OUR PLANETARY SYSTEM, PROPERTIES OF PLANETS AND SPACE EXPLORATION

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Questions and Answers

What shape do all planets follow in their orbits around the Sun?

Random paths

Elliptical paths (correct)

Circular paths

Parabolic paths

What two orbital elements are required to fully define the size and shape of a planet's orbit?

Inclination and true anomaly

Longitude of ascending node and argument of periapsis

Orbital period and mass

Semimajor axis and eccentricity (correct)

Which Kepler's law states that a line segment connecting a planet and the Sun sweeps out area at a constant rate?

Law of Universal Gravitation

Law of Periods

Law of Ellipses

Law of Equal Areas (correct)

The eccentricity of a perfectly circular orbit is equal to which value?

0 Signup and view all the answers

What does the inclination of an orbit refer to?

The tilt of the orbital plane Signup and view all the answers

In Kepler's laws, what does the 'true anomaly' represent?

The position of the planet along its orbit at a specific time Signup and view all the answers

What is the primary focus of all planets' orbits?

The Sun Signup and view all the answers

Which parameter can be determined using the semimajor axis and the orbital period?

Orbital velocity Signup and view all the answers

What is the primary reason for the observed 'flatness' of the planetary system?

Planets grew within a disk in orbit around the Sun. Signup and view all the answers

How can the mass of an object in space be deduced?

By observing the gravitational force it exerts on other bodies. Signup and view all the answers

What was a consequence of the gravitational perturbation caused by Neptune?

It directly led to the discovery of Neptune itself. Signup and view all the answers

Which method provides the most accurate means of determining the masses of planets and moons?

Doppler shift and periodicity measurements from spacecraft tracking data. Signup and view all the answers

What does the Titius-Bode rule predict based on a specific mathematical procedure?

The distances of planets from the Sun Signup and view all the answers

How are the distances of planets predicted by the Titius-Bode rule derived?

By adding 4 to each number in a specific series and dividing by 10 Signup and view all the answers

For planets without moons, which of the following is less accurate for estimating mass?

Analyzing orbital perturbations of other planets. Signup and view all the answers

What technique has been used to estimate the masses of some of Saturn's small inner moons?

Analyzing the amplitude of spiral density waves in Saturn's rings. Signup and view all the answers

What discrepancy does the Titius-Bode rule face with certain planets?

It shows large discrepancies for the orbits of Uranus, Neptune, and Pluto Signup and view all the answers

What unconventional method has been used to make crude estimates of comet masses?

Estimation of non-gravitational forces from gas and dust escape. Signup and view all the answers

What inclination is the Sun’s equatorial plane tilted relative to the ecliptic plane?

7 degrees Signup and view all the answers

Which planet has the most tilted orbit among the eight major planets?

Mercury Signup and view all the answers

What is a characteristic of short-term versus long-term perturbations?

Short-term perturbations are influenced by immediate gravitational interactions. Signup and view all the answers

Why might the radii of the orbits of Uranus, Neptune, and Pluto differ from those predicted by the Titius-Bode rule?

Their orbits were likely altered after formation Signup and view all the answers

What direction do all planets and asteroids revolve around the Sun?

In the same direction as solar rotation Signup and view all the answers

What is the average distance predicted by the Titius-Bode rule for a planet located between Mars and Jupiter?

2.8 AU Signup and view all the answers

How can the diameter of a solar system body be calculated?

Using the product of its angular size and distance from the observer. Signup and view all the answers

What technique is useful for determining the limits of an asteroid in space?

Observing a star as it is occulted by the body. Signup and view all the answers

Which measurement technique is specifically effective for studying solid planets, asteroids, and cometary nuclei?

Radar echoes. Signup and view all the answers

What does the obliquity of a planetary body refer to?

The angle between its spin angular momentum and its orbital angular momentum. Signup and view all the answers

What is a direct consequence of an asteroid occulting a star for observers?

Different observers will see different durations of the star's disappearance. Signup and view all the answers

What can be estimated by combining photometric observations at visible and infrared wavelengths?

The radius and albedo of an object. Signup and view all the answers

How can the mean density of an object be determined?

By knowing its mass and volume. Signup and view all the answers

What is necessary for determining a planetary body's rotation axis and period?

Tracking the movement of surface markings over time. Signup and view all the answers

Study Notes

Properties of Planets

Key properties of planets include orbit, mass, size, rotation, shape, temperature, magnetic field, surface composition, surface structure, atmosphere, and interior.

Orbit

Johannes Kepler formulated three laws of planetary motion in the 17th century:
- Law of Ellipses: Planets follow elliptical orbits with the Sun at one focus.
- Law of Equal Areas: A line segment between a planet and the Sun sweeps out equal areas in equal times.
- Law of Periods: The square of a planet's orbital period is proportional to the cube of its semi-major axis.
A Keplerian orbit is defined by six orbital elements:
- a (semimajor axis): measured in Astronomical Units (AU).
- e (eccentricity): indicates shape; 0 (circle), between 0 and 1 (ellipse), 1 (parabola), greater than 1 (hyperbola).
- i (inclination): tilt of the orbit.
- Longitude parameters: describe the orientation of the orbit.
- f (true anomaly): indicates the planet's position along its orbit at a specific time.
Titius-Bode Rule: Predicts distances of planets from the Sun using a calculated series, showing good agreement with inner planets but discrepancies for Uranus, Neptune, and Pluto.
Orbital inclinations of planets generally lie within a few degrees of the Sun's equatorial plane; Mercury’s orbit is the most tilted at 7 degrees.

Mass

The mass of a planet can be deduced using gravitational interactions with other bodies.
Techniques for mass estimation include:
- Observing the gravitational effects on the orbits of moons and nearby objects.
- Spacecraft tracking data provides accurate mass estimates through Doppler shifts and radio signal periodicity.
- Perturbation method used for planets without moons, which relies on gravitational effects on neighboring planets.
Neptune was discovered due to gravitational perturbations affecting Uranus's orbit.

Size

Size measurement techniques include:
- Using angular size and distance from the observer to calculate diameter.
- Star occultation by objects can help determine size and shape.
- Radar echoes are useful for determining shapes and sizes of nearby objects.
- Combining photometric observations in visible and infrared wavelengths provides estimates of size and albedo.
- Mean density and escape velocity can be calculated from mass and size.

Rotation

Rotation is a vector quantity associated with spin angular momentum.
Obliquity (axial tilt): The angle between the spin axis and orbital axis; a 90-degree tilt indicates retrograde rotation.
Determining a planet’s rotation axis and period can be achieved by observing surface markings’ movements.

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Description

*OUR PLANETARY SYSTEM Basic Features Comparative Planetology Sun & Planets Characteristics Features of Solar System that Provide Clues About Formation Robotic Spacecrafts Solar System Boundaries IAU Definitions

*PROPERTIES OF PLANETS Orbit Mass Size Rotation Shape Temperature Magnetic Field Surface Composition Surface Structure Atmosphere Interior

*SPACE EXPLORATION History of Rocketry Principles of Rocketry History of Space Exploration (Missions, Crew)