Topic 1.3 - The Sun

Question 1

What is the diameter of the Sun?

Answer 1

1.4 million km

Question 2

What is the distance between the Sun and the Earth?

Answer 2

150 million km (1 AU)

Question 3

What gases and its percentages is the Sun comprised of?

Answer 3

Hydrogen - 75%
Helium - 25%
Small amounts of other elements

Question 4

What is the photosphere?

Answer 4

The Sun’s visible ‘surface’

Question 5

What is the temperature of the photosphere?

Answer 5

5800 K

Question 6

What is the chromosphere?

Answer 6

It is above the photosphere and is the ‘sphere of colour’

Question 7

What is the thickness of the chromosphere?

Answer 7

2000 km

Question 8

Why is the chromosphere not normally visible?

Answer 8

The light from the photosphere is too dominant

Question 9

How can the chromosphere be viewed?

Answer 9

Just before totality is reached during a solar eclipse, the chromosphere can be observed as a reddish/pink ring

Question 10

What is the corona?

Answer 10

A glowing region of ionised gas that makes up the Sun’s atmosphere

Question 11

What is the temperature of the corona?

Answer 11

2 million K which is hot enough to emit X-rays

Question 12

What is the source of the Sun’s energy?

Answer 12

In the central core of the Sun, nuclear fusion reactions occur

Question 13

What is the temperature in the central core of the Sun?

Answer 13

15 million K

Question 14

Explain the proton - proton chain reaction.

Answer 14

In the central core of the sun, the temperature is so hot that hydrogen nuclei (protons) are able to fuse together to make helium nuclei in a series of reactions called the proton - proton chain. At each stage in these reactions, matter (m) is ‘lost’ and converted into an equivalent amount of energy (E) according to Einstein’s famous equation E = m c² where c is the speed of light.

Question 15

How can the sun be observed safely?

Answer 15

You can fit the telescope with a H-alpher or Myler filter. But the safest way to observe is to use an indirect projection method in which a pinhole camera, pair of binoculars or a telescope focuses an enlarged image of the sun onto a screen, reducing the brightness to a safe level

Question 16

What is a sunspot?

Answer 16

Sunspots are cooler darker areas of the photosphere that correspond to strong, localised magnetic fields. These appear as small, dark patches on the photosphere but they are actually about the same size of Earth

Question 17

Why are sunspots cooler?

Answer 17

They inhibit the upward motion of convecting solar material and prevent it from reaching the top of the photosphere, resulting in lower temperatures

Question 18

What is an umbra?

Answer 18

A central darker region, about 2000 K cooler than the photosphere

Question 19

What is the temperature of the photosphere?

Answer 19

5800 K

Question 20

What is the penumbra?

Answer 20

A ligher (i.e. less dark) surrounding area to the umbra with a temperature of about 200 K cooler than the photosphere

Question 21

Explain the suns rotational period.

Answer 21

By following the apparent movement of the sunspots across the sun’s disc, astronomers can deduce that the sun does not rotate as a solid body. Its rotational period varies from 25 days at the equator to 36 days at its poles

Question 22

Explain the solar cycle.

Answer 22

Astronomers have deduced that although individual or groups of sunspots can last from a few day to several weeks, the relative number of sunspots follows a well-known regular 11-year pattern called the solar cycle during which the number of sunspots increases to a maximum before falling again

Question 23

What is solar wind?

Answer 23

A steady stream of charged particles (mainly protons and electrons, but with traces of ions of helium and other elements) flowing outwards in all directions from the sun’s corona at speeds of typically 400 km/s.

Question 24

What is the fast solar wind?

Answer 24

There is a second component to the solar wind - the fast solar wind. This is thought to originate from coronal holes (cooler regions of the corona close to the Sun’s magnetic poles) where open magnetic field lines (as opposed to more familiar closed ‘loops’) permit charged particles from the photosphere to escape more easily, at speeds as fast as 850 km/s

Question 25

What are prominences (solar feature)?

Answer 25

Huge clouds of cooler gas in the suns atmosphere

Question 26

What are filaments (solar feature)?

Answer 26

The same as a prominence but as appearing as dark silhouettes against the brighter photosphere

Question 27

What is a solar flare?

Answer 27

Sudden releases of energy

Question 28

What is the sun’s rotational period?

Answer 28

25 days at the equator but 36 days at the poles

Question 29

What does the sun look like at a visible wavelengths?

Answer 29

VISIBLE- How we see it everyday (giant yellow/orange) ball

Question 30

What does the sun look like at H-alpha wavelengths?

Answer 30

H-ALPHA- Plain yellow with a crack and a few visible features

Question 31

What does the sun look like at X-ray wavelengths?

Answer 31

X-RAY- Big deep-red ball bursting with fire

Question 32

What’s solar maximum?

Answer 32

The most active time for sunspots - when there are most sunspots, lasts 5.5 days where often 100 sunspots are visible at a time

Question 33

What’s solar minimum?

Answer 33

When it’s calmest and least sunspots last first 5.5 years, ones that are visible are short lived

Question 34

What is the speed of solar wind?

Answer 34

About 400 km/s

Question 35

What is the speed of fast solar wind?

Answer 35

About 850 km/s