The Solar System

The Solar System Formation

• Formed approximately 4.6 billion years ago from a dense molecular cloud collapse
• Collapse resulted in the formation of the Sun and a protoplanetary disc

The Sun

• Typical G-type main-sequence star
• Maintains equilibrium through fusion of hydrogen into helium at its core
• Releases energy from its outer photosphere

The Planets

• Eight planets orbit the Sun
• Four terrestrial planets: Mercury, Venus, Earth, and Mars
• Two gas giants: Jupiter and Saturn
• Two ice giants: Uranus and Neptune
• Terrestrial planets have solid surfaces
• Giant planets do not have a definite surface, composed mainly of gases and liquids

Mass Distribution

• Over 99.86% of the Solar System's mass is in the Sun
• Nearly 90% of the remaining mass is in Jupiter and Saturn

Dwarf Planets

• At least nine dwarf planets: Ceres, Orcus, Pluto, Haumea, Quaoar, Makemake, Gonggong, Eris, and Sedna

Small Solar System Bodies

• Asteroids, comets, centaurs, meteoroids, and interplanetary dust clouds
• Many bodies in the asteroid belt (between Mars and Jupiter) and the Kuiper belt (just outside Neptune's orbit)

Moons

• Six planets and seven dwarf planets have orbiting natural satellites (moons)

The Heliosphere

• Solar wind, charged particles from the Sun, forms the heliosphere
• Halted around 75-90 astronomical units from the Sun, resulting in the heliopause
• Heliosphere boundary marks the edge of the Solar System to interstellar space

The Oort Cloud

• Theorized outermost region of the Solar System, source of long-period comets
• Extends to a radius of 2,000-200,000 AU

Nearest Star

• Proxima Centauri, 4.25 light-years (269,000 AU) away
• Both the Sun and Proxima Centauri are part of the Milky Way galaxy

Learn about the formation and composition of our Solar System, including the Sun and its orbiting objects. Discover how the Sun maintains its equilibrium and the classification of its star type.