Name___________________

Astronomy 102 Lab 1

Purpose: Today we will gain a better understanding of the relative sizes of the planets in our solar system, their distances from the sun and planetary characteristics as viewed from close flyby missions. We will also gain a better appreciation of the enormous distances to objects in our galaxy and beyond.

Activity: Let's begin with the relative sizes and distances from the sun of the nine planets in our solar system. Below is a table with the average distance from the sun in AU and the equatorial diameter measured in earth diameters for each of the planets.

Planet	Mercury	Venus	Earth	Mars	Jupiter	Saturn	Uranus	Neptune	Pluto
Distance	0.34	0.72	1.00	1.52	5.20	9.57	19.2	30.0	39.5
Size	0.38	0.95	1.00	0.53	11.2	9.50	4.00	3.88	0.18

(My daughter taught me a mnemonic for remembering the planetary order and it goes like this: My Very Energetic Mother Just Served Us Nine Pizzas. The first letter in each word corresponds to the planets listed in the table.)

On the graph paper I have provided for you is an axis showing distance from the sun in AU. I have placed Neptune at 30 AU on the graph and would like you to place the other planets on the graph in a similar fashion. Like I did with Neptune, place the name of the planet and distance in parenthesis at the appropriate locations on the axis. You will need to use arrows to indicate the locations of the innermost planets on the axis. Below the distance axis you will find the earth drawn using the scale of one earth diameter equals one square. Draw the rest on the planets in this space using their diameters given in the table above. Give yourself some space around each planet. They don't have to be in order of distance from the sun but they should have the proper relative sizes. Here is another view of the relative distances between planets and their relative sizes. Note how big (approximately 100 earth diameters) the sun is compared to all the planets.

Now that we know the distances between the planets and their relative sizes let’s take a close up look at each planet starting with the innermost planet, Mercury. What do you think is the most striking feature of Mercury’s surface?______________________________________________

Moving on to Venus we see a cloud covered planet. The droplets making up these clouds, sulfuric acid (the stuff found in car batteries), is very unpleasant for humans. If we could strip away this heat retaining, dense atmosphere, we would see Venus's surface. Do you see what looks like a volcano in the middle of the picture towards the right?___________. Continuing our journey past the Earth, what feature of the Earth’s surface makes our planet seem so inviting?______________

Now on to Mars and the objects in the left most part of the picture are indeed volcanoes that are taller than Mount Everest! If we travel out past Mars and the asteroid belt, which contains thousands of asteroids that look just like the two moons of Mars, we eventually make it to Jupiter. Jupiter is mostly composed of the lightweight elements, helium and hydrogen and is consequently not solid. The bands and red spot are weather features on the planet caused primarily by it’s fast rotation rate. As evidence that the surface is not solid take a look at a piece of comet crashing into the surface gas. The next Jovian planet we encounter in our journey away from the sun is Saturn. Like the Earth, Saturn also has aurora displays. Beyond Saturn is Uranus and Neptune. If the Sun, Earth and Neptune are perfectly aligned with the Earth on one side of the Sun and Neptune on the other how far away would Neptune be from the Earth measured in AU and km (Draw a picture and show your work expressing your answer in both powers of ten notation and as a large number)?

And of course, last but not least is Pluto. But we cannot flyby Pluto because the distant planet has yet to be visited by one of our space probes. We will have to be content with a Hubble Space Telescope picture of the tiny outer planet and it's moon, sometimes referred to as a double planet.

Now let’s continue our journey to one of the closest stars to our solar system, Alpha Centauri A, a star that is essentially identical to our sun (actually this is a picture of our sun but we expect a detailed picture of Alpha Centauri A to be similar), at a distance of 1.3 pc. How far away is this star using astronomical units (AU’s) as a measure of distance?_______________________. Moving out to even greater distances (460 pc) we find the Orion Nebula, a birthing place for many new stars. We will look at the Orion Nebula with a telescope at some point during the quarter, it is the middle star in the sword of the constellation, Orion. In the upper right hand corner of this picture of the Orion constellation is the head (the V) of Taurus the bull. In the constellation, Taurus, we find the famous Crab Nebula, (at a distance of 2,000 pc or 2 kpc) home of the crab pulsar and a supernova (stellar) explosion that occurred about 1,000 years ago. If we could journey out of our galaxy and look back we would see something that looked like this or this, depending on how we left our galaxy. Recall from class that the galactic center at a distance of 8 kpc contains a black hole with a mass of about 3 million suns. As we journey out of our galaxy we would encounter the Large Magellanic Cloud (distance 50 kpc), Small Magellanic Cloud (distance 63 kpc), and Andromeda (distance 750 kpc), all of which are galaxies visible with the naked eye (assuming you are in the appropriate hemisphere of the Earth). Moving out beyond our local group of galaxies, of which Andromeda, the Large Magellanic Cloud, and the Small Magellanic Cloud are a part of, we encounter the Whirlpool Galaxy (distance 8,500 kpc or 8.5 Mpc). At even greater distances (200 Mpc) we discover a cluster of galaxies called the Hercules Cluster because it resides far beyond the direction of the Hercules constellation (stars in our Milky Way Galaxy). We complete our ever so brief excursion into but a tiny portion our Universe with a look at the quasar 3C 48 at a distance of 1,300 Mpc. Express the distance to 3C 48 using the distance unit of light years._____________________________________________ How long does it take light to travel from 3C 48 to the earth?______________. When we look at this distant object we are seeing it as it was how many years ago?__________________ How far away is 3C 48 in AU’s? Express your answer in powers of ten notation and as a very big number.

The Universe is a very big place!

On the second piece of graph paper I have provided for you, I have already placed the distance from the Earth to our galactic center. Starting with Alpha Centauri and continuing through the quasar 3C 48, place the rest of the objects you have just seen on this graph. You will need to use arrows to indicate the distance location of objects to avoid crowding. Place the distance in parenthesis as I have done for the galactic center. Notice that the distance scale is in powers of ten and unfortunately hides the enormous distances we have been discussing.