Solar systems

• The Sun


  • It is the only star in our solar system
  • It is the center of our solar system
  • Its gravity holds the solar system together
  • The planets, asteroids, comets, and tiny bits of space debris revolve around it
  • It is made of super-hot, electrically charged gas called plasma
• Photosphere


  • The surface of the Sun that we see from Earth
• Chromosphere and Corona


  • Thin layers above the Sun's surface where we see solar prominences, flares, and coronal mass ejections
• The Sun doesn't have moons, but it's orbited by eight planets, at least five dwarf planets, tens of thousands of asteroids, and around three trillion comets and icy bodies
• Several spacecraft are currently investigating the Sun
• Sunspots


  Cooler and darker than the rest of the Sun's surface, marked by intense magnetic activity
• Solar prominences


  Plasma loops that connect two sunspots
• Solar flares and coronal mass ejections

  Eruptions of highly energetic particles from the Sun's surface
• Sun's composition by number of atoms

  • 91.0% hydrogen
  • 8.9% helium
• Sun's composition by mass

  • 70.6% hydrogen
  • 27.4% helium
  • oxygen
  • carbon
  • nitrogen
  • magnesium
  • neon
  • iron
  • sulfur
  • aluminum
  • calcium
  • sodium
  • nickel
  • argon
• Mercury


  • Smallest planet in our solar system
  • Nearest to the Sun, with extreme temperatures
  • No atmosphere to retain heat at night
  • Fastest planet, revolving around the Sun every 88 Earth days
  • Not conducive to life
  • No rings
  • Formed about 4.5 billion years ago with a central core, rocky mantle, and solid crust
• Venus


  • Second planet from the Sun, Earth's closest planetary neighbor
  • Similar in size and density to Earth
  • Thick, toxic atmosphere filled with carbon dioxide and sulfuric acid clouds
  • Hottest planet in our solar system
  • Surface temperatures hot enough to melt lead
  • Crushed mountains and thousands of large volcanoes
  • Crushing air pressure at surface
  • Rotates on its axis backward compared to most other planets
  • First planet explored by a spacecraft (Mariner 2 in 1962)
  • Mapped by NASA's Magellan, but Soviet spacecraft made the most successful landings on the surface
• Venus' rotation


  • Rotates very slowly, with one day lasting 243 Earth days
  • Orbits the Sun faster than Earth, with one year taking only about 225 Earth days
• Earth


  • Third planet from the Sun
  • Perfect balance of atmosphere to breathe and live
  • Protects us from incoming meteoroids
  • Has one moon 384,400 km away
  • No rings
  • Axis of rotation tilted 23.4 degrees, causing seasons
  • Composed of four main layers: inner core, outer core, mantle, and crust
  • Lithosphere divided into huge moving plates
  • Global ocean covers nearly 70% of surface
  • Magnetosphere created by rapid rotation and molten nickel-iron core
• Earth's atmosphere


  78% nitrogen, 21% oxygen, 1% other gases
• Mars


  • Fourth planet from the Sun
  • Desert world with very thin atmosphere
  • One day takes a little over 24 hours, one year takes 687 Earth days
  • Thin atmosphere of carbon dioxide, argon, nitrogen, and small amounts of oxygen and water vapor
• Major mountain ranges


  • Andes
  • Rockies
  • Himalayas
• Magnetosphere


  Earth's rapid rotation and molten nickel-iron core give rise to a magnetic field, which the solar wind distorts into a teardrop shape
• Charged particles from the solar wind become trapped in Earth's magnetic field


  They collide with air molecules above the magnetic poles and cause aurorae (northern and southern lights)
• The magnetic field causes compass needles to point to the North Pole regardless of which way you turn
• Mars


  Fourth planet from the Sun, a desert world with a very thin atmosphere
• Mars


  • One day on Mars takes a little over 24 hours
  • Mars makes a complete orbit around the Sun in 687 Earth days
• Martian atmosphere


  Thin, composed of carbon dioxide, argon, nitrogen, and small amounts of oxygen and water vapor
• If you were to stand on the surface of Mars on the equator at noon, it would feel warm (24°C) and close to freezing at your head (0°C)
• Mars has two moons: Phobos and Deimos
• There are no rings around Mars
• The first true Mars mission success was the Mariner 4 flyby in 1965
• Red Planet


  Iron minerals in the Martian soil oxidize, or rust, causing the soil and atmosphere to look red
• Temperatures on Mars


  • As high as 20°C or as low as about -153°C
• Mars


  • A dynamic planet with seasons, polar ice caps, canyons, extinct volcanoes, and evidence of past activity
• Mars is one of the most explored bodies in our solar system, and it's the only planet where we've sent rovers to roam the alien landscape
• NASA currently has two active rovers (Curiosity and Perseverance), one lander (InSight), and one helicopter (Ingenuity) exploring the surface of Mars
• Perseverance rover


  • The largest, most advanced rover NASA has sent to another world
  • Touched down on Mars on Feb. 18, 2021, after a 203-day journey traversing 472 million kilometers
  • The Ingenuity helicopter rode to Mars attached to the belly of Perseverance
• In 2021, three spacecraft arrived at Mars: the Hope orbiter from the United Arab Emirates, China's Tianwen-1 mission (orbiter, lander, and rover), and Europe and India also have spacecraft studying Mars from orbit
• In May 2021, China became the second nation to ever land successfully on Mars when its Zhurong Mars rover touched down
• An international fleet of eight orbiters is studying the Red Planet from above including three NASA orbiters: 2001 Mars Odyssey, Mars Reconnaissance Orbiter, and MAVEN
• These robotic explorers have found lots of evidence that Mars was much wetter and warmer, with a thicker atmosphere, billions of years ago
• Jupiter


  The largest planet in the solar system, orbiting about 778 million kilometers or 5.2 Astronomical Units (AU) from the Sun
• Jupiter


  • Has the shortest day in the solar system, rotating once about every 10 hours (a Jovian day)
  • Takes about 12 Earth years to complete one orbit of the Sun (a Jovian year)
• Jupiter has 80 moons, 57 of which have been given official names by the International Astronomical Union (IAU), and another 23 moons are awaiting names