Lloyd's Astronomy Tutorial

The colors in the lightning image are the result of a mistake of mine in processing. I wish all my mistakes came out so colorful. Download it if you want.

You may find that some of the Power Point files listed here are not available. This is because there was not enough disk space for all of them. You will find the files that my students need here, when they need them. Other files will only be here when I have adequate space.

In order to use the Power Point files you will need Power Point. If you don't already have the program you can download the Power Point viewer, which is public domain. I suspect you will also need the driver. The program and driver were meant for Windows 3.1. I suspect they will work with Windows 95 too. I can't give guarantees any better than Microsoft, which is to say, "Let the user beware."

Download a portion of the study guide in Word 2000, approximately 1 megabyte.

PowerPoint Presentations

Download a Power Point viewer from Microsoft.

Skip to Solar.

Go directly to the comet image.

Skip to galaxies, clusters and nebulea.

Why is the sky blue?

To review solar system images I recommend you browse The Nine Planets, a tutorial with images.

There is no dark side of the moon, but there is a far side of the moon. One side of the moon faces Earth at all times. The other side faces away at all times. Some of the side facing us is in sunlight, and appears bright. The rest appears dark because it is in the shadow. Similarly, you can stand with your back to a bright light and your face will be in the shadow of your head.
 

These two photos are both gibbous moons. Notice the shadow. In both images the edge of the shadow, called the terminator, curves around some point on the visible moon. Also notice that the terrain near the terminator shows detailed shadowing.

Earth has a shadow that stretches out into space. That shadow can only be seen when it touches something. When the geometry is right the full moon passes through Earth's shadow. First, it enters through a gray, fuzzy region called the penumbra. Then it penetrates the penumbra and reaches the umbra. This is when a lunar eclipse is most visible. Then it passes through to the other side and exits through the penumbra.

The two photos on the left are both lunar eclipses. The shadow on the moon is Earth's umbra. Notice that in the far left image the center of the umbra's curve is beyond the moon, unlike the curve of the terminator on a gibbous moon. The image on the near left can even be distinguished from a crescent moon. Note that the edge of the earth's umbra does not show detail, as the terminator does on the gibbous moon and also on the crescent moon on the right.

 

These two pictures compare the full moon to a total eclipse of the moon. Notice that the moon is reddish in a total eclipse. This is because Earth's umbra is not totally dark. It is filled with a dim red light. In this lunar eclipse you can see a pale yellow region at the bottom. This shows that Earth's umbra is a pale yellow ring, filled with a dim red light.

Solar

These two photos show the deepest layer of the sun visible, the photosphere. It looks mostly featureless, except sunspots. Sunspots can be seen in other layers, but they are best seen in the photosphere. SFO25.JPG is one photo of a series. The rest of the series is on my images page.

Also visible in the photosphere is granulation. Granulation can only be seen with high magnification and high resolution. It is a fine structure in the photosphere, much smaller than sunspots.

The chromosphere completely surrounds the photosphere. Various layers can be seen using filters. These photos show the chromosphere through H-alpha filters. You can see sunpots, but you can also see the long filaments. Notice the structure which resembles iron filings standing up on a magnet.

The corona completely surrounds the chromosphere. This layer is always present, but cannot usually be seen because the daytime sky is brighter. How often do we have a clear dark sky while the sun is up? Only when there is a total eclipse of the sun.

This source explains radiocarbon dating, but it doesn't explain the solar connection.

Gas and Dust Tails of a Comet

This photo shows the difference between a gas tail and a dust tail.. Both tails start at the comet head, then run left and up. In this photo the dust tail is above the gas tail. Notice that the dust tail fans out, curves up and thins in visibility.

Galaxies, Clusters and Nebulea

	These first two galaxies are both spirals. Notice how there are several arms spiraling out from the center. This is the basic appearance of all spiral galaxies, when seen from above.
	These two galaxies are also spirals. When seen edge on, they resemble a disk, dark along the center line. The darkness along the center line is because of dust in the disks of spiral galaxies, which blocks our view of many stars within.

 
This galaxy, the Andromeda Galaxy, is also a spiral, though it appears different. The Andromeda Galaxy looks unlike the previous four because it is not seen from a top view, nor an edge on view.

We have no control over our view of galaxies. We see them as they are presented to us.

These are two images of the Milky Way Galaxy, also a spiral. This time we are inside looking out. Compare the right image to the two edge on spirals and notice how it resembles a close up of an edge on spiral. The image on the far right is a panoramic view of the Milky Way. It is the entire galaxy, which is wrapped around our entire sky.

 

The most conspicuous galaxy in this image is elliptical. Notice that it is featureless, compared to spirals. Elliptical galaxies are brightest at the center. They show no spiral arm structure and no dust lane. You see no individual stars in this image. The large bright spots are galaxies, many of them spirals. The smaller dots, which appear to be stars, are globular clusters of stars, which surround the nuclei of galaxies.

 

These are nearby globular clusters. Many of my students confuse globular clusters with elliptical galaxies. There are similarities. They are both brightest in the center. But, look closely at the globular clusters. Notice how you can see individual stars, but near the center they are crowded together so closely that you cannot see the spaces between the stars.

 

	These are regions of star formation. They are mixtures of gas and dust. Notice the cloud-like structures. There are regions of glowing gas and there are regions with enough dust to block our view of gas.

 

These are planetary nebulae. Notice that they are both nearly round clouds with a star at the very center. That star will soon be a white dwarf. The other stars are either in the background or foreground.

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This page updated by Lloyd Johnson February 10, 2009