Saturday, December 21, 2013

Topics for final presentations

Dark matter
Dark energy
Black holes
Pulsars
Exoplanets
Variable stars
Types of galaxies
SETI
Supernovae
End of the universe
Olber's paradox
Cosmic background radiation
WMAP
Death of the dinosaurs
Pluto reclassification 
Origin of life on earth (or elsewhere)
Trip to Mars
Possible life on the moons of Jupiter
Topic of your choosing ?

Thursday, December 19, 2013

Images from class - winter solstice

Winter Solstice!

Saturday, December 21, 2013 at 12:11 PM EST

http://www.timeanddate.com/calendar/december-solstice.html

http://www.space.com/24014-winter-solstice-sun-movement-explained.html


Recall:

http://astro.unl.edu/naap/motion3/animations/sunmotions.swf

The December solstice occurs when the sun reaches its most southerly declination of -23.5 degrees. In other words, it is when the North Pole is tilted 23.5 degrees away from the sun. Depending on the Gregorian calendar, the December solstice occurs annually on a day between December 20 and December 23. On this date, all places above a latitude of 66.5 degrees north (Arctic Polar Circle) are now in darkness, while locations below a latitude of 66.5 degrees south (Antarctic Polar Circle) receive 24 hours of daylight.

The sun is directly overhead on the Tropic of Capricorn in the southern hemisphere during the December solstice. It also marks the longest day of the year in terms of daylight hours for those living south of the equator. Those living or traveling south from the Antarctic Circle towards the South Pole will see the midnight sun during this time of the year.

On the contrary, for an observer in the northern hemisphere, the December solstice marks the day of the year with the least hours of daylight. Those living or traveling north of the Arctic Circle towards the North Pole will not be able to see the sun during this time of the year.

The December solstice in the calendar

December 20 and December 23 solstices occur less frequently than December 21 or December 22 solstices in the Gregorian calendar. The last December 23 solstice occurred in 1903 and will not occur again until the year 2303. A December 20 solstice has occurred very rarely, with the next one occurring in the year 2080.

As with the June solstice, the December solstice’s varying dates are mainly due to the calendar system. The Gregorian calendar, which is used in most western countries, has 365 days in a common year and 366 days in a leap year. However, the tropical year, which is the length of time the sun takes to return to the same position in the seasons cycle (as seen from Earth), is different to the calendar year. The tropical year is approximately 365.242199 days but varies from year to year because of the influence of other planets. The exact orbital and daily rotational motion of the Earth, such as the “wobble” in the Earth's axis (precession), also contributes to the changing solstice dates.

Over the course of history, many different schemes have been devised to determine the start of the year. Some are astronomical, beginning at the September or March equinox, or at the June or December solstice. Solstices are more readily observable either by observing when the midday shadow of a gnomon is longest (winter solstice in the northern hemisphere) or shortest (summer solstice in the northern hemisphere). The solstices can also be observed by noting the point of time when the sun rises or sets as far south as it does during the course of the year (winter in the northern hemisphere) or maximally north (summer in the northern hemisphere).

(*) All dates refer to Coordinated Universal Time (UTC). Dates may vary depending on the time zone.

December solstice in relation to seasons

It is important to note that Earth does not move at a constant speed in its elliptical orbit. Therefore the seasons are not of equal length: the times taken for the sun to move from the vernal equinox to the summer solstice, to the autumnal equinox, to the winter solstice, and back to the vernal equinox are roughly 92.8, 93.6, 89.8 and 89.0 days respectively. The consolation in the northern hemisphere is that spring and summer last longer than autumn and winter (when the December solstice occurs).

The relative position of the Earth's axis to the sun changes during the cycle of seasons. This phenomenon is the reason why the sun’s height above the horizon changes throughout the year. It is also responsible for the seasons through controlling the intensity and duration of sunlight received at various locations around the planet.
Solstice’s influence on cultures

The December solstice has played an important role the lives of many people in ancient times. To this day, the world is still influenced by various traditions linked to the observance of the December solstice.

