February 24, 2011 
Yesterday dawned bright and cold. The overcast skies were now blue and dominated by a large yellow object that appeared to be a source of both light and heat. A little research and I discovered it is called the Sun and it is the ultimate source of all Earth’s energy. Even more amazingly, every star visible at night is also a sun just like ours although some are very much larger and others smaller and cooler. The excellent band “They Might Be Giants” even have a song about it.
I think “The Sun is a mass of incandescent gas” is one of my all-time favourite pop lyrics. Unfortunately it is not a very accurate statement. Gas is just one of the various states in which matter can exist and the Sun is not ‘gas’ but rather plasma. The huge temperatures mean that all the electrons in the atoms that the sun is made from are released, free to whizz around separately. So it would be more accurate to sing “The Sun’s a miasma of incandescent plasma”, which just about scans if you stress the 5th syllable.
The Sun is approximately 150 million kilometres from Earth. This is known as one astronomical unit or 1AU (149 598 000 kilometres to be more precise). It is so massive that it makes up about 99 percent of the mass of the solar system. It is roughly 75% hydrogen, 23% helium and 2% other elements like carbon and neon. At the incredible temperatures (5,600 K on the surface, 13.6 million K in its core) hydrogen atoms are smashed together to make helium atoms. This process is called nuclear fusion and releases the heat that keeps the sun burning.
There are eight planets orbitting the Sun, from closest to furthest, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. They are held in orbit by the gravitational pull of the Sun. Beyond Neptune there are lots of other objects, such as Pluto, that are quite large but too small to be classified as planets. There has been some speculation about another planet, about four times as large as Jupiter, existing way out beyond Neptune. Its presence has been inferred by the gravitational effects it is having on various objects such as comets. It is an interesting notion but it is not yet established science although some newspapers have written about it as though it is fact.
The Sun is just coming out of a dip in activity that is part of its 11 year solar cycle. Activity will increase on its surfce resulting in more flaring, coronal mass ejections and cosmic radiation bursts.
Questions…
- What name has been given to the proposed new giant planet?
- Which planet in the solar system has the most moons?
- How long does it take the Earth to orbit the Sun once?
- What shape is the Earth’s orbit around the Sun?
- What are the maximum (aphelion) and minimum (perihelion) distances the Earth can be from the Sun?
1. ?
2. Jupiter with a total of 63 moons.
3. It takes one year.
4. The shape is elliptical.
5. ?
I can’t remember the answer to Q1, nor Q5. Many of my questions are not about what you currently know but try to encourage you to seek out answers for yourself. Google is your friend!
Well done on the other three questions by the way!
Question 1:
The name is Tyche, and here are some facts about it that I know:
It is a gas giant 4 times the size of Jupiter, although it might not be a gas planet because NASA has just found out about it.
It is in the Oort Cloud, the most remote place in the solar system.
It’s orbit is the Tyche orbit, which would be 15,000 times further from the Sun than the Earth’s orbit, and 375 times further than Pluto’s, which is why it hasn’t been seen until now.
It is in the Oort Cloud – a sphere one light year in radius stretching a quarter of the distance to Alpha Centauri, the brightest star in the southern constellation, and in the Oort Cloub there are lumps of dirty ice at temperatures much closer to absolute zero (-273C).
I also found an article form ‘The Independent’ about this planet:
http://www.independent.co.uk/news/science/up-telescope-search-begins-for-giant-new-planet-2213119.html
The universe is a quite mysterious place, I think. Would be nice to know everything there is to know about it.
Question 5:
The number varies because the earth has an elliptical orbit, as cooldood800 said. The semi-major axis of Earth’s orbit is 149,597,887.5 kilometers. When it is closest to the Sun (perihelion) it is 147,098,074 km or 0.98 AU. At farthest (aphelion) it is 152,097,701 km or 1.02 AU.
We are farthest away during summer in the Northern Hemisphere (around July 4th), and closest around January 4, which is summer in the Southern Hemisphere.
(A.U. = My initials, but in this case ‘astronomical unit’, which is 150 million kilometers, being the approximation of the average distance of the earth from the sun.)
That is the answer that I should have given to Cooldood800 – thank you! It was a great piece of research.
I wrote this article over a year ago and have not kept up-to-date with Tyche.
“The universe is a quite mysterious place, I think. Would be nice to know everything there is to know about it.” It may be a property of the Universe that it is impossible for any one person to know all there is to know about it – not that that should stop you trying!
This is a ‘picture’ from above to show where the Oort cloud is:
http://www.universetoday.com/wp-content/uploads/2011/02/oort-cloud-nasa.jpg
I’m not sure how real this is, but here is a picture of Tyche:
http://www.allwelike.com/wp-content/uploads/2011/02/Tyche1.jpg
+Tyche sound Japanese or Chinese, do you know why? Because the guys who found Tyche were two Americans.
Lovely pictures. I think the second one must be an illustration as there cannot possibly be enough light coming from it to be photographed in any conventional sense.
Tyche was the daughter of Hermes and Aphrodite and there is a statue of her in Antioch (where the holy hand grenade came from if you know your Monty Python!)