can be seen with a pair of binoculars – if you observe them on a clear, wind-less night and you also hold those binoculars very still. The astronomer Galileo Galilei discovered them back in 1609 or 1610 using a modest telescope. He first assumed they were simply background stars – until he observed that they appeared to travel across the sky with Jupiter. Since then, NASA has sent spacecraft to actually study those moons and as a result, scientists have recently confirmed that at least one of those moons, Europa, has a huge subsurface ocean – and potentially, some form of life!

You think time flies here on Earth?A day on Jupiter lasts less than half of ours. The giant planet completes one full rotation on it’s axis in just under 10 hours, which causes it’s middle to bulge slightly. In contrast, a year on Jupiter would last the equivalent of about twelve Earth years, since that’s how long it takes Jupiter to orbit the sun. Someone 54 years old on Earth would only be 4 and a half on Jupiter!

Jupiter has a ring system, although it’s nothing like Saturn’s magnificent ring system. Jupiter’s rings are made of dark, reddish dust while Saturn’s rings are made of 99% water ice, which reflects sunlight extremely well, making them brilliant and very obvious. Because Jupiter’s rings are so dark, only a closeup photo will render them visible.

Finally, Jupiter is big. REALLY big. Jupiter is the largest planet in our Solar System – approximately eleven Earth’s could fit across it’s widest part. And since the larger something is the more gravity it has, Jupiter often acts as a cosmic bodyguard. As life threatening objects (such as asteroids) speed through our Solar System, Jupiter’s enormous gravity gently pulls those potentially deadly objects off of their trajectory, possibly saving our planet from an impact of catastrophic proportions.

Now, The Moon!On May 10th, we’re treated to this month’s full moon, known as the “Full Flower Moon”, since May is the time of year of increasing fertility – with temperatures warm enough for safely bearing young, no more frost and lots of flowers. A few days earlier, on May 7th, mighty Jupiter will accompany the Moon across the sky. Look for both in the east southeast just after sunset and watch Jupiter gradually appear above and to the right of the moon, as these two cosmic beacons wander the sky as a pair, engaged in a brief but spectacular celestial interlude.

Stay tuned next month for the Summer Solstice and the return of Saturn! Until then, KEEP LOOKING UP!