Amazing Astronomy Fact Light from the sun takes 8 minutes to reach you, thus you see the sun as it was 8 minutes ago. It might have blown

up 4 minutes ago and you wouldn't know about it!

How to Measure DISTANCES in Space

• A LIGHT YEAR is the distance light travels in one year

• Example: This galaxy NCG 1300 is 70 million light years away

• That means the light from this galaxy travels 70 million years to reach our eyes.

• Does NCG 1300 look like this today?

How to Measure DISTANCES in Space

• ASTRONOMICAL UNIT

• The distance from Earth to the Sun or 93 million miles

• Used to measure distances inside the solar system and to nearby stars

Astronomical Unit A distance!

• The universe is so ginormous (gigantic + enormous) that scientists came up with a really big unit to measure it

• Astronomical Unit ~ AU

• One AU = 150 million kilometers= 93 million miles

• On average the earth is one AU from the sun

How to Measure DISTANCES in Space

• PARSEC• The distance

between our sun and the nearest star

• The method of parallax gives rise to a natural distance unit that astronomers call the parsec

Speed of Light• Light is the fastest thing we

know

• It travels 300,000 kilometers per second

…that’s 186,000 miles per second

…that’s 5.9 trillion miles per year or one light year

…that’s darn fast

• The speed of light is a constant

Speed of Light A Constant but only in the near vacuum of

space!It actually changes speed as it

moves through materials of different densities

The BIG IDEA!• The BIG Deal:

Astronomers can determine the composition and structure of the universe by studying the electromagnetic energy the universe gives off

• Examples: • Black holes emit X-rays• Stars emit an emmision

spectra-colored bands of light that tell us what the star is made of.

Electromagnetic RadiationA collection of different energies

All these energies travel in waves at the same speed…

the speed of light

Are all the energy waves the same size?

Very Long Waves Very Short Waves

Stars and galaxies that are moving towards us are BLUE shifted

If they are moving away from us they are RED shifted.

Most stars and galaxies are RED shifted

indicating the Universe is EXPANDING at nearly the speed of light!

Galaxies• All galaxies

contain billions of stars and are classified into four basic shapes

• Spiral• Barred Spiral• Elliptical• Irregular

Photographed

by the Hubble

telescope on April 21,

2009this picture appears to be several galaxies colliding together

• THE HUBBLE DEEP Picture - a picture of the farthest galaxies known. This image shows the number of galaxies found in the darkest patch of sky as seen from Earth. It is the size of a period at the end of a sentence held at arms length!

• There are 1500 galaxies in this picture!!

Galaxies

• Spiral Galaxies – are flat, have a concentrated center and pinwheel arms that spiral out

• Gravity pulls matter to the center making it more concentrated

• As the galaxy spins centripetal force makes the galaxy flatten

What our Galaxy would look like from space

What is the name of our Galaxy?

THE MILKY WAY

What is the shape of our Galaxy?IT IS A SPIRAL GALAXY

Our “Milky Way” galaxy from Earth as seen without any light pollution

This photo shows the tremendous gravitational pull and centripetal force on this gigantic galaxy

containing 100’s of billions of stars.

• Barred Spiral Galaxies – also have pinwheel arms, spin, and have a concentrated center and contain billions of stars

• The arrow shows the bar

• They are different from spiral galaxies because their arms extend out straight then curve

Galaxies

• Elliptical Galaxies – contain billions of stars and have an elongated oval shape

Galaxies

What shape is this galaxy?

• Irregular Galaxies – contain billions of stars and have no particular shape

Galaxies

The galaxy, called NGC 1569, sparkles with the light from millions of newly formed young stars. NGC 1569 is pumping out stars at a 100 times faster rate than the Milky Way. This frenzied pace has been almost continuous for the past 100

million years.

Sombrero Galaxy ~ Scientists believe it is a spiral galaxy and have evidence there is a supermassive black hole in the

center. The dust ring around the galaxy gives it the appearance on a sombrero. This light is 28 million years old.

Galactic CannibalismLarger galaxies have been known to pull in matter

from smaller galaxies near by.