In modern times Christians all over the world celebrate the birth of Jesus Christ on Christmas, which falls on December 25. However, it is believed that this date was chosen to offset pagan celebrations of Saturnalia and Natalis Invicti. Some believe that celebrating the birth of the “true light of the world” was set in synchronization with the December solstice because from that point onwards, the days began to have more daylight in the northern hemisphere.

Christmas is also referred to as Yule, which may have derived from the Norse word jól, referring to the pre-Christian winter solstice festival. Yule is also known as Alban Arthan and was one of the “Lesser Sabbats” of the Wiccan year in a time when ancient believers celebrated the rebirth of the Sun God and days with more light. This took place annually around the time of the December solstice and lasted for 12 days. The Lesser Sabbats fall on the solstices and equinoxes.

The Feast of Juul was a pre-Christian festival observed in Scandinavia at the time of the December solstice. Fires were lit to symbolize the heat, light and life-giving properties of the returning sun. A Yule or Juul log was brought in and burned on the hearth in honor of the Scandinavian god Thor.

A piece of the log was kept as both a token of good luck and as kindling for the following year’s log. In England, Germany, France and other European countries, the Yule log was burned until nothing but ash remained. The ashes were then collected and either strewn on the fields as fertilizer every night until Twelfth Night or kept as a charm and or as medicine.

French peasants believed that if the ashes were kept under the bed, they would protect the house against thunder and lightning. The present-day custom of lighting a Yule log at Christmas is believed to have originated in the bonfires associated with the feast of Juul.

Saturnalia in Ancient Rome

In Ancient Rome the winter (December) solstice festival Saturnalia began on December 17 and lasted for seven days. It was held to honor Saturn, the father of the gods and was characterized by the suspension of discipline and reversal of the usual order. Grudges and quarrels were forgotten while businesses, courts and schools were closed. Wars were interrupted or postponed and slaves were served by their masters. Masquerades often occurred during this time.

It was traditional to offer gifts of imitation fruit (a symbol of fertility), dolls (symbolic of the custom of human sacrifice), and candles (reminiscent of the bonfires traditionally associated with pagan solstice celebrations). A mock king was chosen, usually from a group of slaves or criminals, and although he was permitted to behave in an unrestrained manner for seven days of the festival, he was usually killed at the end. The Saturnalia eventually degenerated into a week-long spree of debauchery and crime – giving rise to the modern use of the tern saturnalia, meaning a period of unrestrained license and revelry.
Other Cultures and Modern Day Celebrations

In Poland the ancient December solstice observance prior to Christianity involved people showing forgiveness and sharing food. It was a tradition that can still be seen in what is known as Gody. In the northwestern corner of Pakistan, a festival called Chaomos, takes place among the Kalasha or Kalash Kafir people. It lasts for at least seven days, including the day of the December solstice. It involves ritual baths as part of a purification process, as well as singing and chanting, a torchlight procession, dancing, bonfires and festive eating.

Many Christians celebrate St Thomas’ Day in honor of St Thomas the Apostle on December 21. In Guatemala on this day, Mayan Indians honor the sun god they worshipped long before they became Christians with a dangerous ritual known as the polo voladore, or “flying pole dance”. Three men climb on top of a 50-foot pole. As one of them beats a drum and plays a flute, the other two men wind a rope attached to the pole around one foot and jump. If they land on their feet, it is believed that the sun god will be pleased and that the days will start getting longer. Some churches celebrate St Thomas’ Day on other days in the year.

The ancient Incas celebrated a special festival to honor the sun god at the time of the December solstice. In the 16th century ceremonies were banned by the Roman Catholics in their bid to convert the Inca people to Christianity. A local group of Quecia Indians in Cusco, Peru, revived the festival in the 1950s. It is now a major festival that begins in Cusco and proceeds to an ancient amphitheater a few miles away.

http://www.timeanddate.com/calendar/december-solstice.html

GREAT RESOURCE!

