SCIENCE COURSE: 7th. GRADE.PROF. LIRIETT HERRERA APRIL 20, 2012
“There are no walls at the edge of this universe... Absence of gravity is the limit of space. existence”. Toba Beta
UNIT IUNIT IOBJECTIVES•To identify the different types of celestial bodies.•To discover what a star is and how we can•distinguish one star from another.•To learn about the different shapes of galaxies.To know the Solar System and its components
The celestial bodies in the universe are very diverse•. Here we have a list of celestial bodies from our universe:
•Stars: Like the Sun which continuously radiateenergy into the space around them.•Galaxies: Groups of tens or hundreds of thousandsof stars.• The Universe contains approximately 100,000galaxies.Cluster of Galaxies: Made up of many differentgalaxies
The StarsIf we look at the night sky on a clear night, we can seehundreds of small lights which seem to be twinkling.These are the stars.If we look more closely we can see that some of thestars seem to form groups. These are constellations.The best known constellations are: Ursa Major, andUrsa Minor, Orion, Leo and Pegasus, etc.
Different types of starsStars have different characteristics:•Colour: When we look at the stars through binoculars oreven with the naked eye we can see different tones indifferent stars. Some are blush, reddish, orange, and so on.The Sun is a yellow star.•Size: The Sun is a medium- sized star. Betelgeuse, a star inthe constellation of Orion, is 600 times bigger than a Sun. Onthe other hand, Sirius B in the constellation of Canis Major is100 times smaller than the Sun.
•Brightness: Some stars are brighter than others. Sirius isvery bright. Other stars are so faint that we cannot seethem with the naked eye. They have been discoveredthanks to the use of telescopes.•Light: Some stars emit more light than others. Two starsemitting the same amount of light will not be as bright aseach other if they are at different distances from the Earth.
Groups of starsThe Sun has no other star in its immediatesurroundings, but this is unusual. It is morecommon to find stars in groups.•The Binary Star System: These are two starsthat turn around a common centre point.•Cluster Star System: These are groups oftens, hundreds or thousands of stars.
The GalaxiesGalaxies are made up of groups of stars, gasesand dust (small solid particles).Our galaxy is called the Milky Way. The nearestgalaxy to our own is Andromeda which is morethan two million light years away.This means that when we look at this galaxy weare seeing it as it was more than two millionyears ago.
Shapes of GalaxiesElliptical: More or less sphericalSpiral: A flat disc, with several arms coming out ofthe nucleus of the spiral.Irregular: With no specific shape.
The Solar SystemWe have already seen that there are different typesof celestial bodies in the Solar System.The Sun is the central body. It is a Star. Theplanets, their satellites, comets and asteroidsrevolve around the Sun. The planets revolve around the Sun in practically circular orbits. The planets which are farthest away revolve more slowly and take longer to complete a full revolution
Rocky planets and gaseous planetsThe planets can be classified into two differentgroups: the rocky planets and the gaseousplanets.Mercury, Venus and the Earth, Mars and Plutoare rocky planets. They have a solid surface.Jupiter, Saturn, Uranus and Neptune are allgaseous planets. They do not have a solidsurface.
The planets in the Solar System PLANET DISTANCE FROM PERIOD OF PERIOD OF THE SUN ROTATION REVOLUTIONMercury 0.39 58.65 days 88 daysVenus 0.72 243 days 224.6 daysEarth 1.00 23 h 56 min 365.25 daysMars 1.52 24 h 37 min 1.88 yearsJupiter 5.20 9 h 55 min 11.86 yearsSaturn 9.54 10h 40 min 29.46 yearsUranus 19.19 17 h 14 min 84.07 yearsNeptune 30.06 16 h 7 min 164.82 yearsPluto 39.44 6 38 days 274.70 years