Cosmology

• A star is a colossal mass of gas and mostly made of hydrogen (H).
• Hydrogen atoms fuse to create helium atoms and release energy and visible light.
• Nebulae are interstellar regions filled with gas and dust, and are where stars are born.
• The size of a star determines how long it will live for, as well as the stages in its life cycle, because the size of the star affects how quickly all the hydrogen in its core fuses.
• Bigger mass, more gravity.
• A small star releases a small burst of energy before it dies, and forms a planetary nebula.
• The core remains as an extremely hot, dense and small white dwarf.
• In a large star, gravity causes the star to rapidly contract and then explode.
• This is known as a supernova, and leaves the core of the star as an extremely dense neutron star.
• Galaxies are massive groups of stars, gas, dust and other matter bound together by forces of gravity.
• Light-year: the distance that light travels in one Earth year
• Parsed : 3.26 light-years
• astronomical unit : the average distance between Earth and the Sun (about 150 000 000 km)
• Galaxies are classified by shape: elliptical, spiral and irregular
• The solar system - mercury, venus, earth, mars, jupiter, saturn, uranus, neptune, pluto.
• Rocky planets made from heavier elements, the inner solar system is too warm for substances with low boiling points, hence there are solids.
• frostline: a boundary just inside Jupiter's orbit
• Planets that orbit stars other than the Sun are called exoplanets.
• An optical telescope works by collecting and amplifying light.
• The larger the objective lens or mirror, the more light that can be collected, and the more fine detail can be observed
• This is called resolution.
• The further away an object is, the larger the telescope must be to have good resolution.
• Hydrogen emits radio waves which can be detected by radio telescopes
• Radio astronomy has enabled the discovery and study of pulsars (rapidly spinning neutron stars), quasars (primordial galaxies with supermassive black holes), supernova remnants, and black holes in the centres of galaxies.
• Space telescopes allow astronomers to gather clearer images because they don't experience interference by the atmosphere or light pollution
• The Big Bang theory is the theory for the origin of the universe.
• The theory states that the universe began as a small dense region called a singularity, which then rapidly expanded about 13.7 billion years ago.
• Singularity : an infinitely dense point of matter that existed before the Big Bang
• Universe cooled allowing for formation of particles of matter and antimatter, after 0.001 s they annihilated each other
• After 3 minutes, the protons and neutrons then combined to form the nuclei of atoms
• At about 500 000 years, the universe cooled enough for the electrons to be attracted to the nuclei and so for atoms to form
• The first stars and galaxies then began to form 1 billion years after the Big Bang.
• At about 500 000 years, the universe cooled enough for the electrons to be attracted to the nuclei and so for atoms to form
• After 3 minutes, the protons and neutrons then combined to form the nuclei of atoms
• This released energy in the form of photons of light
• Three major pieces of evidence for Big Bang