In 2.5 billion years the Galaxy of Andromeda will collide with the Milky Way destroying both galaxies and creating a new larger galaxy.

Amazing Astronomy Fact

If you could travel at the speed of light (186,000 miles per second) it would take 100,000 years to

cross our galaxy!

Review

• Galaxies contain billions of stars

• Galaxies are classified into four basic shapes

• Distances between stars and planets are measured in AU’s and light years

• A light year is a distance

• Electromagnetic Radiation ~ energy can travel through space as waves

Other Heavenly

Bodies Nebulas

• A nebula is a large cloud of gas and dust in space, spread out in an immense volume

• All stars begin their lives as nebulas

• A nebula is relatively short-lived, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.

Butterfly Nebula

Red Spider Nebula

Cat’s Eye

Nebula

Horsehead Nebula

Other Heavenly BodiesGlobular Clusters

• A large, round, densely-packed grouping of older stars

• Smaller than a galaxy, most contain less than a million stars

• Stars in globular clusters are all about the same age and the same distance from Earth

Other Heavenly BodiesOpen Clusters

• Open clusters have a loose, disorganized appearance

• Contain no more than a few thousand stars

• They often contain bright supergiant stars

ThePleiades

The Subaru’s logo is

patterned after this

open cluster

Amazing Astronomy Fact   

When you look at the Andromeda galaxy (which is 2.3 million light years away), the light you are seeing took 2.3 million years to reach you. Thus you are seeing the galaxy as it was 2.3 million

years ago.

Review

• Nebulas are the beginning of a star

• Globular clusters contain less than a million stars

• Open clusters contain a few thousand stars

• Asteroids are found in the asteroid belt between Mars and Jupiter

• Comets are made from ice and rocks. Scientists believe they contain exact matter from the beginning of the solar system.

Life Cycle of a Star

Nebulas• A star is born!• All stars begin their

lives as nebulas• In the densest part of

the nebula, gravity pulls gas and dust together and this starts to heat up.

• It is now called a “protostar”

Life Cycle of a Star Stars

• A star will become a small, medium, or large star depending on how much mass is in the protostar

• Small stars last longer and large stars burn out faster

• Our sun is a medium size star and is middle aged at 4.6 billion years old

Life Cycle of a Star H-R Diagram

• The HR diagram has stars on it at every phase in the life cycle. It is like taking a family picture.

• There will be new babies, teenagers, parents, and grandparents. Stars live the majority of their lives in the main sequence (adult) phase

• Today, a star could be residing on the main sequence (adult), but when the star ages by hundreds of millions of years, it begins to run out of fuel. The next "family portrait" may have that exact same star off the main sequence as a red giant (grandparent phase).

Life Cycle of a Star

Death of a Star• Low to medium mass stars

expand and become Red Giants then a small White Dwarf which is the core of the star

• High mass stars expand and become Supergiants, explodes into a supernova, and cooling into a neutron star or black hole.

• This Hubble photo is of a star just after a stellar explosion when it is “dusting off”.

Life Cycle of a Star

Black Holes• Black holes are places

where ordinary gravity has become so extreme that it overwhelms all other forces in the Universe. Once inside, nothing can escape a black hole's gravity — not even light.

•Scientists believe there are millions of black holes in the Milky Way. However, the nearest black hole is many lightyears away, so we don't have to worry about threats to the Earth.

Life Cycle of a Star

Black Holes March 13, 2007• These aren't Christmas

lights; they're supermassive black holes churning away at the centers of distant galaxies.

• This image, taken by a many space- and Earth-based telescopes, is the largest sample ever of the mysterious, light-swallowing giants, which are hundreds of millions of times more massive than the sun.

Hot Topic!! The only thing that gives off light in the universe is…….STARS

Amazing Astronomy Fact

If a piece of the sun the size of a pinhead were to be placed on Earth, you could not safely stand

within 90 miles of it!

Life Cycle of a Star Nuclear Fusion

• The main sequence of a star begins when the star produces fuel

• Two hydrogen atoms collide to form one helium atom

• This collision gives off an enormous amount of energy and is released as electromagnetic radiation