Unit 3.1 The night sky
Stars ✨
-huge balls of gas that give out light
- appear to flicker because light changes direction as it travels through the atmosphere.
-the only objects that continuously give out light at night that we can see
-The Sun is a medium-sized star.
Planets �
-objects made of rock or gas that are
in orbit around stars
-don’t give out light
-can be seen because light from the Sun
is reflected off them into your eyes
-there are 8 planets orbiting the Sun that make up the solar system.
-Mercury, Venus, Mars, Jupiter and Saturn can be seen with the naked eye.
-You need a telescope to see Uranus and Neptune.
-Dwarf planets orbit the Sun but are smaller than planets . Eg; Pluto
-Exoplanets are planets in orbit around a star other than our Sun.
Moons�
The Moon is an object that orbits a planet, sometimes called a natural satellite.
-The Earth has only one moon, made of rock, the only object beyond the Earth that a
person has set foot on.
We can see it on a clear night because light from the Sun is reflected off it into ur eyes.
-Other planets in the solar system have their own moons, but can’t be seen without a telescope.
-Saturn has 60 moons and Titan, one of its moons, is bigger than the planet Mercury.
Comets
A comet is made of ice and dust like a big, dirty snowball
orbiting the Sun.
-A tail that makes a spectacular sight, produced when they get
nearer to the Sun
-Comets can disappear and appear out of nowhere after
hundreds or thousands of
years.
-Comet Encke can be seen every 3 years.
Meteors and meteorites
-Meteor is a particle of dust or a piece of rock that burns up
when it enters the Earth’s atmosphere and produces a streak
of light.
-A meteorite is a piece of rock that survives to reach the ground.
-People called them ' Shooting stars '
-When the Earth moves through a dust left by a
comet, you can see meteor showers and tiny meteorites hits the surface of the Earth all the time.
Man-made objects
-The international Space station is the biggest and brightest of all the manmade objects orbiting the Earth.
-Thousands of man-made or artificial satellites are in orbit around the Earth.
-can be seen when light from the Sun is reflected off them
-The Global Positioning System(GPS) pinpoints the position of something
using a lot of satellites.
Objects that we can see without a telescope ;
the Sun, stars, planets(MVMJS), the Moon, comets,
meteors, man-made satellites
Unit 3.2 Day and Night
Sunrise
-The Sun appears from below the horizon every day at sunrise, rises until it reaches the highest point at noon
and moves down again until sunset.
-The Sun appears to move across the sky because the Earth is spinning.
Day and Night
-We have day and night because the area that is in the light from the Sun changes as the earth completes a
rotation on its axis every 24 hours.
-Half of the Earth lights up(day) and consequently, the other half is in shadow(night).
-Day and night is caused by the earth spinning on its axis,
not by moving around the Sun. It takes one year for the Earth to orbit around the Sun.
-Looking from above the north pole ,the Earth is spinning anticlockwise which means that the Earth rotates
from the west towards the east.
Unit 3.3 The seasons
Changing in day length
-Ever wondered why days seem shorter sometimes and the Sun seems to rise
earlier?
-It’s because the earth’s axis is tilted.
The tilt of the Earth’s axis
-The year taken for the Earth to orbit the Sun once is divided into 4 seasons;
spring, summer, autumn(fall) and winter.
-Countries near the poles have huge differences in weather while the
countries around the equator do not notice much change.
Summer⇒ days get longer and warmer
Winter⇒ days get shorter and colder
Earth’s axis is tilted by an angle of 23.5°(doesn't change), which explains;
● Different day length in summer and winter
● Different temperatures in summer and winter
● The varying height of the Sun in the sky in
summer and winter.
The North Pole faces towards/away the Sun(6 months each),
the South Pole faces towards from the Sun(6 months).
●
Day length
The North Pole/ South Pole faces towards
and away from the Sun for six months
each.
Day length
Northern hemisphere(half of the Earth that is north of the equator)
-Spring; 1 March, Summer; 1 June, Autumn; 1 September, Winter; 1 December
longer presence of the Sun⇒ warms the
Earth longer⇒ hotter
2) The rays of the Sun hit the surface at 90° ⇒ more heat energy per m2 per second
⇒ the Earth’s surface heat up faster⇒ hotter
-It’s colder in winter because
1) shorter presence of the Sun⇒ colder
2) Surface is tilted at an angle⇒
sun’s rays spread out⇒ less heat
energy⇒ colder
** It gets hotter in summer not because
the Earth is closer to the Sun
but because of the angle of the Sun’s rays that hit the Earth.
