The Sun Flashcards
Describe the general properties of the Sun in comparison to the Earth: size, mass, distance
- approx 100 times the radius of the earth
- about 8 light minutes of 1 astronomical unit (AU) dis at ace between earth and sun
- Middle Aged, middle sized star
- several minutes for light from the sun to reach earth
- made up of hydrogen and little bits of helium
Describe the main features of the solar spectrum: the underlying continuous or blackbody part and the absorption lines
Continuous: contains wavelengths of all light in a certain range
Black body:the spectrum of light emitted by a heated object
Absorption lines: same as spectral lines - the tiny gaps in a star’s spectrum - the spectrum caused by absorption of light by various elements in the suns atmosphere
Describe atoms in terms of their constituent particles: protons, neutrons, and electrons
Atoms are made of protons, neutrons and electrons
- protons and neutrons are in the nucleus
- electrons sit in shells that go from lowest energy (closest to the nucleus) to highest energy
Explain how light generated by the Sun is absorbed to produce absorption lines
- the spectrum of the sun is very close to being a black body but with lots of little gaps indicative of its chemical composition
Explain how we can use absorption lines to determine the chemical composition of the Sun, or any celestial object
Looking at absorption lines, associate them with particular chemical elements (what particular colours so particular elements absorb?) to work our what the star is made of
Explain how we can use the shape of a celestial object’s blackbody curve to determine its temperature
Blackbodies produce a continuous spectrum with a characteristic shape
- the warmer it gets, the more light overall, so the area under the curve increases
- warmer blackbodies also shift its curve to the left, since the wavelength at which it emits the most light shifts to shorter wavelengths (produces more blue) (the peak of the black body curve rests at blue)
Explain why we don’t see green stars
- stars that produce light start at approx 500K (remember how cold metal produces no visible light, but as it gets hotter it produces more)
- blackbodies as they get warmer emits more and more of visible light, shifting towards shorter and shorter wavelengths.
- if its peak is at green which is the middle of the visible light spectrum, it will emit equal amounts of all colour and we will perceive it as white
- in order to perceive a star as green wit would have to emit almost only green which is not possible for an object that is approx a black body
Describe how the Sun produces energy
The sun produces energy through nuclear fusion of four protons at a time into a helium nucleus
This nuclear fusion reaction releases some of the mass of the original protons in the form of energy and particles
** solar nuclear fusion combines 4 hydrogen nuclei to create helium and energy
Define nuclear fusion and explain how nuclear reactions are different from chemical ones
- nuclear reaction happens only inside the nucleus - - two light nuclei merge to form a single heavier nucleus but then the resulting nucleus has less than the mass of the two original nuclei added together because the leftover mass becomes energy and some other stuff
- 2 protons smush with 2 other protons
Makes:
- 2 helium atoms
- 2 positrons (antimatter)
- two neutrinos
- two gamma rays (high energy light)
List the main inputs and outputs of the p-p chain
Inputs
- 4 hydrogen nuclei
Output
- 2 helium atoms
- 2 positrons
- 2 neutrinos
- 2 gamma rays (high energy light)
Explain why neutrinos can escape the Sun so easily, focusing on their interactions via the four fundamental forces
Neutrinos only interact with gravity abd the weak nuclear force
They do not interact with electromagnetic or strong nuclear force
- means they pass through most ordinary matter easily
What are the three different kinds of spectra?
- Continuous spectrum
- the rainbow which spans a broad range of wavelengths without interruption - Emission line spectrum
- bright emission lines against a dark background
- we see this when atoms in a warm gas cloud emit light at specific wavelengths determined by the CLOUD’S composition and temperature (collisions of atoms)
- for the sun: some of the light being produced by the body of the star is being absorbed in its outer atmosphere (for sun, the chemical composition is so that it absorbs red and green light) - Absorption line spectrum
- dark absorption lines over the rainbow background
- we see this when a light from a hot source passes through cooler gas cloud which makes atoms in the cloud absorb light at wavelengths determined by the CLOUD’S composition and temp
Sun: (hot light source is the suns core, and the clouds is the gas that makes up the surface)
Assume stars are blackbodies. Imagine we survey the cosmos using a telescope that can only detect UV light. We would preferentially find stars that are
Bluer than the sun
