Comet Ison?

http://www.skyandtelescope.com/observing/home/232699581.html

We haven't chatted about it in class - it's an early morning object, and not terribly bright yet.  Still, it *may* end up great.  Nobody seems to be sure.

FYI - observation night and optics

Observation night is:  December 5, 7 PM.  Backup night:  December 10, 7 PM

Here's the lens applet I was playing with today in class:

http://www.physics.metu.edu.tr/~bucurgat/ntnujava/Lens/lens_e.html

Hella-cool!

Interactive supernova

http://54.225.120.196/tour/seeing-around-remnant-supernova

A bit of background:

http://www.skyandtelescope.com/news/Cassiopeia-A-in-3D-232367901.html

Today

Folks,

I can't come in until around 11:30 today, so I have to miss our class.  Please work on the following stuff:

If you have not done the blog homework from the weekend, do so.  Also, check out some recent blog posts, most of which were there for your information (such as the full Moon names).  If you want to look ahead, read my notes on stellar classification and the H-R diagram (though we'll cover this in our next class).

Find out how realistic it will be for us to see Comet Ison this fall - when will it be visible.

Then, work through this simulation online.  Use the computer lab next door, computers upstairs or in the library, and/or any personal computers.

http://wechoosethemoon.org/


See you Wednesday.

Watch this / HW

http://www.upworthy.com/the-single-most-mind-altering-photograph-humanity-has-ever-taken

You may disagree with some of what Carl Sagan says, but you will probably at least find it poetic on some level.

And see this, mentioned in class today:

http://imgur.com/gallery/ylbWx7I

Cool:

http://www.iflscience.com/space/what-does-space-sound


Re:  Comet Ison

http://earthsky.org/space/comet-ison-has-an-outburst


And other photos worth a look:

http://nssdc.gsfc.nasa.gov/planetary/lunar/apollo_11_30th.html

Refraction notes

Reflection and Refraction

Reflection - light "bouncing" off a reflective surface. This obeys a simple law, the law of reflection!

The incident (incoming) angle equals the reflected angle. Angles are generally measured with respect to a "normal" line (line perpendicular to the surface).

Note that this works for curved mirrors as well, though we must think of a the surface as a series of flat surfaces - in this way, we can see that the light can reflect in a different direction, depending on where it hits the surface of the curved mirror. More to come here.

Refraction:

Refraction is much different. In refraction, light enters a NEW medium. In the new medium, the speed changes. We define the extent to which this new medium changes the speed by a simple ratio, the index of refraction:

n = c/v

In this equation, n is the index of refraction (a number always 1 or greater), c is the speed of light (in a vacuum) and v is the speed of light in the new medium.

The index of refraction for some familiar substances:

vacuum, defined as 1

air, approximately 1

water, 1.33

glass, 1.5

polycarbonate ("high index" lenses), 1.67

diamond, 2.2

The index of refraction is a way of expressing how optically dense a medium is. The actual index of refraction (other than in a vacuum) depends on the incoming wavelength. Different wavelengths have slightly different speeds in (non-vacuum) mediums. For example, red slows down by a certain amount, but violet slows down by a slightly lower amount - meaning that red light goes through a material (glass, for example) a bit faster than violet light. Red light exits first.

In addition, different wavelengths of light are "bent" by slightly different amounts. This is trickier to see. We will explore it soon.

Refraction, in gross gory detail

Consider a wave hitting a new medium - one in which is travels more slowly. This would be like light going from air into water. The light has a certain frequency (which is unchangeable, since its set by whatever atomic process causes it to be emitted). The wavelength has a certain amount set by the equation, c = f l, where l is the wavelength (Greek symbol, lambda).

When the wave enters the new medium it is slowed - the speed becomes lower, but the frequency is fixed. Therefore, the wavelength becomes smaller (in a more dense medium).

Note also that the wave becomes "bent." Look at the image above: in order for the wave front to stay together, part of the wave front is slowed before the remaining part of it hits the surface. This necessarily results in a bend.

