10) Solar Astronomy ✅ Flashcards
What are some ways of observing the sun safely?
- Telescopic projection
- H-Alpha filter
- Pinhole projection
Describe what the Telescopic projection method is
Requires the use of a ‘baffle’ to absorb most of the solar radiation before entering the telescope
Describe what the H-alpha filter method is
The H-Alpha filter absorbs all sunlight apart from a very narrow range of wavelengths centred on a particular spectral line of hydrogen
What are sunspots?
Sunspots are cooler areas of the Photosphere where the Sun’s magnetic field rises from below the Sun’s surface and the magnetic regions poke through. They are darker in colour as they are expending less energy and have a lower temperature
What is the average temperature of a Sunspot?
Umbra is ~3800K
Penumbra is ~5600K
How can you calculate solar rotation period?
If the difference in longitude (ΔL) of a sunspot occurs in a time interval, then rotation period (T) can be calculated by:
T . . 360°
—- = ——
Δt . . ΔL
What is the earliest Nuclear Fusion?
The earliest Nuclear Fusion is when hydrogen (H) nuclei fuse into Helium (He) nuclei.
Why can Nuclear Fusion only happen in the Sun’s core?
The temperature has to be high enough to overcome the mutual electrostatic repulsion of the positively-charged nuclei
What is the chain of reaction that happens in the Sun?
The Proton-Proton or Deuterium-Deuterium chain
What happens in each stage in the proton-proton chain?
At each stage in the chain, mass (m) is lost and converted into energy (E). This is in accordance with Einstein’s equation E=mc², where c is the speed of light
What is the order of the sun’s internal divisions?
core –> radiative zone –> convection zone –> photosphere –> chromosphere –> corona
How much mass does the Sun lose?
The Sun loses 4 million tonnes of mass every second, this is insignificant as the Sun’s total mass is 2.0 × 10²⁷ tonnes
What is the zone above the Sun’s core?
Radiative zone
What happens in the radiative zone?
This zone is where the energy in the form of photons (gamma-radiation) is transferred in a random manner due to the scattering of photons by electrons outwards
What is the zone outside the radiative zone?
The convection zone
How thick is the convection zone?
~200 000 km
What happens in the convection zone?
The convection zone is where the thermal energy is transported to the photosphere by rising convection currents of hot plasma.
What is at the top of the convection zone?
The photosphere
How hot is the photosphere?
The photosphere is ~2 million K at the base. At the visible part of the photosphere, the temperature is 5800 K
How thick is the photosphere?
100 km
How does the Sun’s photosphere radiate energy?
The Sun radiates energy in the form of visible light but also to a lesser extent of infra-red, ultra-violet and X-Radiation
What are the parts of the Sun’s atmosphere?
The chromosphere and corona
How thick is the chromosphere?
2000 km thick
How hot is the chromosphere?
400 K - 100 000 K at the top
How hot is the corona?
2 million K
How far can the corona extend?
The corona can extend outwards for millions of km into space
What is ‘slow’ solar wind?
An outflow of charged particles (mostly protons and electrons)
Where does ‘slow’ solar wind come from?
The Corona
What is the speed of ‘slow’ solar wind?
~400 km/s
Where does ‘fast’ solar wind originate from?
Coronal holes
What is ‘fast’ solar wind associated with?
Coronal mass ejections and Solar Flares
What are the effects of solar wind?
- Aurora
- Creation of cometary tails
- Geomagnetic storms
- Other (radiation poisoning to astronauts, affecting radio communication of aircraft)