Written by astronomer Ninian Boyle for All About Space
Jupiter is the largest planet in our Solar System and the easiest to observe. You can see it with the naked eye, binoculars or a small telescope. During this month, it has been very well placed for observing as it reached opposition in early January. This means that it is directly opposite the Sun in the sky from our point of view here on Earth and is therefore visible all night.
You can find Jupiter nestled among the stars of the constellation of Gemini the Twins, sporting a bright, yellowish tinge of magnitude -2.7. A view through binoculars will show a tiny disc with up to four points of light spaced out either side of it. These are the Galilean moons of Jupiter – Io, Ganymede, Europa and Callisto. You can watch them change position as they orbit around the giant planet almost on an hourly basis and you can certainly note the changes of position from night to night.
A small telescope will show you a lot more. Magnifications of 50x to 100x will show considerable detail, including some of the cloud belts and possibly the Great Red Spot. Earth’s atmospheric conditions will affect what and how much you can see, so be prepared to experiment with more, or even less, magnification. The use of coloured glass filters can help improve your view of the planet too. They boost the contrast and can allow you to see more detail on the planet surface. A light yellow filter can work well as can an orange or even a red one. It’s worth experimenting here too. See if you can see the slightly squashed appearance of the disc – this is caused by the fact that Jupiter is rotating so fast on its axis, in around 10 hours, that it is flattened at its poles.
The moons pass in front of and go behind Jupiter, events respectively known as transits and occultations, which can produce fascinating viewing. Transits are the most interesting of all as you may be able to see the shadows of the moons on the disc of the planet itself as they cross Jupiter’s face. These are known as shadow transits.
Enjoy this great opportunity to see the king of the Solar System!
Image courtesy of NASA/Damian Peach, Amateur Astronomer