The general rule - if a wave is going from a lower density medium to one of higher density, the wave is refracted TOWARD the normal (perpendicular to surface) line. See picture above.

http://stwww.weizmann.ac.il/lasers/laserweb/java/twoangles2.htm

http://lectureonline.cl.msu.edu/~mmp/kap25/Snell/app.htm

http://www.physics.uoguelph.ca/applets/Intro_physics/refraction/LightRefract.html

Electromagnetic Radiation

Recall that waves can be categorized into two major divisions:

Mechanical waves, which require a medium. These include sound, water and waves on a (guitar, etc.) string

Electromagnetic waves, which travel best where there is NO medium (vacuum), though they can typically travel through a medium as well. All electromagnetic waves can be represented on a chart, usually going from low frequency (radio waves) to high frequency (gamma rays). This translates to: long wavelength to short wavelength.

All of these EM waves travel at the same speed in a vacuum: the speed of light (c). Thus, the standard wave velocity equation becomes:

c = f l

where c is the speed of light (3 x 10^8 m/s), f is frequency (in Hz) and l (which should be the Greek letter, lambda) is wavelength (in m).

Parsec image

H-R diagram and stellar classification

One of the most useful tools for identifying star types in astronomy is the H-R Diagram. This idea, independently conceived in 1910 by Ejnar Hertzsprung and Henry Russell, is a graphical representation of intrinsic brightness as a function of temperature. It is largely based on this diagram that stars are classified.

There are a few variations of the H-R diagram:

• Absolute visual magnitude (Mv) vs. Spectral Type
• Absolute visual magnitude vs. Temperature
• Luminosity of star (sometimes given as relative to Sun’s luminosity) vs. Spectral Type
• Absolute visual magnitude vs. Color Index (B - V)


Other variations exist as well. The purpose and effect of each diagram is the same, however. Points plotted fall in limited regions on the graph, rather than in a wide distribution.

The Spectral Types are (in order of decreasing temperature):
O, B, A, F, G, K, M

Further, each of these can be subdivided into 10 categories, 0-9, though most of our stars today will be in the 0-5 range. A graph will resemble the graph noted below.

There is a broad roughly diagonal band running from upper left to lower right. This is referred to as the Main Sequence. Most stars spend the bulk of their lives along the Main Sequence

Full Moon Names and Their Meanings

 http://www.farmersalmanac.com/full-moon-names/

Full Moon names date back to Native Americans, of what is now the northern and eastern United States. The tribes kept track of the seasons by giving distinctive names to each recurring full Moon. Their names were applied to the entire month in which each occurred. There was some variation in the Moon names, but in general, the same ones were current throughout the Algonquin tribes from New England to Lake Superior. European settlers followed that custom and created some of their own names. Since the lunar month is only 29 days long on the average, the full Moon dates shift from year to year. Here is the Farmers Almanac’s list of the full Moon names.

• Full Wolf Moon – January Amid the cold and deep snows of midwinter, the wolf packs howled hungrily outside Indian villages. Thus, the name for January’s full Moon. Sometimes it was also referred to as the Old Moon, or the Moon After Yule. Some called it the Full Snow Moon, but most tribes applied that name to the next Moon.

• Full Snow Moon – February Since the heaviest snow usually falls during this month, native tribes of the north and east most often called February’s full Moon the Full Snow Moon. Some tribes also referred to this Moon as the Full Hunger Moon, since harsh weather conditions in their areas made hunting very difficult.

• Full Worm Moon – March As the temperature begins to warm and the ground begins to thaw, earthworm casts appear, heralding the return of the robins. The more northern tribes knew this Moon as  the Full Crow Moon, when the cawing of crows signaled the end of winter; or the Full Crust Moon, because the snow cover becomes crusted from thawing by day and freezing at night. The Full Sap Moon, marking the time of tapping maple trees, is another variation. To the settlers, it was also known as the Lenten Moon, and was considered to be the last full Moon of winter.

• Full Pink Moon – April This name came from the herb moss pink, or wild ground phlox, which is one of the earliest widespread flowers of the spring. Other names for this month’s celestial body include the Full Sprouting Grass Moon, the Egg Moon, and among coastal tribes the Full Fish Moon, because this was the time that the shad swam upstream to spawn.

• Full Flower Moon – May In most areas, flowers are abundant everywhere during this time. Thus, the name of this Moon. Other names include the Full Corn Planting Moon, or the Milk Moon.

