Download Star

Chapter 30.1:
Characteristics of Stars
Star: ball of gas that gives off a tremendous
amount of energy in the form of heat and
light.
Our own ‘Sun’ is considered an average star!
Characteristics:
1.
2.
3.
4.
5.
6.
7.
Starlight- light given off by stars.
Composition- what elements make up the stars.
Temperature- how hot; how cold?
Size & Mass- how big; how small?
Motion- actual motion vs. apparent.
Distance- how close; how far away?
Brightness- apparent vs. absolute magnitude.
Starlight:
-by analyzing the light stars emit, we can
determine the star’s composition (elements
present) and temperature.
Composition:
-Star composition is determined by analyzing the light
being emitted. Equipment is called a spectrometer.
-Since different elements absorb different
wavelengths of light, elements can be determined.
-Stars are made up of gas elements. (Hydrogen is the
most common!)
Temperature:
-temperature is determined by the star’s color.
-temp.’s range from
2,800 to 50,000 oC.
Size & Mass:
-Some dwarf stars are as small
as the Earth.
-Our sun is a medium size star (1,390,000 km).
-Some stars are 1,000 times larger than our sun.
-Density affects mass…no relationship between
size and mass.
Example: a star can be smaller than our sun, but have a
greater mass…meaning it is more dense!
Motion:
1. Actual motion- what we see with telescopes.
2. Apparent motion- This is motion visible to the unaided
eye in a dark sky; due to movement of Earth.
Stars have three actual motions:
1. rotate
2. revolve
3. move toward (blue shift) or away (red shift)
from Earth
Distance:
-Light Year = 9.5x1012km; Distance that light
travels in one year.
Example: light from the sun takes 8 mins.
to reach the Earth
-Astronomical Unit (AU) - A unit of length used to
measure distances in solar system.
Example: Sun to Earth = 1 A.U.
Brightness: a.ka. Stellar Magnitude
-Absolute Magnitude: true brightness
-Apparent Magnitude: brightness of a star as it
appears to us on Earth.


Brightest stars have lowest numbers.
(negative #’s)
Dimmest stars have highest numbers.
(positive #’s)