Life on a ball – so different, so good – take a look tonight!

Well, wherever you are on this wonderful ball, if you have clear skies when the sun drops below the western horizon, you’ll get a great show tonight! Actually, even if your skies aren’t clear tonight, take a look any time this week and you’ll get a good show. I plan to be out tonight with camera, binoculars, a small modern telescope, and a 200-year-old spyglass, just to see what I can see. But no optical aid is needed – this show’s for everyone and free!

This is the view from Downunder as depicted in the Sydney paper - it will look different here.

This is the view from Downunder as depicted in the Sydney paper - it will look different here.

I’m talking about the arrangement of the crescent moon and the planets Venus and Jupiter. You don’t need any optical aid for this show, but you do need a clear horizon and exactly what you see and when you see it depends on where you stand on this ball we call the Earth. Dom, my friend in Sydney, Australia, will see an astronomical smiley face, as his local newspaper told him. For us here in Westport, MA. the emoticon will be grimmer, but the show will still be spectacular! My comments from this point on all relate to what we see from Westport, MA, but will apply generally for most of the US. But again, exact times and view will differ – both because the sky is dynamic and because we live on the surface of – well, just inside the surface of, but that’s another story – a ball. I’ll explain in a moment.

Dark blue is good and the Clear Sky Clock prediction for Westport tonight looks like we'll get a cloud-free window. I'm keeping my fingers crossed!

Dark blue is good and the Clear Sky Clock prediction for Westport tonight looks like we'll get a cloud-free window. I'm keeping my fingers crossed!

The point is, start looking for this show near your western horizon about 20 minutes after local sunset. The darker it gets, the brighter things get – but the actors also move lower in the sky – by a couple hours after sunset it will be pretty much over. The most dramatic views are at dusk and that’s the best time to take pictures. (If you get any and want to share, please email them to me – I’d love to use them here. gstone@umassd.edu)

All three charts that follow are made from Starry Nights software screen shots.

Here’s what can be seen from various locations.mvj_12108_westport

The view from Westport is to the southwest – azimuth 208° – and at 4:45 pm the grouping will be about 18 degree’s above the horizon – roughly two fists held at arm’s length. In Sydney, Australia – see below – the show will be higher and thus last longer. It will also be closer to due west – 261° and about 33 degrees above the horizon. Which means it will be in darker skies.
mvj_12108_sydney

The moon, a bit more than three days old, will be the brightest, shining at about magnitude -10.6. Brilliant Venus, in a gibbous phase, will be shining at -4.1, and much more distant – but far larger – Jupiter will be shining at -2. For comparison, the brightest star in that general region of the sky will be Vega, at magnitude 0. (Vega will be a bit north of west (281°) and about 54 degrees above the horizon – quite high. It will probably “come out” a bit after Jupiter.

If you use binoculars, try to find a way to hold them really steady. The old spyglass I plan to use is about the same power as binoculars and I’ll try to steady it against a telephone pole or tree. My target will be be Jupiter and it’s four Galilean Moons – the ones Galileo spotted 398 years ago. These are a challenge for binocular users. They will look like faint stars on either side of the planet and very close. My guess is with luck you’ll see three of the four – and they should be easier to see before it gets totally dark. Under a real dark sky the glare of the planet may make them more difficult to see.

Here’s how they would look in a small telescope – this image is right side up, however, and most astronomical telescopes will reverse the view. I post it here in this way because it shows the order of the moons as they would be seen in binoculars at this time. Also note how they are in a straight line pretty much in line with the planet’s equator. Do keep in mind that in binoculars the planet’s disc will barely be detectable and the moon will be dim and close. Also remember that these moons change position hour-by-hour, so this view is for 4:45 pm EST.

jupiter_moons12108

What if it’s cloudy? What will you see on other nights this week? Don’t despair – this is a great show for a couple of weeks and very instructive to watch the changing relationships. By tomorrow night the moon will have gotten brighter and much higher and each night it will get brighter and higher. But that’s the usual moon routine. More fun will be to watch the dance of Venus and Jupiter. Each night Venus will get higher, Jupiter lower. So a week from now Venus will have climbed a couple of degrees higher, while Jupiter will drop lower each night. So on December 8, 2008, the view from Westport at 4:45 pm will be this:

vj120808

What a dance! This is a great exercise for adults and children – observing and drawing – or photographing – the changing relationships. (Hope some teachers make this an assignmennt!)

Among other things it’s a great reminder that we’re all in motion. The Earth is spinning at about 800 miles an hour (Westport) and so each night, minute by minute, the planets get closer to our horizon. We’re also traveling at about 66,000 miles an hour in our orbit around our star and that changes our relationship to the two planets. But at the same time the planets are eaCH moving – Venus in a smaller orbit, Jupiter in a much larger one. They move at different speeds. So all the relationships are changing – and, of course, the moon is moving around the Earth.

You can check out these changing relationships by looking at the wonderful online Orrery here. Taking this view of things you will see how the reality of these motions around the Sun relate to the reality of what we see in our sky. (For pictures and more discussion on this aspect, see my earlier post here.) Then if you really want to put your brain in gear, try to figure out why the moon and planets appear so different from Australia!

Wow! Isn’t it a ball living on this ball?

(Well, in this ball. I really think we should dump that idea about living “on” the Earth. The Earth, quite thankfully, includes a thin, but protective shield called the atmosphere. It’s that atmosphere that we live in – we are like crabs crawling along the surface beneath a sea of gas. But without that atmosphere we wouldn’t be here – and if it weren’t so transparent – generally – we wouldn’t see any of this great show. So we’re really on a spaceship with a great life-support system and viewing port! )

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One Response

  1. […] Australia) a smiley face – a frowney face over us – but by all means a spectacular sky event. (See this earlier post, and this one, and this […]

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