Measuring the Stars pages

Groups of stars – the big ideas 1.Social significance of constellations 2.Why stars move 3.Star clusters 4.Binary systems, and multiple systems

Social significance of constellations 1.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 behind the Sun on the day you were born. 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 move 1.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 move 1.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.

Northern Star

Star clusters 1. 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. Parallax Magnitude Light emitted by stars H-R diagram Parallax 1.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 1/3,600 th 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.

The Doppler effect is when the wavelength or speed of an energy source is apparently changing, based upon the changing location of source or the observer. 45 mph Sound of engine will seem lower Sound of engine will seem higher

Show Doppler effect animation here

Airplane is flying at 400 m/s, and bullet shoots ahead at 400 m/s. What is the speed and direction of the bullet relative to the airplane?

400 meters per second straight ahead

Airplane is flying at 400 m/s, and bullet shoots ahead at 400 m/s. What is the speed and direction of the bullet relative to the ground?

800 meters per second horizontally

Both airplanes are flying at 400 m/s, and the lead airplane shoots straight back, with a bullet that has a speed of 400 m/s. What is the speed and direction of the bullet relative to the first airplane?

400 meters per second straight backwards

Both airplanes are flying at 400 m/s, and the lead airplane shoots straight back, with a bullet that has a speed of 400 m/s. What is the speed and direction of the bullet relative to the following airplane?

400 meters per second, straight at him!!!!!!!!

Both airplanes are flying at 400 m/s, and the lead airplane shoots straight back, with a bullet that has a speed of 400 m/s. What is the speed and direction of the bullet relative to the ground?

It will fall straight down.

Actually, I made all these cases a bit more simplistic, because gravity will have an effect in all of these cases. It will make all of these bullets accelerate towards the Earth with a change in velocity of 9.8 meters per second per second.

Both airplanes are flying at 400 m/s. Will the sound of plane "a" be higher, lower, or the same as plane "b", to the pilot of plane "b"? ab

ab It would be the same, because the relative speed between the two is zero meters per second. There is no Doppler effect.

Both airplanes are flying at 400 m/s. Will the sound of plane "a" be higher, lower, or the same as plane "b", to the person on the ground? ab

ab

ab Plane “a” would be higher, because it is “pushing” the sound ahead of it ~ because of its higher relative speed than plane “b”

Both airplanes are flying at 400 m/s. Will the sound of plane "a" be higher, lower, or the same as plane "b", to the person on the ground? ab Plane “b” would be lower to Albert, because it is stretching out the sound waves.. But to each other, they are the same.

a b Spaceship "b" shoots a "photon torpedo" at "a". What will be the speed of the "photon torpedo" when it reaches "a"? “c” is the speed of light, or 300,000,000 m/s Speed is 1/3 c, 100,000,000 m/s Speed is 0 c

a b Spaceship "b" shoots a "photon torpedo" at "a". What will be the speed of the "photon torpedo" when it reaches "a"? Speed is 1/3 cSpeed is 0 c It MUST be 300,000,000 meters per second. ALWAYS. It will, however, be REDSHIFTED, because the wavelengths are stretched out.

H-R Diagram 1.The H-R diagram shows a relationship between the absolute magnitude / 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.