12.
1 Solar System objects
UNDERSTANDING THE SOLAR SYSTEM
Vocabs
Solar system: consists of the sun, the planets, their moons, and a variety of smaller objects
Astronomical unit: distances between objects in the solar system.
1 AU = 150,000,000 km, from the center of the sun to the center of the Earth
Sun:
is a star with gaseous body
contains no solid surface
about ¾ of the sun’s mass is hydrogen
about ¼ is helium
Planet: is round, orbits around the sun, has cleared out the region of the solar system along its orbit
Moon:
Earth’s natural satellite
A celestial body in orbit
Asteroids: small, rocky bodies
Meteoroids: chunks of rock or dust, smaller than asteroids
Comets:
loose balls of ice and rock
have very long and narrow orbits
develop tails as they orbit the sun
STRUCTURE OF THE SUN
Vocabs
Plasma: a very hot fluid-like gas consisting of electrically charged particles
Convection zone:
the outermost layer of the sun’s interior
Plasma heated by the radiative zone rises up to the surface
Cooling plasma at the surface -> plasma contracts and sinks -> convection loops
Radiative zone: Most heat flows through as forms of electromagnetic radiation
Core: The sun produces an enormous amount of energy here
Nuclear fusion:
The sun’s energy is produced through nuclear fusion
Hydrogen atoms are forced together in the core
Extreme temperature and pressure -> create helium atoms
Photosphere:
the sun’s inner atmosphere
Plasma in this layer is dense enough to be visible and directly observed
Chromosphere:
Middle layer of the sun’s atmosphere
Reddish glow -> “color sphere”
Corona:
The outer layer of the sun’s atmosphere
White halo around the sun
Extend into space for millions of kilometers
Gradually thins into streams of electrically charged particles (solar wind)
Sunspot:
areas of plasma on the sun that are cooler than the plasma around them
Cooler plasma gives of less light -> dark spots
Prominence:
huge loops of plasma that are polarized
Particles following these magnetic forces flow out and back on the sun’s surface
Solar Flare:
The eruptions of prominence (plasma loops)
Loops in the sunspot regions connects, release large amounts of magnetic energy -> heat plasma
up to millions of degrees Celsius -> the eruption
PLANETS AND MOONS
Mercury:
Closest planet to sun (.39 AU)
Smallest planet (4,879 km diameter)
Has no moons
If you weighed 100kg on earth, you would weight 38kg on mercury
1 day on mercury = 59 earth days
1 year mercury = 88 days
At night: -170°C
During the day: 430°C
Has no atmosphere
Venus:
Almost same size as Earth (12,103 km diameter)
90% Earth’s gravity
1 venus day = 243 Earth days
1 year = 225 days
Has no moons
2nd closest planet to sun (.72 AU)
Had oceans billions of years ago
Today, venus has an atmosphere that is 96.5% carbon dioxide (CO2)
Thick atmosphere -> the air pressure at its surface is 92 times of Earth
High CO2 levels make a very strong greenhouse effect -> venus is very hot
Average temperature is 462°C
Its surface is mostly flat lava plains and volcanoes
Has a crust, mantle, and core
The brightest object in the night sky after the moon
Mars:
4th planet from the sun (1.52 AU)
About half the size of Earth (6,792 km diameter)
Gravity is about 38% as strong as Earth’s gravity
1 day on Mars = 24.6 hours
1 year = 687 days
Has 2 small moons
Atmosphere is 95% CO2, 100 times thinner than Earth’s atmosphere
Has weather like dust storms
Average temperature = -60°C in winter
Near the poles, temperature = - 125°C
Has seasons due to its tilted axis
Some of mar’s surface features were formed by water
Used to have oceans and still have sub surface water and ice
Sedimentary rocks only form in the presence of water.
Some of Mars’ surface features were formed by volcanism (and may still be)
Mars has the solar system’s largest volcano. Olympus mons is 22 km tall
Mars has one of the solar system’s largest valleys. Valles Marineris is 4000 km.Long, 200
km.wide and 7 km.deep
Some of Mars’ surface features by impacts from space.
We know a lot about mars because we have sent many probes and landers there.
Jupiter
Jupiter is the 5th planet from the sun (5.2 AU)
Jupiter’s diameter is 11 times wider than Earth (142,800 km diameter)
Jupiter has no surface to stand on, but if you could stand on the surface Jupiter’s gravity would
be 2.4 times stronger than earth’s
Jupiter’s day is 9.9 hours long. it spins at 43,000 km/h
1 year on Jupiter is 12 Earth years.
Jupiter has 95 moons.
The 4 largest moons are known as the Galilean moons (discovered by Galileo and his telescope).
Scientists believe Ganymede, Callisto and Europa all have oceans under the ice and could have
their own forms of life.
Io Has active volcanoes. Its yellow color comes from sulfur.
Callisto is covered in ice and most likely has a liquid salt water ocean.
Ganymede is covered in ice and most likely has a liquid salt water ocean.
