Universe and Solar System - Flashcards (Video Notes)

A set of practice flashcards covering key concepts from the lecture notes on the universe, cosmic epochs, galaxies, star life cycles, and solar system origins.

What is the Big Bang Theory and when did the universe form?

The universe formed approximately 13.7 billion years ago from a cataclysmic expansion that hurled all matter and created space.

What is the Radiation Era in cosmology?

A period after the Big Bang when radiation dominated the universe’s expansion; began about 10^-43 seconds after the Big Bang and ended when matter began to dominate (roughly 30,000–50,000 years later).

Name one epoch within the Radiation Era.

Planck epoch (one of several: Planck, GUT, Electroweak, Quark, Hadron, Lepton, Nuclear epochs).

What characterizes the Planck Epoch?

The earliest epoch, lasting until 10^-43 seconds after the Big Bang, where all forces of nature were thought to be unified.

What is the Grand Unified Epoch?

An epoch lasting from about 10^-43 to 10^-36 seconds after the Big Bang, characterized by the unification of the strong, weak, and electromagnetic forces.

What happened during the Inflationary Epoch?

A period of extremely rapid expansion starting around 10^-36 seconds after the Big Bang.

What occurred during the Electroweak Epoch?

The electroweak force separated into the electromagnetic force and the weak nuclear force as the universe cooled.

What happened in the Quark Epoch?

From approximately 10^-12 to 10^-6 seconds after the Big Bang, quarks, leptons, and their antiparticles existed in a hot, dense plasma.

What happened from 10^-6 seconds to 1 second after the Big Bang?

Quarks combined to form hadrons (like protons and neutrons).

What marks the Lepton Epoch?

A period dominated by leptons (electrons, neutrinos, and their antiparticles) while the universe was still very hot.

What occurs in the Nuclear Epoch?

Nucleosynthesis begins; ends when the universe is about 15 minutes old; electron-positron pairs annihilate, releasing photons.

When did neutral atoms first form in the early universe and what did they form?

Around 30,000 years after the Big Bang, electrons combined with nuclei to form neutral atoms, primarily hydrogen and helium.

What major structure formation followed the creation of neutral atoms?

Gravity pulled together dark matter and gas, forming protogalaxies and eventually stars within galaxies.

What are the three main types of galaxies?

Elliptical, Spiral, and Irregular.

What is the Milky Way?

A barred spiral galaxy that contains our solar system and billions of other stars.

What is baryonic matter?

The ordinary matter that makes up stars, planets, galaxies, and ourselves; composed of atoms and interacts with electromagnetic forces.

What is dark matter?

Matter that does not interact electromagnetically, is non-baryonic, has mass, and exerts gravity; its exact nature is unknown.

What is dark energy?

A mysterious form of energy driving the accelerated expansion of the universe; distinct from dark matter and not matter.

What is the Cosmic Microwave Background Radiation (CMBR)?

The leftover heat from the Big Bang, detected as faint microwave radiation, providing strong evidence for the Big Bang theory.

What does redshift indicate in astronomy?

The stretching of light waves from distant galaxies, making them appear redder and indicating that galaxies are moving away due to expansion.

What did Hubble’s observation of redshift establish?

That the universe is expanding; the farther a galaxy is, the faster it appears to be receding.

What is Hubble’s Law?

The redshift (recessional velocity) of a galaxy is directly proportional to its distance from us.

What are the Steady State and Oscillating theories about the universe?

Steady State: universe expands with continuous matter creation to keep density constant (largely discounted). Oscillating: a cyclical universe with repeated Big Bangs and Big Crunches (not widely accepted).

What is the Nebular Hypothesis?

The solar system formed from a large cloud of gas and dust (a nebula) that contracted under gravity, formed the Sun at the center, and planets from the disc.

What is the Encounter Hypothesis?

A rogue star passed near the Sun; gravity pulled out gas from both stars, forming planets from the captured material.

What is the Protoplanet Hypothesis?

A detailed Nebular hypothesis where leftover material formed planetesimals, then protoplanets, which grew into planets.

Why are rocky planets close to the Sun and gas giants farther away?

Close to the Sun, heat prevented gases/ices from staying solid; farther away, cooler temperatures allowed gases and ices to condense into giant planets.

What leftovers remain from the planet formation process?

Asteroids (mainly between Mars and Jupiter), moons, and comets.

What is the Goldilocks Zone?

The habitable zone around a star where conditions are right for liquid water to exist.

What makes Earth habitable?

Has liquid water, a protective atmosphere (mostly nitrogen and oxygen), and an appropriate temperature range.

What is the Sun’s current age and main-sequence status?

Age about 4.6 billion years; the Sun is currently in the main sequence phase of its life.

What will happen to the Sun in the distant future?

The Sun will become a red giant; the habitable zone will shift, and planets may stay warm for a limited time (~0.5 billion years) before the Sun's later evolution ends life-friendly conditions.

What are the main stellar remnants?

White Dwarf, Neutron Star, and Black Hole; a Black Dwarf is a theoretical end point not yet observed.

What is a White Dwarf made of?

Primarily carbon and oxygen; extremely dense.

What is a Neutron Star?

A highly dense stellar remnant formed when a massive star collapses after a supernova, where neutrons are packed densely.

What is a Black Hole?

A region of space with gravity so strong that not even light can escape; the most massive stars can end life this way.

Why are elements like carbon and iron important in stars?

They are formed in stars and dispersed by supernovae, contributing to the material for new stars, planets, and life.

What is a Supernova?

An enormous explosion that occurs when a massive star runs out of fuel, releasing vast energy and dispersing heavy elements into space.

What constitutes a star’s life-cycle order?

Nebula → Protostar → Main Sequence → Red Giant → Supernova → White Dwarf/Neutron Star/Black Hole.

What is the relationship between life on Earth and stellar processes?

Elements essential for life (like carbon and iron) are forged in stars and spread by supernovae to form planets and future life.

What is the role of planets and moons as leftovers from solar system formation?

Asteroids and moons are leftover bodies from the planet-building process, evidence of the solar system’s early history.