What will you be doing on September 9th, 2040 at 7:00 PM?

I will have just enjoyed a beautiful sunset with Malvika and will be looking up at the Western sky with a telescope, admiring a relatively rare celestial show. At around this time, I will be able to see a lovely crescent moon and 5 planets in close proximity in the sky (Mercury, Venus, Mars, Jupiter and Saturn).

Click on the picture to see a larger resolution version and to be able to read the labels.




I learnt about the solar system in school like everyone else, but I never "really" got a feel for it. I never connected that knowledge to what I would see when I would look up at the night sky. I vaguely remember visitng a planetarium (Nehru Planetarium in Mumbai), but do not remember any astronomical insights I gained from the visit. My wife, Malvika, is an astronomy enthusiast. She volunteers during the summer programs at the Lick Observatory. Thanks to her, I have seen Jupiter and other sky objects through a couple of large telescopes. (a 36-inch refractor and a 40-inch reflector) That experience definitely awed me, but more for the awesomeness of the telescopes than that of the sky.
Until recently, I have never been able to look up at the sky and "feel" my place in the solar system and the galaxy.

What finally gave me that feel is this interactive sky chart at Sky and Telescope. The chart allows you to see the sky as it looks from any place on earth at any given time. That alone would not have done much for me. What was cool is that I figured out a way to quickly change the time and see a kind of a time-lapse. See notes at the end of the article about how to do this. The most meaningful time-lapse I was able to see was the state of the sky at the same time every night. i.e. Imagine making a movie with each frame being the state of the sky at the same time every night and then extending this over multiple years. The resulting movie gave me more insight into the sky and the planets than anything I have encountered so far. Here is a youtube upload of the screen capture. It does not do justice in terms of resolution or frame rate, so you should definitely try this out for yourself.



Insights I gained:

• If you look at the sky each day at the same time, the view shifts ever so slowly. This is a direct result of the earth moving around the sun and thus pointing to a slightly different direction in relation to the sun every day. It completes this cycle once every year. Hence, based on which constellation you are seeing at a particular point in the sky at a particular time, you could tell with precision which day of the year it is.
• I had always heard that the planets move through the constellations. Think about it and it is obvious that as the planets move around the sun, they will appear to move in the cosmic backdrop of stars. However, I never had a feel for exactly how that "looked" in the sky. You see Jupiter and Saturn move more slowly against this backdrop than Mars, Venus and Mercury. (hinting at their relative distances and orbit times).
• You could deduce that Mercury and Venus were in an inner orbit because of the fact that they never cross the sky from east to west in this time lapse like Mars, Jupiter and Saturn do.
• Jupiter and Saturn seem to come really close to each other from earth's perspective every 20 years. The next time this will happen for us is in 2020. Being able to see all 5 planets at the same time in relative close proximity in the sky is pretty rare and the moment in 2040 that is the title of this post is very rare indeed.

and finally...

• The plane of the planetary orbits is not the same plane as the galaxy. You can see this in the movie by seeing the planets cut across the milky way. Had these planes been more aligned, we would have seen the planets move "through" the milky way. For some reason, my internal mental image had always aligned these planes.

This chart turned out to be an awesome tool to let me really "feel" my position in the solar system and the galaxy. I wish this was available to me when I was first learning about the solar system.

How to create this timelapse using the interactive chart:
There are small controls on the left side which allow you to change any component of the time (i.e. year, month, date, hours, minutes, seconds, etc.). There is a "+" and a "-" button which increments any of those selected components. If you press the "+" button and just move your mouse around, the value keeps incrementing.