The Sun Flashcards
Demonstrate an understanding of how the Sun can be observed safely by amateur astronomers.
The easiest way to observe the Sun safely is by projecting its image onto paper or card. A small hole can be put in a card and the light projected onto paper. The outline of the Sun can then be seen. Never leave this unattended as the Sun is a powerful source of heat and may combust your materials. Some projection tools include the Sunspotter or Solarscope which make it easier to do this.
Recall the Sun‘s diameter
1.4 million km
Suns distance from Earth
150 million km/ 1 AU
Recall the temperature of the Sun‘s photosphere
5 800 K/5500°C
Describe the solar atmosphere
chromosphere and corona
Approximate temperature of the corona
2 Million K
Describe the appearance and explain the nature of sunspots.
Sunspots are areas on the photosphere of the Sun that are cooler than the surrounding area and so appear darker.
Typically they travel around the Sun’s disc in groups roughly 1/3 of the surface from 40º north to 40º south of the Equator.
They consist of a central region called an umbra and a surrounding area called a penumbra. Note that these terms are similar to those used in the eclipse section but mean different things.
Temperatures of the umbra are typicaly 4,000k. The penumbra is usually around 5,600k.
Recall that the Sun‘s rotation period varies from 25 days at the equator to 36 days at its poles.
The Sun‘s rotation period varies from 25 days at the equator to 36 days at its poles.
Demonstrate an understanding that the Sun‘s energy is generated by nuclear fusion reactions at its core, converting hydrogen into helium.
The Sun is large enough and contains enough mass that the internal pressure at its centre (its core) is so hot (14 million °C) that it forces the nuclei of the hydrogen atoms to join together (to fuse) to make helium atoms in a process called the proton-proton chain.
A nuclear reaction (fusion) takes place and large amounts of light and heat are produced. 600 million tonnes of hydrogen are converted into 596 million tonnes of helium every second. The remaining four million tonnes gets converted into heat and light.
Describe how astronomers observe the Sun at different wavelengths.
Humans see visible light. This is just one part of the electromagnetic spectrum. The Sun emits light in frequencies across this spectrum. By using instruments that operate in these frequencies scientists can study the Sun and its behaviour.
Demonstrate an understanding of the appearance of the Sun at different wavelengths of the electromagnetic spectrum, including visible, H-alpha, X-ray.
As well as infrared, ultraviolet, x-ray observations, usually conducted at high altitude or in space, other less well known wavelengths exist.
H-Alpha is a specific wavelength in the visible part of the spectrum. It allows astronomers to study the Sun’s surface as well as nebulae. Optical filters are attached to a telescope (by experienced astronomers) allowing the observer to study the Sun. Calcium-K is a similar filter. This allows us to observe on wavelengths that operate only on these frequencies.
Describe the structure and nature of the solar wind.
The solar wind is a flow of charged protons and electrons flowing outward from the Sun. They can reach a velocity of 400 km per second. These particles escape the gravity of the Sun because they have too much energy.
The Solar wind has many effects in the Solar System, notably producing tails on comets and aurorae at the poles of certain planets.
