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Transcript of Science
Prepared by: Siti Nur Aminara binti Mohd Azlan
Stars and Galaxies
We are here
Characteristics of the Sun
1. The Sun is the centre of the solar system.
2. The Sun is the only star in the solar system that produces light energy and generates heat energy,
3. The Sun is also the nearest star to the Earth and is approximately 150 million km from the Earth.
Mass -> 1.989 x 1034kg (333 420 times the mass of Earth)
Diameter -> 1 392 000 km (109 times the Earth diameter)
Surface temperature -> 5100 to 6000oC (227 to 273 times the temperature of Earth)
Gravitational force -> 28 times the gravitational force of Earth
Density -> 1485 kg/m3 (0.27 times the density of the Earth)
The Sun atmosphere
Corona (The outermost layer)
Photosphere (The innermost layer)
Chromosphere (The middle layer)
The Sun's atmosphere is made up of three layers:
Corona (The outermost layer)
The largest and hottest layer
Can only be seen from the Earth during a total eclipse of the Sun
The corona layer appears as a ring of whitish-blue light surrounding the Sun
Has a thin layer of gas. This layer also produces X-rays
Reaches a temperature as high as 2 000 000oC
Chromosphere (The middle layer)
This layer is about 9600 km thick. It is made up of hydrogen, helium and calcium
Can only be seen during an eclipse of the Sun
Appears as a ring of purplish red light
The temperature between 10 000oC to 50 000oC
The corona and chromosphere cannot be seen from the Earth at other times because the glare from the Sun obstructs our view.
Photosphere (The innermost layer)
Photosphere or 'light ball' is the luminous surface of the Sun
The temperature is about 6000oC and its thickness is about 400 km
Allmost all the light energy received by the Earth comes from photosphere
Appears to be a rough layer.
Its surface has many sunspots, prominences and solar flares
Phenomena on the Surface of the Sun
1. Areas of the photosphere that appear dark because they are cooler than the surrounding areas.
2. The temperature is about 4000oC
3. Sunspots are not permanent on the Sun. They appear and disappear over a period of several days, weeks or months.
4. The number of sunspots increase and decrease in a regular pattern called the sunspots cycle.
5. Are related to several phenomena on the Sun's surface such as prominences and solar flares.
1. Also called solar protuberances or the 'giant flames'. They are due to the solar magnetic field associated with sunspots.
2. Prominences are huge, arching column of hot gas (about 10 000oC) spewing about 60 000 km from the chromosphere.
3. Prominences ejected will be drawn back to the chromosphere by the Sun's gravitational force, forming an arch.
4. Some prominences blast material from the Sun into space at speed ranging from 600 km/s to more than 1000 km/s.
1. Sudden eruption of intense, hot gas near a sunspot or prominence.
2. Seen as bright flashes of light that develop suddenly on the Sun's surface.
3. Occur when gas and huge quantity of charged particles explode from the photosphere.
4. Small solar flares last for only 20 minutes while powerful solar flares can last for 3 hours.
4. Can reach a temperature of about 5 000 000oC.
The effects of the phenomena on the surface of the Sun on Earth
Both prominences and suspots can result in strong electromagnetic waves.
These electromagnetic waves contain electrically charged particles that can caused solar winds.
Solar winds are strongest during periods when many sunspots exist and solar activity is high.
Solar winds can affect satellite, radio, television, telegraph and telephone communications.
They disrupt the transmission of telecommunication signals on Earth.
Solar winds are also cause climate disturbances on Earth, such as extreme droughts.
When the solar winds interact with the Earth's magnetic field near each hemisphere, the gas in the Earth's atmosphere ionised and produced coloured lights, called aurora.
In the Northern Hemisphere, it is known as the Aurora Borealis or Northern Lights, and in the South Hemisphere, this phenomena is called the Aurora Australis.
