1. Structure of the Universe

2. Structure of the UniverseOr
What’s Out There and Where is it?

3. Note large separation of inner and outer planets
The Solar System
Note large separation of inner and outer planets
National Geographic Magazine

4. My Mercury Very Venus Elegant Earth Mother Mars Just Jupiter Sat
Remembering the names of the planets in order: My
Very
Elegant
Mother
Just
Sat
Upon
Nine
Porcupines
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto

5. The Inner Planets::
Mercury Venus Earth Mars Asteroids
Close together (Relatively)
Terrestrial (made of rock like Earth)

6. The Outer Planets::
Jupiter Saturn Uranus Neptune Pluto
Spread out (Relatively)
Gassy and icy giants

7. The Kuiper belt and Oort Cloud::
Hundreds of millions of comet like bodies
50,000 AU in radius
Total mass 10 to 100 times Earth’s mass
A tenth planet???
Where comets come from

8. The Solar System (again)
Pluto is most likely a Kuiper belt object
National Geographic Magazine

9. Our Solar Neighborhood:

10. Galaxies (Hubble types):
Contemporary Astronomy, J. Pasachoff

11. Galaxies (Hubble types):
Contemporary Astronomy, J. Pasachoff
Elliptical
Normal Spiral
Barred spiral
Irregular
Peculiar

12. 100,000 LY in diameter, 16,000-3,000 LY thick
The Milky Way Galaxy
You are Here
100,000 LY in diameter, 16,000-3,000 LY thick
Contains a hundred billion stars (1011)
Total star mass about 3 x 1041 kg
The Sun is about 28,000 LY from the galactic center
Not very big as galaxies go.

13. The Sun orbits once every 200 million years
The Milky Way Galaxy
The Sun orbits once every 200 million years
Our speed of orbit is about 250 km/s
National Geographic Magazine

14. The Milky Way Galaxy (closeup)
We are in the middle of a “chimney”
National Geographic Magazine

15. Elliptical Galaxy
(Don’t make many new stars)

16. The Whirlpool Galaxy
(spirals make stars
In their arms in an on-going process)

17. Barred spiral channeling material into its core
Giving birth to stars

20. Andromeda with a couple elliptical companions

21. There are many Galaxies...
There are about 1011 galaxies in the visible Universe
The closest is about 2 x 106 LY from us

22. Star Clusters (These are much smaller than galaxies)
Photo and text courtesy
Of the Hubble Space
Telescope site
This stellar swarm is M80 (NGC 6093), one of the densest of the 147 known globular star clusters in the Milky Way galaxy.
Located about 28,000 light-years from Earth, M80 contains hundreds of thousands of stars, all held together by their mutual
gravitational attraction. Globular clusters are particularly useful for studying stellar evolution, since all of the stars in the cluster
have the same age (about 15 billion years), but cover a range of stellar masses. Every star visible in this image is either more
highly evolved than, or in a few rare cases more massive than, our own Sun. Especially obvious are the bright red giants, which
are stars similar to the Sun in mass that are nearing the ends of their lives.

23. Nebulae
Clouds of gas and dust
Birthplace of solar systems and stars
Types of Nebulae
Emission Nebulae – Actually emit light
Reflection Nebulae – Merely reflect light
Absorption Nebulae – Block the light of stars.
Planetary Nebulae – Ejected star material.

30. Large Scale Structures
Groups
Clusters
Super Clusters, Clouds, Walls, Voids

31. NGS Map of the Universe
National Geographic Magazine

32. Groups A few Million LY wide 3 - 6 conspicuous galaxies
A dozen or so smaller galaxies
Only a few times more dense than the Universe
Some of the smaller galaxies orbit the larger ones
Orbital speeds are km/s

33. Our own Local Group
National Geographic Magazine

35. Clusters (of galaxies)
Million LY wide
Hundreds to Thousands of galaxies
( times more dense than the Universe)
The largest gravitationally bound structures
Orbital speeds are around 1000 km/s (faster)

36. Our own cluster and supercluster:
National Geographic Magazine

37. Super Clusters, bubbles, walls
100 Million LY wide or more
Tens of Thousands of galaxies
Modest enhancement of density
Walls and bubbles:
Much larger than Superclusters

38. Each dot is a galaxy:

39. So, putting it all together:
National Geographic Magazine

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53. So where does all the structure come from??
Chaotic condensation from a superhot state…
National Geographic Magazine

54. None of the ideas in this presentation are my own.
Most of the astronomical images are from the Hubble Website
at (unless otherwise noted)
The solar system images came from The Nine Planets web page at
The map of the Universe came from the October 1999 National
Geographic magazine.
The images of galaxy types (B+W) came from my college textbook
“Contemporary Astronomy” by Jay Pasachoff
The classification of large scale structure, and most of my
knowledge of astrophysics came from the most excellent book
“The Whole Shebang” by Timothy Ferris
I also read Jay Pasachoff’s book to answer really
basic questions like “uh what kinds of galaxies, or nebulae
are there?”
Chris Murray