Lectures+19+-+21

__Lecture #19: "Small Solar System Bodies"__

 * There are five objects presently classified as dwarf planets; Ceres, Pluto, Eris, Haumea and Makemake.
 * "Trans-Neptunian Object" (TNO), Kuiper Belt Objects (KBO), Scattered Disk Objects (SDO), and Oort Cloud objects are small, icy objects in orbit around the Sun, far beyond Neptune's orbit.
 * Comets are such icy objects that develop comas and tails (dust and ion) if they come close to the inner solar system and are heated by the Sun.


 * __Weblinks__: **
 * __ Pluto and the dwarf planets __ :
 * Ahhhh, Pluto!! Poor-not-alive-Pluto-that-doesn't-care-how-we-classify-it! Read all about the reclassification of Pluto by the IAU on August 24th, 2006. The official definition of a planet is now set, though some argue that it is vague.
 * As always, NASA has great pages on the solar system objects, including Pluto (it's five moons) and the other dwarf planets.
 * Wikipedia also has good pages on these smaller objects, as does the web in general.
 * __ Kuiper Belt Objects and Trans-Neptunian Objects __ :
 * A Kuiper Belt Object (KBO) is an object that orbits the Sun (and is named after Gerard Kuiper), roughly co-planar with the ecliptic and with an A between 33 & 55 A.U. There are likely thousands, if not millions of them, but they are far away, and better, bigger scopes are likely needed to be able to image them.
 * Wikipedia's page on KBO is pretty comprehensive, as are Prof. Mike Brown's (CalTech) pages.
 * __ Oort Cloud Objects __ :
 * The Oort cloud, like the Kuiper Belt, is a region of space far from the Sun through which small, icy bodies move. This region is named after Jan Oort...what an awesome name, eh?!) These bodies orbit the Sun, but with an A > 55 A.U. (up to tens of thousands of A.U.).

__Lecture #20: "Dirunal Motion, The Moon, Moon Formation, Moon Phases and Seasons"__

 * Diurnal motion describes the apparent motion of celestial objects across our sky, east to west, resulting from the rotation of the Earth.
 * The Moon shares a common origin with the Earth, and orbits the Earth.
 * The Lunar cycle (phases of the Moon) lasts 29.5 days.
 * The theory that explains how the Moon formed is called the Large Impact Hypothesis.
 * Lunar and Solar eclipses occur when the Sun, Earth and Moon (or Sun, Moon and Earth, respectively) line up exactly and the sunlight is by either the Earth, or the Moon.
 * Seasons occur because of the changing solar irradiance a particular location on the Earth receives, due to the angle of incoming sunlight and the number of hours of sunlight in a 24 hour day. These change over the course of the year, because of the tilt of the Earth's equator with respect to the ecliptic plane.


