Introduction to Astronomy. Define the following terms: Define the following terms: – everything that exists, including all matter and energy everywhere

Introduction to Astronomy

Define the following terms:Define the following terms:

Universe – everything that exists, including – everything that exists, including all matter and energy everywhereall matter and energy everywhere

Astronomy – the study of what is beyond – the study of what is beyond Earth (planets, stars, galaxies, black Earth (planets, stars, galaxies, black holes, etc,)holes, etc,)

Constellations – groups of stars that appear – groups of stars that appear to form shapes or patterns (e.g. big dipper)to form shapes or patterns (e.g. big dipper)

Solar system – the Sun and all the planets – the Sun and all the planets (and their moons) that revolve around it.(and their moons) that revolve around it.

GalaxiesGalaxies

A galaxy is a system of stars and A galaxy is a system of stars and interstellar matter. interstellar matter.

Galaxies may contain thousands of stars Galaxies may contain thousands of stars or trillions of stars.or trillions of stars.

What is the name of our galaxy?What is the name of our galaxy?

Non-luminous – not emitting light

There are many non-luminous objects in There are many non-luminous objects in space. space. Moons and and planets do not give off do not give off light, but are visible because they light, but are visible because they REFLECT lightREFLECT light

Luminous – give off light

Stars and and comets are examples of celestial are examples of celestial objects that emit light. These objects are objects that emit light. These objects are highly visible (especially at night). Our highly visible (especially at night). Our Sun (our closest star) emits light Sun (our closest star) emits light constantly, but we only see it when our constantly, but we only see it when our side of the planet has rotated toward the side of the planet has rotated toward the Sun. Sun.

StarStar – a large collection of matter that emits – a large collection of matter that emits huge amounts of energy (light, UV and huge amounts of energy (light, UV and infra-red radiation, X-rays, ). infra-red radiation, X-rays, ).

Planet Planet – matter (gas or rocky material) that – matter (gas or rocky material) that is generally spherical, and revolves around is generally spherical, and revolves around a star.a star.

How is a star different from a How is a star different from a planet?planet?

Stars- Far beyond our solar Far beyond our solar

system (very far from system (very far from Earth)Earth)

- Usually larger than Usually larger than planetsplanets

- Emits its own lightEmits its own light- Surface is very hotSurface is very hot- Appears to twinkle Appears to twinkle

Planets- Within a solar system- There are many (7)

close to Earth- Usually smaller than

stars- Nonluminous- Have cold surfaces- Produce steady light

(when visible)

Astronomical UnitsAstronomical Units

The distances between the Sun and planets The distances between the Sun and planets in our solar system are great – so large, in in our solar system are great – so large, in fact that it is difficult to comprehend.fact that it is difficult to comprehend.

Astronomers have tried to simplify the Astronomers have tried to simplify the concept by using concept by using astronomical units to to measure and represent these distances.measure and represent these distances.

Astronomical UnitsAstronomical Units

This is defined as the average distance This is defined as the average distance between the Earth and the Sun. About 150 between the Earth and the Sun. About 150 million kilometers.million kilometers.

The equation used to calculate the The equation used to calculate the astronomical unit for other planets is:astronomical unit for other planets is:

Distance of planet from Sun

Distance of Earth from the Sun

Astronomical UnitAstronomical Unit

If the astronomical unit for a planet is less If the astronomical unit for a planet is less than one, the planet is closer to the Sun than one, the planet is closer to the Sun than the Earth.than the Earth.

The astronomical unit for Earth = 1 a.u.The astronomical unit for Earth = 1 a.u.

If the astronomical unit for a planet is greater If the astronomical unit for a planet is greater than one, the planet is further from the than one, the planet is further from the Sun than the Earth.Sun than the Earth.

Light YearLight Year

The distance a beam of light can travel The distance a beam of light can travel through space in one year.through space in one year.63 000 AU63 000 AU9000 billion km9000 billion kmUsed for measuring distances beyond our Used for measuring distances beyond our solar systemsolar system

List the 9 (really 8) planets from List the 9 (really 8) planets from closest to the Sun to furthest.closest to the Sun to furthest.