>

The winter solstice is the solstice that occurs in winter. It is the time at which the Sun is appearing at noon at its lowest altitude above the horizon.  In the Northern Hemisphere this is the Southern solstice, the time at which the Sun is at its southernmost point in the sky, which usually occurs on December 21 to 22 each year.

In the Southern Hemisphere this is the Northern solstice, the time at which the Sun is at its northernmost point in the sky, which usually occurs on June 20 to 21 each year.

The axial tilt of Earth and gyroscopic effects of the planet's daily rotation keep the axis of rotation pointed at the same point in the sky. As the Earth follows its orbit around the Sun, the same hemisphere that faced away from the Sun, experiencing winter, will, in half a year, face towards the Sun and experience summer. Since the two hemispheres face opposite directions along the planetary pole, as one polar hemisphere experiences winter, the other experiences summer.

More evident from high latitudes, a hemisphere's winter solstice occurs on the shortest day and longest night of the year, when the sun's daily maximum elevation in the sky is the lowest. Since the winter solstice lasts only a moment in time, other terms are often used for the day on which it occurs, such as "midwinter", "the longest night", "the shortest day" or "the first day of winter". The seasonal significance of the winter solstice is in the reversal of the gradual lengthening of nights and shortening of days.

Worldwide, interpretation of the event has varied from culture to culture, but most Northern Hemisphere cultures have held a recognition of rebirth, involving holidays, festivals, gatherings, rituals or other celebrations around that time.

History and cultural significance

The solstice itself may have been a special moment of the annual cycle of the year even during neolithic times. Astronomical events, which during ancient times controlled the mating of animals, sowing of crops and metering of winter reserves between harvests, show how various cultural mythologies and traditions have arisen. This is attested by physical remains in the layouts of late Neolithic and Bronze Age archaeological sites such as Stonehenge in Britain and Newgrange in Ireland. The primary axes of both of these monuments seem to have been carefully aligned on a sight-line pointing to the winter solstice sunrise (Newgrange) and the winter solstice sunset (Stonehenge). Significant in respect of Stonehenge is the fact that the Great Trilithon was erected outwards from the centre of the monument, i.e., its smooth flat face was turned towards the midwinter Sun.

The winter solstice may have been immensely important because communities were not certain of living through the winter, and had to be prepared during the previous nine months. Starvation was common in winter between January and April, also known as "the famine months". In temperate climates, the midwinter festival was the last feast celebration, before deep winter began. Most cattle were slaughtered so they would not have to be fed during the winter, so it was almost the only time of year when a supply of fresh meat was available. The majority of wine and beer made during the year was finally fermented and ready for drinking at this time. The concentration of the observances were not always on the day commencing at midnight or at dawn, but the beginning of the pre-Romanized day, which falls on the previous eve.

Since the event is seen as the reversal of the Sun's ebbing presence in the sky, concepts of the birth or rebirth of sun gods have been common and, in cultures using winter solstitially based cyclic calendars, the year as reborn has been celebrated with regard to life-death-rebirth deities or new beginnings such as Hogmanay's redding, a New Year cleaning tradition. Also reversal is yet another usual theme as in Saturnalia's slave and master reversals.

http://en.wikipedia.org/wiki/Winter_solstice

Friday, December 13, 2013

Geminids

http://www.skyandtelescope.com/observing/home/Geminid-Meteors-Fight-the-Moon-234777331.html

Quiz review

Quiz:
Questions about:
1.  H-R diagram.
- know what it means
- the axes and general shape
- the Main Sequence
- where to find white dwarfs and giants/supergiants
- the stellar classification (O B A F G K M)
- what kind of star the Sun is (G2)
I may just draw an H-R diagram and ask you to fill in information.

2.  Doppler effect
- understand the general nature of the DE, not just for sound but also for light (it's all about an apparent change in the frequency)
- know the difference between red shift and blue shift
- know that the red shift of distant galaxies suggested to Edwin Hubble that the universe was expanding

3.  Basics of optics
- how light behaves when it hits a mirror or lens
- be able to draw paths that light would take

4.  Revisit the parsec and recall the definition.
- at a distance of 1 parsec, a length of one AU subtends an angle of one arcsecond.  It also works in reverse - if the Earth travels a distance of 1 AU in orbit, the parallax angle of nearby stars (with respect to further-away background stars) can be used to measure their distances:
d = 1/angle
where d (distance, in parsec) is 1 divided by the parallax angle (in arcseconds).

