Big Deal:

How can astronomers see objects in space that are so far away?

Standard 2.d– Know the types of equipment astronomers use to study space

Objects in space give off different types of electromagnetic radiation which allow us to understand things about them.

Electromagnetic radiation – a wave in space that has both electric and magnetic properties

Visible light – given off by lights in our homeX-rays – used for medical purposes and for security

reasonsRadio waves – used to broadcast music, television

signals

Radio Telescopes

Location

KeyFeatures

Limitations

Advantages

StudySubjects

Very Large Array, New Mexico Arecibo Observatory, Puerto Rico

Radio Telescopes

LocationIsolated regions (valley floors) to avoid other radio signals

KeyFeatures

Large radius because of weak signals; array of many to pinpoint locations

Limitations Interference with other radio signals; poor resolution

AdvantagesImages can be detected through interstellar dust; Images can be detected from objects that are too cool to give off light

StudySubjects

Distant galaxies, supernova remnants

Arecibo Image of Venus

VLA Image of M87 Galaxy

Location

KeyFeatures

Limitations

Advantages

StudySubjects

Palomar Observatory, California

Optical Telescopes

Hubble Space Telescope

LocationTypically up high (mountains, space) to avoid light pollution

KeyFeatures

Large domes to shield out light

Limitations Scattering of light by atmosphere

AdvantagesImages can be directly viewed; most common and user friendly telescope

StudySubjects

Planets, stars, near galaxies

Optical Telescopes

Hubble Image of Messier 101

Palomar Image of Moon Crater

X-ray Telescopes

Location

KeyFeatures

Limitations

Advantages

StudySubjects

XMM Newton X-Ray Telescope

Chandra Space Observatory

X-ray Telescopes

Location Up in space orbiting around Earth

KeyFeatures

Orbiting because x-rays do not penetrate the atmosphere

Limitations Hard to maintain

AdvantagesImages can be detected from objects that do not give off visible light (like black holes)

StudySubjects

Black holes, supernovas

Chandra Image of Cas A SupernovaXMM Image of RSW86 Supernova

Bottom Line:

Astronomers use optical telescopes, radio telescopes, and X-ray telescopes to study different parts of the universe

Standard 2.d– Know the types of equipment astronomers use to study space

Big Deal:

How did the present universe come about?

Standard 2.g– Know the evidence for how the universe has been expanding

Cosmology – the study of the origin, nature, and evolution of the universe

To explain the origin of the universe, most scientists believe in the Big Bang Theory.

Big Bang Theory -- the theory stating that universe began as a point in space about 13.7 billion years ago and has been expanding ever since.

The biggest evidence for the Big Bang was the redshift of galaxies.

Lots of different scientists contributed, but much of the work was done by Edwin Hubble in the 1920’s and 1930’s

What is redshift?

When a wave source moves, waves change shape.

Wave sources that move away cause waves to stretch. Wave sources that move closer cause waves to compress.

Sound changes pitch. Light changes color.

Galaxies are made up of stars that give off light (EM radiation). The types of radiation depends on the source.

Hubble expected to find certain wavelengths of radiation from certain galaxies.

What he actually noticed was that waves were actually longer than expected.

Having longer waves caused them to appear red – a “redshift”

If the majority of galaxies are “redshifted”, they are moving away from the center and the universe is expanding as a whole.

•That everything in the universe started from a single point in space.

•That is all began about 13.7 billion years ago.

•That the universe is continuing to expand

Because of Hubble’s original work, we now know:

Bottom Line:

An explosion 13.7 bya caused all of the matter in the universe to expand from a singular point in space.

Standard 2.g– Know the evidence for how the universe has been expanding

Big Deal:

Where is most of the mass of the universe found?

Standard 2.b– Know what a galaxy is and what it contains

The universe is composed of galaxies that come in different shapes and characteristics.

Galaxy – a group of stars, dust, and gas held together by gravity

Sombrero Galaxy – 29 million ly awayM81 Galaxy – 12 million ly away

Sprial GalaxyCause Contraction

by gravity

Abundance Less common but easily seen

Brightness Very bright

Other Components

Lots of interstellar gas

Star Formation

Forms new stars

Size Very Large

Movement Rotating arms

Shape Disk-shaped

Cause Colliding galaxies

Abundance Most common

Brightness Dim

Other Components

Little gas and dust

Star Formation

Doesn’t make new stars

Size All sizes

Movement No rotation

Shape Elongated or spherical

Elliptical Galaxy

Cause Interacting galaxies

Abundance Rare

Brightness Somewhat Bright

Other Components

Lots of interstellar gas

Star Formation

Forms new stars

Size Small

Movement No rotation

Shape No specific shape

Irregular Galaxy

Galaxies are parts of galaxy clusters, which are groups of galaxies held together by gravity.

