Stars

Astronomy The study of space

How astronomers measure distance 1. Light years– The distance light travels in one year 9.461x km

Measuring distance cont 2. Parsec (pc) – 3.26 light years

What if we cant tell exact distance?

Parallax The shift of nearby stars with the motion of the Earth. The closer the star the more it moves in the night sky in a smaller time

Groups of Stars 1. Constellations– Groups of stars named by ancient people constellations 2. Your location and the time of year determine which constellations can be seen **Circumpolar Constellations rotate around the poles and can always be seen (Little dipper and Southern Cross)

Groups of stars cont. 2. Clusters– Any group of stars gravitationally bound to each other. Some are constellations some are not

Groups of stars cont. 3. Binaries– Two stars that rotate around each other (To the eye they look like 1 star)

What are the different aspects of stars we could look at?

Properties of Stars Diameter Brightness Energy output Surface temperature ** Mass ** Composition

Magnitude Apparent Magnitude: How Bright a star appears (doesn’t take distance into account)

Magnitude Absolute Magnitude– Measures brightness from 10 pc ** Can only be calculated if the distance from Earth is known

Luminosity The amount of energy from the surface of the star ** The magnitude and distance must be known to calculate ** Measured in watts (Joules/ second)

Classifying stars Stars get a letter and a number Letters are based on their temperature (spectral type)

Classifying Stars continued Numbers are based on their absolute magnitude And plotted on the Herzsprung-Russell diagram Temperature vs. Magnitude

Types of stars Main Sequence Stars– Stars that run a normal pattern in cooling and loosing magnitude

Types of Stars Red Giants– Large, cool, luminous Stars (Doesn’t fuse hydrogen, fuses larger elements instead)

Types of Stars White Dwarfs– Small, hot, dim stars (Doesn’t fuse hydrogen)

Fusion How energy is generated on the surface of stars ** Hydrogen atoms collide and make Helium

Life Cycle of Stars Formation– All stars begin as a cloud of dust called a Nebula

Nebulas Clouds of dust that collapse on its self forming a PROSTAR Eventually the prostar will get hot enough to star the fusion process

The amount of mass determines the life of the star

Smallest Stars (Red) 1. Nebulas 2. Prostars 3. Main sequence 4. White dwarf 5. Black Dwarf

Next largest (Yellow) 1. Nebula 2. Prostar 3. Main sequence 4. Red Giant 5. White Dwarf 6. Planetary nebula (will be recycled into a new star)

White Stars (3x the mass of our sun) 1. Nebula 2. Prostar 3. Red supergiant 4. Neutron Star (will start over into a nebula)

Blue stars (The largest 9x the size of our sun) 1. Nebula 2. Prostar 3. Red supergiant 4. Black hole