Cosmology Flashcards
What is an astronomical unit?
An astronomical unit is a unit of measurement for space. it measures the distance from the Earth to the sun (150,000,00km)
What is a light year?
A light year is the distance light travels in an earth year.
how far away is the nearest star?
the nearest star to the earth is about 4 light years away
How big is our galaxy (Milky Way) across?
The Milky Way is around 100,000 light-years(ly) across
How many stars per galaxy (specifically the Milky Way)?
There are around 100 billion stars in the milky and its the same around other galaxies
how many galaxies are there in the universe?
There are around 100 billion galaxies in the universe
what is parallax?
parallax is the apparent change in position of an object when you look at it from different places
what are the different types of galaxies?
There are 3 types of galaxies:
spiral, elliptical and irregular
How do you use parallax to find the position of a star?
- observe a star and mark its apparent position 1
- do the 1st step again 6 months later and mark it apparent position 2
- now you can see the real position of the star which is the intersection between the two apparent positions
how do you use this real position to find the distance
After finding the real position to find the distance of the star you need to:
1. find the average position of the Earth (the middle so the position of the sun is the average position of the Earth)
2. now you can calculate the distance by calculating:
a. measure all the angles
b. the measurement of one side- by using function sin cos or tan to find the lengths of the sides in a right angled triangle
What is nuclear fusion?
Nuclear fusion is the process that accounts for the energy emitted by a star. This process involves joining 2 atomic nuclei.
How do you use the brightness\magnitude of a star to find the distance?
- measure the apparent magnitude of the star (2 this for two stars that seem the same brightness)
- measure the actual magnitude
- compare the stars and see which star has the greater real magnitude whichever has the greater real magnitude is the syar that’s further away
How does nuclear fusion work?
Nuclear fusion is hard because of the electromagnetic repulsion with objects of the same charge. The repulsion of these charges gets weaker at higher temperatures and pressure in a star. This weakness leads to nuclei fusing
What happens when nuclei fuse in nuclear fusion?
When the nuclei fuse small amounts of mass are converted into huge amounts of energy as Einstein’s famous formula
E= mc²
E= energy
m= mass
c=speed of light
What is a spectrograph?
Light going through a spectrograph produces an absorption spectrum depending on the elements it goes through. these absorption patterns are different for each element
what did Edwin Hubble discover using the scpectrograph?
Hubble looked at a lightbulb with hydrogen to see the pattern it made. Then he pointed the spectrograph at a galaxy and saw that the hydrogen pattern shifted towards the spectrum’s red side. this observation Hubble discovered called red shift.
what conclusion did Hubble come to after his discovery?
after looking at many galaxies and seeing a red shift in all of them his conclusions were:
conclusion 1- the light from the galaxy is longer
conclusion 2- the galaxy must be moving away as you observe it causing the light to stretch
conclusion 3- because it is happening to all galaxies the universe must be expanding
conclusion 4- if the universe is expanding it must have been smaller at some point leading to the big bang theory
What is the Big Bang Theory?
Around 3 billion years ago, our universe existed as a small bit of extremely hot energy. For unknown reasons, this bit of energy started expanding and still is. As it expanded it started cooling down and started forming matter which turned into stars, planets, galaxies, etc.
what is the life cycle of a star (steps) meduim size?
first, a nebula is formed which turns into a protostar. After that, it turns into a full star. then while it dies it turns into a red giant into a black dwarf in to a white dwarf when a stars life is over
what is a nebula?
A nebula is a cloud of dust and matter that gathers together
how does a nebula turn into a protostar
the matter in the nebula concentrates and forms a protostar which is not a fully grown star
how does a protostar form into a star?
