I. California K-6 Standards for The Universe

II. Goals of This Module

III. Beginning of the Universe

IV. The Universe Is Lumpy

V. Formation and Evolution of Stars

VI. Brightness of Stars

VII. Measuring Distance in the Universe

VIII. Age of the Universe

IX. Laboratory Exercises

X. Possible Essay Questions

XI. Practice Questions

1. Grade 3
1. Earth Sciences Topics
1. Objects in the sky move in regular and predictable patterns. As a basis for understanding this concept, students know:
1. the patterns of stars stay the same, although they appear to move across the sky nightly, and different stars can be seen in different seasons.
2. telescopes can magnify the appearance of some distant objects in the sky, including the moon and the planets. The number of stars that can be seen through telescopes is dramatically greater than can be seen by the unaided eye.

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• To learn about how the Universe formed.
• To learn about what the Universe is made of.
• To learn the definitions of and proper spelling for scientific terms that are used commonly in newspapers, magazines, and books, and on television and radio programs to discuss the Universe.
• To learn about and grasp an appreciation for the immense size of the Universe.

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• In the beginning, all matter in the universe was crammed into a very small space. The creation of the universe began with the horrendous explosion of this mass of matter.
• The explosion made everything so hot that subatomic particles could not form. All matter existed in this non-structured state called plasma
• As the plasma hurtled outward from the center of the explosion it cooled sufficiently for various subatomic particles to form.
• By 2 seconds after the explosion, electrons, protons, and neutrons had formed.
• By 5 minutes, the nuclei of hydrogen and helium atoms had formed.
• By 300,000 years, the temperature had cooled to 100,000,000°K and electrons could attached themselves to the hydrogen and helium nuclei and form atoms.

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• As plasma, and later on atoms, hurtled outward from the Big Bang, they did not expand in a uniform manner, but broke up into lumps or globs of matter that were separated by space from other lumps of matter.
• As time passed (about 1 billion years) and cooling continued, the gravitational attraction between hydrogen and helium atoms in these lumps caused the lumps to contract and consolidate into denser masses of gas where huge numbers of stars were created.

These immense concentrations of gas and stars are called galaxies. Some galaxies do not rotate and are spherical in form, others are rotating and are more disk shaped. The galaxy that contains our solar system is called the Milky Way.	Click on picture to view a full-size image.
Galaxies are arranged into galaxy clusters, which are separated from other galaxy clusters by larger spaces than those between the galaxies in a cluster.	Click on picture to view a full-size image.

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Gravitational contraction between the hydrogen and helium atoms in a galaxy causes lumps of gas, called nebulae, to form within the galaxy. These nebulae are relatively cold.	Click on picture to view a full-size image.
Each nebula continues to contract or collapse due to gravity until the atoms are close enough to begin to collide and interfere with each other. This causes them to speed up, which creates a renewed source of heat. When the temperature is sufficient, visible light is radiated from the mass and a star is born.	Click on the picture to view a full-size image.
After the star is born, it goes through a series of energy and size fluctuations for a period of time. Gravitational collapse continues to produce energy release which, in turn, causes expansion. This fluctuation in size continues until the pressure in the center (core) of the star is high enough to produce fusion of helium from hydrogen. The fusion process releases a huge amount of energy, which stops gravitational collapse and stabilizes the star.	Click on the picture to view a full-size image.
Stars are of various sizes depending on the amount of matter that was in the original lump of plasma that ultimately became the star.	Click on the picture to view a full-size image.

• Stars are also of various colors depending on their temperature:
• Blue = a very hot star (25,000°K)
• White = a hot star
• Yellow = a star of intermediate temperature
• Orange = a not-so-hot star
• Red = a relatively cool star(3,000°K)
• The closest star to us is a yellow star called the Sun.

 

• The star remains stable for a long time, until 60% of its hydrogen is used up. It will then collapse again until it reaches a temperature sufficient to cause helium fusion into carbon and expansion of the outer part of the star into a red giant star.

In the final stages of stellar life, the surface of the star expands and separates to form a ring nebula and the core contracts into a white dwarf star, which is extremely dense.

Click on the picture to view a full-size image.

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• Apparent magnitude - based on the actual appearance of the star's brightness
• Absolute magnitude - a measure of the star's true brightness
• Compare the apparent magnitude with the distance to the star to determine the absolute magnitude.

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• Light year - the distance that light travels in a year. Calculate this distance in km and mi using the speed of light equal to 300,000 km/sec and 186,000 mi/sec.
• Distance to close stars is determined using the following principles:
• A close star is photographed at six-month intervals and its relative angular position with respect to distant stars is noted. The distance to the star is calculated from the parallax angle and the distance that the earth moved in those six months, which is 300,000,000 km or 186,000,000 mi.

 

• The Doppler effect, the expanding universe, and distance to distant objects -
• When visible-light-emitting objects move away from the Earth, the Doppler effect causes the wavelengths of the light to lengthen, which causes the light to shift toward the red (longer wavelengths) end of the spectrum.
• All objects in the universe show this red shift in the visible spectrum. Hence, all objects in the universe are moving away from the Earth.
• The greater the distance to an object, the greater is the red shift; so the farther away from the Earth an object is, the faster it is moving away from the Earth. Therefore, the universe must be expanding.
• For very distant objects, the amount of red shift is used to determine the distance to the object.

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• The most distant objects observed in the Universe are 12,000,000,000 light years distant.
• What we see today when we look at those objects happened 12,000,000,000 years ago. So the universe is at least that old.

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• EXAMINING APPARENT AND ABSOLUTE MAGNITUDE -
• MAKING A LUMPY UNIVERSE FROM A BIG BANG -

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• Describe the origin of the Universe, including the sequence and timing of the major events.
• Describe the origin, evolution, and death of a star.
• Describe how color is related to the temperature of a star.
• Explain why astronomers believe that the Universe is expanding.
• Define apparent and absolute magnitude and explain how they are related.

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XI. Practice questions -

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