Big Bang Theory and the Universe

• The universe is 13.8 billion years old.
• A light year is the distance light travels in one year and is used to measure very large distances.
• The diameter of the observable universe is 93 light years.
• A light year's distance is calculated by multiplying the number of seconds in a year (86400 in a day) by the speed of light.
• Pluto orbits approximately 40 AU from the Sun.
• The Sun emits a constant wind of charged gas into interstellar space, called solar wind.
• The boundary between the Solar Wind and interstellar space (the Heliosphere) is around 100 AU from the Sun (200 AU in diameter).
• The solar neighbourhood is the region of the Galaxy within about 20 light-years of the Sun (40 light-years diameter).
• The neighborhood stars generally move with the Sun in its orbit around the center of the Galaxy.
• The Milky Way Galaxy is a giant disk of stars, 100,000 light-years across and 1,000 light-years thick.
• The Sun is located at the edge of a spiral arm in the Milky Way Galaxy, approximately 30,000 light-years from the center.
• The Sun takes about 250 million years to complete one orbit around the Milky Way's center.
• The Milky Way contains about 200 billion stars.
• The local group contains 3 large spiral galaxies (Milky Way, Andromeda(M31), and Triangulum(M33)) and a few dozen dwarf galaxies with elliptical or irregular shapes.
• The local supercluster is a huge cluster of thousands upon thousands of galaxies, the largest of which is the Virgo cluster containing over a thousand galaxies.
• The local supercluster is 130 million light-years across.
• Clusters and groups of galaxies are gravitationally bound but spread away from each other as the Universe expands.
• The observable Universe has great walls and filaments of galaxy clusters surrounding voids containing no galaxies.
• The Universe is estimated to contain between 200 billion to 2 trillion galaxies.
• The closest star to Earth is Proxima Centauri.
• One Astronomical Unit (AU) is the average distance between the Earth and the Sun.
• Light travels at a speed of 3 x 10^8 meters per second.
• Measurement of a light year is based on how far light travels in one Earth year.
• Parallax is a method astronomers use to measure distances to nearby stars.
• Parallax is determined by astronomers taking pictures of a star at two different times of the year, using Earth's orbit around the Sun.
• Closer stars have a bigger parallax angle.
• Farther stars have a smaller parallax angle.

Star Formation

• Star formation begins with pockets of dust and gas floating in empty space; these pockets are massive and stretch out over light years.
• Dust particles condense when they have a density of 100 atoms per cubic centimeter, and gravity causes them to collapse, forming a nebula.
• A nebula may be hundreds of light years across and denser than surrounding space; the densest parts grow as gravity pulls particles together.
• Protostars form from dense clouds of hydrogen gas within nebulae.
• Nuclear fusion is a radioactive process where two particles fuse to form a larger particle requiring temperatures in the millions of degrees Celsius.
• Fusion initiates in the core of a star once the temperature is reached.
• A protostar becomes a star when nuclear fusion starts, fusing hydrogen atoms to form helium.
• Dust not used in the star's formation combines to form planets, moons, asteroids, etc.

Star Death

• An average-sized star becomes a red giant when it runs out of hydrogen in its core.
• Gravity brings matter from the outer area toward the core, causing the outer areas to expand and cool.
• Fusion happens at lower temp to light is red instead of white.
• For a medium star transforming into a red giant, fusion occurs at a lower temperature, producing red light.
• The core uses helium as fuel and after 100 million years, helium runs out.
• A red giant turns into a planetary nebula as helium runs out, outer layers escape gravity creating a cloud of gas.
• A planetary nebula transforms into a white dwarf then a black dwarf star as nuclear fusion stops and light dims, and the white dwarf cools over billions of years.
• A large star uses hydrogen more quickly due to its large size and higher gravity.
• Large stars exist for millions, instead of billions, of years.
• A blue supergiant turns into a red supergiant as it runs out of hydrogen and uses helium as fuel.
• The star cools down as it uses other elements as fuel, eventually fusing all matter into iron.
• A red supergiant turns into a supernova as energy production stops, and gravity causes the star to collapse.
• The material rebounds off the solid core, causing a massive explosion called a supernova.
• A supernova turns into a neutron star as electrons and protons become neutrons, shrinking the star to only 20 km across.
• A neutron star turns into a black hole if the star left after a supernova is more than three times the mass of our Sun
• Gravity causes it to shrink down further forming a black hole

Gravity & Stellar Elements

• Gravity is the force that pulls objects toward the center (attraction to the largest mass).
• The bigger the mass, the bigger the force of gravity.
• Scientists theorize that gravity is caused by a particle called a graviton.
• Bigger mass equals larger gravitational force.
• Blackholes are made out of massive stars that explode creating a gravitational pull
• Nebulae are made of dense clouds of hydrogen.
• Gravity contributes to the birth of a star by causing particles or dust to gather together.
• A star enters the main sequence stage after it is fully formed.
• Stars shine because the energy from fusion creates the light and heat that stars emit.
• Elements besides hydrogen and helium come from stars going supernova, which spreads the elements throughout the star.
• When a star explodes in a supernova, it smashes atoms together, creating elements like gold, silver, and iron.
• These elements spread into space, mixing with gas and dust, and help form new stars, planets, and even life.
• Nuclear fusion begins as dust moves so close that it is squished together, the pressure becomes high, the star ignites, and turns into a main sequence star.
• The size of a star determines how long it will burn and what will happen when it runs out of hydrogen.
• A red super giant to super nova pulls matter outside to the inside causing the outside to lose energy and fuel so outside cools down.
• A star ten times larger than our Sun is called a blue super giant.
• AU is typically for distances within the Solar System, while light-years are for much greater distances beyond it
• Gravity keeps planets in the Solar System in their orbits and acts on all objects at all distances, maintaining the order and movement of celestial bodies.
• AU denotes the distance between Earth and the Sun.
• A light year is the distance light travels over the span of a year.
• The Geocentric model is an incorrect earlier belif that Earth is the centre of the universe and everything orbits it.

