The Universe
• Multiple Star Systems- more than one star moving around each other
• Binary Stars- Double star System
• Ex. Algol
• Constellations- groups of stars in
which people thought they saw imaginary figures.
• Novas- a star that suddenly increases in brightness up to 100,000 times in a few hours or days.
• caused by gasses from one star in a
binary system, strike the other star and form a nuclear reaction
• Star Clusters- groups of stars w/no pattern
• Open clusters- spread out
• Nebulae- huge clouds of dust and gas in space, believed to be the birthplace of stars
• Galaxy- major features of the universe, contain various star groups
• 3 types: spiral, elliptical, irregular
Formation of the Universe
• Spectroscope- an instrument which breaks up light from distant stars into the visible spectrum (ROYGBIV)
• used by scientists to determine if
• Blue Shift- the visible spectrum of an object is shifted to the blue. Indicates movement towards the earth.
• Red Shift- the visible spectrum shifted to the red. Indicates movement away from the
earth. (Both of these are due to the Doppler Effect)
• The Big Bang Theory
• Tries to explain the formation of the
• Open Universe- all matter in space will
continue to move outward until the stars die.
• Closed Universe- The Universe will continue to expand until gravity begins to pull
everything back together. A big bang will occur again and the process will repeat.
• Quasars- the oldest and most distant objects in space. 12 billion light years from earth
• quasi-stellar radio sources
Characteristics of Stars
Size- stars vary tremendously in size
• Our sun has a diameter of 1,392,000 km
• Supergiant stars- diameter up to 1,000 times the sun.
• Giant stars- diameter 10-100 times the sun.
• Medium-sized stars- 1/10 to 10 times the sun
• White Dwarfs- smaller than earth
Composition
• astronomers determine composition of stars using a spectroscope
• Certain elements give off characteristic lines in a spectroscope.
• Astronomers have found that all stars
contain 60-80% hydrogen with helium making up the remainder (up to 96-99%).
Surface Temperature
• astronomers determine temperature by studying the color of a star.
• Red- 3,000º C
• Red/Orange- 5,000º C • Yellow- 6,000º C
• White- 10,000º C
Brightness
• depends on star size, surface temperature, and distance from the earth.
• Apparent magnitude- brightness of a star as it appears from earth
• Absolute magnitude- the amount of light a star actually gives off
• Surface temperature affects the absolute
• Measuring Star Distance- scientists use a method called parallax
• Why Stars Shine- stars shine because of nuclear fusion.
• The gravitational pull within the core of
a star pulls together atoms of hydrogen and fuses them together into helium
atoms.
Our Sun
• The sun is important to us because without it there would be no life on earth.
• 150 million km from earth
• 1.39 million km in diameter (1 million
planet earth’s could fit inside)
4 Layers
• Corona- outermost layer of
atmosphere, temp. reaches 1,700,000°C
• Chromosphere- middle layer of atmosphere, temp. 27,800 ° C
• Photosphere- innermost layer of
atmosphere, temp. 6,000 ° C
• Core- interior of the sun, temperature
Activity on the Sun
• Prominences- large, bright arches or loops of gases which originate in the chromosphere
• Solar Flares- bright burst of light on the suns surface, lasts up to 1 hour
• Sunspots- dark, cool regions observed on the suns surface- are storms in the lower atmosphere
Evolution (Life Cycles) of Stars
• Stars form in nebulae.
• Hydrogen gas is clumped together by gravity.
• As the hydrogen atoms collide they give off heat. When the temperature reaches
15,000,000º C nuclear fusion begins and a protostar is formed.
Medium-Sized Stars
• Star shines for a few billion years until most of it’s original supply of hydrogen is used up.
• The core begins to shrink and the shell
expands.
• The star becomes a red giant.
• The red giant eventually becomes a
Massive Stars (6 times suns mass)
• Same as medium-sized stars until the red giant stage.
• After red giant gravity in the core pulls molecules together so tightly that
fusion forms iron.
30 times suns mass
• After supernova explosion it becomes a neutron star.
• Neutron stars that spin rapidly and give off pulses of radio waves are called
More than 30 times the suns mass
• After supernova explosion the core is swallowed up by it’s own gravity and becomes a black hole.
• Black holes swallow all matter and
