origins of the universe Flashcards
List of planets and other celestial bodies in the solar system
- Sun
- Mercury
- Venus
- Earth
- Mars
- Asteroid belt
- Jupiter
- Saturn
- Uranus
- Neptune
- Kuiper Belt
- Oort cloud
Which galaxy is our solar system in
Milky way- a spiral galaxy
Galaxy definition
A collection of billions of stars held together by the force of gravity
Day definition
The time it takes for the Earth to complete 1 full rotation around its axis
Year definition
The time it takes the Earth to complete 1 full revolution around the Sun
Geocentric view of the universe
The Earth is the centre of the Universe and everything else orbits it in rings called heavens
Heliocentric view of the universe
Sun is the centre of the Universe
Modern view of the Universe
- There is no centre of the Universe
- The Universe is changing over time
Definition of a star
A gaseous spherical object of large mass that produces heat and light through nuclear fusion
Constellation definition
A group of stars that form a pattern in the night sky
Hubble’s law
V=HoD
Ho= Hubble’s constant (70km/s/mpc)
V in k/s
D in mpc
Hubble found that the further a galaxy was from Earth, the faster it was moving away from Earth
Evidence for the Big Bang
- Cosmic Microwave Background Radiation
- Redshift
- The amount of helium in the Universe
Cosmic Microwave Background Radiation
- light/ radiation left over from when the early Universe was very hot
- detectable in all directions
- light has been stretched to the microwave part of the spectrum
- Wavelength of CMB corresponds to a temperature of 2.7K (-270 degrees C)- the temperature of the Universe
Redshift
- Galaxies are moving away from us (the universe is expanding)
- This causes the light we see to be stretched to the red end of the spectrum
- If we rewind the Universe, it all started in one single point
Amount of helium
- Stars are the only place in the current universe that is hot and dense enough to fuse hydrogen atoms into helium
- But, there is too much helium in the Universe to be made by stars alone
- The only other time where the Universe was hot and dense enough to make helium was in the Big Bang
Criteria of a planet
A celestial body that:
1. Orbits a star (sun)
2. Has enough mass that its self-gravity pulls it into a spherical shape
3. Has cleared the neighbourhood around its orbit
Why is Pluto no longer considered a planet
Did not meet criteria #3- clearing the neighbourhood around its orbit
Lightyear
1 ly= the distance you can travel in a year at the speed of light
- Used to measure the distance between stars in the same galaxy
Astronomical Unit
1 AU= The distance between the Earth and the Sun
- Used for measuring distances within our solar system
Parsec
d=1/p
d is distance in pc
p is the parallax angle
- Parsecs are used to measure the distance to far away galaxies or stars
Parallax angle
- Used to calculate the parsec distance
- Measures the distance to stars by using its background stars
- Measure at 2 points of the year, 6 months apart
Apparent magnitude
How bright (large) an object appears
Absolute magnitude
How bright (large) an object is, corrected for distance
Spectral class
OBAFGKM (hottest to coldest)
X-axis of a HR diagram
- Based on the wavelength of light
Short wavelengths (blue) on the left
Long wavelengths (red) on the right
Labelled as temperature (K)
Life cycle of a star <8M.
- Gas nebula
- Main sequence star
- Red giant
- Planetary nebula
- White dwarf
Life cycle of a star >8M.
- Gas nebula
- Main sequence star
- Red supergiant
- Supernova
- If core <3M.: Neutron star
If core >3M.: Black Hole
Ways the earth can end
- Hit by a meteorite
- Anihillation by the sun
- Supernova explosion
Hit by a meteorite
- Asteroid hits earth, causing catastrophic events
- Including tsunamis, firestorms and dust in the atmosphere, blocking sunlight and wiping out life
Annihilation by the sun
- When the sun swells into a red giant, during its natural life cycle it will engulf Mercury, Venus, Mars, and possibly Earth
- This will be the end of the Earth
Supernova explosion
- Nearby star becomes a supernova, creating shockwaves
- Radiation/ light from this explosion could kill life on nearby planets
Ways the universe can end
- Big crunch
- Big rip
- Big freeze
The big freeze
- If the density is just right, the Universe will keep expanding but a slower rate
- Everything will be so spread out and stars will run out of fuel that in the end only black holes will be left
- They will eventually evaporate, and the Universe will be empty of all matter and energy
This means there is no more heat left and the heat death of the Universe will have occurs
The big crunch
- High density
- Gravity wins out over the repulsive force expanding the Universe and eventually pull everything back into a very hot, dense Universe
The big rip
- Low density
- Gravity is too weak to stop the expansion of the Universe
- It will keep expanding faster and faster until it rips apart- including atoms and sub-atomic particles
Jovian planets
- Gas planets (giants)
- Jupiter, Saturn, Uranus, Neptune
Terrestial planets
- Rocky planets, usually smaller than jovian planets
- Mercury, Venus, Earth, Mars
