Thursday, November 29, 2012

Jupiter Opposition - 3 Dec 2012

Jupiter Opposition will be happening on next Monday 3 December 2012 at 9:21am Singapore time. This event will be visible in most countries after their local sunset till next sunrise.

Planet: Jupiter
Date: 3 December 2012, Monday
Time: 9:21 am
Visible Duration: Sunset till Sunrise
Apparent Size: 48 arcseconds
Distance from Earth: 608,696,510 km (4.068884851 AU)
Brightness: -2.8 apparent magnitude (smaller value is brighter)

Jupiter Opposition occurs when Sun, Earth and Jupiter forms a straight line with Earth in the middle of this formation. These are the implications:

(1) Jupiter and its moons will be nearest to Earth within a particular year.
(2) Jupiter and its moons will be most brightly lit by the Sun.
(3) When the Sun sets, Jupiter rises from the horizon and stay visible for the whole night till next sunrise.
(4) This is the best time to observe, photography and study Jupiter from Earth.
(5) Using the same astronomical instrument (e.g telescope), one will see and capture more details of Jupiter on this day compared to other days.

For 2012, Jupiter Opposition occurs on 3 Dec. The exact timing of 9:21am is not really that important. This is because Jupiter does NOT suddenly grow larger or shrink in apparent size immediately before and after this opposition timing. The growing and shrinking of its apparent size is a GRADUAL process over many days and weeks.

So you can start observing and photographing Jupiter from now till the next couple of weeks whenever the skies are clear and Jupiter is high in the sky. No need to wait for specific magical timing in early December.

The apparent size of planet can be measured in arcseconds. 1 degree is equivalent to 3600 arcseconds. Jupiter at opposition in Dec 2012 is about 48 arcseconds. When it is very far away from Earth, its apparent size will be smaller. It will also look dimmer from Earth as a result of the increased distance.

This is a scaled illustration of Jupiter's apparent size and distance from Earth at two different dates:

One arcsecond is extremely small and very difficult to detect visually even through a telescope. The apparent size of Jupiter (and all other planets) changes very slowly arcsecond by arcsecond over days. So again, there is really no need to panic if you cannot observe or photography it on 3 Dec 2012. Try again for the next few nights whenever the skies are clear.

Here are few ways to identify Jupiter in the sky:

(1) During the opposition period, other than Venus rising from the East shortly before sunrise, Jupiter is the brightest star-like object in the night sky.

(2) Like all other planets, it does not blink in the sky.

(3) Jupiter is near the bright star Aldebaran which is a red star. Use your hands to shield the stray lights around your eyes and stare at Aldebaran for a few seconds to see its redness clearer.

Face East-North-East at about 8pm in early December 2012
(4) Make use of your planetarium/stargazing app in your phone to find Jupiter. E.g. The free Sky Map for Android phones and Planets for iPhone/iPad.

(5) Install and learn to use the free desktop planetarium software Stellarium (

(6) Trial and error. Using a binocular or telescope pointing at what you think may be Jupiter and observe what you see. Try to focus your binocular or telescope at the object. It should look a small disc of light instead of a pinpoint source of light.

How to observe Jupiter?

You can observe Jupiter with a pair of binocular. Make sure you have adjusted the left and right focus properly for your eyes as well as the pulling the binocular further in or out to match the distance between your eyes before stargazing.

You should see a small white/creamy disc of light which is Jupiter and tiny pinpoints of light which are Jupiter's 4 brighter moons (out of 60+ moons). Whenever one or more of these moons go in front or behind Jupiter, you will see less than 4.

Using a telescope, you can observe the cloud bands on Jupiter. At certain times, you may see the massive storm known as the Great Red Spot (GRS) on Jupiter. You may also see the moons of Jupiter casting their small round shadow on Jupiter. These shadow can drift across Jupiter over a couple of hours!

Here are some useful links to find out when GRS and shadow transits will be visible in the sky:

(1) Sky & Telescope Jupiter's Moons (free online software)
(2) Sky & Telescope Great Red Spot Transit Times (free online software)
(3) Jupiter version 2.0 by Sylvain Rondi (free desktop software)
(4) Galilean for Android Phones (paid app SGD$5.33)
(5) Jupiter Guide and QuickSky for iPhone/iPad (free apps)

Do take note these Jupiter imagery you see here and in most astronomy magazines and books are usually images made from long-exposure astrophotography through telescopes and post-processed in specialised software. The actual live view through an amateur-size telescope will NOT be so detail, colourful and sharp.

BUT, having said that, the sensation and experience of seeing Jupiter LIVE with your own eyes is something that no astrophoto or video can replace! Just imagine how you will feel seeing something that is "alive" and hundreds of million kilometres away!

So, if you do not have access to a telescope, try to join free public stargazing events organised by SINGASTRO members, Friday observation sessions at Singapore Science Centre Observatory and Woodlands Galaxy Community Club.

I will be conducting another free public stargazing talk at Toa Payoh Public Library on 8 Dec 2012 (Saturday) - only 5 days after the opposition. Weather permitting, after the talk, my friends and I may be conducting a free public stargazing session outside the library and you can be sure Jupiter will be in our big telescopic sights! As usual, if I conduct any impromptu free public stargazing sessions, I will announce them in my Twitter which you can also read from the main home page of this blog even if you are not on Twitter.

Wishing everyone clear skies, good luck and have a great time identifying and observing this wonderful planet during the festive year-end season! Do spend time educating your family and friends that the bright "star" or "satellite" in the sky is actually a planet that can fit in 1000 Earths! And the Jupiter that we can see is how it looked like 30+ minutes ago!

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