Curated playlist
Solar System
- Solar SystemThe Sun holds 99.86% of all the mass in the Solar System. Every planet, moon and comet together add up to under 0.002%.
- Mercury (planet)Mercury's day, from one sunrise to the next, lasts about 176 Earth days. That is twice as long as its year.
- SednoidA planet could not have grown where Sedna now travels. Collisions there would shatter small bodies.
- Detached objectSedna orbits so far out that even Neptune cannot pull on it. Its closest approach to the Sun is 76 astronomical units.
- Moons of PlutoOn the 22nd of June 1978, astronomer James Christy spotted Pluto's first moon.
- Terrestrial planetMercury's metal core makes up 60-70% of the whole planet's mass.
- HaumeaHaumea, a dwarf planet, was found to have a ring in 2017. It was the first ring found around a dwarf planet.
- Dysnomia (moon)Dysnomia, the moon of the dwarf planet Eris, reflects just 5% of sunlight. Eris itself bounces back 96%.
- Io (moon)Jupiter's moon Io has over 400 active volcanoes, more than any other object in the Solar System.
- Galilean moonsGalileo first mistook Jupiter's moons for fixed stars. By January 15, 1610, he knew they orbited the planet.
- Europa (moon)Europa, a moon of Jupiter, is the smoothest solid object known in the Solar System.
- Scattered discStudies since 1992 show most periodic comets come from the scattered disc, not the Kuiper belt.
- PlutoIn 2006, astronomers voted to change the meaning of planet, and Pluto became a dwarf planet.
- 4 VestaAbout one in sixteen meteorites found on Earth is thought to come from the asteroid 4 Vesta.
- Moons of NeptuneNeptune's moon Triton orbits backward, which shows it was captured. Its arrival wrecked the planet's original moons.
- Human spaceflightThe Apollo 13 crew used their lunar lander as a lifeboat after an oxygen tank failed.
- Callisto (moon)Callisto, a moon of Jupiter, has the most heavily cratered surface in the Solar System. It has no volcanoes.
- MakemakeThe dwarf planet Makemake is brighter than Pluto. Its surface reflects 82 percent of light, thanks to fresh methane ice.
- Moons of MarsJonathan Swift wrote about two Martian moons 151 years before anyone found them.
- CometA close, bright comet can stretch up to 30 degrees across the sky, the span of sixty full Moons.
- PlanetFor centuries, Earth was not counted as a planet. The word first meant a wandering point of light.
- Natural satelliteThe 1957 launch of Sputnik nearly stole the word moon away. Satellite became tied to spacecraft, and moon came back.
- Kuiper beltIn 1992, Jewitt and Luu found the first Kuiper belt object since Pluto. It took them five years of searching.
- Discovery and exploration of the Solar SystemFor most of human history, the Solar System was simply called the universe.
- Space colonizationNo permanent settlement has ever been built beyond Earth. Space colonization is still only proposals and designs.
- Eris (dwarf planet)Eris was photographed in 1954 and nobody noticed. The dwarf planet's steep orbit kept it out of sky surveys.
- SunA photon born in the Sun's core can take 10,000 to 170,000 years to reach the surface.
- AsteroidA priest looking for a star in 1801 found the first asteroid. Giuseppe Piazzi first thought it was a comet.
- Moons of SaturnSaturn's moon Iapetus has one pitch-black side and one side almost as bright as snow.
- Formation and evolution of the Solar SystemOur Solar System began about 4.6 billion years ago, when a piece of a giant gas cloud collapsed.
- Deimos (moon)Two craters on Deimos honor writers who guessed Mars had two moons. Jonathan Swift and Voltaire were named in 1973.
- Moons of UranusIn 1787, William Herschel spotted two points of light circling Uranus. They were its first moons, Titania and Oberon.
- Trojan (celestial body)A mathematician predicted trojan asteroids in 1772, over a century before anyone saw one.
- AstronomyHenrietta Leavitt found in 1912 that certain pulsing stars reveal their true brightness.
- SpaceflightIn June 1944, a V-2 rocket became the first human-made object to reach space. It climbed to 189 km on a test flight.
- Space explorationSpace exploration began with a German V-2 rocket that reached 176 kilometers up in 1944.
- Moons of JupiterIn January 1610, Galileo aimed a telescope at Jupiter and saw four points of light moving night after night.
- Asteroid beltThe asteroid belt has only 3% of the Moon's mass. Its asteroids average about a million kilometers apart.
- Oort cloudIn 1950, Jan Oort reasoned that an unseen icy cloud must restock the Sun's comets.
- Saturn's hexagonSaturn's hexagon is a six-sided cloud sitting over the planet's north pole. Each side is roughly 14,500 kilometres long.
- EarthA Mars-sized object called Theia hit the young Earth, and the scattered debris became the Moon.
- MoonThe Moon is drifting away from Earth by 38 millimeters every year. That is about the rate human fingernails grow.
- Minor-planet moonIn 1993, the Galileo probe flew past asteroid 243 Ida and spotted a small moon, Dactyl.
- Planet NinePlanet Nine has never been photographed or detected, yet it has split astronomers.
- Trans-Neptunian objectFor 62 years, Pluto was the only known object past Neptune. Then a second one turned up in 1992.
- Solar System modelIn Boston, a basketball-sized bronze Jupiter sits 1.3 miles from the Sun. The Sun stood at the Museum of Science.
- Deep space explorationOn the 25th of August 2012, Voyager 1 crossed into interstellar space. No human-made object had ever traveled that far.
- Local BubbleThe Solar System sits inside the Local Bubble, a cavity in space at least 1,000 light years across.
- Small Solar System bodyThe day Pluto lost its planet status, a new category for small bodies was named.
- Vulcan (hypothetical planet)For decades, astronomers treated the planet Vulcan as real until Einstein's relativity explained Mercury's odd orbit.