Describes what a galaxy is, shows examples of types of galaixes, ends with a view of thousands of galaxies in the Hubble UltraDeep Field.

1. Why Am I Here?Why Am I Here?
To tell you about what’s out there in theTo tell you about what’s out there in the
Universe.Universe.
I’m anI’m an astronomerastronomer, which is a kind of, which is a kind of
scientist.scientist.
I get to study stars and galaxies, and theyI get to study stars and galaxies, and they
pay me to do it!pay me to do it!

2. What do we call the star that isWhat do we call the star that is
the nearest star to Earth… by far?the nearest star to Earth… by far?

3. The Sun!The Sun!

4. WhatWhat IsIs AA StarStar ??
Stars look bright and tiny to us, but theyStars look bright and tiny to us, but they
areare huge dense balls of gashuge dense balls of gas lit up fromlit up from
the inside by their own internal nuclearthe inside by their own internal nuclear
power.power.
All stars were born from gas and dust thatAll stars were born from gas and dust that
collapsed into a fiery ball because ofcollapsed into a fiery ball because of
gravity.gravity.
Stars have different masses. TheStars have different masses. The
heaviest are 100 times bigger than theheaviest are 100 times bigger than the
lightest ones.lightest ones.

5. The Sun is One of Many,The Sun is One of Many,
Many Stars in Our GalaxyMany Stars in Our Galaxy

6. What’s A Galaxy?What’s A Galaxy?
A galaxy is a huge collection of stars,A galaxy is a huge collection of stars,
held together in space by gravity.held together in space by gravity.
Stars are very far apart and do notStars are very far apart and do not
bump into each other.bump into each other.
 Galaxies also have clouds of gasGalaxies also have clouds of gas
and dust between the stars.and dust between the stars.
Those clouds may make new starsThose clouds may make new stars
one day, and recycle the dying ones.one day, and recycle the dying ones.

7. What do we call the galaxy weWhat do we call the galaxy we
live in?live in?

9. The Milky Way isThe Milky Way is OurOur GalaxyGalaxy
Why is it called “Why is it called “MilkyMilky”?”?

10. What the Milky Way Looks Like
from the Inside

11. Where is the Sun inside theWhere is the Sun inside the
Milky Way?Milky Way?
TOP VIEW
SIDE VIEW

12. The Milky Way isThe Milky Way is OurOur GalaxyGalaxy
Our galaxy contains about 200 billionOur galaxy contains about 200 billion
stars – 200,000,000,000stars – 200,000,000,000
But the total mass of the galaxy is 5But the total mass of the galaxy is 5
times more than that.times more than that.
Loose-floating gas & dust onlyLoose-floating gas & dust only
account for “only” about another 200account for “only” about another 200
billion stars’ worth.billion stars’ worth.
The galaxy is about the same age asThe galaxy is about the same age as
the universe: 13 billion years old.the universe: 13 billion years old.

13. The Andromeda Galaxy is similar to ours.

14. GalaxiescomeInmanyshapesandsizes.

16. Elliptical
Spiral
Barred
Spiral

17. The Hubble Ultra Deep Field