Astronomy: Solar System

This page covers anything about the Solar System that isn't covered by Planets (1), Planets (2), or Moons.  (Basically, those pages cover the size, orbits, and physical nature of the planets, dwarf planets and their major satellites or moons.)

Numbers

Age of the solar system (all its major bodies were formed within 10–20 m years)		4.55 billion years
Life on Earth began about		4 billion years ago
Light travels from the Sun to Earth in		8 minutes 20 seconds
Time taken by the Earth to go round the Sun: 365.25 days, less		11 minutes 14 seconds
The Moon's synodic period (the length of its phase cycle as seen from Earth)		29.53 days (29d 12h 44m 3s)
The Moon's orbital period (the time it actually takes to orbit the Earth)		27.32 days (27d 7h 43m 11.6s)
Number of lunar cycles in a year, as seen from Earth (number of lunar months)		12.34
Number of times the Moon orbits the Earth in a year		13.37
Diameter of Jupiter's Great Red Spot (approximately)		13,000 miles
Length of the cycle of sunspot activity		11 years

Halley's Comet

Period of orbit (average)		75.3 years
Last appearance		1985/6
Next appearance		2061

Other

Point at which a planet (or any other satellite of the Sun) is furthest from the Sun		Aphelion
Point at which an Earth satellite (including the moon) is furthest from the Earth		Apogee
Point at which an Earth satellite is closest to the Earth		Perigee
Point in a planet's orbit where it is closest to the Sun		Perihelion

