Download stars and constellations

Measuring the stars pages 813 – 820
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
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 “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 “other side” of the sun.
4.
If a star is visible year round, it must be very far north or south, and it would
be call circumpolar, because it circled the pole.
Seen year round.
These stars would
be circumpolar.
Seen in
summer,
not in
winter.
Seen in
winter,
not in
summer.
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.
2.
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.
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.
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 Diagram
1.
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.
Brightness
Temperature in Kelvin
This would be a good time to go to my web page, and look at Universe Comparisons.
Electromagnetic spectrum pages 748 through 750
We classify electromagnetic radiation according to its wavelength
1.
Gamma – shortest and most energy
2.
X-ray
3.
Ultra-violet
4.
Visible
5.
Infrared
6.
Microwave
7.
Radio – longest and least energy
It would be excellent to develop a mnemonic device to remember that order.
Visible light changes color, depending upon the heat of the material that is being looked
at. A red nail is much cooler than a blue propane flame.
1.
Red – coolest object, longest wavelength, least energy
2.
Orange
3.
Yellow
4.
Green
5.
Blue
6.
Indigo
7.
Violet – hottest object, shortest wavelength, most energy
I remember the name Roy B. Biv
It just seems to work for me.