Astronomy Notes

ASTRONOMY
STUDY NOTES

Geocentric vs. Heliocentric Models of

the Universe/Solar System

▪Geocentric states the Earth is the center
of the solar system and the Sun and other
planets revolve around the Earth.

▪Heliocentric states the Sun is the center
of the solar system and all the planets
including Earth revolve around the Sun.

WHAT IS THE BIG BANG

THEORY AND HOW/WHEN DID

IT OCCUR?

▪The Big Bang Theory is the accepted theory about how
the universe began. It proposes the universe began as
a very small and dense area that expanded very
rapidly. This happened about 14 billion years ago.

The universe continues to expand, getting bigger and
bigger. As the universe expands, the galaxies and solar
systems in the universe spread farther apart from one
another.

What did the astronomers believe?

▪ Copernicus – Heliocentric Theory states the Sun is
the center of the universe and the planets revolve
around the Sun

▪ Kepler – learned planets orbit in ellipses

▪ Ptolemy- Geocentric Theory stated the Earth was
center of the universe. While wrong it was
important because he helped shape thoughts on the
universe for about 1500 years.

NAME THE EIGHT PLANETS

FROM LARGEST TO SMALLEST

▪Jupiter, Saturn, Uranus, Neptune, Earth, Venus,
Mars, Mercury

Gas Giants

▪Gas giants have deep, massive
gaseous atmospheres.
▪Uranus and Neptune are also
known as the ice giants.

HOW DO THE INNER PLANETS
AND OUTER PLANETS DIFFER?

▪Inner planets are smaller and have a dense
rocky surface. Outer planets are much larger,
have thicker atmospheres, many moons, and
rings.

▪Inner Planets = Terrestrial Planets = Rock Planets: Mercury,
Venus, Earth, and Mars

▪Outer Planets = Gas Giants: Jupiter, Saturn, Uranus, and
Neptune

HOW ARE THE PLANETS EARTH
AND VENUS ALIKE? EARTH AND
MERCURY? EARTH AND MARS?

▪Earth/Venus : Similar is size

▪Earth/Mercury: Same density

▪Earth/Mars – both have/had water

WHAT IS AN ELLIPSE? HOW IS

THIS SHAPE RELATED TO
MOVEMENT OF PLANETS?

▪An ellipse is an oval. The planets
orbit the Sun in this shape.

EXPLAIN WHY THE SUN HAS A LESS

GRAVITATIONAL PULL ON NEPTUNE

THAN IT DOES MERCURY.

▪There is a
greater
distance
between
Neptune and
the Sun.

WHAT TWO FACTORS AFFECTS THE
STRENGTH OF GRAVITY BETWEEN

TWO OBJECT IN SPACE?

▪Mass and Distance

WHAT HAPPENS TO THE FORCE OF

GRAVITY WHEN THE DISTANCE

BETWEEN TWO OBJECTS INCREASES?

▪The force of
gravity decreases

WHAT TWO FORCES WORK

TOGETHER TO KEEP

OBJECTS IN SPACE IN ORBIT?

▪Gravity and inertia

What is gravity?

Gravity is
force that is
the attraction
between
objects.

What is inertia?

An object is will continue to be at rest
until some force is applied causing it to
move.

An object will continue to move until a
force is applied causing it to stop
moving.

The objects in space continue to move
in their orbits, unless there is
something to stop them from moving.

WHAT WOULD HAPPEN TO

EARTH IF THE SUN’S

GRAVITY DISAPPEARED?

▪It would float away into space.

Milky Way Galaxy

▪Our solar system is
located in the Milky
Way Galaxy.
▪It is a spiral shaped
galaxy.
▪Our solar system is
located in one of the
spiral arms of the
Milky Way Galaxy.

PINPOINT OUR LOCATION IN THE

UNIVERSE BY DESCRIBING THE

LOCATION.

▪
Our galaxy, the Milky Way Galaxy, is one of
many galaxies in the universe.

▪
Our solar system is located in one of the spiral
arms of the Milky Way Galaxy.

▪
Our planet, Earth, is the 3rd planet from the sun.

How is the Universe

Organized?

From largest to smallest.

Phases of the Moon

Phases of the Moon

What causes the phases of the moon?

The alignment of the sun, moon, and Earth. The phases occur because
the moon revolves around the Earth. It takes about 28 days for the
moon to make one complete revolution around the Earth.

Why do we only see one side of the moon?

Because the Earth and the moon rotate on their axis at the same speed.

Seasons

Why do we have seasons?