SunSunMercury

Venus

Earth

Mars

Jupiter

Saturn

Uranus

Neptune

Pluto

The Effects of Planetary MotionThe Effects of Planetary Motion

Define the following terms:Define the following terms:

Rotation – the spinning of an object around – the spinning of an object around it’s axis. The Earth spins around an it’s axis. The Earth spins around an imaginary axis that appears to run from the imaginary axis that appears to run from the North Pole, through the centre of the planet North Pole, through the centre of the planet to the South Pole.to the South Pole.

Earth’s RotationEarth’s Rotation


It takes the Earth 24 hours (one day) to spin It takes the Earth 24 hours (one day) to spin completely one time around it’s axis. This completely one time around it’s axis. This motion causes objects beyond the Earth motion causes objects beyond the Earth (Sun, Moon, stars and other planets) to (Sun, Moon, stars and other planets) to appear to move across our sky from EAST across our sky from EAST to WEST.to WEST.



Rotation causes us to experience 2 Rotation causes us to experience 2 phenomena:phenomena:

a) Alternating day and night

b) Gravity

Earth’s RevolutionEarth’s Revolution

Like all planets in our solar system, the Like all planets in our solar system, the Earth revolves around the Sun.Earth revolves around the Sun.


It takes the Earth approximately 365.25 days It takes the Earth approximately 365.25 days (a leap year adds the extra day every 4 (a leap year adds the extra day every 4 years) to complete a single orbit around years) to complete a single orbit around the Sun. This is known as an the Sun. This is known as an orbital period.

We call this orbital period We call this orbital period one year on our on our planet.planet.


The revolution of the Earth around the Sun The revolution of the Earth around the Sun causes us to experience causes us to experience different seasons. . Since the Earth spins on it’s axis with a Since the Earth spins on it’s axis with a slight tilt, there are points when the slight tilt, there are points when the Northern and Southern hemispheres of the Northern and Southern hemispheres of the planet are closer or further away from the planet are closer or further away from the Sun than at other times of the year.Sun than at other times of the year.


When the Northern hemisphere is tilted When the Northern hemisphere is tilted toward the Sun, we experience summer. toward the Sun, we experience summer. At the same time, the Southern At the same time, the Southern hemisphere is tilted away from the Sun. hemisphere is tilted away from the Sun. They would be experiencing winter.They would be experiencing winter.


Moon’s RevolutionMoon’s Revolution

Moons (which are natural satellites) revolve Moons (which are natural satellites) revolve around planets. Our moon revolves around planets. Our moon revolves around Earth. Some planets (like Saturn) around Earth. Some planets (like Saturn) have more than one moon. Some planets have more than one moon. Some planets have no moons.have no moons.

It was thought that Pluto may once have It was thought that Pluto may once have been a moon of Neptune, that instead been a moon of Neptune, that instead began revolving around the Sun.began revolving around the Sun.

Moon’s RevolutionMoon’s Revolution

Explain where you would find the Explain where you would find the North Star (Polaris).North Star (Polaris).

Polaris (or the North Star) is a star that seems to be located directly above Earth’s eems to be located directly above Earth’s North Pole. Because we rotate around North Pole. Because we rotate around this pole, we are always able to see this pole, we are always able to see Polaris (it is always directly above us).Polaris (it is always directly above us).

Polaris (the North Star)Polaris (the North Star)

Why do you think that the North Why do you think that the North Star is important to navigation?Star is important to navigation?

Since the North Star is always above the Since the North Star is always above the North Pole, it is always an indicator of North Pole, it is always an indicator of where North is (as a compass point).where North is (as a compass point).

The North Star is part of the Little Dipper The North Star is part of the Little Dipper constellation which is always visible in the constellation which is always visible in the Northern Hemisphere.Northern Hemisphere.

Polaris in the Little DipperPolaris in the Little Dipper

Pointer StarsPointer Stars

Pointer stars are stars that can be used are stars that can be used as points of reference in the sky to as points of reference in the sky to identify the locations of other identify the locations of other constellations.constellations.

Star MapStar Map

Terrestrial vs. Gas Giant PlanetsTerrestrial vs. Gas Giant Planets

The planets in our solar system can be divided into The planets in our solar system can be divided into 2 categories, based on size, location and 2 categories, based on size, location and composition:composition:

Terrestrial or Inner Planets – these are the 4 small, – these are the 4 small, rocky planets that are closest to the Sun.rocky planets that are closest to the Sun.

