July 21, 2004

Tea Break

• It took Voyager 20 years to get to Pluto. At the same speed, how long does it take to get to the nearest star?

• How long will it take to get to the center of the Galaxy?

July 21, 2004

Looking back through space and time

Constellation-X

JWST, FIRST

WMAP, Planck

LISA, GLAST

Big Bang

inflation

first stars, galaxies,

and black holes

clusters and groups of galaxies

microwavebackground

matter/radiationdecouplingEarly Universe Gap

First Stars Gap

July 21, 2004

Size and Scale of the UniverseSize and Scale of the Universe

Image courtesy of The Cosmic Perspective by Bennett, Donahue, Schneider, & Voit; Addison Wesley, 2002

July 21, 2004

EarthEarth• Planet where we all

live

• Comprised primarily of rock

• Spherical in shape

• 12,700 km in diameter

• It would take 17 days to circumnavigate the globe driving a car at 100 km/hr

• At the speed of light, it would take 0.13 seconds to go all the way around Earth.

July 21, 2004

SunSun

• Star that Earth orbits

• Composed primarily of hydrogen and helium gas

• Uses nuclear fusion in its core to generate heat and light to allow itself to resist the crushing weight of its own mass

• Spherical in shape

• 1.39 Million km in diameter

July 21, 2004

Earth & SunEarth & Sun• The Sun’s diameter is

109 times greater than that of Earth

• Over 1 million Earths would fit inside the Sun’s volume

• Earth orbits the Sun at an average distance of 150 million kilometers. This distance is called an Astronomical Unit (AU)

• It would take 11,780 Earths lined up side to side to bridge the 1 AU between Earth and Sun.

July 21, 2004

• 8.5 planets, thousands and thousands of planetoids and asteroids, billions of comets and meteoroids

• Mostly distributed in a disk about the Sun

• Sun blows a constant wind of charged gas into interplanetary space, called the Solar Wind

The Solar SystemThe Solar System

Boundary between Solar Wind and interstellar space at 100 AU from the Sun (200 AU diameter)

July 21, 2004

The Solar The Solar NeighborhoodNeighborhood• The region of the Galaxy

within about 32.6 light-years of the Sun (65 light-years diameter) is considered its neighborhood.

• Here stars move generally with the Sun in its orbit around the center of the Galaxy

• This region is inside a large bubble of hot interstellar gas called the Local Bubble. Here the gas temperature is about 1 million degrees Kelvin and the density is 1000 times less than average interstellar space.

Direction of Galactic Rotation

To C

ente

r of

Gala

xy

The image is 390 light-years across.

July 21, 2004

You Are Here

The Milky Way Galaxy is a giant disk of stars 160,000 light-years across and 1,000 light-years thick.

There are over 100 Billion stars in the Milky Way

The Spiral arms are only 5% more dense than average, and are the locations of new star formation

The Sun is located at the edge of a spiral arm, 30,000 light-years

from the center

It takes 250 Million years for the Sun to complete one orbit

The Milky Way GalaxyThe Milky Way Galaxy

July 21, 2004

The Local GroupThe Local Group

• Contains 3 large spiral galaxies--Milky Way, Andromeda (M31), and Triangulum (M33)—plus a few dozen dwarf galaxies with elliptical or irregular shapes.

• Gravitationally bound together—orbiting about a common center of mass

• Ellipsoidal in shape

• About 6.5 million light-years in diameter

July 21, 2004

The Local SuperclusterThe Local Supercluster• A cluster of many groups and

clusters of galaxies

• Largest cluster is the Virgo cluster containing over a thousand galaxies.

• Clusters and groups of galaxies are gravitationally bound together, however the clusters and groups spread away from each other as the Universe expands.

• The Local Supercluster gets bigger with time

• It has a flattened shape

• The Local Group is on the edge of the majority of galaxies

• The Local Supercluster is about 130 Million light-years across

July 21, 2004

The UniverseThe Universe1

.3 B

illion

lig

ht-

years

• Surveys of galaxies reveal a web-like or honeycomb structure to the Universe

• Great walls and filaments of matter surrounding voids containing no galaxies

• Probably 100 Billion galaxies in the Universe

The plane of the Milky Way Galaxy obscures our view of what lies beyond. This creates the wedge-shaped gaps in all-sky galaxy surveys such as those shown here.

