Note Sheet - Properties of Stars & Stellar Evolution
PROPERTIES
A. Distance to a star, measured in:
- Km. (usually too small of a unit of measure to be used effectively)
- A.U.(astronomical unit) = 1.5 x 108km average Earth – Sun distance
(again, the unit is too small to be of much use)
-
L.Y.(light year) = 9.46 x 1012km, the distance light travels in one year
(this is the typical measure used for stellar distance. Our closest star, other than the Sun, is 4.2 L.Y.
away.)
-
Parsecs = 3.26 light years
1 second of arc or 1/3600o
(used for measuring only the closest stars. See Stellar Parallax)
B. Stellar Parallax –
Why is stellar parallax effective
For measuring distance to only
closest stars?
the
Questions: Stellar Parallax
What happens to the parallax measurement as the distance to the object increases?
The simulated photograph in figure 4 represent pictures of the same section of the evening sky taken four months apart. Examine
these photographs closely. Mark and describe the star in the photographs that you think is closest to the Earth.
Explain your choice. ____________________________________________________________
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C. Composition of a star (p. 676) Spectroscopy
The electromagnetic Spectrum ------------- energy---------
Radio Radar Micro Infrared Visible Ultra Violet x-ray gamma
--------------- wavelength -----
Types of Spectrum:
Continuous spectrum –
Emission spectrum –
Absorption spectrum –
What is meant by “each element has its own fingerprint of energy?”
STOP:
Complete Spectral Lines Activity and Questions
D. STELLAR EVOLUTION
Stars exist because of gravity. Two opposing forces in a star are:
- gravity
- thermal nuclear energy
What is a Protostar?
Stages of a Star
←Birth →
←←←Stellar Stage→→→→→
←Death→
The life cycle of a star is dependent on _________________________
Low Mass
Nebula
Protostar
●
color
Main-Sequence
Medium Mass
Nebula
Protostar
●
color
Main-Sequence
Massive
Nebula
Protostar
●
color
Main-Sequence
____________
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Answer Questions **The H-R Diagram
E. Magnitude
(brightness)
Apparent magnitude Absolute magnitude -
(luminosity – the total amount of energy a star is sending out.
It is independent of how far away the star is. )
Color and temperature
Hot star – temp. above 30,000K
Wavelength Color Cool star – temp. less than 3000K
Wavelength Color Between 5000 & 6000K stars appear “yellow” (e.g. Sun)
E. Other Types of Stars
Binary Stars
Held together by mutual gravitation, both orbit around a common center of mass.
More than 50% of the stars in the universe are binary stars. It is used to determine
Stellar Mass.
Variable Stars - Pulsating variables or Eruptive variables
- Stars that fluctuate in ______________
F. Interstellar matter - between the stars is:
Nebula - cloud of dust and gases, contains the material that forms stars & planets
And Lots and lots of empty ______________
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