Transcript HR diagram ppt

DO NOW:
Write it down 
1. Most of the galaxies in the universe
are moving __________ from us.
2. Our evidence to support this is ___
___________________________.
3. One exception to this is the galaxy
______________ which is moving
toward us (it has a ___________).
4. Why?
AIM: How can we characterize stars?
Constellations: groups of stars
* Human invented
Apparent movement caused by Earth’s
rotation and revolution
Because Earth rotates from WEST to
EAST, the sky seems to turn from East
to West
*Sun moon and stars rise in East
and set in West. Polaris is
stationary
http://www.skyviewcafe.com/skyview.php
Apparent Magnitude- How bright
a star seems to be to an observer
on Earth
* DEPENDS ON HOW
CLOSE A STAR IS TO EARTH
Our Sun
VS.
Our next closest star,
Proxima Centuri
Luminosity- a star’s ACTUAL
brightness. It depends on the size
and temperature.
*DISTANCE FROM EARTH IS
NOT A FACTOR!
Absolute magnitude- measure of
how bright stars would be if they
were the same distance from
Earth
Example) What if I held a light bulb in front of your face and then
walked across Port Blvd? Would it look the same size? Would it still
BE the same size?
Astronomical Unit- the
distance from Earth to
closest star (sun) 150
million km.
Proxima Centuri is the
next closest star (260,000
AU)
FORCES that balance out a star-
1. Nuclear fusion1 Hydrogen + 1 Hydrogen = Helium
http://www.astronomynotes.com/starsun/s3.htm
Pushes outward
2. Gravity – pulls inward
•
HR DIAGRAM
aka stars’ family album
http://aspire.cosmic-ray.org/labs/star_life/hr_interactive.html
Have
you
seen
any
of
these
?
Why does the sky change?
• The sky SEEMS to change
* NIGHTLY- because of Earth’s
ROTATION
*SEASONALLY- because of
Earth’s REVOLUTION
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0408/es0408page01.cfm
~DENEB ~
• Now even though it is a massive
super-giant, Deneb is actually a very
young star, at least compared to the
sun.
• Deneb was born only about 3 million
years ago, long after the Dinosaurs
died out, and is already approaching
the end of its life -- the star can last at
most another million years.
http://my.execpc.com/60/B3/culp/astronomy/Fall/MilkyWay.html