Solar System & Celestial Objects

• A solar system is a system where planets revolve around a star.
• 7 other planets and one dwarf planet orbit the Sun. Names/order is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto (Dwarf planet).
• Heliocentric view: The Sun is the center of the solar system.
• The Milky Way Galaxy contains stars, nebulae, black holes, and asteroids.
• Moons are smaller celestial bodies that orbit around planets.
• Jupiter has 79 moons.
• The Kuiper Belt is a belt of asteroids beyond Neptune and Pluto.
• Comets whiz through the solar system in large paths.
• Arcsecound is a measurement for small angles in space being 1/3600 of a degree.
• Arcminute is 1/60 of a degree.
• Parallax calculations determine the distance to a star.
• A parsec is the distance separating us and a star, if the star's parallax angle is one arcsecound (useful for large distances).
• A megaparsec is one million parsecs.
• A planet is a celestial body that orbits a star.
• A planet must be big enough that gravity forces it into a speherical shape.
• It is big enough that its gravity clears away other objects in orbit
• The Moon is not considered a planet because it orbits the Earth, not a star.
• Pluto is not considered a planet because its orbit is to small

Stars & Galaxies

• Stars are hundreds or thousands of times bigger than planets.
• Planets orbit around stars.
• Stars are giant balls of hot gas that generate heat by fusion.
• Nebulae are large clouds of dust and gas particles held together by gravity to form stars and planets; they often span several light years across.
• Galaxies are gravitationally bound collections of stars, planets, nebulae, dark matter, and other features.
• Most galaxies contain billions of stars.
• Our Universe contains up to trillions of galaxies.
• Galaxies form clusters with other galaxies, forming superclusters.
• Types of stars in the Milky Way galaxy include main sequence stars, red dwarfs, blue supergiants, red supergiants, white dwarfs, and neutron stars.
• A neutron star is a massive star that exhausts its nuclear fuel and undergoes a supernova explosion; the core collapses under gravity, compressing protons and electrons into neutrons.
• Dark matter does not emit, absorb, or reflect light, making it invisible, but is detectable through its gravitational effects on visible matter.
• Dark matter plays a crucial role in the formation of galaxy structures.
• Comets come from outer Solar System regions, while asteroids are mainly found in the asteroid belt between Mars and Jupiter and do not have tails like comets.
• Dark energy makes up 68% of the universe and drives its accelerated expansion.
• A main sequence star begins when nuclear fusion begins at the core of a protostar.
• Transition to a main sequence star means the protostar's gravity and temp increases, causing nuclear fusion and hydrogen converting to helium releasing energy
• Death of a star can be Red giant, white dwarf, or black dwarf
• Tempature of the star indicateas colour
• Stars are classified in colour which include blue, red, yellow, orange and white
• Stars are classified in temperature, stars at a higher temperature will emit radiation at a higher frequency and have a colour on the blue side of the spectrums.
• Stars are classified by distance using the parallax angle (allows us to map out how far these stars are)
• Stars are classified through luminosity which is the Brightness of a star or a measure of how much energy it gives off.
• Stars are classified through spectral class by assigning a letter and having a temperature range and a colour associated with it
• Brightness is an apparent measurement where we judge how intense the light of a star is.
• Luminosity is a measure of how much light a star gives off, not just how much we see.

Hertzsprung-Russell Diagram

• The Hertzsprung-Russell diagram classifies stars according to their luminosity, spectral class, color, temperature, and evolutionary stage.
• White dwarfs on the diagram are located on the left side, indicating high temperatures.
• Giants on the diagram are located toward the right, indicating they are cool.
• More luminocity means the higher the star
• Supergiants are mostly positioned toward the right of the diagram, indicating they are generally cooler than the hottest main sequence stars.
• The Main Sequence spans a wide range of temperatures, from hot blue stars (on the left) to cool red stars (on the right).
• The y-axis represents luminocity.
• The x-axis represents temperature.
• The main sequence location on the Hertzsprung-Russell diagram has 3 main characteristics
  • Shows stars at their most stable stages of life
  • Organised by colour
  • Stars are heavier

Scientific Concepts

• A theory is a thought or assumption of what happened or what might happen
• A scientific theory is a explanation for observation, has evidence and allows predictions to be made
• Steady-state cosmology explains that matter is constantly created as the universe expands.

Beginning of Universe

• During the Planck Era the mass of universe compressed into a small ball its basically energy
• During the Inflationary Era energy becomes mass called singularity.
• During the Quark Era the universe if full of dense plasma
• During the Hadron Era the universe gets bigger and reaches one trillion km across, protons and neutrons are formed from the quarks
• Quarks are the building blocks of protons and neutrons
• During the Era of Nucleos synthesis neutrons and protons get attracted to eachother through gravitation to form nuclei. Elements like hydrogen and helium are created
• During the Photon Era a Soupy mixture of hydrogen (he), (nuclei) & electrons and photons bound off, where these particles filling the universe with light
• During the Dark Era Nebula forms but no stars or planets but after 300 million years galaxies are born
• During the stary era stars and dust gather to create milky way galaxy and the sun takes 4 billion years to make

Explore the Big Bang theory, contrasting it with the Steady-State model regarding matter evolution. Learn how stars' characteristics on the Hertzsprung-Russell diagram offer evidence for stellar evolution post-Big Bang. Understand the sequence from the Planck Era to Nucleosynthesis, and the significance of inflation.