Mercury, Venus, Earth and Mars are terrestrial Mercury, Venus, Earth and Mars are terrestrial planets.planets.

Terrestrial (Inner) PlanetsTerrestrial (Inner) Planets

Mercury Venus Mercury Venus EarthEarth Mars Mars

Terrestrial vs. Gas Giant PlanetsTerrestrial vs. Gas Giant Planets

Gas Giant or Outer Planets – these are the – these are the 4 large planets found outside the asteroid 4 large planets found outside the asteroid belt of our solar system. The outer belt of our solar system. The outer portions of these planets are made of portions of these planets are made of gases (hydrogen, helium, methane), but it gases (hydrogen, helium, methane), but it is believed that they have a small rocky is believed that they have a small rocky core.core.

Jupiter, Saturn, Uranus and Neptune are Jupiter, Saturn, Uranus and Neptune are gas giants.gas giants.

Gas Giant (Outer) PlanetsGas Giant (Outer) Planets

Jupiter Jupiter Saturn Saturn Uranus NeptuneUranus Neptune

Properties of MercuryProperties of Mercury

MercuryMercury is the closest planet to the Sun is the closest planet to the Sun sunlight it receives is about 10 times sunlight it receives is about 10 times

brighter than what we receive on Earth.brighter than what we receive on Earth. It takes only 88 Earth days to revolve It takes only 88 Earth days to revolve

around the Sun.around the Sun. rotates slowly (about 59 Earth days for rotates slowly (about 59 Earth days for

one rotation).one rotation).


has no atmosphere (no layer of gases has no atmosphere (no layer of gases surrounding it’s surface).surrounding it’s surface).

Because it lacks an atmosphere, the Because it lacks an atmosphere, the surface temperature of the planet is surface temperature of the planet is variable. On the side that faces the Sun variable. On the side that faces the Sun the temperature can reach 426the temperature can reach 426 °°C. The C. The side that faces away from the Sun drops to side that faces away from the Sun drops to about - 180 about - 180 °°C.C.


The lack of atmosphere means that there The lack of atmosphere means that there is no protective layer that could potentially is no protective layer that could potentially burn up meteors that hit the planet. burn up meteors that hit the planet. Because of this, the surface of the planet Because of this, the surface of the planet is heavily cratered.is heavily cratered.


Properties of VenusProperties of Venus

Earth’s sister planet – it is similar in size, Earth’s sister planet – it is similar in size, density and chemical composition.density and chemical composition.

the hottest planet, with surface the hottest planet, with surface temperatures reaching 470temperatures reaching 470ooC.C.

surface of Venus is largely volcanic.surface of Venus is largely volcanic.


The atmosphere of Venus is primarily The atmosphere of Venus is primarily made up of Carbon Dioxide (a greenhouse made up of Carbon Dioxide (a greenhouse gas) that traps the heat from the Sun. gas) that traps the heat from the Sun. This is why the surface temperature of the This is why the surface temperature of the planet is so high.planet is so high.


A day on Venus is longer than a year.A day on Venus is longer than a year.

It takes Venus 224 Earth days to revolve It takes Venus 224 Earth days to revolve around the Sun.around the Sun.

It takes 243 Earth days for Venus to It takes 243 Earth days for Venus to completely spin once on its axis. This completely spin once on its axis. This planet spins in the opposite direction to all planet spins in the opposite direction to all other planets.other planets.


The planet is named for the Roman god of The planet is named for the Roman god of love and femininity.love and femininity.


Properties of EarthProperties of Earth

the only planet that we know with life.the only planet that we know with life.has an abundance of liquid waterhas an abundance of liquid water it’s atmosphere contains a large quantity it’s atmosphere contains a large quantity

of oxygen (about 20%).of oxygen (about 20%). temperatures on Earth are moderate, temperatures on Earth are moderate,

ranging from -85ranging from -85ooC to 58C to 58ooC at the C at the extremes.extremes.