• Seasons are the result of the

tilt of the Earth's axis.

• Earth’s axis is tilted 23.5°.
• This tilting is why we have

SEASONS like fall, winter,
spring, summer.

• The number of daylight

hours is greater for the
hemisphere, or half of
Earth, that is tilted toward
the Sun.

Why do we have seasons?

• Also, the days are much longer than the nights during the

summer.

• During the winter, the Sun's rays hit the Earth at an

extreme angle, and the days are very short. These effects
are due to the tilt of the Earth's axis.

Solstices

• Solstices occur twice a year, when the tilt of the Earth's axis is

oriented at its extremes. Tilted the farthest or closest

• Winter solstice is the shortest day of the year. In the Northern

Hemisphere. It occurs on December 21 or 22 and marks the
beginning of winter.

• The Summer Solstice is the longest day of the year. It occurs

on June 20 or 21 and marks the beginning of summer.

Equinoxes

• A day lasts 12 hours and a night lasts 12

hours at all latitudes.

• Equinox literally means "equal night".
• Sunlight strikes the earth most directly at

the equator.

• This occurs twice a year.

Equinoxes

• The vernal (spring) equinox occurs

March 20.

• The autumnal (fall) equinox occurs

September 22 or 23.

The Earth's seasons are not caused by the
differences in the distance from the Sun

throughout the year.

What is an eclipse?

• An eclipse occurs any time a celestial body passes in

front of the Sun, blocking its light. This can be the Earth
or the Moon.

How many types of eclipses are there?
•There are 2 types of eclipses

–Lunar (moon) eclipses
–Solar (sun) eclipses

Lunar Eclipses

What happens during a lunar eclipse?

• Lunar Eclipse- When the Earth casts a shadow on the

moon, causing the moon to go dark.

• Earth comes between the Sun and the Moon and casts a

shadow on the Moon.

• Occurs during a Full Moon.

What happens during a lunar eclipse?

• The Earth moves between the Sun and the Moon,

blocking the Sun’s light, and causing the moon to glow
red.

Solar Eclipses

What happens during a solar eclipse?

• Solar Eclipse- When the Moon casts a shadow on the

Earth, causing the sun to go dark.

• The Moon comes between the Sun and Earth and casts a

shadow on part of Earth.

• Occurs during a New Moon.

Meteors,
Asteroids, &
Comets

Videos

Big Bang Theory

▪https://www.youtube.com/watch?v=HdPzOWlLrbE

Geocentric vs. Heliocentric Models of the Universe

▪https://www.youtube.com/watch?v=S13Sr-H7TWI

▪https://www.youtube.com/watch?v=UtOEnTiAZlU&t=4s

Planets in Our Solar System

▪https://www.youtube.com/watch?v=libKVRa01L8

▪https://www.youtube.com/watch?v=At0w3pnIVgc

Videos

Planets in Our Solar System

▪Mercury - https://www.youtube.com/watch?v=0KBjnNuhRHs

▪Venus - https://www.youtube.com/watch?v=BvXa1n9fjow

▪Earth - https://www.youtube.com/watch?v=HCDVN7DCzYE

▪Mars - https://www.youtube.com/watch?v=D8pnmwOXhoY

▪Jupiter - https://www.youtube.com/watch?v=PtkqwslbLY8

▪Saturn - https://www.youtube.com/watch?v=epZdZaEQhS0

▪Uranus - https://www.youtube.com/watch?v=m4NXbFOiOGk

▪Neptune - https://www.youtube.com/watch?v=NStn7zZKXfE

▪https://www.youtube.com/watch?v=948Of8BUcT

Elliptical Orbits

▪https://www.youtube.com/watch?v=Rq9Wd3RiNrc

Videos

Gravity & Inertia

▪https://www.youtube.com/watch?v=37HbHG0h7PQ&t=143s

▪https://www.youtube.com/watch?v=vyd71p5r62E

▪https://www.youtube.com/watch?v=w0BYfmyWJ0g

Seasons

▪https://youtu.be/WgHmqv_-UbQ

▪https://youtu.be/tX3Y5bzNDiU

▪https://youtu.be/wwdB22opre0

Videos

Eclipses

▪https://youtu.be/cxrLRbkOwKs

▪https://youtu.be/VW2xRR75lKE

▪https://youtu.be/n7tnHPDH5d8

Moon Phases

▪https://youtu.be/wz01pTvuMa0

▪https://youtu.be/4nbnXlhE-aI

▪https://youtu.be/kFR7HLRMx_o

Videos

Meteors, Asteroids, & Comets

▪