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
-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
-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
-Now have ability to study atmospheres on other planets. Can see
clouds on exo planets as it moves through different transits and light
-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
-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
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
Solar System Formation
What is a Planet? Pluto?
Exoplanets: RV Method
Questions of the Day
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.
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