Astronomy



Vocabulary:

Astronomical Unit

Astronomy

Big Bang Theory

Blue Shift

Celestial Objects

Doppler Effect

Galaxy

H-R Diagram

Hubble’s Law

Light Year

Main Sequence

Milky Way Galaxy

Nuclear Fission

Proxima Centauri

Red Giants

Red Shift

Solar System

Spiral Galaxy

Spectral Analysis

Stars

Star Life Cycles

Super Giants

Universe

White Dwarfs

L

K. Billions of Stars make up a galaxy, but what is a Star… are they all the same?

The Main Classifications of Stars:

______________

______________

______________

______________

______________

Our Sun is classified as a

__________________

__________________

The H-R Diagram

The Hertzsprung-Russell

(H-R) Diagram on the right

is a graph of stars, comparing

luminosity and temperature.

Stars are categorized according

to these two properties!

|Mythology |The Sun God. Greeks Called it Hellos |

|Mass |333 400 times the mass of the Earth |

|Diameter |1 392 000 km (109 x Earth’s diameter) |

|Gravity |28 times that on Earth |

|Surface Temperature |6000°C (average). From 4500 to 2000000°C up to 15000000°C in the core. |

|Period of rotation (day) |Equator 26 Earth days, poles 37 Earth days |

|Tilt of axis |122° |

C. Our Solar System:

Planets:

A planet is a body that is in orbit around the Sun, has enough mass for its self-gravity to overcome forces (nearly round) shape, and clears the neighborhood around its orbit.

Planet order (closest to the sun to furthest): Write one interesting fact about each:

MERCURY: ________________________________________________________

VENUS: __________________________________________________________ EARTH: __________________________________________________________

MARS: ___________________________________________________________

JUPITOR: ________________________________________________________

SATURN: _________________________________________________________ URANUS: _________________________________________________________ NEPTUNE: ________________________________________________________

Eccentricity

The _________ of an ellipse is how much it varies from a true circle. The __________ the number, the closer the orbit is to a perfect circle.

Formula for eccentricity:

Eccentricity=

Know when to use your ESRT!

The Three Kepler’s Laws:

1. Planets move around sun in elliptical orbits. Sun is at one focus point.

2. Planet moves faster when closer to the Sun due to gravitational pull of the Sun.

3.The greater the distance from the sun, the longer the period of revolution because Longer orbits and Slower orbital velocities.

Orbital Energy

• ______________ – the force of attraction between 2 objects

• ______________ – the tendency of an object in motion to continue in motion along a straight path

• The interaction of gravity and inertia keep planets in __________

Energy Transfer

• Energy is transferred between ___________ and ______________ as a planet orbits the Sun.

Orbital Velocity

• The Earth’s orbital velocity is _____________ when kinetic energy is the highest.

• This occurs when the Earth is ___________ to the Sun in its orbit.

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Packet 4: The Universe

(

Unit 4: Astronomy

And you think I’m BIG!!! …

P.S. I’m Delilah

Name:___________________ CLass:______ Date: ________

Note Packet #4

Earth Science

Ms. Gill

A. What is Astronomy?

Astronomy is the scientific study of matter in outer space, especially the positions, dimensions, distribution, motion, composition, energy, and evolution of celestial objects and phenomena. (phenomena: is a hard to explain or almost magical occurrence)

B. There are many different Celestial Objects in our Universe

Celestial objects appear in the sky during day and night. They include:

-The Sun -The Moon

- Planets -Stars

-Comets -Asteroids

-Meteorites -Black Holes

C. But where did these objects originate?

-This Big Bang, which actually sounded more like a low hum, is estimated to have occurred between 12-15 billion years ago!!!

-According to the Big Bang Theory, all the matter in the universe started out as a single point! That point was extremely dense. It became unstable and exploded outward.

-Today the universe continues to expand this is called Hubble’s Law – which states that nearby galaxies are moving away slowly while more distant galaxies are moving away more quickly.

D. The Universe is still expanding! Here is the proof!

Scientists have two major pieces of evidence that support the Big Bang Theory.

1) The Doppler Effect

2) Cosmic Background Radiation

Figures A & B: Raisin bread analogy of

the expanding universe

E. So what is the Doppler Effect?

When an object is moving relative to an observer it distorts the way the observer perceives the object’s electromagnetic radiation. Whoa! What does that mean? Think about when an ambulance drives by, going very fast. The pitch of the siren changes as the ambulance approaches you and passes you. This is because the sound waves’ frequency is increased as it approaches you and decreased as it drives away. Visualize this concept using this diagram and the animation on my eboard.

In 1929, Edwin Hubble observed a similar phenomenon occurred with the light emitted from stars.

He discovered that if an object is moving toward earth it’s light shifted toward the blue end of the electromagnetic spectrum since the wavelength is “squeezed together” producing a shorter wavelength. This is called blue-shift! (Blue to You)

But if the object is moving away from earth, its light is shifted toward the red end of the spectrum, since the wavelength is “stretched out” making it longer. This is called Red-shift! (Red Away)

All galaxies show red-shift in their spectra, meaning they are moving away from us.

