Measuring the Starspages 813-820

Groups of stars – the big ideas1. Social significance of constellations2. Why stars move3. Star clusters4. Binary systems, and multiple systems

Social significance of constellations1. Constellations do not look like animals. The ancient peoples used to pick out a piece of the sky, and dedicate it to a deity, concept or person. If you connect the dots, you do not get a picture.2. The twelve houses of the zodiac correspond to the constellation that is just starting to become apparent, over the horizon, when the sun disappears, and darkness closes on the Earth.3. The age, like the age of Aquarius is the house that the axis of the Earth is pointing to for about the next 2,000 years. The Earth has a wobble, and the axis will only point at Polaris for a few hundred years, then, another star will be north. The ancient Egyptians could not have used Polaris as a compass.

Why stars move1. Stars move rapidly across the sky, each night, because of the rotation of the Earth on its axis.2. Each star, at exactly 7:00 p.m., will be a bit farther west, because of the revolution of the Earth around the Sun.

Why stars move1. Stars move rapidly across the sky, each night, because of the rotation of the Earth on its axis.2. Each star, at exactly 7:00 p.m., will be a bit farther west, because of the revolution of the Earth around the Sun.3. Some stars are visible in the summer, and others in the winter, because they are on the ether side of the sun.4. If a star is visible year round, it must be very far north or south, and it would be called circumpolar, because it circled the pole.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Northern Star

QuickTime™ and aTIFF (Uncompressed) decompressor

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QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Star clusters1. Most of the stars in the sky are not just single stars.a. The point of light might be a binary, multiple or even a galaxy.b. The stars are too far away for out eyes to make out the separation.

What stars look like, the big ideas.ParallaxMagnitudeLight emitted by starsH-R diagram

Parallax1. This is the apparent shift in position of something, because of the movement of the observer. You can see this by putting your thumb up in front of your face, and closing one eye and then the other.2. For finding the distance to stars, the change in position of the observer is the movement of the Earth around the Sun.

Because of parallax, it seems that the star moved, when compared to far away stars, but it did not actually do so. The smaller the parallax, the farther away the star is.

Magnitude ~ This is how bright something appears.1. Apparent magnitude ~ this is how bright something appears from Earth.2. Absolute magnitude ~ this is how bright something actually is, from 32.6 light years away, or 10 parsecs. A parsec is a parallax of 1second of arc, or 1/3,600th of a degree.3. Luminosity ~ is the basis of magnitudes. Luminosity is the energy output from the surface of the body.

The light shown by stars are based upon what they are made of, and if the star is moving.

1. Lines of absorption show what elements are in a star, because of dark patches on the rainbow.2. Lines of emission show what elements are in a star, because of bright patches.

The light shown by stars are based upon what they are made of, and if the star is moving.

1. Lines of absorption show what elements are in a star, because of dark patches on the rainbow.2. Lines of emission show what elements are in a star, because of bright patches.3. If a star is moving away, light is stretched out the Doppler effect, and it will appear redder.4. If a star is moving towards an observer, the Doppler effect compresses light, and it will appear bluer.

H-R Diagram1. The H-R diagram shows a relationship between the absolute

magnitude of a star and the temperature of a star, and the size of a star.2. Stars move around on the H-R diagram. Ours is a main sequence star

(most are), but not all.

This would be a good time to go to my web page, and look at Universe Comparisons