** The Earth is slightly closer to the Sun in January(orbit is nearly circular)
Height of the Sun in the sky
In summer, the sun is higher up in the sky
than in winter because
-the sun’s rays hit the surface directly which
make it appear higher in the sky(summer)
-the sun rays hit the earth at an angle(not
direct) which make it appear lower in the
sky(winter)
(because of the Earth’s tilted axis)
Unit 3.4 Stars
Our Sun
-Our Sun is a medium-sized star.
-Arcturus, one of the stars that is hundreds
of times
bigger than our Sun, looks smaller than our Sun
because it’s so much further away.
-We can only see stars at night or in the evening
because the light from the Sun is so bright that it blocks the light of the other stars.
The Earth spins
A timelapse of stars over hours forms circles because the
earth is spinning on its axis.
- From the northern hemisphere, the centre of the photo is the
northern pole star(Polaris), always at the north, doesn’t move,
cuz it’s aligned with the axis of rotation of the Earth.
-From the southern hemisphere, it’s the southern pole
star(Sigma Octantis)
** People used them for navigation in ancient times.
Constellation
A collection of stars that makes a pattern is called a constellation, such as plough
(Ursa Major). It’s easier to describe stars in constellations rather than individually.
-You see different constellations in the southern and northern hemisphere.
North⇒ Cassiopeia, South⇒ Crux
The Earth orbits the Sun
-The Earth orbits the Sun, so we see different stars in
summer and winter.
-You can only see the stars in the direction facing away
from the Sun, the constellations you saw six months ago are
blocked by the Sun.
The life and death of a star
-Our Sun has a life cycle, as an animal does.
-It is born and it will die.
–Like all stars, the Sun was born from a cloud of gas and dust
called nebula.
-Gravity pulled the gas together.
-Hydrogen gas is used in nuclear fusion reactions to produce the energy that makes the Sun shine.
-This is the stage where our Sun is now.
-It’s a main sequence star(the longest stage of a star’s life cycle).
-It will carry on shining for another 5 billion years.
The final stages of the Sun’s life(after the H gas has been used up)
-Become a red giant⇒ swallow up Mercury, Venus and possibly Earth
-outer layers will be thrown out into the space as clouds of gas
-After, shrink back⇒ a hot white dwarf
-it cool down ⇒ an invisible black dwarf
* For a massive star, it will turn into a super red giant, explode to form a supernova and then form a
neutron star or a black hole.
-A massive star is a star that is bigger than our Sun.
-A neutron star is formed when a massive star runs out of fuel.
Unit 3.5 Our solar system
A solar system is a collection of planets in orbit around a star.It contains four inner planets, an asteroid
belt and four outer planets.
-The star of our solar system⇒ the Sun
-it was formed about 5 billion years ago when gravity pulled dust and gas together.
The inner planets
-Mercury, Venus, Earth, Mars
-called terrestrial planets cuz they are
made of rock
Mercury
-closest to the Sun
-up to 430° and cools to -170° at night
Venus
-called the morning/evening star as it
reflects a lot of light from the Sun
-has an atmosphere, mainly CO2, a greenhouse gas that traps heat energy from the Sun that makes its hotter
than mercury
-average⇒ 460°
Mars
-the only other planet that may have had life, mission Curiosity in 2012 launched
to see if it’s true, its features hint that water once flowed there
-known as the Red planet as its surface is made of a red mineral that contains iron.
The asteroid belt
-Between Mars and Jupiter is the asteroid belt.
-Asteroids are pieces of planets or moons, ot lumps of rock left over from
when the solar system was formed.
-There are millions of asteroids in the asteroid belt and they orbit the Sun like
the planets do.
-The largest asteroid, Ceres, is also a dwarf planet.
-It’s one third the size of the moon.
The outer planets
-Further away from the Sun than the inner planets
-Jupiter, Saturn, Uranus and Neptune, all much bigger than the inner planets
-Jupiter and Saturn⇒ gas giants(mainly made of H and He gas)
-Uranus and Neptune⇒ ice giants(made of ice and rock with an outer layer of gas, has the coldest atmosphere
in the Solar system)
-have rings (unlike the inner planets)made of dust, ice particles and pieces of rock(some huge, some as small
as a grain of sand)
Dwarf planets
-Five dwarf planets in the solar system
including,
*Pluto(a planet until 2006)
*Eris
*Haumea
*Makemake
*Ceres(the largest asteroid)
The planets in the Solar system in order
of size(largest to smallest)
The Sun＞Jupiter＞Saturn＞Uranus ＞ Neptune＞Earth＞Venus＞Mars＞Mercury
Size and distance from the Sun