Cosmology, Astrophysics & Solar-System Survey

54 question-and-answer flashcards covering fundamental particles and forces, cosmic composition, Big Bang evidence and timeline, CMB, expansion, stellar evolution, galactic types, solar-system structure, orbital terminology, formation theories, and possible cosmic futures.

What sub-atomic particles make up ordinary (baryonic) matter?

Protons, neutrons, and electrons.

Which fundamental particles combine to form protons and neutrons?

Quarks.

Which particle family includes electrons and neutrinos?

Leptons.

What class of particles includes photons and carries forces?

Bosons.

Which fundamental force is always attractive and acts between masses?

Gravity.

Which force binds protons and neutrons together inside atomic nuclei?

The strong nuclear force.

What mysterious energy causes the accelerated expansion of the universe?

Dark energy.

Roughly what percentage of the universe is baryonic (ordinary) matter?

About 4.6 %.

Approximately what fraction of the universe’s energy–matter budget is dark matter?

About 24 %.

Dark energy makes up about what percentage of the cosmos?

Roughly 71.4 %.

Name the three most abundant chemical elements in the universe.

Hydrogen, helium, and lithium.

How old is the universe according to the Big Bang model?

About 13.8 billion years.

Who first proposed the idea now called the Big Bang theory in the 1920s?

Georges Lemaître.

List the three main observational pillars supporting the Big Bang.

Cosmic expansion (redshift), light-element abundances (H, He, Li), and the cosmic microwave background (CMB).

What 1929 discovery by Edwin Hubble provided evidence for cosmic expansion?

The redshift of galaxies—the farther a galaxy, the faster it recedes.

At what cosmic time did inflation (a burst of exponential expansion) occur?

~10⁻³² seconds after the Big Bang.

When did quarks first combine into protons and neutrons?

Roughly 10⁻⁶ seconds after the Big Bang.

How long after the Big Bang did light nuclei such as helium begin to form?

Within a few minutes.

When did neutral atoms first form, releasing the CMB?

About 380,000 years after the Big Bang.

At what age of the universe did matter and radiation fully decouple?

Around 10,000 years after the Big Bang.

Who discovered the cosmic microwave background radiation in 1964?

Arno Penzias and Robert Wilson.

What is the current average temperature of the CMB?

Approximately 2.7 K above absolute zero.

What phenomenon stretches the wavelengths of light from receding galaxies?

Redshift (a manifestation of the Doppler effect in an expanding universe).

Which theory of gravity is supported by the observed cosmic expansion?

Einstein’s General Relativity.

What is a protostar?

A collapsing cloud of gas and dust that is forming a new star.

What nuclear process powers a main-sequence star by converting hydrogen to helium?

Nuclear fusion.

Which nuclear process involves splitting heavy nuclei and does NOT power stars?

Nuclear fission.

Outline the life cycle of a Sun-like star.

Nebula → Main Sequence → Red Giant → Planetary Nebula → White Dwarf.

Give the end states possible for a massive star after a supernova.

Neutron star or black hole.

Define a galaxy.

A vast system containing billions of stars, gas, dust, and dark matter bound by gravity.

Name the four main galaxy morphologies.

Spiral, barred spiral, elliptical, and irregular.

What type of galaxy is the Milky Way, and roughly how wide is it?

A barred spiral about 100,000 light-years across.

How long does the Sun take to orbit the Milky Way once?

Approximately 240 million years.

Roughly what share of the solar-system mass resides in the Sun?

About 99.9 %.

Which region between Mars and Jupiter contains millions of rocky bodies?

The asteroid belt.

Name the icy region beyond Neptune that is the source of short-period comets.

The Kuiper Belt.

What distant spherical shell of icy objects is thought to spawn long-period comets?

The Oort Cloud.

Differentiate meteoroid, meteor, and meteorite.

Meteoroid: small space rock; meteor: glowing streak as it burns in the atmosphere; meteorite: remnant that reaches Earth’s surface.

How long is one astronomical unit (AU) in kilometers?

About 150 million km—the mean distance from Earth to the Sun.

What term describes Earth’s farthest point from the Sun in its orbit?

Aphelion (~152 million km, around 3 July).

What is Earth’s closest orbital point to the Sun called?

Perihelion (~147 million km, around 3 January).

Define perigee and apogee concerning the Moon’s orbit.

Perigee: Moon’s closest approach to Earth; apogee: its farthest point.

What is prograde motion?

Forward or conventional direction of rotation/orbit (shared by most planets).

Which planets exhibit notable retrograde rotation?

Venus and Uranus.

Summarize the nebular hypothesis for solar-system origin.

The Sun and planets formed from a rotating cloud of gas and dust contracting under gravity.

What does the encounter hypothesis propose?

A close pass by another star pulled material from the Sun, leading to planet formation.

Who advanced the planetesimal version of the encounter hypothesis in 1904?

Chamberlin and Moulton.

Which 1917 idea suggested tidal filaments condensed into planets after a near-collision?

Jeans’ tidal hypothesis.

Describe the Big Freeze scenario for the universe’s fate.

Cosmic expansion continues indefinitely; stars exhaust fuel; the universe becomes cold and dark.

What is the Big Rip?

Accelerated expansion eventually tears apart galaxies, stars, and even atoms.

Define the Big Crunch.

A hypothetical future in which expansion halts and the universe collapses back into a dense state.

What does the eternal inflation model predict?

Inflation never completely ends, spawning multiple (possibly infinite) bubble universes.

What is meant by an oscillating universe?

A cosmos that cyclically undergoes Big Bangs and Big Crunches.

Outline the plasma-universe theory.

Suggests that large-scale behavior is dominated by plasma and electromagnetic forces, denying a Big Bang origin.

What was the main claim of the steady-state cosmology?

The universe is unchanging in time, with matter continuously created to maintain constant density.