Transcript Galaxies and Stars

GALAXIES AND
STARS
Why light years?
The distances in outer space are tremendous!
In order to discuss the incredible distance
between objects the most common term is a
light year.
Light year – the distance it takes light to travel
in one year. (6,000,000,000,000 miles. That’s
6 million millions!!!)
REMEMBER! A light year is a distance, not an
amount of time!
Stars
 Stars are burning balls of gas and dust.
 Stars come in various size and brightness.
 Stars are compared using an H-R diagram.
 Groups of stars are called clusters.
 Example: Sun, Polaris
Sun
Our sun is a star of average size and brightness.
Characteristics of Stars
 Stars are defined by their characteristics
Size
 Stars are classified as:
1. White Dwarfs
2. Main Sequence
3. Giants
4. Supergiants
Color & Temperature
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Red (coolest)
Orange
Yellow (average)
White
Blue (hottest)
Brightness
 Brightness is determined by a star’s
size, temperature and distance from
the observer.
Here, we see gas and dust clouds spreading hundreds of light years across. As the gas
condenses under gravity…
… pillars of dust arise. These pillars and areas of mixed gas and dust combine to
make a nebula.
Eventually these colorful nebulae will become stars.
The universe is an infinitely large place;
much is filled with emptiness. This
emptiness is occupied by different types
and stages of galaxies.
The universe is filled with galaxies….
SO WHAT’S A GALAXY?
Galaxy – a large system of stars held together by the
same gravitational pull and separated from other
large systems.
The Sombrero Galaxy is located 20 million light years from earth and
is 50,000 light years across.
3 Types of Galaxies:
Spiral
Irregular
Elliptical
Spiral Galaxies
 The most common galaxy type
 Pinwheel shape and design
 Examples: Milky Way, Sombrero and
Whirlpool Galaxies
If this was the Milky Way we would be on the outer edge.
This galaxy is 25 million light years away and is over 35,000 light years in diameter.
Earth?
The bright areas that appear to be stars are actually clusters of stars that can sometimes
number in the millions! The arms of this spiral galaxy are filled with the glow of dust and
gasses that will become new stars.
Irregular Galaxies
 No definable shape (randomly shaped)
 Example: Antennae Galaxy
The Antenna Galaxy is 62 million light years away. Formed as two developing galaxies
collided, this image of the system is over 53 light years across.
Elliptical Galaxies
 The rarest type of galaxy
 Round, orb, or ball like shape
 Examples: Andromeda
This 10 million light year sized galaxy is a lonely cluster of stars surrounded by a
view of countless other distant galaxies. The edge of this elliptical galaxy is over
318 million light years from earth.
Even the elliptical Andromeda, our nearest neighboring galaxy is 2.3 million light years
away. That’s over 12,180,000,000,000 miles away!