FC - Asteroids

Forty question-and-answer flashcards covering key facts from the SS 2025 lecture on asteroid geodesy, including asteroid belt structure, major bodies, missions, spectral classes, families, orbital resonances, and physical properties.

What nickname is often given to asteroids because of their role in planetary formation?

They are called the “building blocks of the Solar System.”

Which three small-body types were listed together with asteroids in the lecture?

Comets, meteoroids, and meteorites (including meteors and fireballs).

What is the formula of the Titius–Bode Law as stated in the notes?

a = n + 4 (with n = 0, 3, 6, 12, 24 … and a in units of 0.1 AU).

Between which two planets is the asteroid main belt located?

Between Mars and Jupiter.

Who discovered the first asteroid, Ceres, and in what year?

Giuseppe Piazzi in 1801.

On what basis are ordinal numbers assigned to asteroids?

They are numbered in the sequence of their discoveries.

Which object is the only dwarf planet in the main belt and what is its approximate diameter?

1 Ceres, about 950 km in diameter.

Roughly what fraction of the total asteroid-belt mass is contained in Ceres?

About one-third of the belt’s total mass.

Which NASA mission visited both Vesta and Ceres?

The Dawn mission.

Name the largest known Trojan asteroid and give its approximate size.

624 Hektor, roughly 370 × 200 × 200 km.

The total mass of the asteroid belt is roughly what percent of Earth’s Moon?

About 4 % of the Moon’s mass.

Approximately how many asteroids larger than 100 km are known?

200 asteroids.

About how many asteroids larger than 1 km are estimated to exist in the belt?

700,000 asteroids.

What observational method is primarily used to determine asteroid rotation periods?

Analysis of their light curves.

How do the rotation axes of large asteroids generally compare to those of the planets?

They tend to rotate in the same primordial sense with axes roughly perpendicular to the ecliptic.

What term describes asteroids formed by impact fragmentation followed by reassembly?

“Rubble-pile” asteroids.

As of April 2015, about how many minor planets were known to have moons?

225 minor planets.

List the three main spectral classes of asteroids mentioned.

C-type (carbonaceous), S-type (silicate), and M-type (metallic).

Where are C-type asteroids predominantly found within the belt?

Mostly in the outer main belt.

What process creates asteroid families?

Catastrophic collisions that completely shatter a parent body.

Roughly what fraction of all asteroids belong to recognized families?

About one-third.

What are Kirkwood gaps?

Dips in the distribution of asteroid semimajor axes caused by orbital resonances with Jupiter.

The prominent Kirkwood gap at 2.5 AU corresponds to what orbital resonance?

A 1 : 3 resonance (asteroid period 3.95 yr vs. Jupiter’s 11.86 yr).

Which 1983 infrared mission provided diameters and albedos for over 1,800 asteroids?

IRAS – the Infrared Astronomical Satellite.

Approximately how many asteroids brighter than magnitude 20 is ESA’s Gaia mission expected to observe?

About 500,000 asteroids.

In what year was Gaia launched and to which Lagrange point did it travel?

It was launched in late 2013 and placed at the Sun–Earth L2 point.

What is the name of the lone cryovolcano identified on Ceres?

Ahuna Mons.

What is Vesta’s rotation period?

About 5.342 hours.

What is Ceres’s rotation period?

About 9.075 hours.

What is Vesta’s specific (bulk) density?

Approximately 3.46 g cm⁻³.

What is Ceres’s specific (bulk) density?

Approximately 2.16 g cm⁻³.

What is the semimajor axis (orbital distance) of Vesta?

a ≈ 2.3619 AU.

What is the semimajor axis (orbital distance) of Ceres?

a ≈ 2.768 AU.

Give the approximate tri-axial dimensions of Vesta.

Approximately 573 × 557 × 446 km.

Give the approximate tri-axial dimensions of Ceres.

Approximately 964 × 964 × 892 km.

Why do asteroids in exact orbital resonance with Jupiter often leave those resonant positions?

Their eccentricities and inclinations become chaotic, making their orbits planet-crossing and removing them from the resonance.

What computational approach is used to estimate self-gravity vectors on irregular asteroids?

Integration over a dense mesh of volume elements representing the body.

What does the lecture say the Titius–Bode prediction implied about the gap between Mars and Jupiter?

It suggested a missing planet, later associated with the asteroid belt.

Which two largest main-belt asteroids were imaged by the Hubble Space Telescope before the Dawn mission?

Vesta and Ceres.

What physical property besides rotation period can be inferred from asteroid light-curve amplitude?

Information about the asteroid’s shape and pole orientation.