Properties of EarthProperties of Earth

known as the Red Planet. The soil on the known as the Red Planet. The soil on the surface of the planet is orangish red, due to the surface of the planet is orangish red, due to the high iron content.high iron content.

Mars is thought to have had glaciers and Mars is thought to have had glaciers and running water on it’s surface. It now appears dry running water on it’s surface. It now appears dry and barren. This has led scientists to think that and barren. This has led scientists to think that there may have been some life on the planet, there may have been some life on the planet, though none has been found.though none has been found.

Properties of MarsProperties of Mars


A day on Mars is similar in length to Earth A day on Mars is similar in length to Earth (24.7 hours), but because of it’s distance (24.7 hours), but because of it’s distance from the Sun, it takes twice as long to orbit from the Sun, it takes twice as long to orbit (about 687 Earth days).(about 687 Earth days).

Surface temperature ranges from -120Surface temperature ranges from -120ooC C to 30to 30ooC.C.


Properties of JupiterProperties of Jupiter

the largest planet in our solar system the largest planet in our solar system (diameter is 11 times greater than Earth).(diameter is 11 times greater than Earth).

day on Jupiter lasts approximately 10 day on Jupiter lasts approximately 10 Earth hours.Earth hours.

It takes nearly 12 years to orbit the Sun.It takes nearly 12 years to orbit the Sun.Surface temperature on the planet is about Surface temperature on the planet is about

-160 -160ooC (very far from the Sun).C (very far from the Sun).


The planet has a huge hurricane (larger than The planet has a huge hurricane (larger than 2 Earths), the Great Red Spot.2 Earths), the Great Red Spot.


Properties of SaturnProperties of Saturn

Saturn is the second largest planet in the Saturn is the second largest planet in the solar system. solar system.

Surface temperature on the planet is -Surface temperature on the planet is -180180ooC.C.

the least dense the least dense planet (would float in water)planet (would float in water)


The rings of Saturn are made almost The rings of Saturn are made almost entirely of ice, with some contamination entirely of ice, with some contamination from dust and other chemicals. from dust and other chemicals.


Properties of UranusProperties of Uranus

Uranus takes about 84 years to revolve Uranus takes about 84 years to revolve around the Sun, and 17 hours to rotate around the Sun, and 17 hours to rotate once.once.

Due to it’s distance from the Sun, the Due to it’s distance from the Sun, the surface temperature of Uranus is -210surface temperature of Uranus is -210ooC.C.

Uranus also has rings, similar to Saturn’s Uranus also has rings, similar to Saturn’s rings, but much less extensiverings, but much less extensive

Rotates on it’s sideRotates on it’s side

Properties of UranusProperties of Uranus

Properties of NeptuneProperties of Neptune

Neptune is known as the Blue Planet.Neptune is known as the Blue Planet. It’s surface temperature is -210It’s surface temperature is -210ooC.C. It takes 15.6 hours to rotate, but 165 years It takes 15.6 hours to rotate, but 165 years

to revolve around the Sun.to revolve around the Sun. Neptune has a hurricane known as the Neptune has a hurricane known as the

Great Dark Spot.Great Dark Spot.

Properties of NeptuneProperties of Neptune

Properties of PlutoProperties of Pluto

Pluto is no longer considered to be a planet. Pluto is no longer considered to be a planet. It does not have the same characteristics It does not have the same characteristics as it’s closest planets (the gas giants) and as it’s closest planets (the gas giants) and is thought to have once been a moon of is thought to have once been a moon of Neptune that fell out of orbit around Neptune that fell out of orbit around Neptune and was caught in orbit around Neptune and was caught in orbit around the Sun.the Sun.


Pluto does share characteristics with a Pluto does share characteristics with a group of celestial objects known as group of celestial objects known as dwarf planets (objects that orbit the Sun, are (objects that orbit the Sun, are rounded by their own gravity, but which rounded by their own gravity, but which have not cleared their orbits – meaning it have not cleared their orbits – meaning it has not become gravitationally dominant, has not become gravitationally dominant, and there are other bodies of comparable and there are other bodies of comparable size other than its own moons not under size other than its own moons not under its gravitational influence. its gravitational influence.


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Introduction to Astronomy. Define the following terms: Define the following terms: – everything that exists, including all matter and energy everywhere