Proxima system Proxima CentauriOur nearest stellar neighbor, a small red dwarf whose gravity holds its planets in orbit. Its light takes just over four years to reach us.Distance from the Sun 4.24 light-yearsType M5.5V red dwarfMean radius About 0.14 solar radiiSurface temperature About 3,300 KAge Estimated at about 4.8 billion years Light travel · 4.24 years The Milky WayA barred spiral galaxy, and the vast home that holds our Solar System.Solar System location Orion ArmDistance from galactic center About 26,000 light-yearsDiameter About 100,000 light-yearsEstimated stars 100–400 billion The SunOur star, holding the Solar System together with its gravity and bathing the planets in light.Type G-type main-sequence starMean radius 696,340 kmSurface temperature About 5,500 °CAge About 4.6 billion years MercuryA cratered, airless rocky world with extreme day–night swings.Solar Distance 0.39 AU · 57.9 million kmSize and Gravity 4,879 km diameter · 3.7 m/s²Planetary Age About 4.5 billion yearsAtmosphere and Weather Exosphere; intense solar exposure, no weather like Earth’sMoons and Satellites 0 known moonsDay and Year 58.6 Earth-day rotation · 88-day yearMagnetic Shield Weak global magnetic fieldSurface Temperature About −180 to 430 °CInternal Composition Large iron-rich core, rocky mantle and crustHabitability Verdict Not surface-habitable; no stable liquid water VenusA rocky planet wrapped in crushing clouds and runaway greenhouse heat.Solar Distance 0.72 AU · 108.2 million kmSize and Gravity 12,104 km diameter · 8.9 m/s²Planetary Age About 4.5 billion yearsAtmosphere and Weather Mostly CO₂; sulfuric-acid clouds, crushing pressureMoons and Satellites 0 known moonsDay and Year 243-day retrograde rotation · 225-day yearMagnetic Shield No intrinsic global fieldSurface Temperature About 465 °CInternal Composition Iron-rich core, rocky mantle and crustHabitability Verdict Surface is extremely hostile; cloud layers remain under study EarthOur ocean-rich rocky world is the only place known to host life.Solar Distance 1 AU · 149.6 million kmSize and Gravity 12,742 km diameter · 9.8 m/s²Planetary Age About 4.54 billion yearsAtmosphere and Weather 78% nitrogen, 21% oxygen; active water cycleMoons and Satellites 1 natural moonDay and Year 23 h 56 min rotation · 365.25-day yearMagnetic Shield Strong global magnetosphereSurface Temperature Global mean about 15 °CInternal Composition Iron–nickel core, silicate mantle and crustHabitability Verdict Confirmed habitable; known home of life MarsA cold, dusty desert with traces of a wetter ancient past.Solar Distance 1.52 AU · 228 million kmSize and Gravity 6,792 km diameter · 3.7 m/s²Planetary Age About 4.5 billion yearsAtmosphere and Weather Thin CO₂ atmosphere; cold, dusty, seasonal stormsMoons and Satellites 2 small moons: Phobos and DeimosDay and Year 24 h 37 min rotation · 687-day yearMagnetic Shield No global field; magnetized crustal regionsSurface Temperature Mean about −65 °C; highly variableInternal Composition Iron-rich core, rocky mantle and basaltic crustHabitability Verdict Uninhabitable at the surface today; past microbial habitability is investigated JupiterA vast gas giant with banded clouds, powerful storms and a deep interior.Solar Distance 5.20 AU · 778.5 million kmSize and Gravity 139,820 km diameter · 24.8 m/s²Planetary Age About 4.5 billion yearsAtmosphere and Weather Mostly hydrogen and helium; bands, jets and giant stormsMoons and Satellites 95 confirmed moonsDay and Year 9 h 56 min rotation · 11.86-year orbitMagnetic Shield Extremely powerful global magnetosphereSurface Temperature No solid surface; cloud tops about −110 °CInternal Composition Hydrogen–helium envelope; likely diffuse heavy-element coreHabitability Verdict No solid surface; some icy moons are astrobiology targets SaturnA hydrogen-rich gas giant encircled by broad, icy rings.Solar Distance 9.58 AU · 1.43 billion kmSize and Gravity 116,460 km diameter · 10.4 m/s²Planetary Age About 4.5 billion yearsAtmosphere and Weather Hydrogen and helium; fast winds and long-lived stormsMoons and Satellites 274 confirmed moonsDay and Year About 10.7-hour rotation · 29.4-year orbitMagnetic Shield Powerful global field, closely aligned with rotation axisSurface Temperature No solid surface; cloud tops about −140 °CInternal Composition Hydrogen–helium envelope around a dense, heavy-element interiorHabitability Verdict No solid surface; moon Enceladus has a subsurface ocean of interest UranusA pale-blue ice giant that rotates on its side and has faint rings.Solar Distance 19.2 AU · 2.87 billion kmSize and Gravity 50,724 km diameter · 8.7 m/s²Planetary Age About 4.5 billion yearsAtmosphere and Weather Hydrogen, helium and methane; very cold, hazy atmosphereMoons and Satellites 28 confirmed moonsDay and Year 17 h 14 min retrograde rotation · 84-year orbitMagnetic Shield Off-center, strongly tilted magnetic fieldSurface Temperature No solid surface; cloud tops about −195 °CInternal Composition Hydrogen–helium atmosphere over water, ammonia and methane-rich interiorHabitability Verdict No known habitable environment; some moons remain of scientific interest NeptuneA remote ice giant with dark storms and supersonic winds.Solar Distance 30.1 AU · 4.50 billion kmSize and Gravity 49,244 km diameter · 11.2 m/s²Planetary Age About 4.5 billion yearsAtmosphere and Weather Hydrogen, helium and methane; supersonic winds, dark stormsMoons and Satellites 16 confirmed moonsDay and Year 16 h 6 min rotation · 164.8-year orbitMagnetic Shield Off-center, strongly tilted magnetic fieldSurface Temperature No solid surface; cloud tops about −200 °CInternal Composition Hydrogen–helium atmosphere over water, ammonia and methane-rich interiorHabitability Verdict No known habitable environment; moon Triton is scientifically intriguing