F. How big is the Universe?

It is very humbling to contemplate the size of our Universe because it is unbelievably big and therefore it can make you feel VERY small. However it’s also impressive that our civilization has acquired such great knowledge, and it reminds us that we as people are a part of larger system. It is important for us to respect the natural equilibrium of our planet and the universe to whom it belongs. We must work to limit our environmental impact and continue to educate our peers about the delicate balance of this system.

G. Measuring Distance: In order to grasp and describe the vast size of our Universe, we must first develop a measurement standard.

Distances between celestial objects are extremely large.

Rather than miles, astronomers refer to a ____________________ as a standard unit of distance.

One light-year is the distance light travels in one year.

The speed of light is 186,000 mps (300,000 kps).

Thus, one light-year is about 6 trillion miles.

The nearest star to us (Proxima Centauri) is 4.2 light-years away.

Astronomical unit:

Another unit of distance is the _________________________ (AU).

One AU is the distance from the Earth to the Sun (93 million miles)

Distances to other objects are given in multiples of AU.

What is (approximately) the size of the solar system? ___________________________

H. Did you know…

A light year is the distance light travels in a single year – 9,460,528,000,000 kilometers. So the light we see coming from Proxima Centauri left the star 4.2 years ago. Even being the nearest star, Proxima Centauri is incredibly far away. It would take our fastest spacecraft more than 50,000 years to make the journey.

Have you ever heard someone say that you’re seeing the past when you look up at the stars? It sounds romantic and perhaps even silly, but it is correct. For example, when an astronomer views the Andromeda galaxy, he/she is seeing how it was 2.5 million years ago. This is because it has taken that long for the light to reach us here, offering a window into the past that no history book ever could!

I. Components of our Universe.

The best definition of the Universe is: EVERYTHING!

We are all apart of the universe along with everything else you can think of.

Outside of the edge of the universe is nothing. This is confusing because its hard to imagine “nothing”. The universe is expanding into nothing because nothing is in it’s way. All matter makes up the universe.

I like to think of the components like a system of “Russian Dolls.” These components are organized from largest to smallest and they fit inside of each other:

The universe is made of billions of Galaxies

Galaxies are made of billons of Stars

Stars are the Center Solar Systems

Solar Systems are made of planets, moons, comets, asteroids and meteorites.

Planets moons comet, asteroids and meteorites are made of matter.

J. Galaxies

A ______________ is a collection of millions or billions of stars. Galaxies can be spiral, elliptical, spherical or irregular in shape. The Sun is part of the _________ galaxy, which is a spiral galaxy. The Sun is located on one of the spiral arms, far from the galactic center. When you look up on a clear night there is a hazy lighter band that runs across the sky. When you look at this band you are looking at the side of the spiral arm that is adjacent to the arm that our sun is in. Each arm is made of millions of stars. The stars themselves are too far away to see individually, but together their light combines to make the sky lighter in that area.

Must Know Facts about Star Characteristics

A) A star is a huge, shining massive ball of gas in space that produces a large amount of

light and energy.

B) About 75% of stars are apart of groups that orbit each other.

C) They are grouped in large structures called galaxies. (Milky Way).

D) Stars have life-cycles like humans.

E) A stars color depends on surface temperature.

F) Stars vary in their size, mass, density, temperature and composition.

G) ____________________ is the actual brightness of a star.

H) Luminosity depends only a star’s _____________ and __________

I) Most stars have planets that orbit them because of their immense gravity

Composition

Stars are primarily made of __________________ and Helium. Many other elements are present in stars in small amounts. A star’s composition can be determined by ___________________________.

How Do Stars Radiate Energy?

A stars energy is the result of nuclear fusion, in which Hydrogen atoms combine to form Helium atoms, releasing energy. This Electromagnetic energy is radiated by stars.

Spectral Analysis

_____________________ is the study of the electromagnetic spectrum emitted by a star, using a _______________________.

Each element in the star emits radiation is a specific set of ______________

Color and Temperature

A Star’s color that we see with the naked eye depends upon its surface temperature.

As materials become hotter, their color changes from:

Red to Orange to Yellow to White to Blue

What color are the stars in the

Constellation Orion? (ESRT p 15)

Betelgeuse is ________

Rigel is ____________

The H-R Diagram

The Main Sequence is the band into which most stars fall. They lie somewhere in between a:

High temperature, high luminosity

&

Low temperature, low luminosity

Red Giants and Supergiants – cooler, very luminous stars that are very large

White Dwarfs are hotter, low luminosity stars that are small

Star Life Cycles

Stars are born in a cloud of gas and dust, called a _________________.

Most stars remain as ______________________ stars, until their hydrogen fuel is depleted

An average star, like the sun, would go through the Red Giant phase, eventually becoming a _____________________.

