Summer 2010 Midterm Exam
Format:  14 multiple choice questions (some of which refer to two figures/illustrations); 6 short answer/essay questions, that include one diagram--you will definitely need to dredge some terms up from memory to answer these.
 

Solar system:  All of the material (planets, moons, comets, asteroids, etc.) that is gravitationally bound to our star (the sun, or Sol)

Star: A gaseous sphere that produces enough heat in its interior by nuclear fusion to withstand the force of gravity

Planet:  From a Greek word meaning wanderer. Originally, the little points of light that moved through the constellations.  Now, reasonably large (but not too large) objects that orbit the sun.

Terrestrial Planet:  A planet like the Earth composed of rock and metal

Jovian Planet:  A planet like Jupiter--a gas giant composed of gas/fluid

How many planets are in the solar system?  For sure:  Mercury,  Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune (and you should be able to dredge these names up from memory)

Moons can be planet-sized, but aren't considered planets because they orbit a planet rather than directly oribiting the sun

Summary from first lecture:
"So when we look at our solar system, we see:
 1) A star
 2) Objects made of rock and metal (terrestrial planets, some moons, asteroids)
 3) Very large objects made mostly of gas/fluid (Jovian planets)
 4) Objects made of rocky material plus ices (Pluto, KBOs, some moons, comets)

A star - A huge ball of ionized gas (plasma) producing energy (light) by nuclear fusion - for our sun, the surface is hot enough that you don't expect to see molecules (such as CH4) in its atmosphere.

Electromagnetic Waves: image and nice information from  http://science.hq.nasa.gov/kids/imagers/ems/waves2.html

An electromagnetic wave is a set of perpendicular oscillating electric and magnetic fields.  These waves carry energy.  The amount of energy carried depends on the wavelength of the wave.  Shorter wavelengths = higher energy; longer wavelengths = lower energy.  Visible light is only a small portion of the possible wavelengths of electromagnetic radiation.


image from http://science.hq.nasa.gov/kids/imagers/ems/waves3.html


image from: http://science.hq.nasa.gov/kids/imagers/ems/ems.html

For visible light, red light has the longest wavelength (least energy) and is emitted by cooler stars than is blue/violet light (shorter wavelength, more energy, hotter stars).

Solids liquids and dense gases produce continuous spectra, dilute gases produce either emission or absorption spectra (for dilute gases, each chemical element produces its own unique pattern of lines).

A really nice set of images of continous, emission, and absorption spectra, along with diagrams for the spectral classification of stars can be found at:
http://astro.unl.edu/naap/hr/hr_background1.html

You should also look at the  diagram on
http://www.astronomynotes.com/light/s5.htm
which shows two ways of looking at emission and absorption spectra - the absorption spectra shows absorption "lines" superimposed on a curve that is the continuous spectrum of the sun.

400-700 nanometers (nm) is the wavelength range for visible light - if you are looking at a spectrum in this wavelength, it is either a star, or reflected sunlight off of an object (such as a planet).

Photosphere is the visible surface of a star - the spectral class is based on the average surface temperature of a star's photosphere

HOT  >> O B A F G K M << COLD and be able to dredge these from memory

Our sun is a G type star

Light and the spectrum - recognize a continuous, emission, and absorption spectrum.  Understand that gas has to be cool (as in a planet's atmosphere)for features to be caused by molecules--you'll see elements in a star's spectrum

A nice copyrighted version of an H-R diagram can be seen at:
http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=35774&fbodylongid=1703

You should understand that the axes are how bright the star is (luminosity or total surface energy emission) on the Y axis versus how hot the star is (temperature or spectral class) on the X axis.  It is ONLY for the main sequence that the two (temperature and brightness) are correlated.  If you see a "1" on the Y axis, then what is being plotted is the star's luminosity relative to our sun's luminosity (L/Lsun)

Nebula - a very large interstellar cloud of gas and dust

Main sequence stars are fusing four Hydrogen atoms to form one Helium atom (plus energy) in their cores - this is the longest and most stable period of a star's lifecycle.  Understand what is meant by zero age main sequence.
Giants and supergiants are doing nuclear fusion either in shells around the core, or of heavier elements in the core
White dwarfs are dead stars (no fusion) - gravity is balanced by electron degeneracy

As stars go through the dying process (after the main sequence) they emit their outer layers, either gently (producing a planetary nebula) or explosively (during a supernova).

Massive stars go through each stage of their life faster than low mass stars.

Stars can be bright because they are hot (photospheric temperature) or large

Nucleosynthesis - the formation of the elements by fusion (and decay) during a star's lifecycle and during its death

Element-substance that cannot be broken down into another substance by ordinary chemical processes

Chondrites are a type of meteorite that are agglomerates - the were made from whatever was solid in the solar nebula (dust, chondrules, CAIs) at SOME location and time (assumed to be near present asteroid belt), and never significantly altered after being assembled - the are "solar" in composition

Differentiation - the process whereby material separates into layers of different density

Plate tectonics:  understand what is meant by this, also by subduction, and the three main types of plate boundaries (divergent, convergent, transform).  How is a hot spot/mantle plume related (if at all)?

Plate tectonics:  understand that new oceanic crust is created at a divergent boundary and destroyed at a convergent boundary by subduction

Mercury, Moon, Mars appear to be cooling solely by rising mantle plumes that produce lava flows (including flood basalts) and hot spot volcanoes.  Venus and Earth appear to be cooling by two mechanisms:  rising mantle plumes, but also large-scale mantle convection that produces extensive tensional and compression features on their surfaces (and in the case of earth creates plate tectonics).  The heat comes from several sources including left over from formation (accretion and core formation), and on-going (including tidal and radioactivity)

A habitable planet is a planet on which life can exist

Life requires:
1) building materials primarily H C O N, which are widely available
2) Energy - Either external source (sunlight) or internal source (internal heat)
3) a liquid that will do the following:  dissolve organic molecules making them available for chemical reactions;  transport material into and out of a cell;  be involved in metabolic reactions - we think water is the only good candidate - you should understand why this is the case

What is meant by a star's continuously habitable zone?
 
 

.