Science USA test prep assignment STARS AND GALAXIES · 2018. 2. 1. · Science Tuesday, February 6,...

Science Tuesday, February 6, and 8, 2018

OLS Unit 3 Lesson 1 and 2 USA test prep assignment

STARS AND GALAXIES STARS enormous spheres of plasma formed from strong gravitational forces

PLASMA the most energetic state of matter;

responsible for the characteristic

glow emitted by these heavenly giants

STAR COMPOSITION mostly made up of the element hydrogen. Hydrogen atoms

fuse together in the cores of stars through a process called nuclear fusion. When

hydrogen atoms fuse, helium atoms, energy, and light are produced.

STAR LIFE CYCLE stars only exist for a certain amount of time before they burn

out. They each have their own life cycle.



LIFE CYCLE OF A STAR

1. PROTOSTAR – birth of a star

• within a nebula, which is a huge cloud of dust and gas, gravitational

forces cause dust and gas to collapse and become more dense

• as gravity pulls in more gas and dust from the surrounding nebula,

the ball of material continues to collapse and become more and

more dense

• if the force of the material pushing out equals the force of gravity

making the material collapse, then fusion will take place and a star is

born.



• Once fusion occurs and the protostar becomes a star, the star has

entered the main sequence

2. THE MAIN SEQUENCE

• A star spends the majority of its life fusing hydrogen into helium.

• This fusion keeps the star from collapsing under its own gravity and

causes the star to shine and send out heat into space.

• As the star gets older and begins to run out of fuel, the outer layers

of the star will start to expand as the star loses its flight with gravity.

• The star enters its red giant or super red giant stage (depending on

how big the star originally was)



3. GIANT OR SUPER GIANT

• Once a star runs out of hydrogen fuel, the core begins to quickly

contract and the star begins fusing helium into carbon to fight

gravity.

• While this is happening, the outer layers of the star begin to expand

quickly and the star takes on a much darker red color. This is why it is

called a ‘red giant’ in small and medium sizes and ‘super red giant’ in

larger stars.

• Once the star completely runs out of fuel, it is forced to give into

gravity and the star dies.

4. DEATH OF A STAR

• Once a star runs out of fuel and is forced to give into gravity, the

remaining material is collapsed inward by gravity very quickly.

• In small and medium sized stars, the star contracts as far as gravity

can force it to and it becomes a white drawf. After it cools, which

takes billions of years, a white dwarf comes a black dwarf.

• In larger stars, when fuel runs out and the material contracts, a huge

explosion happens. Depending on the star size, this explosion is

called a nova or super nova. Most of these large stars become

neutron stars which are made of incredibly dense material and

continue to give off radiation.



• The largest stars will end their life by becoming a black hole. Black

holes are dense and have such a strong gravitational pull that not

even light can escape them.

H-R Diagram (Hertzsprung-Russell Diagram)

Tool that shows relationships and distances between stars

Shows stars’ luminosity (light and temperature)

Shows stars at different ages/stages at the same time

WHAT IS A GALAXY?

a. Large group of stars, gas, and dust in space that are held together by

gravity b. Largest galaxies contain more than a trillion stars; smallest galaxies

may have only a few million c. Scientists estimate the number of stars from the size and brightness

of the galaxy.



1. Spiral Galaxies

• Shaped like flattened disks with one or more spiral arms

• Contain nebulas

• Our galaxy, the Milk Way, is a spiral galaxy i. Our solar system is located in one of the spiral arms

ii. The Milky Way galaxy is one of the largest galaxies in the

universe iii. Scientists used to believe that the Milky Way was a classic

spiral galaxy, but they now believe it may actually be a Barred

Spiral Galaxy

• Barred Spiral Galaxies are shaped like spiral galaxies, except their

arms begin spiraling out from the straight line stars instead of from

the center. i. Barred spiral galaxy

2. Elliptical Galaxies



• About 1/3 of all galaxies

• Simply massive blobs of stars

• Round or elliptical in shape

• Contain very little gas or dust

• No new stars are forming because of little gas

• The largest and smallest galaxies are elliptical galaxies

• Do not contain nebulas 3. Irregular Galaxies

• Do not fit into any other category

• Chaotic mix of stars, gas, and dust

• Usually found near large spiral galaxies who may be distorting their

shape

CONTENTS OF GALAXIES

Stars, planetary systems, gas clouds, and star clusters.

