Untitled Deck Flashcards
Why are the minor bodies of the Solar System important to study?
They help us understand impact cratering, elemental abundances in the solar nebula, and processes in the Solar System’s formation.
What is Kepler’s First Law of Planetary Motion?
Planets move in elliptical orbits with the Sun at one focus.
Define perihelion and aphelion in an elliptical orbit.
Perihelion is the closest point to the Sun; aphelion is the farthest point.
How does Kepler’s Second Law relate to orbital speed?
A line from the Sun to a planet sweeps out equal areas in equal times, meaning a planet moves faster when closer to the Sun.
Write the mathematical form of Kepler’s Third Law.
P^2 = k a^3, where P is the orbital period and a is the semimajor axis.
What is the semimajor axis of an orbit?
It is half the longest diameter of an ellipse, representing the average distance from the orbiting body to the Sun.
What is orbital eccentricity?
It is a dimensionless measure of the shape of an orbit, ranging from 0 (circle) to 1 (elongated ellipse).
What happens to a planet’s speed as it approaches perihelion?
The planet speeds up due to the Sun’s stronger gravitational pull.
What are the perihelion and aphelion distances for a planet with a = 5 AU and e = 0.2?
Perihelion: q = 5(1-0.2) = 4 AU; Aphelion: Q = 5(1+0.2) = 6 AU.
What is the significance of inclination in an orbit?
It measures the tilt of an orbit relative to the ecliptic plane, defined by Earth’s orbit.
What are prograde and retrograde orbits?
Prograde orbits have inclinations between 0° and 90° (anticlockwise from above the north pole), while retrograde orbits have inclinations between 90° and 180° (clockwise).
What is tidal heating?
A mechanism where gravitational interactions cause internal frictional heating, as seen on moons like Io.
Why does Io remain volcanically active?
Orbital eccentricity causes gravitational interactions that lead to tidal heating within Io.
What are Kirkwood Gaps?
Regions in the asteroid belt with few asteroids, caused by orbital resonances with Jupiter.
What are Near Earth Asteroids (NEAs)?
Asteroids with orbits that bring them close to Earth.
What are Potentially Hazardous Asteroids (PHAs)?
NEAs that have orbits crossing Earth’s path and could potentially collide with Earth.
What is the composition difference between C-type and S-type asteroids?
C-type asteroids are carbonaceous and dark, while S-type asteroids are stony and more reflective.
What is the Kuiper Belt?
A region beyond Neptune filled with icy bodies and dwarf planets like Pluto.
What are Centaurs?
Minor bodies with unstable orbits between Jupiter and Neptune, thought to originate from the Kuiper Belt.
What is unique about the Centaur Chariklo?
It is surrounded by two rings, the only known such object outside the giant planets.
How do comets develop tails?
Sublimation of ices near the Sun releases gas and dust, forming ion and dust tails.
What is the difference between ion and dust tails of comets?
Ion tails are gaseous and point away from the Sun due to solar wind; dust tails reflect sunlight and follow the comet’s orbit.
What are long-period comets?
Comets from the Oort Cloud with semimajor axes of hundreds to thousands of AU and unpredictable appearances.
What are short-period comets?
Comets with orbits confined to the planetary system, often originating from the Kuiper Belt.
What is the Oort Cloud?
A distant spherical shell of icy bodies surrounding the Solar System, the source of long-period comets.
Why are meteoroid streams formed?
Comets release dust particles into space, which continue orbiting the Sun along similar paths.
What causes meteors (shooting stars)?
Meteoroids entering Earth’s atmosphere at high speeds vaporize, producing a streak of light.
What is the zodiacal light?
A faint glow caused by sunlight scattering off interplanetary dust particles.
How does radiation pressure affect small particles in space?
It pushes tiny particles outward from the Sun, acting like a solar wind.
What is the Poynting–Robertson effect?
A process where dust particles spiral towards the Sun due to the braking effect of solar radiation.
How are the orbits of Kuiper Belt objects classified?
Into Plutinos (3:2 resonance with Neptune), Classical objects, and Scattered Disc objects.
What evidence supports the existence of the Kuiper Belt?
Discovery of objects like 1992 QB1 and over 1800 others with orbits beyond Neptune.
What are binary asteroids?
Two asteroids orbiting each other, like Ida and its moon Dactyl.
What is the main composition of cometary nuclei?
A mix of water ice, frozen gases (e.g., CO2, NH3), and dust particles.
What is sublimation in the context of comets?
The process where ices turn directly into gas as the comet approaches the Sun.
What are meteoroids?
Solid fragments from asteroids or comets, smaller than 1 mm to several meters in size.
How does Jupiter influence comets and asteroids?
Its gravity perturbs orbits, creating phenomena like Kirkwood Gaps and influencing short-period comet paths.
Why are asteroids in the asteroid belt irregularly shaped?
Frequent collisions prevent the formation of large, spherical bodies.
What is the typical density of C-type asteroids?
Around 1200–1300 kg/m^3, indicating high porosity.
What are the two main types of comet orbits?
Long-period (from the Oort Cloud) and short-period (from the Kuiper Belt).
How can impacts influence the appearance of Kuiper Belt objects?
Impacts may expose subsurface ice, leading to transient atmospheres or changes in reflectance spectra.
What is the purpose of the New Horizons mission?
To study Kuiper Belt objects and Pluto up close, providing insights into icy bodies.
Why do some asteroids have moons?
Gravitational interactions during collisions or captures can create binary systems.
What are Potentially Hazardous Asteroids (PHAs)?
NEAs that have orbits crossing Earth’s path and could potentially collide with Earth.
What happens to comets after many perihelion passages?
They lose mass through sublimation and may fragment, eventually disintegrating.
What is an example of an asteroid visited by a spacecraft?
Eros, visited by the NEAR mission, which even landed on its surface.
What determines the reflectance spectrum of an asteroid?
Its surface composition and how it reflects sunlight at different wavelengths.
