Study Notes

Sky Science Study Notes

EMIT VS REFLECT
- Things in space that emit (give off and create own light) – sun and stars 

- Things in space that reflect light (do not create their own light) – moons, planets, comets,

asteroids 

CONSTELLATIONS

A cluster of stars in the sky that are grouped together in a particular pattern or shape and have been

given a name. 

- Constellations seem to move across the sky at NIGHT because the earth rotates on its axis.
- The constellations appear to move from east to west, moving "backwards" from the real rotation of the
earth.
- The Ancient Greeks used their imagination to name star patterns based on mythical beings
and heroes

Constellations may look different throughout the night because the Earth is rotating on its axis. 

Stars look different from season to season and you may not see every constellation throughout the year.
This is because the Earth revolves around the SUN. 

Circumpolar constellations are ones we can

see all year in the Northern Hemisphere

E.g. Ursa Minor, Ursa Major and Cassiopeia 

Circumpolar constellations look different throughout 

the year because the earth is rotating around the sun! 

Look at the diagram. Cephus looks different throughout the year! 

THE EARTH AND IT’S ROTATIONS

- The Earth has an imaginary line (running from North to South) through its middle called

THE AXIS.
- The axis is tilted at 23.5° 
- The Earth rotates around its axis and this takes around 24 hours (1 day)
- The Earth also rotates around the sun and this takes approximately 365.25 days.
- This is why we have leap years to make up for the extra ¼ of a day. If we didn’t it would mess up when we have our seasons! We might be in summer but have winter weather!

DAY AND NIGHT

- We have day when the Earth has rotated and we are facing the sun - We have night when the Earth has rotated and we are facing away from the sun 

SEASONS

The reason we have seasons is because of Earth’s tilt.  

In summer, the Northern Hemisphere is tilted towards the sun. Therefore we are getting more direct

sunlight and warmer weather. 

In winter the Northern Hemisphere is tilting away from the sun. Therefore we are getting indirect

sunlight and colder weather.

• In the summer the sun appears to be higher in the sky so our days are longer
• In the winter the sun doesn’t go as high in the sky so are days are shorter
• The sun always rises in the east and sets in the west 

EQUINOX AND SOLSTICE

Equinox: This is when we have an equal amount of daylight and nighttime. This happens in Spring and
Fall. March 21 and September 21

Solstice: These are the days when we have the most hours of sunlight (June 21st) and the least
amount of sunlight (Dec 21st)

SHADOWS

• Throughout the day our shadows changes size and direction. In the morning our shadow starts out longer and gradually gets shorter until midday (when the sun is at its highest) when it is at its shortest point. Then as we head into the afternoon and evening our shadow is growing again until it reaches the same length as the the morning. 
• Our shadows also move from facing west in the morning to facing east in the evening (THE OPPOSITE TO HOW THE SUN RISES)

PHASES OF THE MOON

- The moon is orbiting around the Earth which means what we see is different each night! This is because the moon reflects the sun’s light. 

- Half of the moon is always lit whilst the other half is dark but because the moon is orbiting the
Earth how much of the bright half we see depends on where in the orbit the moon is. 

- The moon orbits the Earth counter clockwise. 

Waxing: this means growing (light is seen on the right)

Waning: this means shrinking (light is seen on the left)

• The moon's cycle occurs approximately once every month (12 times a year). 

ECLIPSES

When the moon is orbiting the Earth it doesn't do it in perfect rotation. It is a tilted rotation.
However, when the Earth, Moon, and Sun line up we can get Eclipses. 

Solar Eclipse: The Moon is directly between the sun and earth and casts a shadow on the earth
(the moon appears black with a red ring or glow around it). Total Solar Eclipse happens when the
moon completely covers the sun’s light. As these create a smaller shadow on Earth only certain
locations will actually see the Total Solar Eclipse. 

Lunar Eclipse: Lunar Eclipses happen when the earth is directly between the sun and the moon. The earth casts a shadow on the moon. 

PLANETS IN OUR SOLAR SYSTEM

In our solar system, we have 8 planets (Pluto is no longer considered a planet). 

The Planets are split up into two categories: Rock (Terrestrial) and Gas 

Planets in order from the sun:

MERCURY  (many)

VENUS (vile)

EARTH (earthlings)

MARS (munch)

JUPITER (jam)

SATURN (sandwiches) 

URANUS (under) 

NEPTUNE (newspaper)

THE SUN

- Our Sun is the center of the Solar System

- The Sun is a star. However, compared to other Sun’s ours is relatively small!

- All the planets orbit the Sun. 

Safety

It is not safe to directly look at the sun. Eye medical doctors (ophthalmologists) caution us that too
much exposure to UV light raises the risks of eye diseases. 

Sunglasses and pinhole cameras are good safety measures but will not fully protect you from the
sun’s radiation. The best way to view the sun is by looking at a picture!