Hi! Here’s Chapter 14 – The Sun, if you see anything that looks like it might be wrong, let me know in the comments! 🙂
1. a) What is the approximate temperature of the surface of the Sun?
The temperature of the photosphere is between 4000 and 6000 degrees Celsius.
1. b) The corona is at a very high temperature, but produces little ‘heat’. Explain this.
Although the corona has a high temperature, it doesn’t produce very much thermal energy. This is because it does not have very much mass. If something is extremely light and has a high temperature, it does not mean that it will have lots of heat energy. Something that had quite a bit of mass and a high temperature would give out heat energy.
1. c) What are the Fraunhofer lines?
The Fraunhofer lines are dark bands in the light spectrum from the Sun.
2. What is a sunspot? Describe the appearance of a typical spot-group, and explain why no spot can be kept in view for more than two weeks consecutively.
A sunspot is a temporary dark, cool blotch which occur on the surface of the Sun. They usually appear in groups, and are rarely seen alone. They consist of a dark umbra (the middle) and then surrounded by the lighter penumbra (the surrounding area).
These spots cannot be watched continuously for more than two weeks because the Sun rotates completely every 4 weeks, meaning two weeks in sight, two weeks out of sight.
3. Write briefly about (a) the corona, (b) prominences, (c) magnetic storms, (d) the chromosphere, (e) faculae.
a) The corona is the area outside of the photosphere and chromosphere. This is where solar winds originate from and X-rays have been emitted from here. The corona can usually only be seen during a total solar eclipse.
b) The prominences are luminous red clouds that are in the corona. They often form arc shapes that relate to the shape of the magnetic field on the Sun.
c) Magnetic Storms are when solar flares disturb compasses, cause surges in the power grid, which them cause electrical blackouts. They usually happen during a solar maximum.
d) The chromosphere is the area above the photosphere. If we looked at the sun, we would be able to see the photosphere. However, we cannot see the chromosphere.
e) Faculae are bright regions on the photosphere, located in active areas of the Sun’s surface. They usually occur prior to and after sunspots.
4. a) Describe how you would set out to observe sunspots. Explain the precautions which must be taken, and give your reason for them.
Firstly, you would need a telescope. The best telescope would be a refractor, as a reflecting telescope would run a risk of being damaged by the light onto the mirror. Next, draw a circle on a piece of paper,between 10-15 cm. Then, holding behind the eyepiece, navigate the telescope until you find the Sun. WHATEVER YOU DO YOU MUST NOT LOOK THROUGH THE TELESCOPE WITH YOU EYES! When you have the Sun on the sheet, move the paper forwards or backwards until the Sun fits into you circle. I would them recommend using something to stand it there. Then, if any sunspots are visible, draw on the sheet where they are.
To observe the sunspots, there is only really on safety precaution; which is not to look through the telescope itself. To look at the sun with the naked eye is not recommendable, and looking through the telescope will increase the risk of permanent eye damage massively. Also, take the finder off the telescope, as it is sufficiently small and powerful it can damage a surface beneath it with concentrated light.
4. b) How are the dark lines in the solar spectrum produced?
When atoms in the Sun’s lower photosphere are heated, they give out light; in the full spectrum. However, certain elements in the higher layers of the photosphere absorb certain wavelengths of this light. For example, sodium absorbs some yellow light at a wavelength of about 5.89×10-7m. So when we observe the solar spectrum, we see a dark line in the yellow, because of sodium.
4. c) Why were there more sunspot groups visible in 1980 and in 1989 than in 1985 and 1986?
Sunspots run in cycles. These cycles last for around 11 years, though they are not exact. They will start with having nearly no sunspots at a high latitude. This is during the time known as solar minimum. During the 11 year cycle, the sunspots begin to occur more and more and they move down in latitude on the Sun’s surface. Once it has been the 11 years, and there is a lot of sunspots near the base of the Sun, this is called solar maximum. After that, the cycle starts again.
In 1980, there was a solar maximum and in 1989, it was nearing the solar maximum. This is why there were many sunspots. In 1985 and 1986, it was the period of solar minimum, meaning little sunspots were occurring on the surface of the Sun.
5. a) What is a total solar eclipse? Explain, with the aid of a diagram, why a total eclipse occurs. Why is it not visible over complete hemisphere of the Earth? Why do astronomers regard total solar eclipses as important?
A total eclipse is when the Sun, Moon and Earth are in the perfect enlignment causing the Moon to block out the Sun. Because the Sun’s diameter is 400 times greater than the Moon’s, it shouldn’t look the same. But the distance between the Moon and Sun is 400 times greater than that between the Earth and Moon, making the Sun and Moon the same size. A total solar eclipse does not cover a complete hemisphere, because the shadow from the Moon only just reaches the Earth, meaning only a small band of shadow occurs. Astronomers regard total solar eclipses as important, because they do not occur very often. Before modern technology managed to find ways of viewing the chromosphere and the corona without totality, Astronomers needed to use the totality of an eclipse to view them; using the few minutes to observe them.
5. b) What are the other two kinds of solar eclipses? (Use diagrams.)
The other two kinds of solar eclipses are Partial Solar Eclipse and an Annular Solar Eclipse.
5. c) Why does not a solar eclipse occur every month?
Because the Moon’s orbit is slightly elliptical, it will not constantly at the right distance, making it smaller. Also the angle of the Moon’s orbit to ours is just over 5 degrees, meaning that the Moon and Sun usually just miss each other each month.
6. a) Why does a sunspot look dark?
A sunspot looks dark because it is cooler than the surrounding photosphere. Though it is not actually cold, it’s cooler.
6. b) During a solar eclipse, what is the phase of the Moon?
During a solar eclipse, the Moon’s phase has to be a new moon, because it is in between us and the Sun, so the back of Moon gets lit up, and not the the side we see.
6. c) What effects does a solar flare have upon the Earth.
A solar flare causes changes in the Earth’s magnetosphere and cause magnetic storms. These storms can interfere with compasses, cause power surges and in turn cause mass electrical blackout.