July 21, 2004

The UniverseThe Universe

Computer Simulation

The observable Universe is 27 Billion

light-years in diameter.

July 21, 2004

1) 1) The Standard RulerThe Standard Ruler• Use knowledge of physical and/or geometric properties of an

object to relate an angular size with a physical size to determine distance.

• Ex: Parallax, Moving Clusters, Time Delays, Water MASERs• Considered to be a direct or absolute measurement.

There are two basic methods for measuring astronomical distancesThere are two basic methods for measuring astronomical distances

R

d

d = R/Tan() R/

July 21, 2004

Trigonometric ParallaxTrigonometric Parallax• Requires very

precise measurements of stellar positions, and long baselines

• Need telescopes with high resolution, and must observe over several years.

• Hipparchos satellite measured distances to tens of thousands of stars within 1,500 light-years of the Sun.

July 21, 2004

2) 2) The Standard CandleThe Standard Candle• Use knowledge of physical and/or empirical properties of an

object to determine its Luminosity, which yields distance via the Inverse Square Law of Light.

• Ex: Cepheid Variables, Supernovae, TRGB, Tully-Fisher• Considered to be relative until tied to an absolute calibration.

b = L/4d2

July 21, 2004

Cepheid Variable StarsCepheid Variable StarsThere is a kind of giant star

whose surface pulsates in and out with a regular period. That period of pulsation is related to the Luminosity of the star.

LMC contains hundreds of known Cepheids all at the same distance. Which allows for robust determination of the Period Luminosity Relationship.

July 21, 2004

To measure cosmological distances a ladder of methods is used to reach further out into the Universe.

Each “rung” in the ladder of distance measuring methods depends on the calibration of the methods “below.”

July 21, 2004

Objects in the UniverseObjects in the UniverseAn overview of what and where…An overview of what and where…

Science Concepts: • The scale and structure of the

Universe is vast and complex. • Objects in space are viewed across

the whole electromagnetic spectrum.

• The Earth is one of many planets, in one of many solar systems, in one of many galaxies in our Universe.

Goals: • To give students a better grasp of

where objects viewed by scientists in our Universe are located relative to Earth.

• To give the students a better understanding of how and why scientists view objects.

• To give students a better understanding of the structure and evolution of our universe and the objects it contains.

Guiding Question: “What’s in the Universe?”

July 21, 2004

Where does everything go• What do they know about these objects? Size, Distance, Age, and

where are they relative to us. • Are they inside our Solar System (near by), outside our Solar

System but inside the Milky Way (Far), or outside the Milky Way (really far)?

Now you try it!• In groups take the little images of the objects and place them on

the poster where you think they should be located in our Universe. • Note these objects are images in various wavelengths.

Objects in the UniverseObjects in the UniverseAn overview of what and where…An overview of what and where…

July 21, 2004

Objects in the UniverseObjects in the UniverseAn overview of what and where…An overview of what and where…

Now that you have placed your images on the poster…•In your groups discuss the image cards together. •With the information given on the cards fill out the worksheet so you have a better understanding of where those objects should be in our Universe.

July 21, 2004

Now go back and check you images on the poster…Are they all in the correct spot?How do they need to be changed?

Change them!

Objects in the UniverseObjects in the UniverseAn overview of what and where…An overview of what and where…

July 21, 2004

How old is the Universe?

• Insert Lindsay’s things here.

July 21, 2004

Reflection and Debrief

July 21, 2004

Reflection and Debrief(Evaluate)

• Now what do we know?

• What are the big ideas here?

• What do our students need to know?

• Is there anything else we need to know?

• Misconceptions

(take notes)

July 21, 2004

Reflection and Debrief (Evaluate)

• What are some of the effective ways to teaching these topics?

• Standards???

(take notes)

July 21, 2004

Backup (CGRO)

July 21, 2004

CGRO (1991-2000)

July 21, 2004

BATSE

July 21, 2004

OSSE

July 21, 2004

COMPTEL

July 21, 2004

EGRET