A large star would become a ___________________, then explode as a supernova. The result may be a neutron star, pulsar or black hole.

A. Which is bigger: Our Solar System or Our Sun?

Naturally our ____________________ is bigger since the sun is apart of it. An object must always be bigger than something it includes. For example, a shoebox must always be bigger than the shoes. And your shoe must be big enough to fit your foot.

B. Our Sun:

-The sun is a star.

-A ball of hot glowing gases.

-It gets hotter as you go deeper.

-Central force that has a high influence on planets orbits.

-Without the sun’s energy and heat there would be no life on Earth

-It holds everything in place by its gravity.

-It contains about 99% of the mass of the solar system.

The Solar System includes:

• The Sun, a ______________size, middle-aged star

• The eight planets and associated moons

• ________________chunks of rock found mostly in a belt between Mars and Jupiter

• __________________– mass of frozen gas and rock

• These are considered __________________ which appear in the sky during day and night.

D. The Formation of Our Solar System:

• ______________________ large cloud of gas, ice & dust existed

• It began to contract & slowly rotate

• Contraction increased density & rotation

• Gravity began to pull material toward the center

• Density increases = increased rotation & gravity

• Begins to form disk with large center

• Central mass begins to heat up due to contraction

• Temperatures reach 10 million °Kelvin

• Hydrogen atoms begin to fuse together forming Helium

• Fusion occurs, driving the formation of our Sun

• The material outside the central mass forms planets

Size Comparison Jovian vs. Terrestrial

E. The Parts of Our Solar System:

• The ______ is the center of the Solar System

• _______________, also called ___________: (meaning earth-like) the first four planets

• __________________: band of rocks orbiting the sun

• ________________, also called ___________: the four planets farthest from the sun.

Terrestrial Planets:

• Four ___________ planets of the solar system

• Relatively __________ in size and mass (Earth is the largest and most massive)

• __________ surface

• Surface of Venus cannot be seen directly from Earth because of it’s _______________________.

Jovian Planets:

• Much _____________ in mass and size than terrestrial planets

• Much lower average ___________________

• All have rings (not only Saturn!)

• Mostly _________; no solid surface

• Also known as Gas Giants because they are made of mostly hydrogen and helium

Asteroids

• Rocky objects with ____________ or _____________ shapes

• Most orbit in a wide belt between _________ and ____________

• The total mass of all the asteroids is less than that of the Moon

• Believed to be a planet that never formed

• Range in size from dust to almost Moon size

• Photographed by Galileo probe

• Some Named Asteroids:

❖ Ceres: 940 km (Largest known)

❖ Pallas: 523 km

❖ Vesta: 501 km

❖ Juno: 244 km

❖ Gaspra & Ida:

Comets:

• Only visible when they are close to the ________

• Icy nucleus, which evaporates and gets blown into space by solar wind pressure.

• Mostly objects in highly _____________ orbits, occasionally coming close to the sun

• Comet Composition: Dust, rock, frozen methane, ammonia, and water

• Comets normally look like dirty ________________

• When they get close to stars, they begin to vaporize & _______________.

• Forms a coma (tail) from the nucleus (head)

• ___________: glowing trail of particles which always points away from the star

• Comets eventually break up into space debris

• Oort Cloud: large collection of comets beyond ________

Meteoroids, Meteors & Meteorites:

Meteoroids: chunks of randomly moving through space. Usually leftover comet or

asteroid debris

Meteor: Meteoroid that collides with Earth, evaporates in the atmosphere producing

streaks of visible light (“shooting stars”) Most burn up before reaching

the surface

Meteor Shower: Many meteors at one time

Meteorite: Meteor that does not totally burn up, & strikes the Earth’s surface.

The impact creates a crater

How do the Planets move around the Sun?

• All planets move in the same plane (a large imaginary flat surface)

• Orbits generally inclined by no more than 3.4o except for Mercury at 7°

• All planets in almost circular (elliptical) orbits around the sun

• Sense of revolution: counter-clockwise

• Kepler’s Laws govern the planets’ orbits

Orbits

• ____________ – the movement of an object around another object

• __________ – the path taken by a revolving object

• Celestial objects have _______________ orbits

• Velocity changes during revolution; planets further from Sun revolve slower

Elliptical Orbit

• A circle has one central point, called a __________.

• Ellipses have two points, called __________.

• Therefore an ellipse is not a perfect circle.

• Eccentricity is a measure of how off the ellipse is from being a perfect circle.

Calculate the eccentricity of the ellipse below:

foci

foci

Regents Question: Which object is located at one foci of the elliptical orbit of Mars?

(1)the Sun (3)Earth

(2)Betelgeuse (4)Jupiter

Laws of Planetary Motion

• Devised by German astronomer Johannes Kepler

• He discovered the line joining the Sun and a planet sweeps equal areas in equal intervals of time

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