ASTRO 7N Unit 3 P1 and P2

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Astronomy

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Feb 20, 2024

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ASTRO 7N Unit 3 Part 1  What is the sun? o The sun is a star like any other star in the nighttime sky. It is the nearest star to us and provides light to our solar system  Spots on the sun o Sunspots, occur when strong magnetic activity in the suns outer layers causes some relative cooling in small regions. Cooler regions on the suns surface look darker than the rest  Like how we humans and animals, etc., all glow in o Infrared light  The sun is 109 time the earths radius. That would mean you could fit about ____ earths inside the suns volume. o A million  What about the mass, about 333,000 earths. About how much of the total mass of all the objects in the solar system is contained in the sun alone? o 99% of all the mass in the entire solar system in in the sun.  Remaining 1%, about 70% in Jupiter, 20%ish is in Saturn, and the last 10% is in Earth, Neptune, all the other planets, and all of the asteroids and comets  The sun is mostly made of Hydrogen (H) and Helium (He). 73% H and 25% He by mass and about 92% H and 8% He by atom count. With the remaining percent, it is made up of

chemical elements. Dominated by carbon and oxygen, some iron an trace amounts of everything else.  Most obvious layer of the sun is the photosphere . It is the outermost layer of the sun, but is the region of the sun from which the most visible light is emitted. About 5780 Kelvin  Outside the photosphere is the chromosphere which is thinner. In this region neartest to the photosphere it is made up of cooler thinner gas.  Toward the upper regions of the chromosphere, towards the outer region called the corona the solar atmosphere becomes much less dense. Typically not seen unless a total solar eclipse comes  Granules the grainy texture of the sun, bubbly hot material  The bubbly hot material comes up through the convective zone , a large region beginning below the photosphere  A powerful burst of material, influenced by local magnetic activity will creates a solar flare (volcano looking) or a prominence (the “hoop”). This depends on the strengths, flares or prominences can result in material being expel from the sun into deep space, other times the material falls back onto the sun  Below the convective zone is the radiative zone . Through this region there aren’t any convective cells to transfer material energy outward. Energy travels outward instead through absorption and re-emission of photon from one atom to another.  Sun gets hotter the deeper in you go  The core has an energy output of about 4 x 10^26 watts  We’ve been peeling this sucker apart to see what makes it tick but what physical process would generate this kind of energy?

o Nuclear fusion  Atoms in the suns core region are incredibly energetic  In the interior of the sun, temps are so high that atoms of hydrogen and helium have lost their electrons  E= mc^2 o E= Energy, m= mass, c= speed of light (squared)  Can you tell how many protons a hydrogen atom (H) has, and how many protons a helium atom (He) has? o Hydrogen has 1 proton and helium has 2 protons  In the sun, the proton-proton chain makes “4He” (helium-4) the dominant form of helium. 4He has… o Two protons, because it is helium, and two neutrons to make 4 total particles in the nucleus  What is the first step in the p-p chain? o A proton combines with a proton to make Hydrogen-2 (Deuterium)  What happened to the protons during the first step of the chain? o One of the protons converted into a neutron, still contained with the Hydrogen- 2  Why was there a big burst of energy? o Because the mass of the particles starting the reaction is more than that of the products. Mass is converted to the energy via E=mc^2  What is the second step in the reaction? o Hydrogen-2 combined with an additional proton, to make Helium-3  What happened?

 Again there is some energy released (a gamma-ray photon) and we end up with Helium-3  What is the final step in the p-p chain? o Helium-3 combines with another Helium-3, to make Helium-4 (and two protons are left over)  What else do you see?  Again a burst of energy and Helium-4 is produced, with two protons moving off to the side  So “luminosity” refers to ____ whereas “brightness” must mean ____ o Absolute power output at the source / apparent output as observed at some distance  After doubling the distance from the light source, the bottom telescope’s brightness readout ____, to about ____ the top detector's value. o Decreased / one quarter  On tripling the distance from the light source, the bottom detector’s readout_____, to about _____ the top detectors vaule. o Decreased / one ninth  2 x distance… ¼ the flux  3 x distance… 1/9 the flux  How far out would you need to move the bottom detector, next to a star set to luminosity 100, to read the same as the top one at distance = 1 by the 25 stars? o Out to twice the distance (R=2)  Brightness = luminosity / (4 x pi x distance^2)

 Like some of the other mathematical relations we have discovered already, does this mean that the parallax angle vary directly with distance, or is it inverse relation.? o The size of the parallax angle is inversely proportional to the distance to the star  1 parsec = about 3.26 light-years, or 1 parsec = 206,265 AU \  Alpha Centauri is one of the nearest stars to the sun, parallax angle of about 747 milliarcseconds  Copper Quiz 1 o What is the general result of the proton-proton chain?  4H  He + energy + other products o The corona of the sun…  Is visible during a solar eclipse o In the convective zone of the sun…  Columns of hot gas rise, cool, and descend o What part of the sun do we typically see?  Photosphere o In nuclear fusion, energy is produced because…  The mass of the reacting chemicals is larger than that of the products.  Copper Quiz 2 o When using different points in the earths orbit as a baseline for a parallax experiment it is best to the observation…  6 months apart o One star is four times farther away than another. The parallax angle of the more distant star is…

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