Solar System — Set 6

Correct Answer: A. Cosmology

• **Cosmology** = the scientific study of the origin, evolution, structure, and ultimate fate of the Universe. • **Big Bang central theory** — the Big Bang theory (universe began 13.8 billion years ago) is the cornerstone of modern cosmology. • 💡 Wrong-option analysis: Geology: study of Earth's rocks and physical structure; Astrology: belief that celestial positions influence human affairs (not a science); Seismology: scientific study of earthquakes.

Correct Answer: A. Pulsar

• **Pulsar** = a highly magnetized, rapidly rotating neutron star that emits beams of electromagnetic radiation from its magnetic poles. • **First discovered 1967** — Pulsars were first discovered by Jocelyn Bell Burnell in 1967; their regular pulses were initially nicknamed 'LGM' (Little Green Men). • 💡 Wrong-option analysis: Supernova: a massive stellar explosion, not a rotating neutron star; Quasar: an extremely luminous active galactic nucleus powered by a supermassive black hole; White Dwarf: a stellar remnant that does not emit regular pulses.

Correct Answer: C. Stars (White Dwarfs)

• **White Dwarfs** = the Chandrasekhar Limit defines the maximum mass (~1.4 solar masses) a white dwarf star can have before collapsing. • **1.4 solar masses** — above this limit, electron degeneracy pressure cannot support the star and it collapses into a neutron star or black hole. • 💡 Wrong-option analysis: Black Holes: the Chandrasekhar Limit applies to white dwarfs, not black holes directly; Planetary orbits: governed by Kepler's laws; Speed of light: defined by special relativity, not related to stellar mass limits.

Correct Answer: A. 76 years

• **76 years** = Halley's Comet has an orbital period of approximately 76 years, making it the most famous short-period comet. • **Last appeared 1986** — Halley's Comet was last visible in 1986 and is expected to return in 2061, visible to the naked eye from Earth. • 💡 Wrong-option analysis: 100 years: far too long for Halley's known short period; 12 years: Jupiter's orbital period, not Halley's; 50 years: approximately half of Halley's actual orbital period.

Correct Answer: C. Venus

• **Venus** = has a day (243 Earth days rotation) longer than its year (225 Earth days orbit), due to its extremely slow retrograde rotation. • **243 vs 225 days** — Venus's rotation period is 243 Earth days while its orbital period is only 225 Earth days, making its day longer than its year. • 💡 Wrong-option analysis: Mercury: day is 59 Earth days, year is 88 days; Pluto: not a planet (dwarf planet); Mars: day is 24.6 hours, year is 687 Earth days.

Correct Answer: A. Io

• **Io** = the most geologically active object in the solar system, with over 400 active volcanoes driven by tidal heating from Jupiter's gravity. • **400+ active volcanoes** — Io's volcanic activity is caused by tidal flexing from Jupiter's immense gravitational pull and orbital resonance with Europa and Ganymede. • 💡 Wrong-option analysis: Europa: has a subsurface ocean but is not the most volcanically active; Callisto: heavily cratered but geologically inactive; Ganymede: largest moon but not the most volcanically active.

Correct Answer: B. Earth's rotation

• **Earth's rotation** = the Foucault Pendulum provides direct visual proof of Earth's rotation by demonstrating the apparent rotation of the pendulum's swing plane. • **1851 by Léon Foucault** — Foucault first demonstrated this pendulum in Paris in 1851; the pendulum's plane appears to rotate once in ~32 hours at Paris. • 💡 Wrong-option analysis: Earth's revolution: refers to Earth's orbit around the Sun, not what a pendulum shows; Moon's orbit: the pendulum has no connection to lunar orbital mechanics; Gravity variation: measured by gravimeters, not pendulums.

Correct Answer: D. Coriolis Force

• **Coriolis Force** = an apparent force caused by Earth's rotation that deflects moving air to the right in the Northern Hemisphere and left in the Southern. • **Affects large-scale winds** — the Coriolis Effect creates cyclones (counterclockwise in NH, clockwise in SH) and shapes global wind patterns like trade winds. • 💡 Wrong-option analysis: Centrifugal Force: causes the equatorial bulge, not wind deflection; Gravitational Force: pulls objects toward Earth's center; Frictional Force: opposes motion at surface level.

Correct Answer: A. During Full Moon and New Moon

• **Full Moon and New Moon** = Spring Tides occur when the Sun, Earth, and Moon are aligned (Syzygy), causing maximum gravitational pull on oceans. • **Highest tidal range** — during Spring Tides the difference between high and low tide is at its maximum due to combined gravitational forces. • 💡 Wrong-option analysis: First Quarter Moon: produces Neap Tides (minimum tidal range) when Sun and Moon are at right angles; Only during Equinox: equinoxes affect day length, not necessarily tidal timing; Third Quarter Moon: also produces Neap Tides.

Correct Answer: A. Perigee

• **Perigee** = the point in the Moon's orbit where it is closest to Earth; if it coincides with a full moon, it creates a 'Supermoon'. • **356,500 km minimum** — the Moon's distance at perigee is approximately 356,500 km compared to 406,700 km at apogee. • 💡 Wrong-option analysis: Apogee: the farthest point of the Moon from Earth (opposite of perigee); Perihelion: the closest point of a planet to the Sun (not Moon to Earth); Aphelion: the farthest point of a planet from the Sun.