The Sun - Presented on Tuesday, April 12th, 2011

Hi everyone!

For my celestial body project, I was the first one in line to present. And you know why? Because I was studying the Sun, the center of our solar system and since we were going in order of the planets, the Sun has to start. After me, we go in order; Mercury-Venus-Earth... So I'm going to tell you more about the Sun in this post!
First of all, the Sun is not, I repeat NOT a planet. It is a star and that is what makes it special! It got its name from the Romans who named it "Sol". That is also how solar system got its name - because the Sun is the center of it! It has been known forever - all the discoverer had to do was look up! It is also 4.6 billion years old, which makes it middle-aged. As we learned from Ms. D, it is also middle-sized and middle-hot!

Here you can see a comparison of the sizes of planets (including the Sun), but also how small the Sun is to some other stars:


It is, as you can see in the video, much bigger than all the planets and is the biggest celestial body in our solar system. Its symbol is a circle with a dot in the middle.
It looks like this:

The Sun was born in a spinning cloud of gas and dust that was held together by gravity, which later formed a ball. The Sun also rotates, just like Earth; but it takes longer. One rotation takes 25.38 Earth days at the Equator and 35 days at the poles! This is because at higher latitudes, there is less solid, so it is harder for the gas to spin. All planets revolve around the Sun - so you must think that the Sun doesn't revolve. But it does! It revolves around the center of the Milky Way galaxy, which takes 225-250 million years. This can also be called a cosmic year. The star is one of over 200 billion in the Milky Way galaxy!

Do you like numbers? Well, you will see a lot of them when talking about the Sun!

• The distance to Earth is 149,598,000 km, also known as an Astronomical Unit (AU).
• The diameter is 1,393,000 km (approximately 110 x Earth's diameter.
• The density is 1.409 g/cm^3 (approximately 0.26 x Earth's density)
• The mass is 1.989 x 10^30 kg (approximately 333,000 x Earth's mass)
• The circumference is 4,370,005.6 km (approximately 1100 x Earth's circumference)
• The volume is 1,409,272,569,059,860,000 km^3 - (approx. 1,300,000 x Earth's volume).

The Sun is an extremely hot celestial body, although some stars are hotter! The temperature at the surface is 5,000 °C, and at the core, the temperature is 15,000,000 degrees Celcius! Some of these numbers are rounded - more exact ones can be found here.

There are also storms on the Sun. One type of storm is a Solar Flare. This is an explosion in the atmosphere of the Sun, and happen when the magnetic fields tangle. Another type of storm is a Coronal Mass Ejection (CME) which happens in the corona (you can read more about the corona below) and increase solar winds which show up as auroras, or Northern and Southern lights, here on Earth!
Here is an example of an aurora:


The Sun is always hot and doesn't change climates, but it does affect the climate we have on Earth! You can read more about that at this website.

Basically, the Sun is just a big ball of hot gas, and in the core, nuclear reactions happen which produce light, energy, and radiation from the sun. Here's something interesting: Galileo Galilei, a famous Italian scientist (whom you can read more about here), thought that there was no solid material in the Sun at all, but NASA has now proven that there is solid in the core, made up of calcium ferrite (calcium + iron). There are also three layers of the atmosphere:

• The photosphere, which people consider to be the surface, is made up of hydrogen and helium gas (as is the whole Sun) and is approximately 5,000 km thick. Most of the light we see comes from here.
• The chromosphere is 2500 km thick, and is less dense but way hotter.
• The outmost layer, the corona, is visible from Earth only when there is a solar eclipse (the corona is the white part around it) because it is so thin and the photosphere blocks the view at all other times.

There have also been several missions to the Sun, but two of the biggest ones are:

• Chandra, launched in 1999, which focuses on taking x-ray pictures of the Sun and other stars. It takes very crisp and clear pictures and helps scientists study the universe. You can read more about it and see photos from it here.
• SoHo (Solar and Heliospheric Observatory) was launched in 1995 by NASA and the ESA and is locked in orbit around the Sun just like Earth, which means that it travels at the same speed as us. It helps scientists study the Sun the way we see it, but closer. You can read more about it at its website.

Here are some pictures from SoHo and Chandra, and some pictures even have captions or objects labeled!:


And here are some interesting facts:

• There are things called "sunspots" which are "colder" spots (temperature "only" 3500 degrees Celcius... You can see these at 1:22 (they are the white spots) on the video above.

• Every 11 years, the Sun's magnetic poles (which we have on Earth, too) flip! This happens when there are lots and lots of sunspots on the surface. You can read more about them in this outdated yet informative article.
  
• I'm sure you love being out in the Sun, but be careful of its ultraviolet (UV) rays! They can burn your skin and cause you to have skin cancer! You might end up looking like this:
• Also, solar energy has become very popular these days. You can heat and cool your house with it, as well as get electricity through solar panels! It saves both money and the environment!
  

So now you know a little bit about the Sun - and I hope you enjoyed this post! Remember to be just as happy as the Sun is:

The next scribe should be Sophie - she was the only person who finished her presentation other than I, and if you are looking for any of our notes, visit the Moodle page for this week! There you will also be able to find blogging directions.

Good luck to the next presenter (who already started), Teréz!!
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Vocabulary used in this scribe post:
Note: all definitions are from Merriam-Webster

Star: A self-luminous gaseous spheroidal celestial body of great mass which produces energy by means of nuclear fusion reactions
Solar System: The Sun together with the group of celestial bodies that are held by its attraction and revolve around it
Aurora: a luminous phenomenon that consists of streamers or arches of light appearing in the upper atmosphere of a planet's magnetic polar regions and is caused by the emission of light from atoms excited by electrons accelerated along the planet's magnetic field lines
Nuclear Reaction (from http://www.wordiq.com/definition/Nuclear_reaction): A process in which two nuclei or nuclear particles collide, to produce products different to the initial products
NASA: National Aeronautics and Space Administration
ESA: European Space Agency


Note: ^ stands for exponent!