10 Largest Moons in the Solar System
- Ganymede (Jupiter)
- Titan (Saturn)
- Callisto (Jupiter)
- Io (Jupiter)
- Moon (Earth)
- Europa (Jupiter)
- Triton (Neptune)
- Titania (Uranus)
- Rhea (Saturn)
- Oberon (Uranus)
5 Largest Moons of Saturn
- Titan (5149 km diameter)
- Rhea (1527 km)
- Iapetus (1469 km)
- Dione (1123 km)
- Tethys (1062 km)
5 Nearest Stars to the Sun
- Alpha Centauri system (4 light years - Proxima Centauri, Alpha Centauri A & B)
- Barnard’s Star (6 LY - in constellation Ophiuchus)
- Luhman 16 (7 LY - in constellation Vela)
- WISE 0855−0714 (7 LY - brown dwarf in Hydra)
- Wolf 359 (8 LY - in Leo)
5 Recognized Dwarf Planets
- Pluto - Slightly largest - Moons: Charon, Nix, Hydra, Kerberos, Styx
- Eris - In the Scattered Disc region - Moon: Dysnomia
- Makemake - In the Kuiper Belt - Moon: S/2015 (136472) 1 - Named for a Rapa Nui deity
- Haumea - Kuiper Belt - Moons: Hiʻiaka, Namaka - Named for a Hawaiian goddess
- Ceres - Asteroid Belt - No moons - Discovered in 1801
Arrokoth
A trans-Neptunian object in the Kuiper Belt - Visted by New Horizons in 2019, becoming farthest y most primitive object in the Solar System visited by a spacecraft - A 36 km long contact binary formed by two planetesimals joined together - Named for the Powhatan word meaning “cloud,” y was formerly nicknamed Ultima Thule
Centaur (astronomy)
Minor planets with unstable orbits between the gas giants - Typically behave with characteristics of both asteroids y comets - Notable centaurs incl. Chariklo (largest - 248km), Chiron, Asbolus, and Nessus - Most thought to have originated in the Kuiper Belt or Scattered Disc
5 Largest Constellations by Area
- Hydra
- Virgo
- Ursa Major
- Cetus (the whale)
- Hercules
Oort Cloud
A theoretical cloud of predominantly icy planetesimals believed to surround the Sun to as far as somewhere between 50,000 and 200,000 AU (0.8 and 3.2 ly) - The Kuiper belt y the scattered disc are less than one thousandth as far from the Sun as the Oort cloud - Never directly observed, but thought to be the source of some long-period comets y centaurs - Named for Dutch astronomer Jan Oort (1900-92)
Other Trans-Neptunian Objects
Most are likely dwarf planets, and are in the Kuiper Belt
- Gonggong - Diameter 1230km - Largest non-dwarf planet TNO - One moon, Xiangliu - Named for a Chinese water deity
- Quaoar (pronounced “Kwawar”) - Diameter 1110km - One moon, named Weywot - Named for deity of the Tongva people of S California
- Sedna - Diameter 1000km - Exteremely elongated orbit takes it to 937AU at aphelion - Named for an Inuit deity
- Orcus - Diameter 800km - One moon, named Vanth - Named for a Roman god of the underworld
- Salacia - Diameter 850km - One moon, named Actaea - Named for Roman goddess of the sea
- Varda - Diameter 722km - One moon, Ilmarë - Named from Tolkein mythology
- Varuna - Diameter 678 km - No moons - Named for a Hindu deity
5 Smallest Constellations by Area
- Crux (the Southern Cross)
- Equuleus (the foal)
- Sagitta (the arrow)
- Circinus (the compass)
- Scutum (the shield)
Van Allen radiation belt
A zone of energetic charged particles that is captured by and held around a planet by that planet’s magnetic field - The Earth has two permanent belts, extending from an altitude of about 500 to 58,000 km, y sometimes has other temporary belts - Most of the particles are thought to come from the solar wind, or from cosmic rays - Discovered in 1958 by the Explorer 1 spacecraft
ʻOumuamua
An apparent interstellar object passing through the Solar System, the first of a new class called hyperbolic asteroids - Appears to have come from roughly the direction of Vega, in the constellation Lyra - Highest orbital eccentricity (1.20) of any object observed in the solar system - Discovered in Oct. 2017 by the Pan-STARRS telescope in Hawaii - Name comes from Hawaiian for “scout”