Astronomers' name for red sky in the morning or evening		Aurora
A comet's tail points		Away from the Sun
String of arcs of brilliant sunlight along the edge of the Moon, before or after a solar eclipse		Baily's Beads
Defines the distance of the planets from the Sun		Bodes' Law
96% of the atmosphere of Venus (also most of Mars's) is		Carbon dioxide
The biggest gap in the rings of Saturn (between the A and B rings) – named after the Italian–born astronomer (working in France) who discovered it in 1675		Cassini Division
The smallest of the three dwarf planets classified in 2006 – the largest in the asteroid belt (previously the largest known asteroid)		Ceres
The largest moon (satellite) of Pluto – discovered in 1978		Charon
Consists of a nucleus, a coma, and a tail		Comet
Faint halo of hot gases (around 2,000,000°C) around the Sun, boiling from its surface, seen during a solar eclipse (if there aren't too many clouds!)		Corona
The only planet in the Solar System that's not named after a Greek or Roman god; the only one that has one and only one moon		Earth
The sixth largest moon of Saturn (mean diameter slightly over 500 km): believed to fulfil many of the conditions necessary to support life, including an ocean of hot liquid water underneath its surface of water ice		Enceladus
The largest of the three dwarf planets classified in 2006: orbits in the scattered disc with a radius of between 38 AU and 98 AU (cf. Pluto, 30 – 50 AU). Previously known as 2003 UB313 and nicknamed Xena		Eris
Difference between meteors and meteorites: meteors don't ...		Fall to earth
Jupiter's largest satellite – equatorial diameter 3,270 miles – the biggest moon, bigger than Mercury or Pluto, and thus the ninth largest body in the solar system		Ganymede
Meteor shower that occurs in December		Geminids
Word used to describe the Moon when it's more than half illuminated (from the Latin for "humped")		Gibbous
Cause of the extreme surface temperature of Venus		Greenhouse effect
The Orionids – a meteor shower that occurs in late October – and also the less spectacular Eta Aquariids in May – are composed of debris from		Halley's Comet
The region of space that's dominated by the Sun; a 'bubble' created by the solar wind, which is a stream of plasma (charged particles) released from the upper atmosphere of the Sun; it extends for about 120 astronomical units (the orbit of Pluto is between 29 and 50 AUs)		Heliosphere
Second most abundant element in the Sun, after Hydrogen (7%)		Helium
Comet seen in the Northern sky in Spring 1996		Hyakutake
92% of the sun is; the surface of Jupiter is a swirling mass of liquid		Hydrogen
The moons of Saturn are made of		Ice (water ice)
'Oumuamua, formally designated '1I/2017 U1', is an asteroid–like body, less than one kilometre across, which was first observed in October 2017 when it was about 20 million miles from the Earth. The I (in 1I/2017 U1) stands for		Interstellar
Jupiter's core – about the size of Earth – is, like the Earth's core, made of		Iron
The surface of Mars is made to look red by		Iron oxide (rust)
Largest planet; has a Great Red Spot (which is a storm); shortest day (9 hrs 56 mins at the poles, 9 hrs 50.5 mins at the equator)		Jupiter
The area of the solar system extending from within the orbit of Neptune (about 30 AU from the Sun) to about 50 AU – named after the Dutch–American astronomer (1905–73) who suggested that small planets or comets may have formed there (but believed that few, if any, would exist there today); see scattered disc		Kuiper Belt
Meteor shower, occurring in mid–November and known for its spectacular proliferation about every 33 years – when its parent body, comet Tempel–Tuttle, reaches perihelion		Leonids
Phobos and Deimos are dwarf satellites of		Mars
Olympus Mons, one of the highest mountains known to man (21,900 metres / 71,850 feet – nearly three times as high as Everest) is on
Most asteroids orbit the Sun between		Mars and Jupiter
Nearest planet to the sun; has the shortest 'year'		Mercury
Planets with no moons		Mercury, Venus
Hoba (West), Tent (Abnighito), Baruberito, Williamette: some of the largest		Meteorites
The Perseids, Leonids, Geminids and Orionids are examples of		Meteor showers
Before 2006, the Asteroids were officially classified as (term now includes dwarf planets and small Solar System bodies)		Minor planets
The Bay of Rainbows, Sea of Serenity, Ocean of Storms, Humboldt's Sea and the Sea of Showers (a.k.a. Sea of Rains) are (where?)		On the Moon
The Apennines, Caucasus, Harbinger and Cordillera mountain ranges (where?)
Discovered in 1846 – the only planet discovered in the 19th Century		Neptune
In 1989, the NASA spacecraft Voyager 2 discovered a Great Dark Spot on
Spherical cloud of comets, approximately 1 light year from the sun (25% of the way to Proxima Centauri, 1,000 times as far away as Pluto) – a remnant of the original nebula that collapsed to form the sun and the planets		Oort cloud
Spectacular meteor shower seen every August		Perseids
Second largest of the three dwarf planets classified in 2006 – previously a planet		Pluto
Nix and Hydra (discovered in 2005) are moons of
The point in the night sky from which a meteor shower appears to originate		Radiant (point)
The least dense planet		Saturn
Named after the Roman equivalent of Cronos, the ruler (not the father) of the Titans of Greek mythology
First observed in 1876 by the American astronomer Asaph Hall, the Great White Spot is a periodically–recurring feature of
Zone defined to explain the behaviour of objects discovered from 1996 onwards: now believed to be where comets originated (rather than in the less extensive Kuiper Belt)		Scattered disc
Name given to the TNO that was discovered in 2003 and described at the time as "the tenth planet"		Sedna
Comet that collided with Jupiter in 1994 (after its discoverers)		Shoemaker–Levy 9
Stream of nuclear particles (mainly protons and electrons) flowing away from the sun's corona		Solar wind
Venus is covered by clouds of (vapour of)		Sulphuric acid
Comet that causes the Perseid meteor shower (when Earth passes close to its path): named after the two astronomers that discovered it independently in 1862; period approx. 130 years, nucleus about 17 miles across; the largest object that repeatedly passes close to Earth, making it "the single most dangerous object known to humanity"		Swift–Tuttle
Largest of over 20 satellites of Saturn, and the tenth largest body in the solar system after Ganymede (diameter 3,200 miles – larger than Mercury or Pluto)		Titan
Happens twice with a gap of 8 years, then not for another 121.5 or 101.5 years (2004, 2012, 2117)		Transit of Venus
Two groups of asteroids that move in the same orbit as Jupiter		Trojans
Named after the Greek personification of the sky – the only planet that's named after a Greek rather than a Roman god		Uranus
The other planet with rings
Spin axis tilted at 98o, so that one pole points almost directly at the sun
Surface is a superheated ocean of water
Known as the Morning Star (Phosphorus in ancient times) or the Evening Star (Hesperus in ancient times); also known as the Horned Planet		Venus
The only planet that rotates clockwise and so has a day longer than its year
Highest surface temperature (thanks to the greenhouse effect)
Nearest in size to the Earth (diameter 7,519 miles)
Karen Blixen, Maria Callas, Edith Piaf and Mary Queen of Scots can be found on the surface of
Maat Mons – a massive 'shield volcano' – is the second–highest mountain, and the highest volcano, on
The second–largest object in the asteroid belt (after Ceres)		Vesta
Hypothetical planet, proposed in the nineteenth century by the French mathematician Urbain le Verrier to orbit the Sun inside Mercury		Vulcan
Imprecise term (not approved by astronomers) for a typical star like the Sun – more correctly known as a 'G–type main–sequence star'		Yellow dwarf

© Haydn Thompson 2017–24