Download Irregular Galaxies

A Trip Through the Universe
Part II
What are binary stars?
What are constellations?
What is an asterism?
How do you find Polaris from Ursa
Major?
What are circumpolar
constellations?
• What are some circumpolar constellations
for our area?
Nova
• Nova: A star that suddenly increases in
brightness in just a few hours or days.
• With a nova, the star may get up to 100 times
brighter.
• Novas are believed to be caused when a star in
a binary-star system captures gas from the
companion star.
• This gas strikes the surface of the nova star,
causing a nuclear explosion.
• After a nova, the star returns to normal.
• Many novas are reoccurring.
1
In January 2002, this
star, now called 838
Monocerotis, became a
nova. Its temperature
increased to 600,000 its
normal temperature,
making it temporarily the
brightest star in the Milky
Way.
It has since returned to
its normal brightness.
The explosion that you
see is the shell of dust
around the star as it is
being lit up by the
increased light of the
eruption.
This is known as a
“light echo.”
Supernova
• Although this is a similar term, a nova and a supernova
are very different.
• A supernova is when a massive star that has a
tremendous increase in its energy output due to a
catastrophic explosion of its core.
• Supernovas can light up the sky for many weeks.
• The core of the star becomes tremendously hot, fusing
iron atoms into new elements.
• Huge clouds of dust, gas, and the new elements explode
into space.
• This forms a new nebula.
• Once a star supernovas, the core that remains of it will
become either a neutron star or a black hole.
SN 1986 Supernova remnants
The two photos are of the same part of the sky, taken in
1987. The one on the left is after SN 1987A had its
supernova. Supernovae are one of the most energetic
explosions in nature, making them like 1028 megaton
bomb.
http://imagine.gsfc.nasa.gov/docs/science/know_l2/supernovae.html
Kepler’s
Supernova
Remnant—this
star
supernovaed
over 400 years
ago.
Star Cluster
• Stars that appear to be grouped together
are said to be “clustered” together.
• There are two types of star clusters.
• Open Clusters: Unorganized clusters of
stars with hundreds of stars.
• Globular Clusters: Clusters of stars that
are grouped in a spherical shape and
often contain more than 100,000 stars
Magellanic Open Star Clusters
M80 Globular Cluster
Star Clusters
• Both types of star clusters appear to be a
faint, white cloud when viewed from Earth
without a telescope.
• When a telescope is used to view them,
the different stars begin to be visible.
Nebula
• Nebula: An diffuse area of dust and gas
where stars are born.
• Nebulae are best seen with infrared,
ultraviolet, Xrays and radio waves.
• These huge clouds of dust and gas
between stars glow with heat rays.
Eagle Nebula
Eagle 2 Nebula, M16
Close-up of Eagle Nebula
Orion Nebula
Boomerang and Cat’s Eyes Nebulae
Galaxies
• A galaxy is a huge group of stars, gas,
and dust that are gravitationally bound.
• How big is the Milky Way?
• It is 100,000 light years wide…In other
words, it would take light 100,000 years to
travel across it. Even so, the Milky Way is
only one tiny piece of many, many
galaxies.
• The Milky Way is a spiral galaxy.
Spiral Galaxy
• Spiral Galaxies are
shaped like
pinwheels. They
have huge arms that
twirl around the
central core.
• This is Messier 101
galaxy
Barred Spiral NGC 1300
Elliptical Galaxies
• Elliptical galaxies can be almost
spherical to flat disks..
• Elliptical galaxies have very little dust and
gas.
• These galaxies tend to be much older than
other galaxies.
• (Remember that a nebula a huge area of
dust and gas where stars are born)
Elliptical Galaxy M87
Anglo-Australian Telescope
Irregular Galaxies
• Irregular Galaxies tend to be in irregular
shapes.
• The closest galaxies to the Milky Way are
irregular.
• Irregular galaxies are much less common
than spiral and elliptical galaxies.
NGC 1705
Irregular Galaxy
The Milky Way
• Our galaxy is a huge pinwheel shaped
disk with a bulge in the center.
• Older stars in the Milky Way tend to be in
the center of the galaxy.
• Stars in the center of the galaxy are
crowded much closer together than those
in the spiral arms.
The Milky Way
• Scientists believe the Milky Way is 100,000 light
years in diameter and about 15,000 light years
thick.
• There are nearly 100 billion stars in the Milky
Way. Our sun is one of these.
• Our sun is located on one of the spiral arms,
about 30,000 light years from the center.
• Our sun is one of the younger stars in the Milky
Way.
• All stars in the Milky Way rotate counterclockwise about the center.
Big Bang Theory
• The theory that everything in our universe
started with one big explosion.