Download CHAPTER 2 NOTES (STARS AND GALAXIES)

2-1
Multiple-Star Systems- more than one star
Ex
triple-star (3) system- Alpha Centauriclosest star system to our sun
Ex
double-star (2) system (Binary stars)- Algol
(ghoul)
Our Sun- single star system, which is the closest star
to Earth
Constellations- groups of stars in which people at
one time thought they saw imaginary
figures of animals and people:
ex
Ursa Minor (Little Bear)- containing the
Polaris (North Star)
Orion (Hunter)- containing the bright
supergiant stars, Betelgeuse and
Rigel
Siruis (Dog Star)- middle sized star, which is the
brightest star in the night sky
Nova- a star that suddenly increases in brightness
up to 100 times in just a few hours to days
then grows dim again (maybe because of
a companion star’s gases that strike its surface,
causing explosions)
2 types of cluster stars: 1. open clusters- not well
organized ex Pleiades
2. globular clusters (more
common)- arranged in
spherical or round shape
Nebula- huge clouds of dust and gas, probably the
birthplace of new stars
Galaxy- huge collection of stars
3 types of galaxies are: 1. spiral- arms like a
pinwheel ex our galaxy- Milky Way
2. elliptical- nearly spherical to
flatdisks (older than other galaxies)
3. irregular- no orderly or definite
shape, not very common
Milky Way Galaxy- pinwheel shaped disk with
bulge in center
-the older stars are near the center nucleus
-our sun is on one of the spiral arms
because it is younger
2-2
spectroscope- breaks up the light from a distant
star into its characteristic colors
Stars rapidly approaching the Earth have light
waves from the star that will be compressed
(pushed together) and appear shorter- blue and
violet light (blue shift)
Stars moving away from the Earth have light
waves from the star that will be expanded
and appear longer- red (red shift)
Doppler effect- apparent change in the
wavelengths of light that occurs when an object
is moving toward or away from Earth
Every galaxy in the universe is moving away from
the Earth, therefore the universe is expanding
Big-Bang- states that the universe began to expand
with the explosion of concentrated matter and
energy and has been expanding ever since
Background radiation supports the Big-Bang
theory because energy left from it should
be evenly spread out throughout the universe
Open, eternal universe- universe that will
continue to expand and lead to total emptiness
Closed universe- universe that periodically
expands and then contracts back on itself
Quasars (quasi-stellar radio sources)- most distant
known objects in the universe (12 bil light-yr)
-Starlike objects that give off tremendous
amounts of energy in the form of radio and
x-ray waves
-Thought the be the earliest stage of galaxy,
at the very edge and very beginning of universe
2-3
5 sizes of stars: Neutron star- smallest (approx. 16 km)
White Dwarf- smaller that the continent
of Asia (Van Maanen’s star is smallest)
Middle-sized star- majority of stars, like our Sun
Giant star- 10 to 100 times larger than our Sun
Supergiant star- 1000 times larger than our sun
Mass is determined by composition (what it is
made of)- determined by spectroscope
“fingerprint” or a characteristic set of lines
of the element
hydrogen- the most common element of a star
makes up 60% - 80% of the total mass
helium- the second most common element of a
star (hydrogen and helium is 96% - 99%)
other elements such as oxygen, neon, carbon,
and nitrogen make up 4% of the star’s mass
Color is a good indicator of the surface temperature
of a star. Hottest- blue or blue-white color (50,000oC)
Coolest-red (3000oC)
Brightness- depends on the star’s size, surface
temperature and distance from Earth
Apparent magnitude- brightness as it appears
from Earth
Absolute magnitude- actual brightness
Pulsating variable star- changes in brightness and
size ex Polaris
Hertzsprung-Russell diagram (H-R diagram)relationship between absolute magnitude
(brightness) and temperature- as the absolute
magnitude (brightness) increases then the temperature
increases
x-axis surface temperature
y-axis absolute magnitude (actual brightness)
main sequence stars make up 90% of the stars
in the sky
Distance depends on how far away from Earth
a star is:
1. Parallax (close to Earth)- apparent change
in position of a star in the sky, which would
change because of the Earth’s position as
it moves around the sun
2. Use Brightness (more than 100 light-years
from Earth)
3. Spectroscope (more than 7 mil light-years
from Earth)
Nuclear Fusion- why stars shine
-gravity pulls together the hydrogen gas
atoms in the core so they fuse to form
helium releasing energy in the form of
heat and light
2-4
Our sun- middle-aged, medium sized yellow star
approximately 4.6 billion years old in terms
of size, temperature, and mass
4 main layers of the sun: 1 interior layer- core
where hydrogen changes to helium in nuclear
fusion
3 atmosphere layers- 1. corona- outer most
2. chromosphere- middle layer
3. photosphere- inner most layer
Solar storms: prominences- arches or loops of gas
solar flares- bright bursts of light on the
sun’s surface
solar wind- continuous stream of high-energy
particles released into space in all
directions can interfere with radio
and telephone signals
sunspots- dark areas on the sun’s surface
(cooler than the rest of the sun’s surface
interfere with Earth’s communication
in 11 year cycles
The sun rotates on its axis (imaginary vertical line
through the center of the sun)