See Jupiter and Venus in the twilight and solve a puzzle

Our southwestern sky is providing a nice pair of planets to enjoy with the naked eye about an hour after sunset. The higher – and dimmer – of the two is giant Jupiter shining at -1.9 magnitude. The bright one – magnitude -4 – is Venus. My friend Hank Walter was at Horseneck Beach in Westport, MA last night and got this beautiful shot of the two at dusk with one of the new Horseneck beach houses in the foreground.

hw_venus_j1

You can just enjoy the aesthetic beauty of these two planets, or you can get a closer look at either with a small telescope. (Jupiter will easily show it’s four Galilean moons and Venus a rather gibbous disc, though with Venus you should start looking about half hour after the Sun goes below the horizon so the sky behind Venus is not entirely dark – otherwise the brilliance of the planet makes it hard to detect its shape.) I should add, that this view is good for mid-northern latitudes, such as mine (roughly 42 degrees N) . At other latitudes the relative position of the planets changes.

If you know something about the planets one thing might puzzle you – why are they so close together in the same section of the sky? Afterall, Venus is between us and the Sun and Jupiter is much more distant – we’re between it and the Sun. So why are the two seen together here?

What I really like to do when I see a pair of planets like this is picture in my mind what is really going on. The first thing to notice – and this is part of the answer to the preceding question – is if you drew a line through the two it would point very close to where the Sun has only recently vanished beneath the western horizon. That line represents the plane of our solar system – the same plane we and the other planets are on. I tend to see it as a flat disc – a record, or when hungry, a pizza 😉 It’s just easiest to visualize when you have at least two planets in view at the same time. But it is because all of the planets are roughly on this same plane that they all appear in the same general area of our sky marked by the ecliptic – the patht he Sun follows in our sky.

Getting that straight in your head, you now can put yourself in a spaceship high above the solar system and looking down and if you haven’t figured it out yet, you’ll get the answer to the question asked earlier. That’s what the online orrery (Solar System Live) does for you here. The picture it provides – with an arrow I’ve added – is this:

venus_jupiter1108

Now I will grant you, you don’t get the proportions correct this way – but you do see the relationships. So the answer to the question is simple. Although the orbit of Venus is between us and the Sun, the planet right now is emerging from the other side of the Sun – the side away from us – and this puts it in our line of sight with much more distant Jupiter.

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2 Responses

  1. […] moon is just fun to see – and pretty. To understand how the planets end up aligned this way, take a look at this earlier post. The moon gets added to the mix because right ont his night it’s lined up between us and the […]

  2. […] Posts See Jupiter and Venus in the twilight and solve a puzzleThe most terrifying video you’ll ever seeStupid, vicious and did I say stupid […]

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