 * __Weblinks__: **
 * __Diurnal Motion (result of the Earth's rotation)__:
 * A nice explanation from of diurnal motion can be found as this australian site.
 * Wikipedia's take on diurnal motion.
 * Optional but cool: [|Stellarium a free downloadable Planetarium]
 * [|Diurnal (Daily) Motion overview]
 * Video:[|The Sky in Motion]
 * A cool simulator for the apparent motion of the Sun.
 * __Seasons (results of the Earth's revolution and the tilt of the obliquity of the ecliptic)__:
 * There are many good links that explain the reasons for the seasons. You can find some of them here, here and here (keep in mind this last one was written in June)!
 * Images to help you understand the two primary reasons for the seasons can be found all over the internet, by a simple google search.
 * ScienceNetLinks has a page explaining some of the common misconceptions about the seasons.
 * A somewhat repetitive video explaining the causes of the seasons.
 * ScienceU's link on seasons...a lovely way of explaining away the misconceptions.
 * __The Moon__:
 * Moon rocks were brought back to Earth by the Apollo astronauts. These rocks are similar to Earth rocks (especially the isotopic ratios of oxygen) though are "dried out" (non-hydrated). They are rare, which naturally has led some less than sterling individuals to hatch all sorts of nefarious plans. (Lesson = don't mess with NASA!)
 * Moon phases, as explained for kids
 * The Large Impact hypothesis (shown here & here in these videos) is the leading theory to explain the formation of the Moon, and it's compositional similarity to Earth. A summary can be found here. And, in the news, that "Mars-sized impactor" is now named! It's called (or it was, since it was destroyed 4.5 Gyr ago!) Theia.
 * A cool space.com video is shown here...it shows how the Moon has changed over time, and has high resolution imagery from the LRO(Lunar Reconnaissance Orbiter).
 * __Lunar Motion__:
 * A nice animation for the Moon phases can be found at McGraw-Hill's website, as well as explanations and exercises to help further your understanding of when and where you can see different phases.
 * [|Explanation of Lunar Phases]
 * [|Moon Phase Simulator]
 * There are many (confusing) images that show the different phases of the Moon.
 * StarDate shows the current month's Moon phases.
 * WHY we see the Moon go through its phases, as told by the folks at UNC, MoonConnection,
 * the UniverseToday andHowStuffWorks.
 * You also might be interested in the fact the only one side of the Moon faces the Earth, due to tidal locking.
 * Also, ever notice that the full Moon looks bigger when it is near the horizon? Well, surprise, it actually doesn't. That's an optical illusion.
 * Yes, the Moon does look orange/red/yellow at the horizon. That's because of the way the ... well, just read this!
 * __Eclipses__:
 * [|Eclipses described in Wikipedia]
 * [|NASA's Eclipse Site]

__Lecture #21: "Exoplanetary Systems"__

 * Exoplanets have only been know for ~20 years, and are believed to have formed exactly the same way that the Sun's planets formed, though around their respective stars.
 * There are currently five methods for discovering exoplanets. We discussed three:
 * Transit method: the planet passes in front of its star (from our perspective) and blocks out the light of the star. We see this dimming.
 * Radial velocity method: the gravitational pull of a massive planet on its star can be seen in the Doppler shifting of the starlight.
 * Direct imaging: if the glare of the starlight is blocked, the infrared radiation from the planet can be detected.
 * __Weblinks__: **
 * As of 2 June 2017, exoplanet.eu has confirmed 3610 extra solar planets. These are planets orbiting other stars. There are 2704 planetary systems out there, so clearly some of those stars have more than one planet. Well, the Sun certainly does, but it isn't the record holder...HD 10180 is with seven confirmed and other two suspected planets.
 * The recently discovered "Earth like" planet, [|Kepler-186f], is described [|here].
 * There are various telescopes dedicated to exoplanets, including the (now defunct) Kepler mission, JWST, TESS and will detect those exoplanets by a variety of methods.

__Lecture #22: "The Search for Life in the Universe"__

 * To search for life in the Universe, you need to look at planets or moons that have a source of energy. Either a nearby star, heat released from the planet's/moon's interior, or heat generated by tidal flexing.
 * Carbon is a likely element for life (we are carbon based), as it makes stable molecules with single, double, and triple bonds. Silicon isn't as good, as it makes only single bonds and those degrade in sunlight.
 * Complex life on Earth has d ioxyribonucleic acid (DNA). Mutation happen within this huge molecule, which are necessary for life to survive (not become extinct) as environments change. This is evolution.
 * Solvents are needed to allow for chemical/biological reactions to occur, and to bring nutrients to and carry waste from the life form. Water is the solvent for life on Earth, but methane, ammonia and possibly hydrogen sulphide are possibilities for life elsewhere in the universe.
 * Frank Drake formulated "The Drake Equation" ( N c = N * x F p x N hz x F l x F i x F s ) which seeks to quantify how many communicative civilizations are in the galaxy.
 * __Weblinks__: **
 * Ingredients for life include carbon, water and energy, as is showcased in this NOVA video.
 * DNA is a huge, complex, interesting and necessary molecule for complex life.
 * The Drake Equation is our go to estimate for calculating life beyond the Solar System.