Europa is covered in ice and most likely has a liquid salt water ocean.
Jupiter’s outer layers are hydrogen (90%) and helium (10%) gas
Jupiter’s inner layers are metallic hydrogen
The temperature in the clouds of Jupiter is about minus 145 degrees Celsius.
The temperature near the core may be about 50,000 degrees Celsius.
Saturn
Saturn is a gas giant. A planet made mostly of gas, Unlike the inner planets which are rocky.
All the outer planets have rings, including Saturn.
Saturn is the 6th planet from the sun (9.6 AU)
Saturn’s diameter is about 120,000 km.
Saturn has no surface to stand on, but if you could stand on Saturn, it’s gravity would be 7%
stronger than earth’s. Saturn is big but not very dense.
Saturn’s density is actually less than water, which means it would float.
Saturn’s atmosphere is made of mostly hydrogen gas with a smaller amount of helium gas.
Saturn's average temperature varies from about - 185°C to -122°C
The core could be as hot as 11,700 c.
Saturn’s day is 10 hours 39 minutes long. it spins at 35,500 km/h
1 year on Saturn is 29 Earth years.
Saturn has 62 moons.
Titan has a thick atmosphere that makes it hard to see the surface.
Titan has methane rain, rivers, lakes and oceans.
These rocks on titan’s surface are made of water ice.
Enceladus Is covered in ice and we see very few craters which means the surface of the moon is
young.
The plumes were water vapor coming from Enceladus’s liquid ocean.
minerals and chemicals that come from hydrothermal vents on the bottom of the ocean.
Saturn’s rings are one of the most distinct features in the solar system.
Saturn’s rings are made of many small particles, ranging in size from micrometers to meters.
The ring particles are made almost entirely of water ice, with a small amount of rocky material.
Earth has hydrothermal vents on its ocean floor also.
On earth the vents provide chemical and heat energy for bacteria, shrimp, crabs and worms.
Uranus and Neptune
Are ice giants. They have atmospheres similar to Jupiter and Saturn but have more ices (water,
ammonia and methane).
All the outer planets have rings, including Uranus and Neptune.
Uranus is the 7th planet from the sun (19.2 AU)
Uranus’s diameter is about 50,724 km.
Neptune's diameter is about 49,244 km.
If you weigh 100 kg. on earth, you would weigh 86 kg. on Uranus and 110 kg. on Neptune.
Uranus and Neptune both have atmospheres made mostly of hydrogen gas with a smaller
amount of helium gas. They both have layers of ices and rocky cores.
Uranus's average temperature is -224°C. Uranus’s core is about 5,000°C.
Neptune is warmer, with an average temperature is -214°C. Neptune’s core is about 7,000°C.
Uranus’s day is 17 hours 14 minutes long. it spins at 9,320 km/h
Neptune’s day is 16 hours 6 minutes long. it spins at 9,650 km/h
1 year on Uranus is 84 Earth years.
Uranus is tilted 98 degrees off axis and basically rolls around the sun.
1 year on Neptune is 165 Earth years.
Uranus has 27 moons
Neptune has 14 moons
Neptune’s moon triton is geologically active. ITS SURFACE is young with very few craters.
SMALL SOLAR SYSTEM OBJECTS
• Dwarf planet
• Trans Neptunian object (Kuiper belt objects)
• Asteroid
• Asteroid belt
• Meteoroid
• Meteor
• meteorite
• Comet
• Oort cloud
• Kuiper belt
• There are many (many) objects in the solar system that are smaller than planets.
• Asteroids are rocky or metallic objects often found in the asteroid belt, between the orbit of
mars and Jupiter.
• Smaller pieces of rock in space are called meteoroids.
• Sometimes meteoroids enter earth’s atmosphere and burn up making a streak of light. These
are called meteors.
• If a meteoroid reaches earth’s surface it’s called a meteorite.
• Comets are loose collections of frozen gases and dust.
• Comets usually come from the Kuiper belt or the oort cloud.
• the oort cloud Is a giant spherical shell of icy objects that surrounds our solar system.
• The oort cloud may contain billions or trillions of comets. It is 50,000 to 100,000 AU from the
sun.
• Dwarf planets are rounded by gravity but don’t have their own orbits.
• Dwarf planets are also known as trans Neptunian objects or Kuiper belt objects.
SOLAR SYSTEM FORMATION
• Nebula
• Protoplanetary disk
• Protostar
• Nuclear Fusion
• planetesimals
Clouds of gas and dust in space are called nebulas.
Nebulas can form when stars explode
Some nebulas are leftovers from the early universe.
Stars are formed in nebulas.
This flat rotating disk of materials is known as a protoplanetary disk.
A Protostar is a young star that has not started nuclear fusion yet.
Nuclear fusion is how the sun produces energy.
Planetesimals are 0bjects formed from dust, rock, and other materials. They can be as small as
a couple of meters or as large as hundreds of kilometers.
