Telescopes. Discussion. If you had a Coke bottle and you wished to fill it with rainwater falling from the sky, how would you do it?. Telescopes Serve 3 Functions. To collect light To resolve fine detail To magnify the image. Discussion.
If you had a Coke bottle and you wished to fill it with rainwater falling from the sky, how would you do it?
Of the three telescope functions which do you think is the most important in astronomy and why?
Refraction(Marching Band Analogy)
What happens to the marching band if it hits a muddy part which causes the individual band members to slow?
Light moves slower in glass than in a vacuum
Speed of light through glass is different for different frequencies and each frequency has a slightly different focus.
The ability to separate two closely spaced objects, such as a double star.
The bigger your telescope objective the better your resolution will be.
Atmospheric turbulence limits the resolution of even the largest telescopes on Earth to about that of a 6 inch telescope.
Stars are so far away that they appear as points of light no matter how big a telescope you observe them with.
Bigger stars in photographs are simply brighter.
The apparent size of the stars as viewed through the telescope.
Good seeing is typically 1 arcsec.
What can astronomers do to try and improve resolution of their observations?
Actuators deform the primary mirror hundreds of times a second to try and remove atmospheric distortion.
Adaptive optic telescopes work best in the infrared region of the spectrum and not in the visible. Why do you think that is?
What do you think happens when very high energy gamma rays from space hit the Earth’s atmosphere?
Why can’t the very long wavelength radio waves make it to Earth’s surface?
Why does the Sun emit light?
How do you know the Sun is hot?
Radius: 109 Earth radii
Mass: 333,000 Earth masses
Mean density: 1.41 g/cm3
Composition: 74% hydrogen
Luminosity: 3.86 1026 Watts
Suppose every human being on Earth turned on
1000 100-watt light bulbs. With about 6 billion
people this would only be 6 1014 watts. We
would need 670 billion more Earth’s doing the
same thing to equal the energy output of the Sun.
Why is there less solar intensity at sea level than there is at the top of Earth’s atmosphere?
Where do you think that energy goes?
Why isn’t the Sun a perfect blackbody?
More heavy elements in a star’s atmosphere means more absorption lines, the redder a star will appear as higher frequency light is absorbed and re-emitted at lower frequencies.
The Sun releases lots of energy each second, what if it were cooling down over time. How could we tell?
The Sun is not measurably heating up or cooling down.
Given the composition of the Sun, why is it unlikely that it could be heated by the burning of wood or coal?
As things contract gravitationally, they become hotter.
Why do you think gravitational contraction leads to a temperature increase?
If the Sun is getting its energy from Kelvin-Helmoltz contraction, how could you prove this? Do you think this is an easy thing to do? Explain.
The Sun is not measurably expanding or contracting
From Einstein’s Special theory of relativity, energy equals the mass times the speed of
Matter is a form of frozen energy.
H – one proton
He – two protons and two neutrons
Neutrons are electrically neutral protons with slightly more mass
4 hydrogen atoms have a mass of 6.693 10-27 kg
1 helium atom has a mass of 6.645 10-27 kg
Thus, 0.048 10-27 kg are converted into energy.
A neutron, left by itself will decay into a proton, an electron and a neutrino.
Likewise a proton can change into a neutron by emitting a positron and a neutrino.
You can think of a neutron as a proton/electron pair.
Why must matter be so hot, 10 million K, for H to fuse into He?
How can atoms with more than one proton in the nucleus stay together? Why don’t they just fly apart?
Fusion keeps the Sun hot, but fusion requires the Sun to be hot. How did the Sun ever get hot enough to start fusion?
1. Hydrostatic equilibrium
2. Thermal equilibrium
To maintain equilibrium, the pressure below each
layer of the Sun must be greater than the pressure
above that layer.
What does this tell you about how the density changes with depth in the Sun?
What does this tell you about how the temperature changes with depth in the Sun?
According to the previous graphs, where is fusion taking place in the Sun? Explain.
What would happen if the Sun started to
contract? What would happen if the Sun
started to expand?
What would happen if all fusion ended in the Sun?