Characteristics Of Stars

Galaxy: A collection of stars, gases and dust.

Universe: Contains billions of

galaxies.

The Milky Way galaxy has a whopping circumference of

roughly 250-300 thousand light years! Within the main body

of the Milky Way there are estimated to be between

200 and 400 billion stars.

Types of Galaxies1. Spiral2. Elliptical3. Irregular

Spiral Galaxies:Arms spiral outward like a pinwheel

Our galaxy, The Milky Way, is a spiral galaxy

Elliptical Galaxies:Look like flattened football.

Have billions of stars, but little gas and dust.

Contain the oldest galaxies

Irregular GalaxiesNo definite shapeExample: Large Magellanic Cloud

( Light will travel 10 trillionkilometers in one year!)

Scientists use LIGHT YEARS to measure distances in space. A light year is the distance light travels in one year.

Light travels at the speed of 300,000,000 meters/second.

Classifying StarsStars are classified by 3 Main Characteristics:

1. Size2. Temperature3. Brightness

Hottest (20,000-50,000*C)

: (10,000*C) (6,000*C) (4,000-5,000*C) (3000*C)

Color reveals the temperature of a star.

Brightness of StarsApparent Magnitude: Brightness as seen from earth

Absolute Magnitude: Brightness of a star from a standard distance

Hertzsprung-Russell Diagram

A graph plotting brightness and temperature.

90% of stars are Main Sequence

Solar flare

Overview of Star Life Cycle

Lifetimes of Stars

A star’s life depends on its mass. Stars smaller than the sun live up to 200

billion years. Medium sized stars like the sun live around

10 billion years. Stars 15 times more massive than the sun

live about 10 million years.

·Clouds of gas – made up of elements and compounds·As they spin and condense, heat energy is transformed, forming stars

NEBULA

·Medium sized star·By speed of light, only takes 8.3 minutes to get to Earth from the Sun·Located on the edge of a spiral of the Milky Way galaxy·Center of Solar System

SUN

·Dense gravity well in space·Light cannot escape the gravitational pull of a black hole·Observed because astronomers can see light and energy being given off by objects being pulled into them·No volume, infinite density·Could be a result of a Supernova explosion

BLACK HOLE

http://chandra.harvard.edu/resources/flash/bh_truth.html