 Unit 5: Sixth Grade

 Did you know that planets, when viewed from Earth, look like stars to the naked eye?  Ancient astronomers were intrigued by these “stars” which seemed to wander in the sky

 Ancient astronomers named these “stars” planets, which means “wanderers” in Greek.  These astronomers knew planets were physical bodies and could predict their patterns.  But it was not until Galileo used a telescope in the 1600’s that we able to explore these other worlds.

 Our solar system includes the Sun, the planets and many other smaller objects.  Some planets, such as Saturn, have several moons that orbit them, and in this way, our solar system is a combination of many other systems

 Up until the 1600’s, the universe was thought to have only 8 bodies (things): the Earth, the Sun, the Earth’s Moon, and Mercury, Venus, Mars, Jupiter and Saturn.  They are the only bodies visible without a telescope

 After the discovery of the telescope, more discoveries were made and the current model of our solar system was in place by the 1900’s

 Our solar system is divided into two main parts:  The inner solar system  The outer solar system  The inner solar system contains the four planets that are closest to the sun  The outer planets contains the planets farthest from the sun

Inner Planets  Mercury, Venus, Earth, Mars.  More closely spaced  Known as terrestrial planets as they are dense and rocky Outer Planets  Jupiter, Saturn, Uranus, Neptune, Pluto*  Larger in size and tend to be made of gases  Known as “Gas Giants”

 Inner planets are also called terrestrial planets because they are very dense and rocky.  They are the four planets closest to the sun: Mercury, Venus, Earth, Mars

 Distance from the sun: 3.2 light minutes  Period of revolution: 88 days (year)  Period of rotation: (59 days)  Average temperature:332F, 167C  Diameter: 3,032 miles, 4,879 K  Closest planet to the sun.  Because there is less gravity, you would only weigh 38% of what you do here on Earth!

 6.0 light minutes from the sun  Period of revolution: 224 days  Period of rotation: 243 days  Average temperature:457F, 854C  Diameter: 7,520 miles, 12,100K  Sun rises in the west and sets in the east.  Sometimes called “Earth’s Twin” as it is similar in size and distance from the sun.

 Distance from the sun: 8.3 light minutes  Period of revolution: days  Period of rotation: 24 hours  Average temperature: 57F, 15C  Diameter:7,926 miles, 12,756K  The only planet to support life in our solar system.

 We have life on Earth due to several reasons:  The “perfect” star  The right distance from the star  Revolution around the star  23.5 degree tilt  Rotation on our axis  WATER

 Distance from the sun: 12.7 light-minutes  Period of revolution: 687 days  Period of rotation: 24 hours, 40 minutes  Average temperature: - 81 °F, --63 °C  Diameter: 4,222 miles, 6,794 km  The most studied planet after Earth.  While there is no water on Mars presently, there is evidence that it was once present

 Because they are so much larger than the inner planets, the outer planets are called gas giants.  Gas giants are planets that have deep, massive atmospheres rather than hard, rocky surfaces like the inner planets have.  The Outer Planets include: Jupiter, Saturn, Uranus, Neptune, and Pluto*

 Distance from the sun: 43.3 light minutes  Period of revolution: 11 years, 313 days  Period of rotation: 9 hours, 54 minutes  Average temperature:- 202F,- -130C  Diameter: 88,846 miles, 142,984 km  The largest planet in our solar system  The red spot is a 400 year old storm that is 3 times the diameter of Earth!

 Distance from the sun: 1.3 light-hours  Period of revolution: 29 years, 155 days  Period of rotation: 10 hours, 42 minutes.  Average temperature:-202 °F, 130 °C  Diameter: 74,900 miles, 120,536 km  The second largest planet.  The rings around Saturn are made of icy particles.

 Distance from the Sun: 2.7 light- hours  Period of revolution: 83 years, 273 days  Period of rotation: 17 hours, 12 minutes  Average temperature:-328 °F, °C  Diameter: 31,763 miles,51,118 km  Uranus is tipped on its side and one of its poles is always dark, depending on where the planet is on its journey around the sun.  This tilting is thought to be a result of being hit by a massive object.

 Distance from the Sun: 4.2 light-hours  Period of revolution: 163 years, 263 days  Period of rotation: 16 hours, 6 minutes  Average temperature:-328 °F, -200 °C  Diameter: 30,779 miles, 49,532 km  Neptune has a Great Dark Spot similar to Jupiter’s Great Red Spot.  Neptune has a narrow set of rings.

 Distance from the Sun: 5.4 light- hours  Period of revolution: 248 years, 4 days  Period of rotation: 6 days, 10 hours  Average temperature:-378 °F, -228 °C  Diameter: 1430 miles,2,390 km  Pluto was reclassified as a dwarf planet in  Less than half the size of Mercury and mainly made of ice and rock.  It’s moon, Charon, is almost the same size as Pluto.  hill.com/sites/ /student_view0/brainpop_movies.ht ml# hill.com/sites/ /student_view0/brainpop_movies.ht ml#

 Two words: gravity and inertia!  Gravity is the force that keeps the planets in the Sun’s orbit.  Inertia is the law that an object in motion will stay in motion unless acted upon by an outside force.

 In the case of the sun and the planets, the Sun is larger and has more mass, and thus a stronger gravitational pull.  It’s always tugging us toward it, wanting to suck us in and burn us alive!!!  So it’s a wonderful thing that we also have inertia…

 Inertia works against that gravity to keep us from being sucked into the sun.  Because of inertia, planets want to travel in a straight line and never stop moving in that straight line.  So it’s a good thing that we have gravity …

 Because gravity keeps us from flying off into space (never to be seen again)!  Gravity and inertia’s fight for the planets is what keeps us in the Sun’s orbit.

 Pluto never made a full orbit around the sun from the time it was discovered to when it was declassified as a planet.  There are more stars in space than there are grains of sand on every beach on Earth.  It rains diamonds on Saturn and Jupiter.  If you dug a hole to the center of the Earth and dropped a book down, it would take 42 minutes to reach the bottom.