Nebulae are giant clouds of gas and dust where stars may be formed (found in

spiral galaxies, but not elliptical galaxies)

Galaxy Clusters – groups of galaxies that are bound together by gravity;

made up of star clusters; star clusters are made up of stars bound together by

gravity

Stars star clusters galaxies galaxy clusters

http://antwrp.gsfc.nasa.gov/apod/image/9912/sexaubv_hunter.jpg



Deep Sky Objects most of the objects that astronomers study are far beyond

our own solar system including clusters of stars and several kinds of nebulae or

clouds

Extra vocabulary

Nebula – (plural is nebulae) is a cloud of dust and gas that

exists in space, usually between stars

Planetary nebula – a relatively small, ball-shaped nebula

that surrounds a star. The nebula forms from material

ejected from the star’s outer layers as the star begins to collapse.

Diffuse nebula – larger nebula with an irregular shape.

Diffuse nebulae located near stars reflect starlight or

give off their own bright light.

Star cluster – group of stars bound to each other by gravity.

Star clusters can be classified into 2 general categories,

galactic clusters and globular clusters.

Galactic cluster – an open cluster of stars that

are loosely bound to each other by gravity

Globular cluster – spherical cluster of stars that



are tightly bound to each other by gravity

Star life cycle video: https://www.youtube.com/watch?v=PM9CQDlQI0A

LIGHT YEARS AND THE HR DIAGRAM

Video on light years: https://safeshare.tv/x/ss588f68fdbbb9f

LIGHT YEARS

The distance that light will travel through a vacuum in a year

Light can travel 7 times around Earth in 1 second

SPEED OF LIGHT

Light travels at 299,782,485 meters per second or 186,00 miles per second

It takes 8 minutes for the light from the sun to reach

the Earth. It would take 180 years to drive nonstop at 60 mph to go the same

distance.

https://www.youtube.com/watch?v=PM9CQDlQI0A



HERTZSPRUNG-RUSSELL DIAGRAM (HR DIAGRAM)

Used to classify stars by…

Size – how massive the star is

Temperature – A star’s color reveals its temperature

Red stars have a cooler temperature, and blue stars have a warmer

temperature

Brightness/Magnitude – The amount of light a star gives off depends on the size

and temperature

BRIGHTNESS OR MAGNITUDE

How bright a star looks fromm the Earth depends on both how far the star

is from Earth and how bright the star actually is

A star’s brightness can be described in two ways: apparent magnitude and

absolute magnitude

APPARENT MAGNITUDE

The brightness of a star as seen from the Earth

ABSOLUTE MAGNITUDE

The brightness of a star as if it were 32.6 light years from Earth

The brightness of the stars is compared to the brightness of SUN. We call this

LUMINOSITY.



HOW WE RECORD LIGHT WAVES CAN DETERMINE THE DIRECT OF STARS

MOVEMENT

HR DIAGRAM

An HR diagram shows the most important characteristics of stars, which are

temperature and absolute magnitude (brightness) and/or luminosity.

Scientists plot the surface temperatures of stars and their brightness on a

graph.



OLS UNIT 3 LESSON 1

The universe before the big bang was a densely packed space.

If a star is moving away from the earth, its visible light will be shifting toward red.

One fact used as evidence that the universe began with the big bang was leftover

energy in the universe from the event.

OLS UNIT 3 LESSON 2

The number of stars found in a galaxy are billions.

An irregular galaxy does not have a distinctive shape.

A barred spiral galaxy often looks like this

The word elliptical refers to an oval.

What best describes how galaxies exist in the universe is they form clusters that

are light years away from each other.

A light-year is the distance light travels in one earth year.

A star that is 8 light years away will take 8 earth years to reach earth.

Science USA test prep assignment STARS AND GALAXIES · 2018. 2. 1. · Science Tuesday, February 6,...

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