Transcript Measuring the Stars pages 813-820

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 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 1/3,600th 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.
http://www.astro.ubc.ca/~scharein/a311/Sim/doppler/Doppler.html
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.
Sound of
engine will
seem lower
45
mph
Sound of
engine will
seem higher
Show Doppler effect animation here
http://www.lon-capa.org/~mmp/applist/doppler/d.htm
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?
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?
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?
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?
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?
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"?
a
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 pilot of plane "b"?
It would be the same, because the relative speed
between the two is zero meters per second. There
is no Doppler effect.
a
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?
a
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?
a
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?
Plane “a” would be higher, because it is “pushing”
the sound ahead of it ~ because of its higher
relative speed than plane “b”
a
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?
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
a
Speed is 0 c
b
Speed is 1/3 c,
100,000,000 m/s
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
a
Speed is 0 c
b
Speed is 1/3 c
Spaceship "b" shoots a "photon torpedo" at "a". What
will be the speed of the "photon torpedo" when it
reaches "a"?
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.