highschool/Grade 9/Science/SNC1DZ/Unit_5_Astronomy_Study_Sheet.md

Unit 5: Astronomy

Terms

• AU = Astronmical Unit, which is the distance between the sun and the Earth = \(`1.5 \times 10^8km`\)
• 1 Light year = \(`9.46 \times 10^{12}km`\)
• Satellite: Celestial objects that travel around a planet (or dwarf planet)
• Orbit: Closed path of a celestial object/satellite as it travels around another celestial object.
• Celestial Object: Any object that exists in space.
• Universe: Everthing that exists, including all energy, matter and space
• Electromagnetic Spectrum: is the range of frequenices (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.
• Electromagnetic Radiation: refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
• Our milky way is a spiral yeet (forgot full lesson, think this is all you need).

Layers of the Sun

Layer	Temperature	Description
Corona	5800oC	- Gleaming white, halo-like - extends millions of km into space
Chromosphere	65 500oC
Photosphere	5 500oC	- The layer just below the Chromosphere where the light we see originates

Inside Of The Sun

Zone	Descrption
Convection Zone	- The outermost ring of the sun, comprosing of the 30 percent of its radius
Radiative Zone	- The section immediately surrounding the core, comprising 45 percent of its radius

Core

• Hottest part of the sun, reaching \(`15,000,000^o`\)C
• Energy released by nuclear fusion continues to move outward until it reaches the photosphere

• Compostion

  • 75% hydrogen
  • 25% helium (with small amounts of other gases)

Nuclear Fusion

• The sun is made out of hydrogen atoms.
• The Sun’s energy comes from the nuclear fusion reactions that occur in the core of the Sun.
• High temperatures and pressure cause particles to collide at extremely high speeds. The hydrogen atoms of the sun fuse together forming helium atoms.
• Gives off enormous amounts of energy.

Suns Affect on Earth

The Aurora Borealis (Northern Lights)

• The Northern Lights are the result of collisions between gaseous particles in the Earth’s atmosphere with charged particles released from the sun’s atmosphere.
• Solar winds travelling toward Earth follow the lines of magnetic force created by Earth’s magnetic field (which is strongest near the NORTH and SOUTH poles).
• Near the poles, they come in contact with particles in Earth’s atmosphere, producing a display of light in the night sky.
• Northern Lights = Aurora Borealis.
• Southern Lights = Aurora Australis.

Earth’s Rotation And Seasons

• The reason of why we have seasons is due to Earth’s rotation around the sun (orbit), its like an egg shaped orbit, we have have summer when the earth is the closest to the sun, and winter when its the farthest away.
• Earth spins on an angle, and makes one revolution per 24 hours, and the side facing the sun is morning and the other is night.

Lunar Eclipses

• Lunar eclipses occur when Earth’s shadow blocks the sun’s light, which otherwise reflects off the moon. There are three types — total, partial and penumbral — with the most dramatic being a total lunar eclipse, in which Earth’s shadow completely covers the moon
• A total lunar eclipse occurs when the moon and the sun are on exact opposite sides of Earth. Although the moon is in Earth’s shadow, some sunlight reaches the moon. The sunlight passes through Earth’s atmosphere, which causes Earth’s atmosphere to filter out most of the blue light. This makes the moon appear red to people on Earth.
• A partial lunar eclipse happens when only a part of the moon enters Earth’s shadow. In a partial eclipse, Earth’s shadow appears very dark on the side of the moon facing Earth What people see from Earth during a partial lunar eclipse depends on how the sun, Earth and moon are lined up.

A lunar eclipse usually lasts for a few hours. At least two partial lunar eclipses happen every year, but total lunar eclipses are rare. It is safe to look at a lunar eclipse.

Solar Eclipses

• Sometimes when the moon orbits Earth, it moves between the sun and Earth. When this happens, the moon blocks the light of the sun from reaching Earth. This causes an eclipse of the sun, or solar eclipse. During a solar eclipse, the moon casts a shadow onto Earth
• The first is a total solar eclipse. A total solar eclipse is only visible from a small area on Earth. The people who see the total eclipse are in the center of the moon’s shadow when it hits Earth. The sky becomes very dark, as if it were night. For a total eclipse to take place, the sun, moon and Earth must be in a direct line.
• The second type of solar eclipse is a partial solar eclipse. This happens when the sun, moon and Earth are not exactly lined up. The sun appears to have a dark shadow on only a small part of its surface.
• The third type is an annular solar eclipse. An annular eclipse happens when the moon is farthest from Earth. Because the moon is farther away from Earth, it seems smaller. It does not block the entire view of the sun. The moon in front of the sun looks like a dark disk on top of a larger sun-colored disk. This creates what looks like a ring around the moon.

