Unit 1 – T

Apuntes

Unit 1 – The Universe and the Earth 1. The Big Bang and the Universe 1.1 Origin of the Universe – The Big Bang ● The Universe began about 13.8 billion years ago from a single point of extremely high temperature and density. ● This event is called the Big Bang. ● After the explosion, matter and energy expanded and cooled, forming the first subatomic particles, then hydrogen and helium atoms. 1.2 Evidence for the Big Bang ● Cosmic Microwave Background (CMB): leftover radiation from the early Universe. ● Redshift of galaxies: most galaxies are moving away from us, showing the Universe is expanding. ● Abundance of light elements (hydrogen and helium) predicted by Big Bang theory. 1.3 Formation and Life Cycle of Stars ● Clouds of gas and dust (nebulae) collapse under gravity forming protostars. ● When nuclear fusion begins, a star is born. ● Life cycle: ○ Low-mass stars → red giant → white dwarf → black dwarf. ○ High-mass stars → red supergiant → supernova → neutron star or black hole. 1.4 Star Clusters and Galaxies ● Star clusters: groups of stars formed together. ○ Open clusters: young stars, loosely grouped. ○ Globular clusters: old stars, spherical and dense. ● Galaxy: large groups ...