Structure of the Universe

Or What’s Out There and Where is it?

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

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

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

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

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

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

Our Solar Neighborhood:

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

The Milky Way Galaxy 100,000 LY in diameter, 16,000-3,000 LY thick Contains a hundred billion stars (10 11 ) Total star mass about 3 x kg The Sun is about 28,000 LY from the galactic center Not very big as galaxies go. You are Here

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

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

Elliptical Galaxy (Can you see the black hole in the middle of this galaxy?)

The Whirlpool Galaxy

Barred spiral channeling material into its core Giving birth to stars

Andromeda with a couple elliptical companions

There are many Galaxies... There are about galaxies in the visible Universe The closest is about 2 x 10 6 LY from us

Star Clusters (These are much smaller than galaxies) 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. Photo and text courtesy Of the Hubble Space Telescope site

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

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

Groups A few Million LY wide conspicuous galaxies A dozen or so smaller galaxies Some of the smaller galaxies orbit the larger ones Orbital speeds are km/s

Our own Local Group National Geographic Magazine

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)

Our own cluster and supercluster: National Geographic Magazine

So, putting it all together: National Geographic Magazine

So where does all the structure come from?? Chaotic condensation from a superhot state…

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