Jupiter ends retrograde on September 8
2 comments Print Me Email to FriendTonight's Sky for Monday, Sep 08 2008
See Jupiter tonight? It’s not far from the moon on the sky’s dome. It so happens that today is a special day for Jupiter, because it marks the end of a four-month period in which the giant planet appeared to be moving backward in front of the stars.
If you were to watch Jupiter over the course of its yearly appearance in our sky, you’d find that this planet generally moves eastward among the stars, something that can’t be seen on a single night, but is obvious over weeks and months. However, approximately every 13 months, Jupiter appears to change directions for about four months in what is called retrograde motion. In 2008, Jupiter’s retrograde motion started on May 9, and it ends today. This is not a real motion. Jupiter doesn’t really reverse direction, of course. Instead, it is an apparent motion caused by orbital geometry.
In other words, it happens when our Earth and Jupiter -moving in their respective orbits around the sun – align just so. It’s like what happens when you in your fast car are passing a slower-moving car on the highway. The slow car can, for a time, appear to move backwards against the distant landscape. So, as seen from our faster-moving Earth, Jupiter at times appears to move backwards in front of the stars.
Generally, the best time to observe an outer planet like Jupiter is when the planet is retrograding. That’s because then it is roughly opposite the sun in Earth’s sky. This causes it to be brighter (think of it as full like the full moon), and be visible longer at night. Now that its retrograde motion has ended, Jupiter will seem to slip closer to the setting sun each evening. Although it will be visible for several more months, now is the best time to observe it.
are the views and most of all your caluations for the northern hemishphere if not were do i find for the southern
Benjamin, yes indeed most of the material here is for the Northern Hemisphere, although we do include information of value to Southern Hemisphere viewers as well. But if you need specific info for the Southern Hemisphere, I suggest that you contact my friend, Ian Mclean, the “Science Guru” at his website:
Ask the Science Guru
Ian is well knowledgeable about southern matters and especially Australia, and blogs about them from his home in Gove, NT.