The Solar System

Planets

1. A planet must orbit a star
2. A planet must be big enough for its gravity to pull into a round shape
3. It must be big enough to clear most asteroids out of its path for its orbit.

• If they can’t do these things, it’s not a planet, it’s a dwarf planet.

Drawf Planets

• A celestial object that orbits the Sun and has a spherical shape but does not dominate its orbit.
• Ceres, Pluto, Haumea, Makemake, and Eris
• Pluto’s tilted orbit crosses Neptune’s orbit
• 

The Inner Planets

• Mercury, Venus, Earth & Mars.
• Small rocky planets.
• Located between the Sun and Asteroid Belt.

Planet	Orbital Period	Rotation	Atmosphere	Temperature	Number of Moons	Rings?	Unique Characteristics
Mercury	88 days	59 days	None	180 to 400oC	0	No	- No atmosphere to trap heat - Contains craters - Rarely visible in our night sky because its is so close to the sun
Venus	224.7 days	243 days, (Opposite rotation)	Carbon dioxide, nitrogen	462oC	0	No	- Brightest object in the sky after the Sun & Moon
Earth	365.26 days	24 hours	Nitrogen, Oxygen	-88 to 58oC	1	No	- Ozone filters some of the damaging radiation from the Sun - Temperatures are constant - 70% of planet’s surface is water
Mars	687 days	24.65 hours	Carbon dioxide, Nitrogen	-90 to -5oC	2	No	- Called the red planet due to its rusty soil - Very dry - Once had volcanoes, glaciers, & water

The Outer Planets

• Jupiter, Saturn, Uranus, Neptune
• Large, composed of gas.
• Atopsheres consist mainlyof the gases hydrogen and helium.

Planet	Orbital Period	Rotation	Atmosphere	Temperature	Number of Moons	Rings?	Unique Characteristics
Jupiter	11.9 years	9.85 hours	Hydrogen, Helium, methane	-148oC	63	Yes	- Largest planet (11x the diameter of the Earth) - Features are its coloured bands, the Great Red Spot & hurricanes - Orbiting rings of rocks
Saturn	29.5 years	10.65 hours	Hydrogen, Helium, Methane	-178oC	60	Yes	- Second largest, no solid core - Cloudy & windy, over 1000 separate rings
Uranus	84.1 years	17.3 hours (on its side)	Hydrogen, Helium, Methane	-216oC	27	Yes	- Winds blow up to 500km/h
Neptune	164.8 years	15.7 hours	Hydrogen, Helium, Methane	-214oC	13	Yes	- Uneven orbit, Bright blue & white clouds - Has a dark region called the Great Dark Spot, which appears to be the center of a storm

Asteroids

• They are composed of rock & metal.
• Although they orbit the Sun, they are too small to be considered planets.
• Most asteroids lie in the asteroid belt, located between Mars & Jupiter.
• A meteroid is a piece of metal or rock that is smaller than an asteroid.
• Sometimes a meteroid get pulled in by Earth's gravity. They burn up in the Earth’s atmosphere, creating a bright streak of light across the sky, know as meteor (shooting star).
• Larger meteors do not burn up completely in the atmosphere and their remains, which we call meteorites, crash to the ground.
• 

Asteroid Belt

• 700,000 to 1.7 million asteroids with a diameter of 1 km or more.
• Over 200 asteroids are known to be larger than 100 km.
• 

Comets

• Comets are large chunks of ice, dust, and rock that orbit the Sun.
• As a comet approaches the Sun, radiation and solar wind from the Sun, causes a gaseous tail to form, pointing directly away from the Sun.
• A dust tail forms in the direction from which the comet originated.
• Most comets have 2 tails;
  • gaseous tail
  • dust tail
• 

Big Bang Theory

• It happened around 13.7 billion years ago when the Universe was a infintely dense point.
• Formed from an extremely dense singularity (centre of a black hole)
• Prior to that there was nothing

Evidence to support theory

• Redshift and Hubble’s Law

  • Hubble observed the line spectra from many different galaxies in sky, and most of spectra for galaxies were shifted towards the red end of the spectrum, a red shift
  • Hubble concluded that if most of galaxies were redshifted, they must be moving in all directions and the Universe is expanding from a single point
• Space between galaxies expand, not the galaxies themselves
• Dark Matter: the rest of the Universe appears to be made of a mysterious, invisible substance called dark matter (25%) and a force that repels gravity known as dark energy (70%)
  • 90% of matter in and between galaxies is of an unknown form that does not emit or absorb light
  • Can be detected through its gravity by the way it affects objects we can see
  • Without dark matter, normal matter would have been unable to clump and form stars and galaxies

