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Solar System

The Sun's planetary system, located about 26,600 light-years from the centre of the Milky Way

Solar SystemSolar System (astronomy)the solar system

The Solar System

The solar system is the Sun and everything held by its gravity: eight planets, five officially named dwarf planets, hundreds of moons, and millions of asteroids and comets. It formed about 4.6 billion years ago when a cloud of interstellar gas and dust collapsed into a spinning disk, and the Sun gathered more than 99% of the matter. Nearest the Sun are the rocky terrestrial planets — Mercury, Venus, Earth and Mars — followed by the giants Jupiter, Saturn, Uranus and Neptune. Beyond Neptune lie the Kuiper Belt and the vast Oort Cloud. In 2006 the International Astronomical Union defined what a planet is, reducing the census from nine to eight and reclassifying Pluto as a dwarf planet; NASA's New Horizons has since shown Pluto as a complex world.

25/25 claims verified 12 min read· 2026-09-18

The Milky Way

The Milky Way is the galaxy that contains the Solar System: a large barred spiral whose disk spans about 100,000 light-years, with roughly 100–400 billion stars and a total mass of about 1.5 trillion solar masses — most of it dark matter. Astronomers map it from the inside with ESA's Gaia mission, and test the laws of gravity on stars whipping around Sagittarius A*, the four-million-solar-mass black hole at the centre.

25/25 claims verified 12 min read· 2026-09-18

The Sun

The Sun is the G2 V yellow-dwarf star that holds the solar system together, containing more than 99 percent of its mass. In its core, hydrogen fuses into helium at about 15 million °C; energy takes some 170,000 years to work its way out, and the visible photosphere glows at about 5,500 °C. Around it, an 11-year cycle of magnetic activity rhythmically builds and clears the sunspots, tracked as a numbered series since Solar Cycle 1 in 1755 and now observed by NOAA's Space Weather Prediction Center. Cycle 25 began in December 2019; the 2019 prediction panel expected a peak of 115 sunspots in July 2025, while the smoothed sunspot number has already peaked so far at 160.9 in October 2024. The record of human observation stretches back to the first telescope drawings of 1610, through Schwabe's patient 43-year register and Carrington's 1859 flare, to a fleet of spacecraft — SDO, SOHO, STEREO, Hinode and Wind — joined by Parker Solar Probe, which touched the corona in 2021 and flew within 6.1 million kilometres of the surface on 24 December 2024, and ESA's Solar Orbiter, which returned the first close-up images of the Sun's poles in June 2025. This fact base collects the numbers, dates and quoted evidence behind that story.

25/25 claims verified 15 min read· 2026-09-18

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