Learn the Solar System with 111 Flashcards: Planets, Dwarf Planets, Comets and the Oort Cloud

The Solar System is one of those topics where you think you know the basics, until a quiz asks how many known moons there are (758), where the frost line sits (about 5 AU) or which moon orbits backwards (Triton). The Solar System deck on Flip It (deck code BS5695, 111 cards) is built to close exactly those gaps: it moves from the eight planets to formation theory, the Sun's future, asteroids, comets and the edge of the heliosphere.

Here is how to work through it efficiently.

What the 111 cards actually cover

The deck is organised in five natural blocks. Instead of studying the cards in order, study by block, because each block has its own logic:

1. Structure and numbers — the Sun holds 99.86% of the system's mass; Jupiter and Saturn hold nearly 90% of what's left; 1,462,402 known minor planets, 4,629 known comets, 758 natural satellites.
2. Planets and dwarf planets — the four terrestrial planets (Mercury, Venus, Earth, Mars), the gas giants (Jupiter, Saturn), the ice giants (Uranus, Neptune), the five IAU dwarf planets (Ceres, Pluto, Eris, Makemake, Haumea) plus the four likely candidates (Orcus, Quaoar, Gonggong, Sedna).
3. Formation and future — pre-solar nebula, protoplanetary disc, accretion, frost line, soot line, Nice model, Late Heavy Bombardment, red giant phase, white dwarf.
4. Small bodies — asteroid types (C, M, S), Trojans, near-Earth asteroids, centaurs, comet nuclei, ion vs dust tails, meteoroid vs meteor vs meteorite, Halley's Comet, Perseids.
5. Boundaries and neighbourhood — heliopause at ~120 AU, Oort cloud beyond 2,000 AU, Hill sphere, Local Bubble, Proxima Centauri at 4.2465 light-years, a 230-million-year galactic orbit at 720,000 km/h.

Sample cards from the deck

Two study tips specific to this deck

Tip 1 — Anchor every distance to the AU ladder. A surprising number of cards are just positions on one scale: asteroid belt at 2–4 AU, frost line at 5 AU, Kuiper belt just past Neptune (~30 AU), heliopause at ~120 AU, Oort cloud beyond 2,000 AU, Hill sphere at 178,000–227,000 AU, Proxima Centauri at 269,000 AU. Sketch that ladder once on paper and the "where is X" cards stop feeling like random trivia.

Tip 2 — Pair the opposites. The deck is full of contrast cards that are easiest to learn as pairs: perihelion/aphelion, gas giant/ice giant, short-period comets (Kuiper belt, < 200 years) vs long-period comets (Oort cloud), ion tail/dust tail, inner/outer Solar System, meteoroid/meteor/meteorite. When one side of a pair comes up in review, say the other side out loud before flipping.

A realistic plan

Around 20 new cards per session, one block per day, gets you through the deck in five sessions, with Flip It's spaced repetition handling the reviews. The formation block (nebula → disc → accretion → migration) is the one most people fail on first pass, so give it a second dedicated pass before you consider the deck done.

To start, log in at flip-it.app, open the library and search for Solar System or the deck code BS5695.