5.  Electromagnetic radiation
Know a little about the EM spectrum chart:
- it goes from low frequency waves to high frequency waves
- you can also think of it as going from long wavelength to short wavelength waves
- Radio, microwave, IR, visible, UV, X, gamma
- ALL of the waves travel at the speed of light (c) in a vacuum.  

Scroll back to blog posts as far as Tuesday, November 12.

Observing 2 - the early winter sky

Observing II:  The Winter Sky

Despite the cold, the late fall and early winter skies present some of the best opportunities for viewing.  Heat haze is at a minimum, though precipitation can be a problem for telescopes.  In this lab, you will locate several gems of the winter sky, drawing and identifying what you see.  So throw on some gloves, bundle up, and dig the night sky!
Check out the December and January maps on www.skymaps.com.  You can also see the maps from Abrams Planetarium (Michigan State University), distributed in class.
Answer the following questions based on your map reading and/or field experience.  Good luck.  Take hot chocolate with you.  And cookies – definitely take some cookies, even if you never get outside.

1. What planet(s) is/are visible in the evening (before midnight)?  Find it.
2. What planet(s) is/are visible after midnight?
3. Where in the sky is the Andromeda Galaxy (M31 ? that’s Messier object #31)?
4. Draw the constellation Orion as it appears to you.  Identify Rigel and Betegeuse, and note their colors.
5. Where is the great square of Pegasus?
6. Find the Northern Cross.  In what constellation is it?  Name any star in the Cross.
7. Name the three brightest stars visible tonight – find them, also.
8. What are the two brightest stars in the constellation of the twins?
9. Draw the Big Dipper as it appears to you, facing it.
10. Identify any other winter constellations or objects of interest.
11.  Find the 3 stars in the belt of Orion.  What are their names?
12.  Follow these 3 stars in a line to a bright star.  What star is that?
13.  Where is the Orion nebula?.
14.  Find the winter triangle and name the 3 stars in it.

If a telescope or binoculars are available, find the following objects and describe them:
Pleiades cluster, Hyades cluster, M42 (the Great Orion Nebula)

Questions

1.  What are the easiest ways to tell the difference between a star and a planet?
2.  Are there any comets viewable right now (with telescope)?
3.  When is the next full Moon?
4.  What is the brightest star visible in the evening sky?
5.  Tell me something about the mythology of Orion.
6.  How does the winter sky compare to the fall sky?  You may need to reference an earlier star map.
7.  Anything else worth mentioning about the sky?



Wednesday, December 4, 2013

Wednesday, November 20, 2013

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

Monday, November 18, 2013

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.


Thursday, November 14, 2013

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).


Tuesday, November 12, 2013

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

Wednesday, November 6, 2013

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.

Monday, November 4, 2013

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

Tuesday, October 29, 2013

Angular Measurement, etc.

Angular Measurement


Consider the following convention which has been with us since the
rise of Babylonian mathematics:

There are 360 degrees per circle.
Each degree can be further divided into 60 minutes (60'), each called
an arcminute.
Each arcminute can be divided into 60 seconds (60"), each called an arcsecond.
Therefore, there are 3600 arcseconds in one degree.

Some rough approximations:
A fist extended at arm's length subtends an angle of approx. 10º.
A thumb extended at arm's length subtends an angle of approx. 2º.
The Moon (and Sun) subtend an angle of approx. 0.5º.

Human eye resolution (the ability to distinguish between 2 adjacent
objects) is limited to about 1 arcminute – roughly the diameter of a
dime at 60-m.  Actually, given the size of our retina, we're limited
to a resolution of roughly 3'

So, to achieve better resolution, we need more aperture (ie., telescopes).