Apparent and Absolute Magnitude

• Luminosity: Total amount of energy produced by a star per second
• Apparent Magnitude
  • Brightness of a star in the night sky as they appear on Earth
  • The lower the number, the brighter the star is
• Absolute Magnitude
  • Brightness of a star as if they were located 33 ly from Earth
  • The lower the number, the brighter the star is

Size of stars changes their lifestyle

Hertzsprung Russel Diagram

• The Hertzsprung-Russell Diagram is a graphical tool that astronomers use to classify stars according to their luminosity, spectral type, color, temperature and evolutionary stage.
• Basically plotting the class of the stars based on their lumionsity (how bright they are) and their temperature (how hot they are).
• 

Low Mass Stars

• With less gravity, burns hydrogen fuel slowly and lasts for 100 billion years, matures into red dwarf, and when fuel for nuclear fusion runs out, becomes a white dwarf

Medium Mass Stars

• Lasts for 10 billion years
• When a medium mass star runs out of fuel, it collapses under its own gravity, collapse heating up and pressure increases causing nuclear fusion of helium
• Star expands and becomes a red giant, eventually burning out to form a white dwarf
• When white dwarfs become cool enough to no longer emit heat or light, they become black dwarfs, however since the time required for a white dwarf to reach this state is older than the Universe, no black dwarfs currently exist

High Mass Stars

• Lasts up to 7 billion years, 10 times size of our Sun
• When high mass star runs out of fuel it collapses and expands to form a supergiant
• Supergiants end in a violent massive explosion called a supernova
• End results - Cosmic debris (nebula), a neutron star (or pulsar) or a black hole

Supernova

• Supergiants that run out of fuel end in a massive explosion
• Nuclear fusion reactions occur and new elements form and explode into space
• Debris from explosion is source for a new nebula, and what happens to the stars remaining core depends on original size of the star

Neutron Stars

• Remaining core of a supergiant that is less than 40 times the size of our Sun
• Also called a pulsar, very dense matter made of neutrons

Black Holes

• Remaining core of a supergiant that needs to be more than 40 times the size of our Sun
• Core of the supergiant after a supernova is so dense that its gravitational pull sucks in space, time, light, and matter
• Thought to be at the centre of all galaxies

Formation of Stars

Stage	Description	Picture
1. Birth and Early Life	- Life for a star begins in a nebula, which are HUGE, unevenly distributed clouds of dust and gases (mainly H & He). - Denser areas gather surrounding material due to greated gravitational pull - As material is added, gravity increases , drawing in even more material… then density and pressure increase as well. - This core and surrounding material start spinning more as they continue to condense. (like a figure skater) - Any surrounding dust and gases that aren’t drawn into the core will flatten out to look like a disc around the core. (the natural tendency for all spinning objects) - Temperature begins to rise due to atomic collisions and start emitting low level energies like microwave & infrared. - This is now called a protostar.
2. Main sequence phase (adult star)	- As core temperature reaches a critical point (15 million °C), NUCLEAR FUSION begins and it becomes a *star. - H atoms join to form He atoms, releasing enormous amounts of high energy radiation, which also emits light energy.**
3. Old Age	- Once a star’s core has used up its H, it fuses He, which releases even more energy. - This causes the star to swell into a red giant or red supergiant depending on their original mass.
4. Death	- An average star “dies” when it doesn’t have enough energy to continue nuclear fusion (usually once it forms carbon). - For a star like our sun, the core shrinks/collapses, releasing the outer layers of gases. - The small, hot, and dense core becomes a white dwarf, while the outer gases form a new nebula around it. This combo is called a planetary nebula. - A more massive star will do fusion up until iron then collapse, but the outer layers will explode off this iron core to form a supernova.
5. Remains	- Small red giants collapse & shrink into a white dwarf, which will slowly cool down and eventually fade out (no energy emitted) to be a black dwarf. - Large red giants explode as a supernova, & will form either a neutron star or even a black hole if the core has enough mass.

Space Composition

• 

Dark Matter

• The rest of the universe appears to be made of a mysterious, invisible substance called dark matter (25 percent) and a force that repels gravity known as dark energy (70 percent). Scientists have not yet observed dark matter directly.
• 90% of matter in and between galaxies is of an unknown form that does not emit or absorb light (so we can’t see it).
• It can be detected through its gravity by the way it affects objects we can see.
• Without dark matter, normal matter would have been unable to clump and form stars and galaxies - and US!