Download Star Systems and Galaxies

Star Systems and Galaxies
Star Systems and Galaxies
hazy band of light stretched across the sky
is the Milky Way, a spiral barred galaxy.
It looks as if the Milky Way is very far
away from Earth. Actually, though, Earth
is inside the Milky Way!
Star Systems and Planets
Our solar system has
only one star, the sun.
Half of all stars are
members of groups of
two stars called binary
star systems.
In this star system you
would see two or more
suns in the sky.
Double and Triple Star Systems
The prefix bi means “two.” What does Tri mean?
An example of a binary star system is in the
handle of the Big Dipper.
Those with three stars are called triple stars.
An example of a triple star system is that of
Alpha Centari.
Alpha Centari is the closest star to ours, but it is
really three stars.
Eclipsing Binaries
A dim star in a binary star may pass in
front of a brighter star and eclipse it.
From Earth, the binary star would
suddenly dimmer.
A system in which one star periodically
blocks the light from another star is called
an eclipsing binary.
Planets Around Other Stars
Triple star system, astronomers found a
world called HD 188753 Ab.
We could not set foot on this planet
though, since it’s a “gas giant”, roughly the
mass of Jupiter, orbiting its parent star
every 3.3 days!
Gliese 581-New
Earth-like planet
Star Clusters
Many stars belong to larger groupings
called star clusters.
All the stars cluster form from the same
nebula at about the same time.
There are two major types of star clusters:
open clusters and globular clusters.
Star Clusters
Open clusters have a
loose, disorganized
appearance and
contain no more than
a few thousand stars.
They often contain
many bright
supergiants and
mostly gas and dust.
Star Clusters
Globular clusters are
large groupings of
older stars.
Globular clusters are
round and densely
packed with stars—
some may contain
more than a million
stars.
Galaxies
A galaxy is a huge groups of single stars, star
systems, star clusters, dust, and gas bound
together by gravity.
There are billions of galaxies in the universe.
Astronomers have classified most galaxies into
three main categories: spiral galaxies, elliptical
galaxies, and irregular galaxies.
Spiral Galaxies
Spiral galaxies are
galaxies that have the
shape of twin spirals.
Our galaxy has the
same spiral, pinwheel
shape.
The spiral arms
contain many bright,
young stars as well as
gas and dust.
Elliptical Galaxies
Not all galaxies have
spiral arms.
Elliptical galaxies look
like flattened balls.
These galaxies
contain billions of
stars but have little
gas and dust between
the stars.
Irregular Galaxies
Some galaxies do not
have regular shapes.
Because of this, they
are known as
irregular galaxies.
Irregular galaxies are
typically smaller than
other types of
galaxies.
Quasars
A quasar is an enormously bright, distant
galaxy with a giant black hole at its center.
Each of these black holes has a mass of a
billion times or more as great as the sun.
As enormous amounts of gas revolve
around the black hole, the gas heats up
and shines brightly.