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 = \(`1.5 times 10^8`\)
• 1 Light year = \(`9.46 \times 10^{12}`\)
• 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.

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!