Topic 1.3 - The Sun Flashcards
What is the diameter of the Sun?
1.4 million km
What is the distance between the Sun and the Earth?
150 million km (1 AU)
What gases and its percentages is the Sun comprised of?
Hydrogen - 75%
Helium - 25%
Small amounts of other elements
What is the photosphere?
The Sun’s visible ‘surface’
What is the temperature of the photosphere?
5800 K
What is the chromosphere?
It is above the photosphere and is the ‘sphere of colour’
What is the thickness of the chromosphere?
2000 km
Why is the chromosphere not normally visible?
The light from the photosphere is too dominant
How can the chromosphere be viewed?
Just before totality is reached during a solar eclipse, the chromosphere can be observed as a reddish/pink ring
What is the corona?
A glowing region of ionised gas that makes up the Sun’s atmosphere
What is the temperature of the corona?
2 million K which is hot enough to emit X-rays
What is the source of the Sun’s energy?
In the central core of the Sun, nuclear fusion reactions occur
What is the temperature in the central core of the Sun?
15 million K
Explain the proton - proton chain reaction.
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.
How can the sun be observed safely?
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
What is a sunspot?
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
Why are sunspots cooler?
They inhibit the upward motion of convecting solar material and prevent it from reaching the top of the photosphere, resulting in lower temperatures
What is an umbra?
A central darker region, about 2000 K cooler than the photosphere
What is the temperature of the photosphere?
5800 K
What is the penumbra?
A ligher (i.e. less dark) surrounding area to the umbra with a temperature of about 200 K cooler than the photosphere
Explain the suns rotational period.
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
Explain the solar cycle.
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
What is solar wind?
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.
What is the fast solar wind?
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
What are prominences (solar feature)?
Huge clouds of cooler gas in the suns atmosphere
What are filaments (solar feature)?
The same as a prominence but as appearing as dark silhouettes against the brighter photosphere
What is a solar flare?
Sudden releases of energy
What is the sun’s rotational period?
25 days at the equator but 36 days at the poles
What does the sun look like at a visible wavelengths?
VISIBLE- How we see it everyday (giant yellow/orange) ball
What does the sun look like at H-alpha wavelengths?
H-ALPHA- Plain yellow with a crack and a few visible features
What does the sun look like at X-ray wavelengths?
X-RAY- Big deep-red ball bursting with fire
What’s solar maximum?
The most active time for sunspots - when there are most sunspots, lasts 5.5 days where often 100 sunspots are visible at a time
What’s solar minimum?
When it’s calmest and least sunspots last first 5.5 years, ones that are visible are short lived
What is the speed of solar wind?
About 400 km/s
What is the speed of fast solar wind?
About 850 km/s
