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AS105 Quiz 2 Review.docx

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Department
Astronomy
Course
CAS AS 105
Professor
Rich West
Semester
Fall

Description
Habitability of exo planets graph -Star type slash size relative to the sun -Radius or orbit relative to earth is 1 AU -If smaller star need to be closer to have liquid water if your star is big you can be a little farther and still have sufficient heat -Can also have liquid water and be habitable if too far from your star if you have internal heat -Can be dry terrestrial planet, earth like planet, or hydrogen atmosphere planet -Why do some worlds have atmospheres and some don’t? -Worlds like mercury and the moon have a very thin atmosphere -Three terrestrial plants in the solar system with significant atmospheres are Venus earth and mars. -Surface pressure, average surface, and temperature, are important for the formation of atmospheres -Venus’s pressure is 92 time stronger than earth and if you go there you will get instantly crushed. Venus is as astronomical warning to us about global warming because it is a similar distance from the sun as earth but much hotter because of its greenhouse gases and can not hold life. -Venus’s average temperature is much higher and mars is much lower. -Mar’s pressure is much lower than earth. -Abundance of elements is important also most of earth atmosphere is nitrogen, a lot of oxygen a little water and carbon dioxide. Venus has no oxygen. -Now have ability to study atmospheres on other planets. Can see clouds on exo planets as it moves through different transits and light changes. -How do we detect exo planet atmospheres? -Star light filters thru planet then to spectrograph -Dips in atmosphere charts are sodium blocks and black spots in spectrum. -Some exo planet spectrums have water. -Galaxy must be full of planets if we found so many in a randomly selected patch of the galaxy that we looked at with keplar -What creates and sustains an atmosphere? Primary Atmophere (stuff the sun or star it orbits is made of and what the planet is made of) huge amount of hydrogen a lot of helium and a little oxygen nitrogen carbon neon argon sodium aluminum magnesium iron silicon sulfur. -Astronomers only have these on their periodic tables. However the elements in our atmospheres in the previous charts are very different, because this atmosphere went away and was replaced by a secondary atmosphere. Outgassing from volcanoes and ocean vents change the atmosphere, also evaporation and sublimation (straight from solid to vapor) -Volcanoes produce a lot of water, debate between astronomers and geologists about where the water comes from on earth. Not all secondary atmospheres are the same at outgassing. Need ways of destroying atmosphere. 4 methods. 1. First is thermal escape aka atmosphere can escape, its just little atoms and if gravity is not strong enough to hold on to it, it goes away. 2. Next is solar wind stripping, solar wind and light from the sun can blow molecules apart aka separate elements, heavy ones stay and lighter ones with less mass and less gravity leave the atmosphere. Hydrogen around the earth is from water that has been disassociated by UV light. 3. Next is condensation which is the opposite of evaporation stuff turns into water and rain and takes vapor out of the atmosphere. 4. Last is chemical reactions that destroy atmospheres like rocks interfering with water destroys the atmosphere. -What we will discuss most is thermal escape or atmospheric escape. Even if we cant measure a planets atmosphere we can measure if they would be able to sustain an atmosphere. See Graph with temperature and speed. -Two different speeds. Average speed of given molecule and other is one tenth the escape speed of the planet. All escape speed given as 1/ 10 of normal escape speed so that it works with the equation. Escape speed is speed it would take to throw something off the surface of a world and have it not come back by gravity. -Dashed lines on the chart are different gasses with inconsistent speeds because temperature changes. Temp is how fast they are moving. planets are plotted in 1/10 escape speed. What is graphed is the average speed. Which means some must be a little faster or slower. (see graph) -Earth can hold on to water methane ammonia oxygen nitrogen carbon dioxide etc according to chart and what is below it Moon cant hold anything. Escape velocity of a molecule is 157 times the square room of the temperature (of the planet) over the mass of the molecule (given on the periodic table) AS105 Quiz 2 Review States of Matter, Light Transiting Planets Apollo Planet/Moon Formation Solar System Formation Terrestrial Atmospheres What is a Planet? Pluto? Exoplanets: RV Method Earth Impacts   Questions of the Day Lecture 6 What do we learn from the Kepler satellite? -It was looking for an Earth like planet orbiting a sun-like star.  It helped us discover exoplanets in other solar systems via the transit method. What details do we learn about planets from the transit method? -We can tell how big the exoplanet is by how much light of the star it blocks. -We can tell how fast it is orbiting the star by how long it blocks the light out. Lec 7 Why do humans see only visible light? -Because we can only detect a certain range of light. What color do you get when you combine all of the colors of light? -White! It’s the combination of all light. -Black is absence of color/light. How do energy and wavelength vary along the electromagnetic spectrum? -Higher energy – shorter wavelengths -Lower ene
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