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Stars & Their Characteristics

Objectives:

Key Terms:

Notes: (28-2)

Constellations - Constellations (alphabetical)

Names given to groups of stars
88 have been named so far
not natural groupings or solar systems (man derived)
some are considered pointer stars
Polaris - north star
Big dipper (part of Ursa Major) - points toward Polaris and the little dipper
Little dipper (part of Ursa Minor) - includes Polaris
Some remain fixed throughout the year  - made of fixed stars
Some can only be seen in the different times of the night and seasons - made of circumpolar stars

Constellations(www.csc.tcd.ie/~tass/images/ constellation.gif)

 

Apparent Magnitude

is the measure of how bright a star is
the brightest are 1st magnitude
the dimmest are 6th magnitude
some can be less than 1 
sun -26.7

(www.ap.stmarys.ca/.../Stars/ Distance/Brightness/)

Distances to Stars

Are measured in astronomical units (AU)
distance from the Earth to the sun
~150 million km
next closest star is Proximus Centari ~260,000AU
Also measured in light years
~9.5 trillion km
next closest star is Proximus Centari ~4.2 light years
Distance can be measured based on parallax
is the apparent change in the position of a star due to the observer's change in position
measured using angles and the movement of the Earth around the sun
measured in parsecs - "Parallax second" = 3.258 light years

(www.as.utexas.edu/.../spring01/ lambert/parallax.jpg)

Elements in Stars

most stars are made almost entirely of H & He gases 
1-2 % can exist as heavier gases (O, C, N, Na)
the element %s in stars are much like fingerprints with no two being exactly alike
scientist us spectroscopes to analyze the wavelengths of emitted light to determine the composition and temperature of the different stars

Mass, Size, and Temperature

Mass
cannot be measured
calculated based on its inertial properties an its influence on other objects
listed as solar mass (1 solar mass = our sun's mass)
the masses of stars as variable as their size and densities
Betelgeuse is 
~ 2000 x the diameter of the sun
~20 x the mass of the sun
~1/10,000,000 the density if the sun

(blueox.uoregon.edu/~courses/BrauImages/ Chap17/FG17_006.jpg)

Temperature, Luminosity and Color
the color of a star is largely related to its temperature
the temperatures of stars follow the electromagnetic spectrum
hottest stars are blue, hot stars are white while the cooler stars are red
the luminosity of a star is its brightness
depends only on its size and temperature
does not depend on its distance from the Earth
measured in absolute magnitude
brightness at 10 parsecs from Earth

(members.shaw.ca/blbattersby/ images/startemp_big.JPG)

diagram of star temperature vs. brightness(www.llnl.gov/str/May02/ gifs/Dearbornbox3.jpg)

 

 

 

 

 

 

 

Last modified: March 16, 2004