Generation of Energy by the Sun
The main gaseous components of the Sun are hydrogen (92%) and helium (7%)
Hydrogen is the main fuel in the generation of energy of the Sun
The Sun obtains energy from the thermonuclear reaction/nuclear fusion that takes place in the core of the Sun
During this reaction, extremely high pressure and temperature cause hydrogen nuclei to combine to form helium nuclei. This process generates a lot of heat and light energy.
The temperature reached in this reaction is about 15 000 000oC
Energy generated is then distributed from the core to the surface of the Sun by radiation and convection
A large portion of the Sun energy will be emitted as electromagnetic waves. A small portion of energy reaches the Earth
Definition of a Star
Stars are bright spheres in the space that emit their own energy
There are many stars in the universe but the Sun is the only star in the solar system
The stars are made up of hot and blazing dusts and gases like hydrogen and helium
All stars might appear to e simillar, but they are quite different in many characteristics
The distance between the stars and the Earth is measured in light years. One light year is the distance that light can travel in one year, at the rate 300 000 km/s
1 light year= 9 500 000 000 000 km
* Types of Stars *
Colour and Temperature
* The colour of a star depends on its temperature.
* Stars having different temperatures will emit different colour lights.
* Stars can be divided into 7 classes by colour and temperature.
* The amount of light produced by a star within 1 second. It is often refers to the brightness of a star.
* All stars do not have the same brightness. The brightness of a star depends on its distance from the Earth, surface temperature, mass and size.
There are 2 methods of measuring brightness, the apparent magnitude and the absolute magnitude.
Mass and Density
*The mass of stars do not differ a lot because all stars are made up of gas.
* The density of stars varies from about 10 000 to 10 000 000 g/cm3.
* Small stars with bigger mass have higher density than large stars with small mass.
* Stars have different sizes.
* The Sun which is a hundred times larger than the Earth, is only an average=sized star.
* There are also larger or smaller stars than the Sun.
Supergiant star is the largest and brightness star in the sky. It is more than a 100 times the size of the Sun.
* The star smallerthan the Sun is a dwarf star.
Formation of a Star
Death of a Star
There are 3 types of galaxies
* It has diameter between 3000 and 10 000 light years.
* It is shaped like smooth, rounded or oval and has no arms.
* It is the brightest at the core and gradually fades towards the edge.
* It is made up of old yellow stars and does not contain gas and dust, so new stars are not formed.
*It has a diameter of about 20 000 to 100 000 light years.
* It is a disc-shaped and made up of stars gathering in a whorl with spiral arms at the edge. These arms contains dust and gas.
* It has a bright centre. Its centre has a red giant star. Its arms have newly-formed stars, white dwarf stars and nebulae. The arms rotate around its centre.
* It has a diameter between 25 000 and 32 000 light years.
* It does not have definite pattern or shape.
* It exist in various different forms and is usually made up of whitish-blue stars that are very hot and gaseous clouds (nebulae)
The Milky Way
The Milky Way is a spiral-shaped galaxy in the Univerese.
The thickness of its centre is about 10 000 light years while its length is about 100 000 light years.
The Sun is one of the million stars located in the Milky Way. It is located about 30 000 light years from the galaxy centre in one of the spiral arms.
The Sun takes 240 million years to complete its orbit around the centre of the Milky Way at the speed of 235 km/s.
At night, the Milky Way is seen as a band of light in the sky. It light comes from millions of stars that are very close to one another so that they are visible as luminous clouds.
Made up of millions of galaxies where each galaxy has its particular characteristics.
The Universe is infinite. To this day, the astronomers have been unable to determine the immensity of the Universe.
The galaxies in the Universe are found together in clusters or groups. The cluster that the Milky Way belongs to is called the Local Group.
Galaxies in the Local Group are not far apart from one another. There are more than 30 galaxies exist in the Local Group.
Among these galaxies, only the Cloud of Magellan and Andromeda can be seen with naked eye.
The Clouds of Magellan are about 200 000 light years from the centre of the Milky Way while Andromeda is about 2 millionslight years.