Transcript Characteristics of Stars

Characteristics of Stars
Gosser
Earth and Space Science
Constellations
Unnatural groupings of
stars
Most created by ancient
astronomers
Almost like a map to the
sky to find stellar objects
The image to the left is an
example of how to find
bright star “Arcturus”
http://msnbcmedia4.msn.com/j/msnbc/Components/Photo_StoryLevel/080425/080425-space-ns-arcturus-213.standard.jpg
Stargazing Basics
Terms to Know
Ecliptic – The apparent path of the Sun on
the celestial sphere
Celestial Equator – a great circle on the
imaginary celestial sphere in the same
plane as the Earth’s equator.
Terms to Know
Right Ascension – astronomical term for
one of the two coordinates on the celestial
sphere similar to latitude.
Declination – the angular distance north or
south on the celestial sphere similar to
longitude
The Celestial Sphere
This may help
SIDE NOTE: Observing the Sky
Stargazing Basics
Video
Magnitude
Two Types:


Apparent – measure of
how bright a star
appears to be to an
observer
Absolute – measure of
how bright the star
would be if all stars
were at the same
distance
http://oobleck.ifa.hawaii.edu:8080/where/images/orion.jpg
Magnitude cont.
The lower the star’s magnitude the
brighter it is
Luminosity – The actual brightness of a
star

Depends on its size and temperature
Distance to Stars
Astronomical Unit –
average distance
between the earth
and the sun = 150
million km

Closest star other than
the sun is Proxima
Centauri = 260,000 AU
Distance cont.
Light Year – the
distance a ray of light
travels in one year =
9.5 trillion km
Parsec = 3.258 light
years or
3.086x1013km
Parallax
Astronomers can
calculate the distance
to a star by knowing
the angle between
two observed
positions and the
distance between the
observation points
CLICK HERE

Scroll to “stellar
parallax interactive”
http://physics.weber.edu/carroll/expand/images/parallax.gif
Elements in Stars
A star is a sphere of
super-hot gases mostly hydrogen and
helium

Heavier elements
make up about 1 or 2
percent of a stars
mass
chemistry.bd.psu.edu
http://www.astro.queensu.ca/~hanes/PHYS015-2007/Notes/DAH_Figs/Emission_Spectra_Examples.jpg
Mass and Size
Mass and size are all
based off of the Sun

Mass is expressed in
solar masses
1 solar mass is
approximately 2 x
1030kg or 330,000
Earths

Size is expressed in
solar radii
Temperature and Color
Its not what you
think!!
Blue is hot
Red is cool
Havard Spectral Classification Scheme
On page 622 of your textbook, fill in the chart below
Oh Be A Fine Girl/Guy Kiss Me
Surface Temp
(0C)
Color
Prominent
Element
Class
Above 30,000
Bluish White
Ionized Helium
9500 – 30,000
Bluish White
Neutral Helium
7000 – 9500
White
Metals, Hydrogen
6000 – 7000
Yellow White
Metals, Hydrogen
5200 – 6000
Yellow
Metals, Hydrogen
3900 – 5200
Yellow to Orange
Metals, Hydrogen
Below 3900
Red
Titanium oxide
O
B
A
F
G
K
M
H-R Diagram
H-R stands for
Hertzsprung and
Russel who
developed this
diagram
The diagram plots
temperature vs.
luminosity of stars
Groups represent
stages in the life cycle
of stars.