Milky Way Galaxy 100,000 ly across

Andromeda Galaxy 2.5 million ly away

(closest spiral galaxy)

The Milky Way Galaxy and the Andromeda Galaxy belong to the Local Galaxy Cluster (LGC)

Bottom Line:

Most of the mass of the universe is found in one of three types of galaxies – spiral, elliptical, or irregular galaxies.

Standard 2.b– Know what a galaxy is and what it contains

Big Deal:

How do astronomers measure distances in space?

Standard 2.b– Know how big a galaxy is

Distances on the Earth are measured in miles

Circumference of Earth -- 25,000 miles.

Distance to moon -- 240,000 miles

Distances in our solar system are most conveniently measured in astronomical units (AU).

1 AU = the distance from the Earth to the Sun (93 million miles)

Distance to Mars -- 1.5 AU (140 million miles)

Distance to Neptune -- 30 AU (2.8 billion miles)

Distances beyond our solar system are most conveniently measured in light years (LY)

Light travels 186,000 miles per second.

1 light year = the distance light travels in one year (6 trillion miles)

Proxima Centauri is the closest star outside of our solar system.

It is 270,000 AU away or 4.2 light years away.

Canis Major is the closest galaxy outside of the Milky Way

It is 1.6 billion AU away or 25,000 light years away.

Bottom Line:

Astronomical units are used to measure things in our solar system and light years are used to measure things beyond that

Standard 2.b– Know how big a galaxy is

Big Deal:

What happens inside of a spiral galaxy like the Milky Way?

Standard 2.b– Know what a galaxy is and what it contains

The galaxy we belong to is called the Milky Way Galaxy. A few facts about the Milky Way:

•Our sun is one of over 100 billion stars in the Milky Way galaxy

•The Milky Way is just one of billions of galaxies in our universe

•The Milky Way is about 100,000 light-years across and 10,000 light-years thick

100,000 light years

10,000 light years

•It is a spiral galaxy with arms that rotate around the center because of gravity

•It is believed that there is a black hole at the middle

Black Hole

Basic Parts of the Milky Way (and other spiral galaxies)

Arms – the rotating projections coming out of the center. This is where stars are born

Nucleus – the center of the galaxy where stars eventually die

Disk – the collection of arms that project in a plane from the center

Basic Parts of the Milky Way (and other spiral galaxies)

Halo – the region in space above and below the disk containing small clusters of stars

Globular Clusters – groups of stars around the galactic disk that move independently

Bottom Line:

Spiral galaxies rotate because of gravity and are where stars are born.

Standard 2.b– Know what a galaxy is and what it contains

Big Deal:

How do other stars compare to the Sun?

Standard 2.b– Know the different types of stars

All stars exist because of a balance in the star between gravity and nuclear fusion (like in our Sun).

Stars are different due to their:

•Temperature

•Brightness

•Size

•Elements that form

Star Temperature

Blue stars are very hot

White stars are hot

Yellow stars are warm

Red stars are cool

Star Brightness

Apparent Magnitude – measures how bright a star appears to be based on how big it is, how hot it is, and how far away it is (the larger the number, the dimmer the star)

Absolute magnitude – measures a star’s actual brightness regardless of its distance away (as if they were side-by-side

A H-R diagram categorizes stars based on their temperatures, their sizes, and their brightness

Star Size

Low-mass stars:

•Are red in their main sequence stage and produce helium from hydrogen

•Have NO giant phase

•Change to white dwarfs when fusion stops

Star Size

Medium-mass stars (like our Sun):

•Are yellow in their main sequence stage and produce helium from hydrogen

•Change to red giants and produce carbon/oxygen

•Change to white dwarfs when fusion stops

Star Size

Massive stars:

•Are blue in their main sequence stage and produce helium from hydrogen

•Change to supergiants and produce heavier metals like iron and nickel

•Collapse dramatically when fusion stops forcing an explosion called a supernova (which creates even heavier metals like gold)

•Form either a neutron star or a black hole if large enough

Star Size

Bottom Line:

Spiral galaxies rotate because of gravity and are where stars are born.

Standard 2.b– Know what a galaxy is and what it contains