B. 2) Viewing The Night Sky

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VIEWING THE NIGHT

SKY

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NIGHT SKY

• _{When you look up, you probably notice a bunch of}

bright lights on a clear night.

• _{Whether you see the sun, moon, stars, or other}

planets, you are staring at what latin people referred to as caelum (Ki-Loom), which means heavens or sky.

• _{CELESTIAL OBJECT}_{– any object that exists in}

space (Celestial comes from the Latin word caelum)

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STARS

• STARS – massive collection of gases in space that emits large amounts of energy

• They are called LUMINOUS because they produce and emit (give off) their own light.

• They look very small, but that is only because they are very far away from Earth.

• PROXIMA CENTAURI is the closest star (after our SUN) to Earth and it is

4.243 LIGHT YEARS away from Earth.

• A light year is how far light can travel in a vacuum (space with no matter) in one Julian year, 365.25 days.

• Light can travel 9 460 730 472 581 km in one year!

• Based on that figure, Proxima Centauri is approx. 40 141 022 000 000 000 km away (Forty Quadrillion!!!)

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THE SUN

• The sun is actually just a star and compared other stars it is a

MEDIUM-SIZED star.

• The reason why it looks so big is because it is closer to us than any other star at about 150 000 000 km away.

• There are a lot of stars brighter and dimmer than the sun, but again, it is because of how far they are to us that they look tiny and dim.

• Without the Sun, life on Earth wouldn’t exist.

• Even though it isn’t the biggest star, it is still huge compared to the Earth.

• The sun has a mass 340 000 times that of Earth and the volume is 1 300 000 times the volume of Earth.

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PLANETS

• PLANETS – a large, round celestial object that orbits around a star

• ORBIT – a closed or continuous path that a celestial object takes around another object; elliptical or circular in shape.

• Orbit is caused by the perfect balance of forward motion and the pull of GRAVITY on a celestial object from another one.

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HOW TO BECOME A

PLANET

• _{To be considered a planet, a celestial object}

must:

1. Orbit a star (like the Sun) and no other

celestial object.

2. Contain enough mass so that its gravity

pulls it in to a round or spherical shape,

and

3. Be able to clear other celestial objects out

of its orbit.

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SOLAR SYSTEM

• _{SOLAR SYSTEM}

_{– the Sun and all the}

celestial objects that travel around it

• _{Our solar system contains}

_EIGHT

_{planets in}

it.

• _{The 8 planets are}

_MERCURY

_,

_VENUS

_,

EARTH

,

MARS

,

JUPITER

,

SATURN

,

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TYPES OF PLANETS

TERRESTRIAL PLANETS

(Made of solid material)

GAS GIANTS

(Made up of mostly gases and much larger than

Terrestrial planets)

Mercury Jupiter Venus Saturn

Mars Uranus

Earth (Only planet with living

things and liquid water) Neptune

• Planets seem bright, but only because they reflect

radiant energy (light) from the sun.

• 5 planets can be seen using just your eyes: Mercury,

Venus, Mars, Jupiter, and Saturn.

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MOONS

• Like we orbit the sun, many planets have smaller celestial objects that orbit around them.

• NATURAL SATELLITE – a celestial object that orbits a larger celestial object

• Planets are natural satellites of the sun and MOONS are natural satellites of the planets.

• Moons are also not LUMINOUS and instead reflect the light of the sun.

• Each planet has a different number of moons.

• Mercury and Venus have no moons, but Jupiter and Saturn each have over 60 moons!

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MOONS OF OUR SOLAR

SYSTEM

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GALAXIES

• _GALAXIES_{(from Greek, galaxias, meaning “milky”) – huge, rotating,}

collections of gas, dust, stars, planets, and other celestial objects.

• _{They contain}_BILLIONS_{of individual stars!}

• _{They are very far away and can only be seen in detail using a telescope.} • _{There are}_MILLIONS_{of galaxies and everything that exists together,}

including all matter, energy, and space are called the UNIVERSE.

• _{Earth is part of the}_{MILKY WAY}_{galaxy, named this way because}

ancient observers thought it looked like spilled milk.

• _{At night, you can see the Milky Way as a band of light spread across the}

sky.

• _{Other cultures had different names for it. For example, the Chinese}

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MILKY WAY

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THINGS ARE MOVING

• _{Even though it looks like celestial objects are moving in the sky, it is}

actually the Earth SPINNING while it orbits the Sun.

• _{This is called}_{APPARENT MOTION}_{, when you are moving, but things}

around you look like they are moving. (Like if you spin around in a chair and the walls look like they are moving.)

• _{If you looked down at the Earth from above the North pole, you}

would see it rotates COUNTER-CLOCKWISE direction from west to east

• _{This makes everything seem like they are moving from}_EAST_to

WEST.

• _{Ex. The Sun rises in the east and sets in the west.}

• _POLARIS_{or the}_{NORTH STAR}_{, appears to not move because it is}

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TOOLS TO VIEW WITH

• _TELESCOPES_{allow us to see objects that are very far away.}

• They use MIRRORS and LENSES to collect beams of light

from a source and produce a magnified image.

• _{In 1608, the invention of the spy glass (lower power}

telescope) created by Hans Lippershey of Holland, was able to

magnify the view a few times over. (1st Refracting Telescope)

• _{In 1609,}_{GALILEO GALILEI}_{(physicist, mathematician,}

astronomer, and philosopher) created a higher power

telescope and was helped by his friend Paolo Sharpi, who convinced the Venetian government to not buy from

foreigners and wait for Galileo to make his better version. (1st

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TWO TYPES OF

TELESCOPES

• _{REFRACTING TELESCOPE}_{– a simple tube with a lens (piece of}

curved glass) at each end. The lenses refract (bend) the light in to an eyepiece somebody looks through or you can attach a

camera and record what is seen. (Works like a magnifying glass)

• _{Created images that are not always clear because the lens}

bends the light and the size of the lens is limited.

• _{In 1688, Isaac Newton replaced the lenses with mirrors to solve}

this problem. Mirrors could make clearer images because they could be made much larger than the lenses.

• _{REFLECTING TELESCOPES}_{– mirrors are used to collect the}

light to form the image, then sends it to an eyepiece that magnifies the image. We still use these today.

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REFRACTING & REFLECTING

TELESCOPES

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SPACE TELESCOPES

• _{Earth’s atmosphere makes it hard to get clear images}

using telescopes from the ground.

• At first, they tried putting them on mountain tops,

which explains why you will see observatories on high mountains.

• _{In 1990, the}_{HUBBLE SPACE TELESCOPE}_{(HST) was}

launched in to orbit around the Earth.

• The largest mirror is 2.4 m in diameter.

• The HST produces images that are 4 times the size