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.
- 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?