Astrophysics: Big Bang Theory and Star Life

Study Notes

Big Bang Theory

The Big Bang theory proposes that the universe started from a singular point about 13.8 billion years ago.
It suggests that the universe is expanding since that point, which is supported by observations like redshift and cosmic microwave background radiation (CMB).
The CMB is leftover heat from the Big Bang, providing evidence for a hot, dense beginning.

Redshift

Distant galaxies appear shifted towards the red end of the spectrum, meaning they are moving away from us.
This is a result of the expansion of the universe, stretching the light as galaxies grow further apart.

Hubble Constant

This constant (H₀) measures the rate at which the universe is expanding.
It is calculated using the formula v = H₀ × d where v is galaxy velocity ,d is distance and H₀ is the Hubble constant
The Hubble constant is crucial for understanding the age of the universe and its expansion rate.

Life History of Stars

A star's life starts as a nebula, a cloud of gas and dust.
Gravity causes the nebula to condense, forming a protostar that heats up.
Stars spend most of their time in the main sequence phase, where nuclear fusion occurs.
When hydrogen fuel runs out, stars grow into a red giant or supergiant.
Eventually, stars reach the end of their life.
- Low & medium mass stars evolve into white dwarfs and then black dwarfs.
- High mass stars explode in a supernova, forming neutron stars or black holes.

Cosmic Microwave Background Radiation (CMB)

Faint radiation from the Big Bang that fills the universe.
Uniformity of CMB supports the Big Bang theory.

Earth's Spheres

The Earth system is comprised of four main spheres:
Atmosphere: The layer of gases surrounding the Earth.
Hydrosphere: All water on Earth, including oceans, lakes, rivers, and groundwater.
Lithosphere: Earth's solid outer shell, consisting of the crust and upper mantle.
Biosphere: All living organisms on Earth and their ecosystems

Carbon Cycle

Carbon movement through Earth's different systems.
Carbon is released and absorbed through various processes:
- Combustion: Releases carbon dioxide (CO₂) into the atmosphere from burning fossil fuels (coal, oil, gas).
- Respiration: Living organisms release CO₂ as a byproduct of cellular respiration.
- Decomposition: Decomposition of plants and animals releases CO₂ into the air.
- Photosynthesis: Plants consume CO₂ from the atmosphere to produce oxygen and glucose.
Carbon is stored in diverse locations: the atmosphere, oceans, soils, and living organisms.

Greenhouse Effect

Natural process where greenhouse gases trap heat in the Earth's atmosphere, keeping the planet warm enough for life.
Key greenhouse gases include carbon dioxide (CO₂), methane (CH₄), water vapor (H₂O), and nitrous oxide (N₂O).
- Solar radiation reaches Earth's atmosphere.
- Some energy is reflected back into space, while the rest is absorbed by Earth's surface and re-radiated as heat.
- Greenhouse gases trap this heat, stopping it from escaping into space, warming the planet.
Enhanced Greenhouse Effect: Human activities, such as burning fossil fuels and deforestation, have increased greenhouse gas concentrations, trapping more heat, leading to global warming.

Description

This quiz explores fundamental concepts in astrophysics including the Big Bang Theory, redshift, the Hubble constant, and the life history of stars. Test your understanding of how these elements contribute to our knowledge of the universe and its expansion. Perfect for students interested in astrophysics and cosmology.