The Universe and Galaxies The Universe and Galaxies

Glencoe Ch.26 Sec. 3: Glencoe Ch.26 Sec. 3:

pages 831-835pages 831-835

I. What is the universe?I. What is the universe?

- universeuniverse - sum of all matter and energy - sum of all matter and energy that ever has, does, and ever will existthat ever has, does, and ever will exist

everything physical that exists in space everything physical that exists in space and timeand time

- - cosmologycosmology – the study of how the – the study of how the universe began, what it is made of and universe began, what it is made of and how it continues to evolve and changehow it continues to evolve and change

- Of what is the universe made / - Of what is the universe made / composed?composed?

stars, planets, rocks, comets, asteroids, stars, planets, rocks, comets, asteroids, dark matter, dark energydark matter, dark energy

- Of what is the universe made / - Of what is the universe made / composed?composed?

- - Dark matterDark matter – theoretical unseen and – theoretical unseen and undetectable mass that adds to the gravity undetectable mass that adds to the gravity of a galaxyof a galaxy

- - Dark energyDark energy – theoretical energy that – theoretical energy that might be causing accelerated expansion of might be causing accelerated expansion of the universethe universe

Most things we see in space are Most things we see in space are starsstars

- - starsstars - huge balls - huge balls of hot gases that of hot gases that emits lightemits light

- stars are grouped - stars are grouped together by the together by the millions and millions and billions into billions into galaxiesgalaxies

A. Astronomical distanceA. Astronomical distance

- measured in light years (ly) - measured in light years (ly) a distance a distance measurementmeasurement

- - light yearlight year - the distance - the distance light travels in one yearlight travels in one year

1 light year = 9.5x101 light year = 9.5x101515mm

light travels at 3.0x10light travels at 3.0x1088m/sm/s

B. Seeing the pastB. Seeing the past

- - time is required for light to travel through time is required for light to travel through spacespace

- light travels a little over 8 minutes from the - light travels a little over 8 minutes from the sun to earthsun to earth

- the farther away an object/star is, the longer it - the farther away an object/star is, the longer it takes for light to get to us, and the older the takes for light to get to us, and the older the light is when it gets to us = “Light is OLD”light is when it gets to us = “Light is OLD”

- we see the past of other stars in the night sky- we see the past of other stars in the night sky

II. GalaxiesII. Galaxies

- - galaxygalaxy - grouping of millions or billions of - grouping of millions or billions of stars, and dust and gas held together by stars, and dust and gas held together by gravitygravity

- there are an estimated 100 billion galaxies there are an estimated 100 billion galaxies in the universein the universe

A. 3 Types of Galaxies - classified by shapeA. 3 Types of Galaxies - classified by shape

II. GalaxiesII. Galaxies1. Spiral - disk shaped with spiral arms of 1. Spiral - disk shaped with spiral arms of

dust and gas (fig 26-15, pg. 831)dust and gas (fig 26-15, pg. 831)

- dust and gas provide a place for new - dust and gas provide a place for new

stars to formstars to form

- young stars are - young stars are

bluish in color bluish in color

gives spiral gives spiral

galaxies a blue tintgalaxies a blue tint

- looks like a pin wheel- looks like a pin wheel

Spiral GalaxiesSpiral Galaxies

II. GalaxiesII. Galaxies

2. Elliptical (fig. 26-16, pg. 832) 2. Elliptical (fig. 26-16, pg. 832) most most common type of galaxycommon type of galaxy

- spherical and egg shaped spherical and egg shaped

NO spiral arms, NO spiral arms,

little dust and gaslittle dust and gas- generally have older generally have older

stars (reddish in color)stars (reddish in color)

Elliptical GalaxyElliptical Galaxy

II. GalaxiesII. Galaxies

- Range of sizes- Range of sizes

a. Giant - trillions of stars, millions of light a. Giant - trillions of stars, millions of light years in diameteryears in diameter

b. Dwarf - millions of stars, thousands of b. Dwarf - millions of stars, thousands of light years in diameterlight years in diameter

II. GalaxiesII. Galaxies3. Irregular (fig. 26-17, pg. 832) 3. Irregular (fig. 26-17, pg. 832) least least

common type of galaxycommon type of galaxy

- NO well defined shape or structure- NO well defined shape or structure- some have little some have little

dust or gas, some dust or gas, some

have lots of dust have lots of dust

and gasand gas

Irregular GalaxiesIrregular Galaxies

B. Milky Way galaxyB. Milky Way galaxy

- the galaxy we live in- the galaxy we live in

- consists of stars, and, clouds of dust and - consists of stars, and, clouds of dust and gas between stars (gas between stars (interstellar matterinterstellar matter))

- all the stars we see at night are in the Milky - all the stars we see at night are in the Milky Way galaxy (about 400 billion stars)Way galaxy (about 400 billion stars)

Milky Way Galaxy – side viewMilky Way Galaxy – side view

- a huge spiraling disk of stars and a huge spiraling disk of stars and interstellar matter (fig. 26-20 pg. 834) interstellar matter (fig. 26-20 pg. 834) 1000 l.y. thick 1000 l.y. thick

Milky Way Galaxy – overhead viewMilky Way Galaxy – overhead view

- A huge bulge in - A huge bulge in

the center the center

10,000 l.y. thick10,000 l.y. thick

Where Are Where Are We In The We In The Galaxy?Galaxy?

- Our solar system Our solar system is about halfway is about halfway between the between the center and the center and the edge of the edge of the galaxy (26,000 galaxy (26,000 light years from light years from the center)the center)

B. Milky Way galaxyB. Milky Way galaxy

- the nearest galaxy the nearest galaxy to ours is the to ours is the Andromeda Andromeda

galaxy galaxy 2.6 2.6 million l.y. awaymillion l.y. away

C. Gravity holds galaxies togetherC. Gravity holds galaxies together

- dust and gases and stars are attracted to - dust and gases and stars are attracted to each other by gravity each other by gravity

- galaxies are grouped galaxies are grouped

into into clustersclusters group group

of galaxies bound of galaxies bound

together by gravitytogether by gravity

C. Gravity holds galaxies togetherC. Gravity holds galaxies together

- Milky Way and Andromeda galaxies are in a - Milky Way and Andromeda galaxies are in a cluster of ~45 galaxies called the cluster of ~45 galaxies called the “Local Group”“Local Group”

- SuperclustersSuperclusters - have - have

thousands of galaxiesthousands of galaxies

largest structure largest structure

in the universein the universe