The Greeks and the Copernican Revolution
How do you measure the Earth in 200 BC?
Eratosthenes (276 BC-195 BC)
o Geometer of the heavens and Earth
o Read that on a given day, sunlight reached the bottoms of wells in Syene.
o Made a careful measurement of l
The Motion of the Sky
The Local Sky
o Meridian: line passing through zenith and connecting N and S points on horizon
o Zenith: the point directly overhead
o Horizon: all points 90 away from the zenith
o An objects altitude (above horizon) and azim
Exam 3 Review
1. What do impact craters tell us about the surface of a planet?
a. They tell us how old or young a planet is
2. What are the sources of heat inside a terrestrial planet?
a. Radioactivity, planet formation, and differentiation
3. Why is so c
The Sun Continued and the Solar System
The Surface and Atmosphere of the Sun
Visible surface of the Sun
Are cooler than other parts of the Suns surface (4000 K)
Are regions with strong magnetic fields
Loops of bright gas
Keplers Laws & Gravity
How did Copernicus, Tycho, and Kepler challenge the Earth-centered model?
Kepler first tried to match Tychos observations with circular orbits
But an 8-arcminute discrepancy led him to eventually to ellipses
If I had believed that w
Study Guide for ASTR 1400 001 Exam 2 (Thursday, April 6th, in class)
Review Session (Tuesday, April 4th, in class)
The Exam 2 will cover materials in from weeks 7 - 10 of class, including all lectures,
readings, and homeworks 5-7. Homework 8 and exoplanet
Exam 2 Review
1. What types of objects emit blackbody spectra?
a. Planets and Stars
2. Where in the EM spectrum does the Suns emission peak?
a. Visible Light
3. How does the intensity of radiation change with temperature and size of an object?
a. The more
Gravity, Energy, & Orbits
Notes about the exam review next class
I will not have an agenda prepared for the review session. It is up to you to ask questions
about the material you need clarified. So, start reviewing now if you havent already!
A study guid
The Geology of Terrestrial Planets
Core: highest density; nickel and iron
Mantle: moderate density; silicon, oxygen, etc.
Crust (Lithosphere): lowest density: granite, basalt, etc.
o Gravity pulls
Light and Telescopes
What is light?
Light is both a wave and a particle AT THE SAME TIME!
Actually, so are all elementary particles
Particles of light are called photons
Depending on the situation it is usually easier to treat light as wither a particle o
Moons of the Outer Solar System
Moons are natural satellites of larger objects (usually a planet)
Medium and Large Moons
Enough self-gravity to be spherical
Have substantial amounts of ice
Circular orbits in same direction as planet rotation in the plan
Comparative Planetology II
Venus atmosphere forces us to explore Venuss surface through radar mapping
Cratering on Venus
Venus has impact craters, but fewer than the Moon, Mercury, or Mars
Impact craters are relatively rare on Venus and are distribute
Doppler Shift and The Sun
The Doppler Effect
The Doppler effect works for all waves, so not just sound but also light!
It is how light tells us the speed of a distant object
Measuring the Shif
We generally measure the Doppler effect from shifts in the
Exoplanets Part 2
Using mass, determined using the Doppler technique, and size, determined using the
transit technique, density can be calculated
Measuring both mass and radius is giving us a first glimpse into the composition of
The Gas Giants
Cooling allows CO2 to build up atmosphere
Heating causes rain to reduce CO2 in atmosphere
Due to an increasingly brighter Sun, in ~600 million years CO 2 levels will drop below the
point needed for photosynthesis
Planet Formation II
The Frost Line
Inner parts of disk are hotter than outer parts
Rock can be solid at much greater temperatures than ice
Inside the frost line: too hot for hydrogen compounds to form ices
Outside the frost line: cold enough for ices to
The Electromagnetic Spectrum & Blackbodies
Wavelength and Frequency
Wavelength x frequency = constant speed of light =constant
Wavelength (frequency) is what we experience as color
White light is made up of many different wavelengths
Shadows have two parts:
Penumbra-source partially obscured (lighter)
Umbra-source fully obscured (darker)
When it is light we are in Earths umbra
Total Lunar Eclipse-moon passes entirely through umbra
Partial Lunar Eclipse-part of
Why is it so challenging to learn about the exoplanets (extrasolar planets?)
Brightness and Distance
o A sun-like star is about a billion times brighter than the light reflected from its
o Planets are close to their stars,
Astronomy Test Review 1
1. What does the universe look like from Earth?
a. 2,000 stars may be visible to the naked eye along with a whitish band of light we
call the Milky Way
2. How do we make scale models of the Universe?
3. Why do stars rise and set
Motion of Large Bodies
All large bodies in the solar system orbit in the same direction and in nearly the same
Most large bodies in the solar system also rotate in that direction
Two Major Planet Types
Terrestrial planets are ro
The Doppler (RV) Method
Two bodies orbit each other around their combined center of mass
Measuring a stars Doppler shift can tell us its motion toward and away from us
Current techniques can measure motions as small as 1 m/s
Spectral Lines & Doppler Shif
Atomic number= # of protons in the nucleus
Atomic mass number= # of protons + neutrons
Isotope: same # of protons but different # of neutrons
What are the phases of matter?
o Solid (ice)
In Class Test Review
Two ways to find them
o Transit method
Measures how much light is blocked off when a planet crosses it
We make a transit light curve to measure the light being blocked off
We measure the depth to get the planets radi
The Solar System in Space & Time
Order of Magnitude Estimates
Many times, a rough guess is all you really need to figure something out
The idea is to get the answer within an order of magnitude in other words within a
factor of 10 or so
This kind of back
The Reasons for the Seasons and Moon Phases
The Earths rotation axis is titled from its orbit by 23.5 degrees
Above the Arctic Circle, the Sun becomes circumpolar on the June 21, solstice! (Dec. 21
solstice for Antarctic Circle)
The sub-solar point is the
1. As services are delivered by people, they are susceptible to _, or
variation in quality. heterogeneity
2. The pricing for _ is usually set based on time involved in delivering the
service rather than on the performance of specific tasks. Piano
March 6, 2015
The current mission to a terrestrial planet that I chose was NASAs Curiosity.
This SUV sized rover was sent to Mars in 2011 as apart of their Mars Science
Laboratory mission (MSL). After landing in t