Solar System, Sun, Planets & Eclipses

Flashcards covering key concepts regarding the solar system, its planets, orbits, and related phenomena.

Why are inner planets smaller and rockier while outer planets are larger and gaseous?

Due to proximity to the Sun; metals/silicates condensed in warm inner region, while ices accumulated in cooler outer regions beyond frost line.

How did the conservation of angular momentum influence solar system structure?

It caused the collapsing pre-solar nebula to flatten into a rotating protoplanetary disc.

Why are Jovian planets able to retain hydrogen and helium atmospheres unlike terrestrial planets?

Lower solar wind intensity and higher gravity allowed gas retention in outer regions.

What physical property of the solar system determines the distance spacing of planets?

Angular momentum and early particle accretion dynamics cause increasing AU gaps outward.

How do solar winds help differentiate between Jovian and terrestrial planetary composition?

Intense solar winds swept away lighter gases from inner planets, but not from the outer ones.

What does Kepler’s first law imply about Earth’s perihelion and aphelion positions?

Earth is closest to the Sun in January (perihelion) and farthest in July (aphelion), affecting solar insolation.

Why are orbits of Kuiper belt objects more elliptical than planetary orbits?

Due to gravitational perturbations from Neptune and historical collisions.

How does the retrograde rotation of Venus challenge planetary formation models?

It suggests late-stage collisions or tidal interactions after formation.

Why do most planets rotate and revolve in counter-clockwise direction?

They inherited angular momentum from the original rotating solar nebula.

Why does the Sun contain most of the system’s mass but little angular momentum?

Mass is centralized in the Sun, but angular momentum is transferred to planets through gravitational interactions.

Why is the photosphere considered the Sun’s surface despite not being solid?

It's the layer from which visible light escapes, giving the appearance of a defined surface.

What causes temperature inversion from photosphere to corona?

Magnetic reconnection and heat bombs in the chromosphere transfer energy upward.

Why do solar flares correlate with sunspot cycles?

Magnetic field anomalies and plasma turbulence peak during sunspot maximum.

What is the implication of sunspots for Earth’s climate?

Fewer sunspots correlate with minor global cooling due to reduced solar irradiance.

How does solar wind interact with Earth’s magnetosphere to create auroras?

Charged particles guided by magnetic lines excite atmospheric gases near poles.

Why does Venus lack a protective magnetosphere despite being similar in size to Earth?

It has a slow retrograde rotation and lacks an internal dynamo effect.

What role does plasma play in shaping the visible universe?

Ionized gases dominate cosmic structures from stars to nebulae.

How do coronal ejections disrupt Earth-based technology?

They induce geomagnetic storms affecting satellites and power grids.

Why are solar wind particles able to escape the Sun’s gravity?

High thermal velocity from corona’s million-degree temperatures surpasses solar escape velocity.

Why is Mercury geologically inactive today despite its past volcanism?

Its small size led to rapid heat loss, halting tectonic activity.

What explains the extreme greenhouse effect on Venus?

Thick CO2 atmosphere traps heat via radiative feedback with sulfuric acid clouds.

Why is Mars’ atmosphere unable to sustain liquid water on its surface?

Low pressure allows water to sublimate directly from ice to vapor.

Why do gas giants have strong magnetic fields compared to Earth?

They contain metallic hydrogen or ionized ammonia driving powerful dynamos.

What caused Uranus’ axial tilt of 98°?

It was likely a massive oblique impact during early solar system formation.

Why do outer planets have more moons than inner planets?

Greater gravity and extended spheres of influence allowed moon capture.

What makes Io the most volcanically active body in the solar system?

Tidal heating from gravitational interactions with Jupiter and other moons.

Why does Saturn’s density allow it to float in water?

It has a very low mean density (~0.7 g/cm³), lower than water.

How are planetary rings believed to form?

From disintegrated moons or unaccreted material within the Roche limit.

Why does Titan intrigue scientists searching for extraterrestrial life?

It has a dense atmosphere and surface hydrocarbon lakes.

What distinguishes meteoroid, meteor, and meteorite in impact science?

Meteoroid = space; meteor = atmospheric burn; meteorite = ground impact.

Why are Trojan asteroids gravitationally stable?

They occupy Lagrange points of Jupiter’s orbit, maintaining constant position.

How are short-period comets different from long-period ones in origin?

Short-period comets come from the Kuiper Belt, while long-period comets come from the distant Oort Cloud.

What causes a comet’s tail to always point away from the Sun?

Solar radiation pressure and solar wind push ionized particles outward.

Why are asteroids and comets important for early solar system study?

They preserve primitive, unchanged material from planetary formation.

Why don’t eclipses happen every month despite new/full moon cycles?

The Moon’s orbital plane is tilted ~5° to Earth’s orbit, leading to rare alignments.

What is the Saros cycle and how does it help predict eclipses?

An 18-year period after which similar solar/lunar eclipses recur.

Why do total solar eclipses appear different in duration?

Due to varying Earth-Moon-Sun distances causing angular size shifts.

What is an annular eclipse and how is it different from a total eclipse?

Occurs when the Moon is too far to fully cover the Sun, leaving a ‘ring of fire’.

Why are lunar eclipses visible from more places on Earth than solar eclipses?

Earth casts a wider shadow on the Moon than the Moon’s shadow on Earth.

What role do Kuiper Belt Objects play in redefining planetary criteria?

The discovery of Eris and others led to redefining 'planet', demoting Pluto.

Why was Pluto reclassified as a dwarf planet?

It fails to clear its orbital neighborhood despite orbiting the Sun.

What does planetary ‘differentiation’ imply for rocky planets?

Heavier elements sank to the core, forming layers like crust, mantle, and core.

Why is Earth’s magnetosphere asymmetrical?

Solar wind compresses it on the sun-facing side and stretches it on the far side.

Why are exoplanets challenging existing solar system models?

Many exhibit hot Jupiters and elliptical orbits, unlike classical expectations.

What does the Roche limit explain in planetary ring formation?

It defines the minimum distance at which a celestial body will disintegrate due to a planet's tidal forces.

Why is Earth's axial tilt crucial for the diversity of seasons?

It causes varying angles of solar incidence during Earth's orbit, leading to seasonal changes.

What determines the strength and duration of geomagnetic storms?

Magnitude of solar CMEs, their orientation, and the structure of Earth’s magnetosphere.

Why is the barycenter of the Earth-Moon system not at Earth's center?

The Moon’s mass causes both bodies to orbit a common point beneath Earth’s surface.

What evidence supports the capture theory for irregular moons?

Retrograde orbits and high eccentricities inconsistent with co-formation scenarios.