Stars and Galaxies Created by the Lunar and Planetary Institute For Educational Use Only Image at

Welcome!  Please complete the pre-assessment  It’s for us—it’s not about you  Please let us know how much YOU know, not how much your friends sitting next to you know

What are we going to cover?  Our Place in the Universe  The Electromagnetic Spectrum  Classifying Stars  Classifying Galaxies  History of the Universe

First up…  Our Place in the Universe  What is our Universe made of?  How big are things? How far away?  How do we know?

What is our Universe made of?  Stars and planets  Gas and dust  Organized into star clusters  Organized into nebulae  Organized into galaxies  Other things:  Black holes  Dark matter  Dark energy What was in your drawing? Image from

Activity!!  Use the Venn diagrams to place the stickers—where does everything go?  After you’re finished, let’s discuss…

Examining the Components  Stars  Gas and dust (Nebulae)  Star clusters  Galaxies

Different types of stars Image from

Types of Stars  Big  Small  Red  Blue  Yellow  In groups  Alone  More later

What is a “star cluster”?   stars formed together at same time   stars may be gravitationally bound together   two types: open (galactic) and globular Image at

Open Clusters   dozens to thousands of stars   young stars! only a few million years old   may still be surrounded by nebula from which they formed   located in the spiral arms of a galaxy   example: Pleiades Image at

More open star clusters Image from

Globular Clusters   millions to hundreds of millions of stars   old! 6 to 13 billion years   mostly red giants and dwarfs   stars are clumped closely together, especially near the center of the cluster (densely)   surround our disk as a halo Image at

What is a “nebula”?  A cloud in space  Made of gas and dust   Can have stars inside  Most of the ones we see are inside our Milky Way Galaxy  Different types Orion image at

Large, massive, bright nebulae Emission Nebula The hot gas is emitting lightThe hot gas is emitting light Orion image at

Colder, darker nebulae Dark dust blocking the hot gas behind it NOAO/AURA/NSF Image from

Leftovers from an Explosion Supernova remnant (smaller, less gas) Image at

What is a “galaxy”?  A large group of stars outside of our own Milky Way  Made of billions to trillions of stars  Also may have gas and dust  Spiral, or elliptical, or irregular shaped Image at

Spiral galaxy--Andromeda NOAO/AURA/NSF Images at and

Elliptical Galaxies Images at and

Irregular Galaxies NASA and NOAO/AURA/NSF Images at and

Our Galaxy: the Milky Way   has about 200 billion stars, and lots of gas and dust   is a barred-spiral (we think)   about 100,000 light-years wide   our Sun is halfway to the edge, revolving at half a million miles per hour around the center of the Galaxy   takes our Solar System about 200 million years to revolve once around our galaxy

The Milky Way Image at

Mapping the Milky Way We can see stars  star clusters  nebulae  Galaxies  Let’s try to Map our Galaxy How do we know what our Galaxy looks like?

Measuring Distances  Parallax (let’s model it)   As Earth orbits the Sun, we see nearby stars move relative to more distant stars   How many degrees did the plate move, relative to the background?   Can you calculate the distance to the plate?   Sine of the parallax (angle) x Earth’s distance to the Sun = Distance to the star   The angles involved for strellar observations are very small and difficult to measure. Proxima Centauri, has a parallax of 0.77 arcsec. This angle is approximately the angle subtended by an object about 2 centimeters in diameter located about 5.3 kilometers away.

Measuring Distances  What is a Light Year?  A light year is the distance light travels in a year. Light moves at a velocity of about 300,000 kilometers (km) each second; how far would it move in a year?  About 10 trillion km (or about 6 trillion miles).  Why do we use light years?  Show me how far 5 centimeters is.  Now show me 50 centimeters.  Now tell me (without thinking about it, or calculating it in meters) how far 500 centemeters is. 2000? 20,000?  We need numbers that make sense to us in relationship to objects; we scale up and use meters and kilometers for large numbers.

Time for a Break! Next Up  Our Place in the Universe  The Electromagnetic Spectrum  Classifying Stars  Classifying Galaxies  History of the Universe

Let’s check your knowledge  Please draw an electromagnetic spectrum on a sheet of paper, and label the parts.  You can work in groups.

Radiation  There are lots of types of light (radiation), including visible and invisible Electromagnetic spectrum

Let’s Observe A Spectrum  What will the spectrum look like with a red filter in front of your eyes? A blue filter?  Hypothesize and test your hypothesis.  Now let’s examine the invisible parts— using our cell phones and a solar cell.

 There are different types of spectra  Continuous  Emission or Bright Line (from ionized gas, like a nebula or a neon sign)  Absorption or dark line (from stars) Illustration at

Radiation  All stars emit radiation  Radio, infrared, visible, ultraviolet, x-ray and even some gamma rays  Most sunlight is yellow-green visible light or close to it The Sun at X-ray wavelengths Image at ience/know_l1/sun.html ience/know_l1/sun.html Image and info at

Using a Star’s Spectrum  We can use a star’s spectrum to classify it. NOAO/AURA/NSF image at

Stellar Evolution

Time to Create a Stellar Graph  Everyone will receive several “stars”  Place them on the large paper, according to their color and their brightness  This is a version of the Hertzsprung-Russell diagram.

Hertzsprung-Russell Diagram Images from and

Young stars form in nebulae from Small Magellanic Cloud Image at

Star-forming region in the Large Magellanic Cloud:

Orion image at

Interstellar “eggs” Movie at

Our Sun is a Regular/ Small Star Image at On the “Main Sequence”

In a few Billion years… Red Giant Image at

Our Sun’s Habitable Zone Billions of years ago, things may have been different  The Sun was cooler (by up to 30%!)  Earth’s atmosphere was different (thicker, carbon dioxide)  Conditions will be different in the future  By many accounts, increases in the Sun’s temperature will make Earth uninhabitable in 1 billion years or less  These changes will also affect other planets… Mars? Animation at gov/97994main _BHabitableZon e.MPG gov/97994main _BHabitableZon e.MPG

By 5 billion years… White Dwarf Image at Small, but very hot

Image at