The Earth's atmosphere limits detail resolution to objects bigger than
0.5", the diameter of a dime at 7-km, or a human hair 2 football
fields away.  This is usually reduced to 1" due to atmospheric
turbulence.

The parsec (pc)

The distance at which 1 AU subtends an angle of one arcsec (1") is
definite as one parsec – that is, it has a parallax of one arcsec.



For example, if a star has a parallax angle (d) of 0.5 arcsec, it is
1/0.5 parsecs (or 2 parsecs) away.


The parsec (pc) is roughly 3.26 light years.


Distance (in pc) = 1 / d

where d is in seconds of arc.


Measuring star distances can be done by measuring their angle of
parallax – typically done over a 6-month period, seeing how the star's
position changes with respect to background stars in 6 months, during
which time the Earth has moved across its ellipse.


Unfortunately, this is limited to nearby stars, some 10,000.  Consider
this:  Proxima Centauri (nearest star) has a parallax angle of 0.75" –
a dime at 5-km.  So, you need to repeat measurements over several
years for accuracy.


This works for stars up to about 300 LY away, less than 1% the
diameter of our galaxy!
[If the MW galaxy were reduced to 130 km (80 mi) in diameter, the
Solar System would be a mere 2 mm (0.08 inches) in width.]

Apparent magnitude (m) scale


This dates back to the time of Hipparchus who classified things as

bright or small.
Ptolemy classified things into numbers:  1-6, with 1 being brightest.
The brightest (1st magnitude) stars were 100 times brighter than the
faintest (6th magnitude).  This convention remains standard to this
day.  Still, this was very qualitative.

In the 19th century, with the advent of photographic means of
recording stars onto plates, a more sophisticated system was adopted.
It held to the original ideas of Ptolemy


A difference of 5 magnitudes (ie., from 1 to 6) is equivalent to a
factor of exactly 100 times.  IN other words, 1st magnitude is 100x
brighter than 6th magnitude.  Or, 6th magnitude is 1/100th as bright
as 1st mag.


This works well, except several bodies are brighter than (the
traditional) 1st mag.


So….. we have 0th magnitude and negative magnitudes for really bright objects.
Examples:
Sirius (brightest star):  -1.5
Sun:  -26.8
Moon:  -12.6
Venus:  -4.4
Canopus (2nd brightest star):  -0.7
Faintest stars visible with eye:  +6
Faintest stars visible from Earth:  +24
Faintest stars visible from Hubble:  +28


The magnitude factor is the 5th root of 100, which equals roughly
2.512 (about 2.5).


Keep in mind that this is APPARENT magnitude, which depends on
distance, actual star luminosity and interstellar matter.
Here's a problem:  What is the brightness difference between two
objects of magnitudes -1 and 6?


Since they are 7 magnitudes apart, the distance is 2.5 to the 7th power, or 600.
For the math buffs:  the formula for apparent magnitude comparison:
m1 – m2 = 2.5 log (I2 / I1)


The m's are magnitudes and the I's are intensities – the ratio of the
intensities gives a comparison factor.  A reference point is m = 100,
corresponding to an intensity of 2.65 x 10^-6 lumens.

Absolute Magnitude, M


Consider how bright the star would be if it were 10 pc away.  This is

how we define absolute magnitude (M).

It depends on the star's luminosity, which is a measure of its brightness:


L = 4 pi R^2 s T^4


R is the radius of the body emitting light, s is the Stefan-Boltzmann
constant (5.67 x 10-8 W/m^2K^4) and T is the effective temperature (in
K) of the body.


So, a star's luminosity depends on its size (radius, R) and absolute temperature (T).

If the star is 10 pm away, its M = m (by definition).
m – M = 5 log (d/10)


We let d = the distance (in pc), log is base 10, m is apparent
magnitude and M is absolute magnitude.




A problem:  If d = 20 pc and m = +4, what is M?  (2.5)
And another (more challenging):
If M = 5 and m = 10, how far away is the star?  (100 pc)