🪐 A Grand Tour of the Solar System

What you’ll learn

1. The Sun: Our StarUnderstand the Sun as the dominant body of the solar system, including its mass, structure, energy source, and far-reaching heliosphere.The Sun holds about 99.8 percent of the solar system's mass and fuses hydrogen in a core near 15 million degrees Celsius, while its visible photosphere is a comparatively cool 5,500 degrees. Its solar wind inflates a vast bubble, the heliosphere, that surrounds all the planets and ends far beyond Neptune at the heliopause.
2. The Inner Rocky WorldsCompare the four terrestrial planets and their standout features, from Mercury's extremes to Venus's greenhouse and Mars's giant volcano.The inner planets are small, dense, and rocky. Mercury swings over 600 degrees between day and night, Venus's runaway greenhouse drives its surface to about 465 degrees Celsius, and Mars hosts Olympus Mons, the tallest known planetary volcano, plus evidence of ancient water.
3. The Gas Giant JupiterExplore Jupiter's scale, atmosphere, the Great Red Spot, and its major moons including ocean-bearing Europa.Jupiter is a hydrogen-helium giant so large more than 1,300 Earths could fit inside, banded by fast rotation and home to the centuries-old, now-shrinking Great Red Spot. It has around 100 known moons, including the four Galilean moons, with Europa hiding a global subsurface ocean that makes it a key target in the search for life.
4. Saturn and the Ringed RealmExamine Saturn's iconic ice rings and its standout moons Titan and Enceladus as ocean-world candidates.Saturn's spectacular rings are made mostly of water-ice particles and are vast yet razor-thin. Its moon Titan has a thick atmosphere and surface lakes of liquid methane, while tiny Enceladus jets plumes of water and organics from a subsurface ocean, both prime astrobiology targets sampled by Cassini.
5. The Ice GiantsDistinguish Uranus and Neptune as a separate class of ice giants and explain their tilt, winds, and composition.Uranus and Neptune are ice giants rich in water, methane, and ammonia rather than mostly hydrogen and helium. Uranus is tipped about 98 degrees onto its side, and Neptune hosts the fastest winds known, up to roughly 2,000 kilometers per hour; both were visited only once, by Voyager 2.
6. Dwarf Planets and the Asteroid BeltUnderstand the asteroid belt as planetary leftovers and learn the IAU criteria behind Pluto's 2006 reclassification.The asteroid belt between Mars and Jupiter is mostly empty, holding only a few percent of the Moon's mass, with Ceres alone accounting for nearly a third. In 2006 the IAU defined a planet by three criteria; Pluto fails to clear its neighborhood and was reclassified as a dwarf planet, later revealed by New Horizons as a surprisingly active world.
7. Comets, the Kuiper Belt and Oort CloudMap the icy outer reaches of the solar system and explain where comets come from and how they form tails.Beyond Neptune lies the Kuiper Belt, a ring of icy bodies and home to Pluto and many short-period comets, while the distant spherical Oort Cloud is the source of long-period comets. Comets are icy, dusty bodies that grow glowing comas and tails, always pointing away from the Sun, as they approach and vaporize.
8. How We Explore: The Great MissionsAppreciate landmark robotic missions, especially Voyager and Cassini, and how they transformed our view of the solar system.The Voyager probes, launched in 1977, toured the outer planets and have since crossed into interstellar space carrying the Golden Record, with Voyager 2 the only craft to reach Uranus and Neptune. Cassini orbited Saturn for 13 years, discovered Enceladus's plumes, landed the Huygens probe on Titan, and ended in a deliberate plunge into Saturn in 2017.

Questions this course answers

Grounded in trusted sources

• NASA Science Solar System Exploration (science.nasa.gov)
• International Astronomical Union (iau.org) — IAU 2006 planet definition and Minor Planet Center moon confirmations
• ESA / NASA-JPL mission archives — Voyager, Cassini, and Hubble (esa.int, jpl.nasa.gov)

Every Wunder lesson is built from real, reputable sources — never invented.

Related Science courses