Hi again. I decided to start the blog towards the cosmos before jumping to news, animal life and more intricate subjects. I will start off with some basic and very interesting information of space and our Solar System.
I dedicate this article to my favorite two teachers of all time: Profº Michele and Profº Jackson.
Have a good reading.
The sun is the most important star in your life. You depend on it to survive. Even very ancient civilization recognized its power and importance on their lives. They recognized it so well that they started calling it God, where some religions arose and stories were developed to worship it as a way to thank the Sun for all the benefits and allowances, such as, for example, the permission to practice agriculture, keeping the plants producing fruits, thus favoring human life and its evolution.
But like many other stars the Sun is not all about wonders. It is a raging star and can be one of the closest definitions of hell. Its core temperature is 15,000,000 °C and surface temperature is about 6,000 °C. Temperature is not alone in the extreme tier. Pressure on the surface is about 340 billion times Earth's air pressure at sea level. Such pressure is so high that even if you could place a ship that tolerates 6,000 ºC on the surface of the Sun, the ship would be totally smashed by the atmospheric pressure. There is a simple law explaining gravitational force: The greater the mass of the subject, the bigger and more powerful will be the subject’s gravitational field. There is really nothing unexpected here, considering the size of the Sun.
Even though the Sun mass is about 3 times less dense than the Earth’s, it represents 99.8% of the entire mass on the Solar System. The other 0.2% comes from Jupiter, the largest planet on the system. We are nothing.
If we use x-ray filters and sensors it is possible to see that the Sun has a mass of gas surrounding it, burning at millions of degrees Celsius. This mass of gas is known as the Solar Corona.
At normal visible light we can visualize darker regions on the Sun’s surface. They are holes in the Solar Corona. These holes are called the Sun spots. Where there is a dark spot you may have a big surge of flaming gas, so big that it would engulf the entire Earth if it was close to it. These tongues of fire forms what astronomers call Solar Winds, and 6.7 billion tons of solar matter are lost every hour caused by these fire gushes.
It is known that the greater the number of Sun spots present on the Sun's surface the more extra energy will be released to space. Global temperatures variations are driven by the Sun. In the past, Sun activity have been much more intense than now. One example situates around 8000 years ago, when a warm period called The Holocene Maximum began. Earth's temperatures were from 3 to 9 ºC higher than today.
Sun, as a star, is not only responsible for conditioning Earth's environment and making it habitable by different forms of life, but also for the creation of majority of all chemical elements known. The two simplest elements, hydrogen and helium, compose most of the Sun’s mass. In such hot environment, and not only in the core of our Sun, but also in the core of all stars, extreme temperatures on the area of tens of millions of degrees Celsius makes possible the creation of new chemical elements by rearranging and grouping different amounts of neutrons, electrons and protons of existing matter on the reaction (hydrogen and helium). Those reactions are what scientists believe to be the origin of different forms of matter. This also implies that we and everything is made of stars, since that’s where the ingredients came from.
The concept of creation of new elements is fairly simple, though. As Carl Sagan once explained, you could transform, for example, Mercury to something else. By removing 1 proton and 3 neutrons of it, you have gold. By just varying the number of protons—which is always the same number of electrons—and the number of neutrons—which holds the nucleus of the atom togheter—it is possible to create any element. From this point of view it’s a very simple process indeed. Do you want to create a new element? Take hydrogen gas and you can make gold, iron, or any other element known of it, but ultra-high temperatures are needed to complete the reaction, and this is achieved in the nucleus of the stars.
I once wondered what’s behind the process which makes stars glow, as our Sun. As stated above, atoms (chemical elements) are made inside stars using hydrogen and helium. The jamming of hydrogen forms helium, and the jamming of helium can produce various different elements. When hydrogen nuclei produce a helium nucleus a photon of light is emitted. If there is a huge amount of this process in activity concentrated somewhere, there is a strong glow. That’s why stars shine.
It’s interesting to note that when you go outside on a clear dark night to look up at the sky many of the stars you are looking at doesn’t even exist anymore. Some of them are thousands of light-years away. So, what does it mean when a star you’re seeing at the sky is, for example, 2000 light-years of distance away from Earth? It means that the visual information you are receiving from that star is a 2000 years old image. In other words, the light of this star takes 2000 years to get to your eyes. If at this exact moment a change in its appearance occur, like color or intensity of light, you could only observe the change 2000 years later, here, on Earth. The star could well have hit its final life stage and died already, but you still see it because of the limitations of physics: the maximum speed at which light can travel. So, if there is a delay in the process you’ll have to wait until the travel is completed. Even if our Sun is only 150,000,000 km away from Earth, there is a good 8 minutes time necessary to a photon emitted there to get here.
If you want to know more about our great and marvelous Sun, check out the sources. There is much more to know.
If you want to know more about our great and marvelous Sun, check out the sources. There is much more to know.
On the next blog posts I’ll be talking about nebulas, cycle of life of a star, red giants, supernovas and black holes.
References and recommended links:
Carl Sagan's Cosmos: A Personal Voyage Documentary (1980)
Meyer-Vernet, Nicole (2007). Basics of the Solar Winds. Cambridge University Press
Uzan, J-P; Leclercq, B (2008). The Natural Laws of the Universe: Understanding Fundamental Constants. Springer. pp. 43–4.
V.L. Koshkarova and A.D. Koshkarov (2004). Regional signatures of changing landscape and climate of northern central Siberia in the Holocene.
B.A.S. Davis, S. Brewer, A.C. Stevenson, J. Guiot (2003). The temperature of Europe during the Holocene reconstructed from pollen data. 
