02.10 Oral Assessment

a scientific theory that describes the beginning of the universe. All matter in the universe was once a single point. Gravity and energy caused the matter to expand The universe is still expanding

A galaxy is a group of stars, planets, gas, and dust that is held together by gravity. Our galaxy, The Milky Way, is thought to have around 100,000,000,000 stars and there is thought to be about 100,000,000,000 other galaxies in the Universe. That leaves the universe with trillions and trillions of stars. Many scientists estimate that the universe has 400,000,000,000,000,000,000,000. stars.

Irregular galaxies are young galaxies. Because of this, they contain mostly young stars. These galaxies have many stars that are still forming. Irregular galaxies also contain lots of gas and dust. This gas and dust can form into new stars or planets.

Spiral galaxies are medium aged galaxies. Because of this, they contain some older stars and some younger stars. They still have a few stars that are still forming. Spiral galaxies also contain some gas and dust. This gas and dust could condense to form new stars and planets.

Elliptical galaxies are old galaxies. Because of this, they contain mostly old stars and they do not have new stars forming. Because elliptical galaxies do not have new stars forming, they do not have much gas and dust.

Because light is so fast, it is used to measure distances in space. A light year is the distance that light can travel in one year. So if an object is one light year away, it will take light one year to get there. Light years are used to measure distances in space because their large size allows us to talk about vast distances using smaller numbers. For instance, it is much easier to talk about three light years, than it would be to talk about 17637000000000 miles!

Star Size Scientists use four different characteristics to help them classify and describe stars. Giant Medium-sized Dwarf Neutron Supergiant Star Brightness The distance light source is from your eye. The size of the light source. The strength of the light source. Star Temperature Every star has a different temperature. The temperature of the stars can be different based on the size of the star and the type of elements that make up the star. The temperature of a star is very important because it determines the color of the star. Star Composition By studying the light that comes off stars, scientists can determine what the star is made of. Every star gives off a different fingerprint of light and this light gives scientists a clue as to what elements are located in the star. The most common element in stars is hydrogen. The second most common element in stars is helium. Stars do contain other elements but these two are the most common.

We can see that there is a relationship between brightness and temperature. The brighter an object is the hotter the object will be. This is also true of stars. If we compare the absolute magnitude and temperature of stars, we will see that the brighter a star is, the hotter it will be. A HR diagram is a graph used by scientists to study the stars. The main reason that the HR Diagram is so useful is you can tell the size of the star by plotting it on the HR Diagram. The different sizes of stars form a pattern on the HR diagram. On the following HR Diagram, select Dwarfs, Main Sequence, Giants, and Supergiants to learn more.

Protostar A nebula is a region of gas and dust in space. Over time the gas and dust collects in a spinning cloud. This condenses more to from a protostar. A protostar is the birth place of a star. It is similar to the fetus stage in the human life cycle. Fusion ignition - Main Sequence As the gases in a protostar become more and more compact, the pressure and heat will get to a point where the gas will ignite and a star is born. The main sequence is when the star is in its youth. These stars are of average size. Giant or Supergiant After a star has burned for awhile, it will become a giant or supergiant. Giants and supergaints are stars that are middle aged. Dwarf or Black Hole At the end of a stars life, it will become a dwarf or a black hole. The giants will turn into dwarfs and the supergiants will turn into blackholes.

Solar Prominence A solar prominence is a violent eruption of gas that loops out into space. These eruptions can push out into space so far that more than ten earths could fit into the loop. Solar Flare A solar flare is a violent eruption on the sun's surface. This eruption sends light and energy blasting into space. Because of the huge amount of energy, the temperature of a solar flare can reach more than twice that of the rest of the sun's surface. Sunspots If you were to look at the surface of the sun through a solar telescope, you would see areas of dark spots. These are sunspots. Corona The corona is the outermost part of the suns atmosphere. The temperature of the corona exceeds one million ºC. The chromosphere is the middle layer atmosphere of the sun. Temperatures in the chromospheres average more than 25,000 ºC. The photosphere is considered the surface of the sun. Temperatures in the photosphere are usually around 6,000 ºC.

The electromagnetic spectrum is the range for light. Usually the electromagnetic spectrum is shown in graphical form. Light allows us to see our surroundings. At night, we need to use artificial light to find our way around our homes. During the day, the sun provides all the light we need. Without light, we would be living in the dark. However, light is more than what we can see. Radiation is light. Microwaves are light. Radio waves are light.

Scientists can use a special instrument called a spectrometer to collect the light coming off stars and planets. They can then use the light \"fingerprint\" to determine what atoms are on the star or planet. The light \"fingerprint\" is called an emission spectrum. When an atom lets off or emits light it does not let off just one color. It emits a combination of a few colors. The emission spectrum is all the colors that the atom emits. Spectroscopes are the instruments that scientists use to see the atoms emission spectrum. They take the light and bend it through a prism. Spectroscopes take the light coming off objects and break them down into their colors.

The amount of light a star gives off.

The brightness of a star as it appears from the earth, without the effect of the earth's atmosphere.

A supergiant star that can be seen with the naked eye in the night sky.

The middle layer atmosphere of the sun.

The outermost part of the suns atmosphere.

The range for light.

All the colors that the atom emits.

The number of times a wave crest passes by a point in one second. If you could stand next to a wave, and count the number of wave crests pass you in one second, that is frequency.

A group of stars, planets, gas, and dust that is held together by gravity.

This law states: All objects that have mass attract each other. Large objects like planets and stars have a large amount of attraction Small objects like people, houses, and cars have a very small amount of attraction

Considered the surface of the sun.

The birth place of a star.

Other than the sun, the nearest star to us.

A violent eruption on the sun's surface.

A violent eruption of gas that loops out into space.

A special instrument used to collect the light coming off stars and planets.

When the gravity of supergiants gets too big, the star will explode.