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  5. The Giant Planets

The Giant Planets

Introduction

This lab will acquaint you with the gas giants - Jupiter and Saturn.

The main goals of this lab are to give you a sense of the scale of these monsters, by analyzing real images and using the small angle formula to determine their true size.

Part 1:  The Rings of Saturn

For this part, you need to review the material listed here:

"Everything you need to know about Saturn's Rings"

You will do the same thing you did in the Mass of Jupiter lab - measuring the pixels that Saturn's rings are across, and calculate the size using the small angle formula.

The following image of Saturn was taken:

Saturn 1: DATE-OBS= '2012-04-03 T08:22:00.456' / UTC

 

Now recall that Saturn looks small because it is far away.  It has a small angular size because its distance from us is so great.

If we want to determine how large Saturn is, we can use the small angle formula, along with the distance to saturn (D), to determine its actual size (a).

Saturn.png

Use Wolframalpha.com to query: "distance to saturn on April 3, 2012".  

This is D.

Now, measure the number of pixels across saturn is.  You might think this is 'a', but this is actually the anglular size of Saturn, 'ø'.

For this particular telescope, each pixel represents 0.73 arcseconds.

So take your pixels, and multiply it by 0.73 arcseconds.

Now you have ø in arcseconds.

But we need it in radians.

There are 206,265 arcseconds in every radian, so take your arcseconds and divide it by 206,265 arcseconds per radian.

Example: Let's say you measured 105 pixels.  You need it in radians:

(105) x (0.73) / (206,265) = 0.0003716 radians

Ok follow that example with your own pixels.

So now that you have an angle ø measured in radians, the small angle formula says:

ø = a / D

So we can rearrange to get 'a':

a = ø x D

If your distance 'D' is in AU, then 'a' will be in AU, too.  You can use google or wolframalpha to convert AU into km.

Now you will repeat this but instead of measuring the total width from one side of Saturn's rings to the next, just measure the width of the ring system.  (For example, measure from the inner right rings to the outer right rings.). Recall that the rings that you see in the image are the combined A and B rings - they look like one ring system in this image.

Part 2:  Jupiter and its Great Red Spot

For this part, you need to review the material listed here:

Jupiter's Great Red Spot Up Close

The following image of Jupiter was taken on DATE-OBS= '2013-03-26T03:41:20.858' / UTC