Astronomy — Comets, Asteroids, and Meteorites

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Accessibility: This is the accessible version of the lab, built following WCAG 2.1 AA guidelines. It adds screen-reader support, full keyboard navigation, and text descriptions of the interactive diagrams. If you encounter any barrier, please let us know through e2innovations.ai so we can address it.

Theory — Comets, Asteroids, and Meteorites

The small bodies are the debris left over from the birth of the solar system about 4.6 billion years ago. They never grew into planets, so they preserve primitive material.

1. Asteroids

Asteroids are rocky or metallic bodies. Most orbit in the main belt between Mars and Jupiter, roughly 2 to 3.5 AU from the Sun. Some, the near-Earth objects, follow orbits that bring them close to the Earth, which is why they are watched carefully.

2. Comets

Comets are icy bodies from the cold outer solar system, the Kuiper belt beyond Neptune and the distant Oort cloud. When a comet nears the Sun, its ices sublimate and it grows a glowing coma and two tails: a bluish ion tail pushed straight out by the solar wind, and a curved dust tail. Comets typically have very elongated (eccentric) orbits.

3. Orbits and periods

A small body obeys the same laws as a planet, so its period follows from its orbit:

Period and perihelion P = √(a³) (P in years, a in AU)
q = a (1 − e) (perihelion distance, e = eccentricity)
Where the orbit lies tells you what kind of body it is.

A nearly circular orbit at 2 to 3.5 AU marks a main-belt asteroid; a perihelion inside about 1.3 AU marks a near-Earth object; a large, highly eccentric orbit marks a comet.

4. Meteoroids, meteors, and meteorites

A small fragment in space is a meteoroid; the streak of light as it burns in our atmosphere is a meteor; a piece that survives to the ground is a meteorite. Meteorites come in stony, iron, and stony-iron types, and the most primitive of them are dated to the solar system’s birth, which is how we know its age.

Apparatus

Studying small bodies uses tools for tracking orbits, spreading light, and examining fallen samples. In the simulation these are modelled, but the readings match what each instrument would give.

Asteroid

An irregular rocky or metallic body, most common in the main belt between Mars and Jupiter.

Comet

An icy body with a bright coma and an ion and a dust tail streaming away from the Sun.

Meteorite

A fragment that survived its fall; types include stony, iron, and stony-iron.

Orbit diagram

A plot of a small body’s elliptical orbit relative to the planets, used to classify it.

Spectrometer

Reveals the composition of an asteroid or comet from its reflected or emitted light.

Analytical balance

Used to weigh and examine meteorite samples in the laboratory.

Instructions

Work through both tabs. Calculate first by hand, then press the button to compare.

Part A — Orbit, period, and classification

Set the semi-major axis a (AU) and eccentricity e of a body.
Compute the period P = √(a³) in years, and the perihelion q = a(1 − e), by hand.
Enter your period and press Check. Then classify the body from where its orbit lies.

Part B — Identify the body

View a small body and its features (tails, shape, composition).
Predict whether it is an asteroid, a comet, or a meteorite type, then press Check.

Simulation

Semi-major axis a (AU)

Eccentricity e

Your period P (years)

Classification

New body

Your identification

Team Questions

1. Most asteroids orbit in the main belt, which lies between:

Earth and Mars Mars and Jupiter Jupiter and Saturn Neptune and the Sun

2. A comet’s tails form because, near the Sun, its ices:

Freeze harder Turn to rock Sublimate, releasing gas and dust Absorb sunlight silently

3. A rock that survives its fall and reaches the ground is a:

Meteorite Meteor Meteoroid Comet

Example Report

Worked example: a main-belt asteroid

An asteroid has a semi-major axis a = 2.8 AU and eccentricity e = 0.10.

Period: P = √(a³) = √(2.8³) = √(21.95) ≈ 4.69 years.

Perihelion: q = a(1 − e) = 2.8 × 0.90 = 2.52 AU. The orbit is nearly circular and sits between Mars and Jupiter, so this is a main-belt asteroid. Computing the period and classifying from the orbit is the calculate-then-compare core of the lab.

Comets, Asteroids, and Meteorites