the sun AND STARS
Now we arrive at the sun, The centre of our solar system.
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The Sun is at the center of the Solar System. The planets, asteroids and comets all revolve around the Sun. The Sun’s role as the center of the planetary system comes from its high mass; it has 99.8% of the mass in the Solar System and, therefore, guides the movement of the other objects via gravitational forces.
The Sun is at the center of the Solar System. The planets, asteroids and comets all revolve around the Sun. The Sun’s role as the center of the planetary system comes from its high mass; it has 99.8% of the mass in the Solar System and, therefore, guides the movement of the other objects via gravitational forces. Over the course of human history the Sun has been feared and worshipped, rightfully so. What our ancestors knew on a fundamental level was that the Sun provides a vital ingredient for most of the life on Earth. Without the energy provided through sunlight, vegetation cannot grow, and without vegetation animals do not have a source of nourishment. However, what we know today that our ancestors did not is just how far reaching the scope of the Sun's influence is. The light emitted by the Sun brings energy to the rest of the Solar System and largely dictates the temperatures on the planets. As you can see in the images below the Sun is incredibly large. Those small 'balls' beside it are actually all the other planets and look very tiny when so they are so close.
The sun is big enough to fit every single planet inside it very easily and its actually so big that it can fit 1.3 million of our Earth inside it without overflowing. The Sun is a star. The reason it looks so big and bright as compared with the stars in the night sky is that it is very close to the Earth. If the distance from the Sun to Earth (about 150 million km; or about 93 million miles) is scaled to about 15 m (45 ft), the nearest star to the Sun would be located over 4,000 km (2,490 miles) away.
That is, if the Sun and the Earth were located in Brisbane, the nearest star to the Sun would be in Perth. Most stars that we see are much further away from the Earth; this is why they look so small in the night sky, even if they are similar to the Sun. SIZE OF THE SUN
The size of the Sun compared to the largest known stars (red giants) is not very big. However, if compared to the most common type of star in the universe, the red dwarf, the Sun is quite a bit larger. Thus, the Sun is not the biggest type of star in the universe, but it is definitely larger than most. As far as the Sun’s mass compared to other bodies found in our solar system, the Sun is easily the most massive. The Sun alone contains 99.8% of the total mass in the Solar System. In terms of size, the Sun has a diameter of roughly 1.4 million kilometers (870,000 miles). To put this in perspective, this is almost 110 times the diameter of the Earth. What this means is that about one million Earth’s could fit inside the Sun. |
WHAT TYPE OF STAR IS THE SUN?
Although we think of our Sun as a unique celestial body, it is, in fact, one of trillions of stars in the universe. On top of this, the Sun is rather ordinary as far as stars go. The official classification for our Sun is G V star (often referred to as a Yellow Dwarf star), which means that it is a main sequence star whose surface temperature is between 5027°C and 5727°C.
Some estimates for stars similar to the Sun in the Milky Way galaxy alone are as high as 7 billion. If this number is correct, there could be over one trillion stars that are roughly the same as our Sun in the universe.
Although we think of our Sun as a unique celestial body, it is, in fact, one of trillions of stars in the universe. On top of this, the Sun is rather ordinary as far as stars go. The official classification for our Sun is G V star (often referred to as a Yellow Dwarf star), which means that it is a main sequence star whose surface temperature is between 5027°C and 5727°C.
Some estimates for stars similar to the Sun in the Milky Way galaxy alone are as high as 7 billion. If this number is correct, there could be over one trillion stars that are roughly the same as our Sun in the universe.
The stars
You've seen stars every night of your life but now is the time to learn about themAs you can see our Sun isn't so big after all.
Pictured above is our Sun compared to 3 other gas giants, Sirius, Pollux and Arcturus. But don't worry those stars are very far away so they won't heat us up much. |
So the Sun is a star but what is a star and where are they?
Well let me tell you. A star is a luminous sphere of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations.
However, most of the stars in the Universe, including all stars outside our galaxy, the Milky Way, are invisible to the naked eye from Earth. Indeed, most are invisible from Earth even through the most powerful telescopes. For at least a portion of its life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. Almost all naturally occurring elements heavier than helium are created by stellar nucleosynthesis during the star's lifetime, and for some stars by supernova nucleosynthesis when it explodes. Near the end of its life, a star can also contain degenerate matter. Astronomers can determine the mass, age, metallicity (chemical composition), and many other properties of a star by observing its motion through space, its luminosity, and spectrum respectively. The total mass of a star is the main factor that determines its evolution and eventual fate. Other characteristics of a star, including diameter and temperature, change over its life, while the star's environment affects its rotation and movement. A plot of the temperature of many stars against their luminosities produces a plot known as a Hertzsprung–Russell diagram (H–R diagram). Plotting a particular star on that diagram allows the age and evolutionary state of that star to be determined.
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In general, the larger a star, the shorter its life, although all but the most massive stars live for billions of years. When a star has fused all the hydrogen in its core, nuclear reactions cease. Deprived of the energy production needed to support it, the core begins to collapse into itself and becomes much hotter. Hydrogen is still available outside the core, so hydrogen fusion continues in a shell surrounding the core. The increasingly hot core also pushes the outer layers of the star outward, causing them to expand and cool, transforming the star into a red giant.
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If the star is sufficiently massive, the collapsing core may become hot enough to support more exotic nuclear reactions that consume helium and produce a variety of heavier elements up to iron. However, such reactions offer only a temporary reprieve. Gradually, the star's internal nuclear fires become increasingly unstable - sometimes burning furiously, other times dying down. These variations cause the star to pulsate and throw off its outer layers, enshrouding itself in a cocoon of gas and dust. What happens next depends on the size of the core.
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