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Astronomy 101

The Planets

Hi again!

This lab is meant to give you a good feel for the nature of the Planets in our Solar System. 
The Solar System is the system of planets and other objects dominated by the gravity of our sun.  The sun’s proper name is “Sol”.. hence the “Solar System”.

Follow the directions below.  Either type your answers into something like Microsoft Word, or type them directly into the text Box in Canvas after clicking "Submit Assignment".  

Part 1) The Size of the Planets

Go to this website: http://callumprentice.github.io/apps/celestial_bodies/index.html#  (NOTE:  If the site does not seem to work, try reloading, waiting longer for it to load, or using a different web browser.  If that does not work, you can accomplish the same thing at this site (although it's not as visually fun:  

http://sciencenetlinks.com/interactives/messenger/psc/PlanetSize.html  -- Select the two planets and click "compare")

 When the website loads it should look something like this:


This website exists to show the relative sizes of the Sun, the other planets, some major moons, Pluto and another nearby star/planet system called "Trappist 1".  Along the bottom, icons of the Sun, the eight planets in order from the Sun from left to right, and Pluto and Trappiast 1. 

QUESTION 1)  List the eight planets in the correct order from the Sun.

Experiment by clicking on the Pluto icon -- the one all the way to the right along the bottom.  You will see Pluto's size correctly displayed next to the large earth like this:


If you drag the mouse from left-to-right it will rotate the images like this:



Also notice that the actual radii of both Pluto and the Earth are displayed along the top.

By clicking on the earth icons along the bottom, you can turn on and off as many of the planets and moons as you wish.  You can also hover over the "?" and click on the "X" to reset the display.  

Example:  Pluto:  A) Pluto is very small with a diameter only about 1/5th the earth. B) it is brown and grey. C) It seems to have large light and dark areas and I think I see some craters.

QUESTION 2) Do this same comparison between the Earth and the Sun  (NOTE: The Sun is so big compared to the earth that you might not even be able to see the earth next to the Sun's image. Drag the mouse from left-to-right on the Sun and you should see the earth superimposed in front of the Sun  and see it's relative size.)
QUESTION 3) Do this same comparison between the Earth and Venus
QUESTION 4) Do this same comparison between the Earth and the Earth's Moon
QUESTION 5) Do this same comparison between the Earth and the Mars
QUESTION 6) Do this same comparison between the Earth and the Jupiter
QUESTION 7) List the eight planets and Pluto in correct order of size, from smallest to largest.  (You do NOT have to include the Sun, or any moons or Trappist 1.)

QUESTION 8) Three planets are smaller than the Earth.  The Earth and these three smaller planets are the "terrestrial" or Rocky Planets.  List these three other terrestrial planets (Do NOT include Pluto which is no longer considered a planet by astronomers.)

QUESTION 9) Four of the Planets are quite a bit larger than the earth.  These are the "jovian" or Gas Giant Planets.  List these four planets.

Part 2) Your weight on Different planets

Your weight on the surface of a planet depends on the pull of gravity on the surface of that planet.  That force of Gravity depends on two things… 1) the mass of the planet (the GREATER the mass the GREATER the pull of gravity) and 2) the size (radius) of the planet (The GREATER the radius the LESS the pull of gravity).

Go to this website:  http://www.exploratorium.edu/ronh/weight/index.html

You should see this:

18) No, Cassiopeia A does not emit visible light.



QUESTION 10) Of the seven other Planets, the Moon, and Pluto, on which object would your weight be the LEAST?
QUESTION 11) Of the seven other Planets, the Moon, and Pluto, on which object would your weight be the MOST?
QUESTION 12) What do you think would happen to you if you could be on the surface of a neutron star?  Explain.

Part 3) Planet Density

Density can be thought of as "How heavy is something for its size?"  Something that is very heavy but has small size, is DENSE.  

There is an old riddle, "Which is heavier, a pound of feathers or a pound of iron?"  The answer, of course, is that they both weigh the same... one pound.  You might be tempted to say iron, but iron is more DENSE than feathers.  A pound of iron is very small compared to a big one-pound pile of feathers.

The planets have a variety of densities.  The most dense planet is actually the Earth!  



These colored cubes are cubic centimeters.  On average, a cubic centimeter of the earth weighs 5.5 grams -- a little more than a nickel.    Water has a density of exactly 1.  Anything with a density less than 1 would float in water.



The Density of some common items

QUESTION 13) In the above table, what substances would float in water?


QUESTION 14) What is the one planet that would actually float?

QUESTION 15) The planet you found in answering question #14... A) Is it more or less massive than the Earth?   B) Explain in your own words how something MORE massive than the earth could be LESS dense.

Part 4) Synodic and Sidereal periods of the Planets

Watch the video introduction to the website "Solar System Scope" HERE

NOTE: The website has been improved with more slick features since the above demo video was made, but it still functions essentially the same.

Go to "Solar System Scope" by clicking HERE

NOTE: The "Solar System Scope" app is also available with free versions for both Android and IOS.  In those versions you cannot drag the planets around to move through time, but you can still do so using the controls that become available after touching the date along the bottom.

NOTE 1: If the Solar system scope does not run properly at the above link, try another browser (Chrome or Firefox or...)
NOTE 2: If no browser works, try going to the Public Broadcasting Service site HERE and click on "Launch Interactive" found part-way down the page.  If it runs, make the simulation full-screen by hitting the space bar.
NOTE 3: If none of the above steps work on your computer, use an alternate site that works almost the same way found HERE.


Play with the website, and do the things you saw demonstrated in the video.

As a planet orbits the Sun, there are two important periods of time for that planet, 1) The time it takes to orbit the sun ("Sidereal" period) and 2) the time it takes to line back up with the Earth ("Synodic" period).  Most students don't automatically understand why the "Synodic Period" is important, but remember, we are observing the planets in our sky from the Earth which is also a moving planet.  The synodic period is how long it will be for a given planet to repeat its behavior (rise times, set times, visible in the morning or the evening) as we see it from the Earth.

Watch this instructional video to show you how to find the synodic and sidereal periods of the planets HERE

A website that calculates the duration between two dates can be found HERE

Use the method shown in the video to answer these questions NOTE: In questions 16-19 you MUST include the dates you used or you will receive NO CREDIT:

QUESTION 16) What is the sidereal period of Mars, and what are the two dates you used to find it?
QUESTION 17) What is the synodic period of Mars, and what are the two dates you used to find it?
QUESTION 18) What is the sidereal period of Venus, and what are the two dates you used to find it?
QUESTION 19) What is the synodic period of Venus, and what are the two dates you used to find it?

QUESTION 20) What feature of Solar System Scope or the other sites did you find most interesting?  

That's it!  Either upload your WORD document or copy your answers into the canvas Submission box.