• Full Strawberry Moon – June This name was universal to every Algonquin tribe. However, in Europe they called it the Rose Moon. Also because the relatively short season for harvesting strawberries comes each year during the month of June . . . so the full Moon that occurs during that month was christened for the strawberry!

• The Full Buck Moon – July July is normally the month when the new antlers of buck deer push out of their foreheads in coatings of velvety fur. It was also often called the Full Thunder Moon, for the reason that thunderstorms are most frequent during this time. Another name for this month’s Moon was the Full Hay Moon.

• Full Sturgeon Moon – August The fishing tribes are given credit for the naming of this Moon, since sturgeon, a large fish of the Great Lakes and other major bodies of water, were most readily caught during this month. A few tribes knew it as the Full Red Moon because, as the Moon rises, it appears reddish through any sultry haze. It was also called the Green Corn Moon or Grain Moon.

• Full Corn Moon or Full Harvest Moon – September This full moon’s name is attributed to Native Americans because it marked when corn was supposed to be harvested. Most often, the September full moon is actually the Harvest Moon, which is the full Moon that occurs closest to the autumn equinox. In two years out of three, the Harvest Moon comes in September, but in some years it occurs in October. At the peak of harvest, farmers can work late into the night by the light of this Moon. Usually the full Moon rises an average of 50 minutes later each night, but for the few nights around the Harvest Moon, the Moon seems to rise at nearly the same time each night: just 25 to 30 minutes later across the U.S., and only 10 to 20 minutes later for much of Canada and Europe. Corn, pumpkins, squash, beans, and wild rice the chief Indian staples are now ready for gathering.

• Full Hunter’s Moon or Full Harvest Moon – October This full Moon is often referred to as the Full Hunter’s Moon, Blood Moon, or Sanguine Moon. Many moons ago, Native Americans named this  bright moon for obvious reasons. The leaves are falling from trees, the deer are fattened, and it’s time to begin storing up meat for the long winter ahead. Because the fields were traditionally reaped in late September or early October, hunters could easily see fox and other animals that come out to glean from the fallen grains. Probably because of the threat of winter looming close, the Hunter’s Moon is generally accorded with special honor, historically serving as an important feast day in both Western Europe and among many Native American tribes.

• Full Beaver Moon – November This was the time to set beaver traps before the swamps froze, to ensure a supply of warm winter furs. Another interpretation suggests that the name Full Beaver Moon comes from the fact that the beavers are now actively preparing for winter. It is sometimes also referred to as the Frosty Moon.

• The Full Cold Moon; or the Full Long Nights Moon – December During this month the winter cold fastens its grip, and nights are at their longest and darkest. It is also sometimes called the Moon before Yule. The term Long Night Moon is a doubly appropriate name because the midwinter night is indeed long, and because the Moon is above the horizon for a long time. The midwinter full Moon has a high trajectory across the sky because it is opposite a low Sun.


As for "blue moon" --

From Neil deGrasse Tyson (via his facebook feed):

The average time the Moon takes to complete a cycle of phases is 29.5 days. So all months but February can host a second full Moon, if the timing is right. We call these "Blue Moons" and we get one on Friday, August 31. Chances of a full Moon on the first of a month is about 1 in 30, so you'd expect a Blue Moon every 30 months or so -- about once every 2.5 years. Not rare. So when the cosmically literate want to reference something that's uncommon, they **never** say "Once in a Blue Moon". -NDTyson

Doppler effect

See this simple, but effective applet:

http://lectureonline.cl.msu.edu/~mmp/applist/doppler/d.htm

In this simulation, v/vs is the ratio of your speed to the speed of sound; e.g., 0.5 is you, or the blue dot, traveling at half the speed of sound. Note how the waves experienced on one side "pile up" (giving an observer a greater detected frequency, or BLUE SHIFT); on the other side, the waves are "stretched apart" (giving an observer a lower detected frequency, or RED SHIFT).

Play with this for a bit, though it's a little less obvious:

http://falstad.com/ripple/

In astronomy, the red shift is very important historically: Edwin Hubble found that light from distant galaxies (as measured in their spectra) was red shifted, meaning that distant galaxies were moving away from us (everywhere we looked). The conclusion was obvious (and startling): The universe is expanding. Last year, local astrophysicist Adam Riess discovered that the rate of expansion was accelerating.

http://www.nobelprize.org/nobel_prizes/physics/laureates/2011/


It's worth noting that the effect also works in reverse. If you (the detector) move toward a sound-emitter, you'll detect a higher frequency. If you move away from a detector move away from a sound-emitter, you'll detect a lower frequency.

