The document discusses the universe and galaxies. It defines the universe as all matter and energy that exists, and describes it as containing stars, planets, and different types of matter. Galaxies are groupings of millions or billions of stars that are held together by gravity. There are estimated to be 100 billion galaxies in the universe. Galaxies come in three shapes: elliptical, spiral, and irregular. The Milky Way galaxy, which contains around 400 billion stars, is a spiral galaxy that our solar system is located in.

1. The Universe and Galaxies
By; Feras and Mari

2. Astronomy
• The study of objects and
matter outside the Earth’s
atmosphere and of their
physical and chemical
properties.

3. What is the universe?
- sum of all matter and
energy that ever has, does,
and ever will exist
- everything physical that
exists in space and time
• - the universe is composed
of stars, planets, rocks,
comets, asteroids, dark
matter, dark energy

4. •- Dark matter – theoretical
unseen and undetectable mass
that adds to the gravity of a
galaxy
•- Dark energy theoretical energy
that might be causing accelerated
expansion of the universe

5. Galaxies
• groupings of millions or billions of stars, and dust and gas held
together by gravity
- there are an estimated 100 billion galaxies in the universe
- There are three types of galaxies; elliptical, spiral, and irregular.
They’re identified by their shape

6. Spiral
• disk shaped with spiral
arms of dust and gas.
• dust and gas provide a
place for new stars to form
• young stars are:
bluish in color
gives spiral
galaxies a blue tint
• looks like a pin wheel

7. Elliptical
• most common type of
galaxy
- spherical and egg
shaped
 NO spiral arms,
• little dust and gas
• stars (reddish in color)

8. Irregular
• least common type
of galaxy
• NO well defined
shape or structure
- some have little dust
or gas, some have
lots of dust and gas

9. Milky Way galaxy
•the galaxy we live in consists of stars, and, clouds
of dust and gas between stars (interstellar matter)
• all the stars we see at night are in the Milky Way
galaxy (about 400 billion stars)
Milky Way Galaxy – side
view
- a huge spiraling disk of stars
and interstellar matter  1000
l.y. thick

10. Where Are We In The
Galaxy?
- Our solar system
is about halfway
between the
center and the
edge of the
galaxy (26,000
light years from
the center)

11. Gravity holds
galaxies together
- The Milky Way galaxy is
in a cluster of ~45
galaxies called the
“Local Group”
Superclusters - have
thousands of galaxies
largest structure in the
universe

12. - astronomical
distance is
measured in
light years
(ly)
- light year - the
distance
light travels
in one year
 1 light year
= 9.5x1015m
 light travels
at 3.0x108m/s
How is space
distance measured?

13. - Most things we see
in space are stars-
huge balls of hot
gases that emits
light
- stars are grouped
together by the
millions and billions
into galaxies

14. Sources
http://www.windows.ucar.edu/tour/link=/the_universe/images
/galaxies/aat017_image.html
http://seds.lpl.arizona.edu/messier/Jpg/m100.jpg
http://www.forum.seds.org/messier/Jpg/m32.jpg
http://antwrp.gsfc.nasa.gov/apod/image/m82_moo.gif
And wikipedia

15. Listening 👍🏻👍🏻👍
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