Science Class 5th Grade » The Solar System
||The Solar System
Unit 1: The Solar System
In our first unit we will be learning about planets, the moon, the sun, stars, comets, meteors, asteroids, telescopes, and space exploration.
The solar system is the sun and the bodies orbiting it: the sun and all the planets, satellites, asteroids, meteors, and comets that are subject to its gravitational pull.
Planets are spherical objects which orbit a star. Planets can vary greatly in size although they are never larger than the star they orbit. Planets can be rocky or gaseous. Smaller planets tend to have solid surfaces while larger planets are balls of mostly gas. There are 8 planets known to orbit the sun.
See an example of the Planet Eduglog Project here.
In addition to the 8 traditional planets, there are several Dwarf Planets in the Solar System. Like the 8 main planets, they are round and orbit the Sun. However, what makes them Dwarf Planets is their size and also the fact that they haven't "cleared the neighborhood" of their orbits. This could mean that they orbit the Sun in an asteroid belt or the route they take around the Sun crosses the orbit of another object also orbiting the Sun. The most famous Dwarf Planet is Pluto, which since its discovery in 1930, was recognised as the ninth planet in the Solar System until being reclassified in August 2006. Other objects recognised as Dwarf Planets are Ceres, which orbits the Sun between Mars and Jupiter, and Haumea, Makemake and Eris, which like Pluto, orbit the Sun beyond Neptune.
Accompanying Earth on its journey around the Sun is the Moon, Earth's only natural satellite. The Moon is the second brightest object in the sky after the Sun and is thought to have formed from the debris when a planet-sized object collided with Earth billions of years ago. The Moon is larger than dwarf planet Pluto and is the only object, other than Earth, to have been stepped on by human beings. Although the Moon's appearance changes due to its phases, you are only ever able to see one side of it as it always faces Earth.
Stars are massive balls of gas that produce heat and light. The Sun is the nearest star to Earth, but it is just one of billions of stars in the Milky Way galaxy, and the Milky Way is one of billions of galaxies in the universe. Although stars are many many times larger than Earth, and often much larger than the Sun, they appear as small dots of light in the sky because they are so far away. Stars can be different sizes and different colours which tells us a lot about their age and temperature.
Comets are often described as dirty snowballs. They are balls of rock and ice which formed in the outer edges of the Solar System, beyond the orbit of Pluto in a cloud of condensation called the Oort Cloud. A typical comet is about 20 kilometres in diameter. Comets orbit the Sun in elliptical orbits, travelling from a great distance to become very close to the Sun. They spin around the Sun and are then flung back outwards. When a comet is close enough to the Sun to be affected by its heat and radiation, it begins to burn off gas and dust and forms a bright tail. Some comets take thousands of years to orbit the Sun, some take a few years and some are thrown out of the Solar System for good after they spin around the Sun!
Asteroids are small lumps of rocks and ice which orbit the Sun like mini-planets. They are sometimes called planetoids because they were probably formed in the same way as the planets.
Some people believe that different seasons happen because sometimes the Earth is farther from the Sun and sometimes it is closer -- but this is not true. The Earth travels around the Sun in an almost perfect circle (it is only slightly eliptical -- the most accurate way to draw the earth's path around the Sun is as a circle). So it really doesn't change by much how far away we are from the Sun. The earth's axis is tilted about 23.5 degrees, so the Earth is never straight up and down compared to the Sun. During the summer, the Sun is high in the sky. Therefore, rays of light from the Sun hit us more directly during summer, making the sunlight more intense and warmer. In winter, the Sun is low in the sky. The rays of light are spread more thinly, and they do not warm us as much.
To learn more about our Solar System, do interactives, and find Solar System activities click on the binder below:
Mrs. Travis' Classroom
Dorchester County Public Schools
1103 Maces Lane
Cambridge, Maryland 21613