Mind you, these Doppler effects only happen WHILE there is relative motion between source and detector (you).

And of course, they also work for light. That's why we care about them. In fact, the terms red shift and blue shift refer mainly to light (or other electromagnetic) phenomena.

In practice, for astronomy:

v = [ (change in wavelength) / (original wavelength) ] c

Formation of Solar System

~ 4.6 billion years ago huge cloud of gas and dust
started collapsing gravitationally

• As it collapsed it spun faster (conservation of
angular momentum)

• No (or little) spin in the perpendicular plane

• Local clusters of dust and gas condensed - protosun
formed first

• As material cooled, it condensed but never stopped
rotating (rotates still since there’s nothing to stop
it)

• Cores probably formed first, then attracted
neighboring materials to form:  planetesimal,
protoplanet

• Probably not a unique system - there is increasing
evidence for the existence of many other planetary
systems

• Still an evolving theory

• All planets revolve around the sun in the same
direction, but 3 have different directions of rotation
(relative to the rest and to the direction of solar
system motion) - Uranus, Venus, (Pluto)


The Terrestrial Planets:  Mercury, Venus, Earth, and
Mars

Relative Characteristics:

Planet   Distance        Period          Radius          Mass

Mercury  0.4             0.24            0.38            0.055
Venus    0.7             0.62            0.95            0.82
Earth     1               1               1               1
Mars     1.5             1.88            0.53            0.11

The Jovian Planets (gas giants)

Jupiter  5.2             11.9            11.2            318
Saturn   9.5             29.5             9.3             95
Uranus   19                84             4.0            14.6
Neptune  30               165             3.9            17.2

Planet Quest (Lab)

Planet "lab"

A Tour of the Planets

Please determine many interesting tidbits of trivia about our solar neighbors. You may like the following website:

http://nineplanets.org/

Please answer the following questions, based on your reading and web discovery. Some questions might have several answers, while the answer to others might be "none of them."  

Which planet(s):

1. Rotates backwards?
2. Revolves backwards?
3. Rotates nearly on its side?
4. Have more than 10 moons?
5. Have only one moon?
6. Has an orbit with the greatest inclination to the ecliptic?
7. Is the furthest planet known to the ancients?
8. Has a largely methane atmosphere?
9. Has a nondescript, pale greenish color?
10. Has a blemish known as the great dark spot?
11. Has a fine iron oxide regolith?
12. Is most similar to Earth in its surface gravity?
13. Has the greatest mass?
14. Has the smallest diameter?
15. Have been visited by humans?
16. Has the strongest magnetic field?
17. Has rings?
18. Has sulfuric acid clouds?
19. Has the tallest mountain in the Solar System (and what is it)?
20. Has a day longer than its year?
21. Has been landed on most recently by spacecraft?
22. Experiences global dust storms?
23. Has a moon that rotates retrograde (and what is it)?
24. May be an escaped Kuiper object?
25. Was once thought to be a failed star?
26. Is heavily cratered?
27. Has moons which are likely candidates for life?
28. Was hit by a large comet in the last several years?
29. Is most oblate?
30. Has a central pressure 100 million times Earth's atmospheric pressure?

Now for the minor bodies.

1. Which body is an asteroid with its own orbiting asteroid?
2. Which moon has erupting volcanoes?
3. Which body is the largest asteroid?
4. Approximately how many known asteroids are there?
5. Approximately how many known Kuiper objects are there? What is the Kuiper belt?
6. How large is the Oort Cloud? What is the Oort Cloud?
7. Which moon was the first discovered after the Galilean satellites?

8.  How many "extrasolar" planets are there?  Which was the first discovered?

9.  What is the status of Pluto and why was is "demoted" from planet status?

Additional - list anything you found interesting in your hunt.  Or multiple things.

Habitable Earths?

http://blogs.smithsonianmag.com/science/2013/11/there-are-probably-way-more-earth-like-exoplanets-than-we-imagined/?utm_source=facebook.com&utm_medium=socialmedia&utm_campaign=11042013&utm_content=surprisingscienceexoplanets3