|Short Questions about the Sky|
|Sky Matching Exercise||Intro||Larson||This one's hard! A matching activity of locations on the Earth and things that happen in those locations.|
|How big is big?||Intro||Balick|
|Suntanning||Intro||Balick||Notes for Teachers|
|Short Questions about the Solar System|
|Solar System Scale||Intro||Balick|
|Sizes of Astronomical Objects||Intro||?|
|Short Questions about the Stars|
|Spectra Problem Set||Intro||?|
|The Lifetime of the Sun||Intro||?|
|Solar Power||Intro||Agueros||Modification of above.|
|Properties of Sun and Stars||Intro||?|
|Short Questions about Stellar Evolution|
|H-R diagram||Intro||?||This exercise has some serious inconsistencies and graphing problems. Improvements are currently underway, but we recommend you do not use this exercise until this message disappears. -- AML|
|Short Questions about Galaxies|
|Distance to the Center of the Milky Way||Intro||Larson|
|Short Questions about Cosmology|
|Expansion of the Universe||Intro||Balick|
|Short Questions about Miscellaneous Topics|
|Marbles in a Beaker||Intro||?|
At right is a pictogram of the Earth, with the labels of various locations on the Earth listed. Match up the locations with the descriptions of the sky from that location. More than one location may apply to each description.
|Location||Description of Sky|
|a. North Pole||_________||1. The Sun can be seen at the zenith twice during the year.|
|b. North of the Arctic Circle||_________||2. North circumpolar stars are seen.|
|c. Arctic Circle 66.5 deg N latitude||_________||3. The Sun can be seen at the zenith only once during the year.|
|d. South of the Arctic Circle||_________||4. North celestial pole seen at the zenith.|
|e. North of the Tropic of Cancer||_________||5. All stars rise and set.|
|f. Tropic of Cancer||_________||6. All northern stars are circumpolar.|
|g. South of the Tropic of Cancer||_________||7. Celestial poles are seen on the horizon.|
|h. North of the Equator||_________||8. South celestial pole is seen at the zenith.|
|i. Equator||_________||9. All southern stars are circumpolar.|
|j. South of the Equator||_________||10. The ecliptic can be seen directly overhead at local noon on June 21.|
|k. North of the Tropic of Capricorn||_________||11. The ecliptic can be seen directly overhead at local midnight on December 21.|
|l. Tropic of Capricorn||_________||12. The Sun is at the zenith on March 21.|
|m. South of the Tropic of Capricorn||_________||13. The Sun fails to rise above the horizon between March 21 and September 21.|
|n. North of the Antarctic Circle||_________||14. Only place on Earth where Pisces and Virgo can be seen at the zenith.|
|o. Antarctic Circle 66.5 deg S latitude||_________||15. Location that is closest to the Sun at winter solstice.|
|p. South of the Antarctic Circle|
|q. South Pole|
Summary In this homework, you will learn the types of objects in the Universe, develop an idea of the sizes of objects and the typical distances between them. You will also recall how to express very large numbers using powers of ten notation. A scientific calculator will help you. Background and Theory Suppose someone asks you how far it is from Seattle to Vancouver, B.C. You might reply "Oh, about three hours." Obviously, what you mean is that a car traveling at about 50 mph can drive the distance in three hours. So the distance is "three car hours". We can launch rockets that travel at about 25,000 mph, or 40,000 km/hr. Such rockets can orbit the Earth in just over an hour. The circumference of the Earth is "one spaceship-hour". Similarly, the Moon is about 1/2 a spaceship-day away. Questions:
|Object||Diameter (km)||Diameter (spaceship travel-time)|
|Moon||my answer The diameter of the Moon (D) is 3,476 km.|
|Milky Way Galaxy|
|Virgo Cluster||1.67X1019 km|
|Object||Distance (km or A.U.)||Distance (light travel time)|
|Nearest Star (not the Sun)|
|Nearest Large Galaxy (M31)||2 Mly = 2 million light years|
|Nearest Cluster of Galaxys|
SummaryIn this lab you and your lab partner will be assigned a month of the year. You're going for a virtual all-expense-paid, one-weekend trip (Friday evening to Sunday evening) to get a great suntan in your appointed month. Where will you go? How do you select the perfect place? My report is I go to San Diego since it is not too hot for those unwanted sun burns while getting a tan. More damage to skin could come if went to Valparaiso since the temperatures are in the low 70s and upper 60s. Not a lot of sunshine in Seattle or Barrow. Colder. More likely to get skin cancer in San Diego then in Seattle or Barrow. More sun rays of sun light in San Diego. Mean Monthly Temperatures at Five Locations Avg Daily Temps (oF) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Valparaiso (33oS) 72 72 70 67 64 60 62 63 64 66 68 71 Quito (0oS) 59* 59* 59* 58* 58* 58* 58* 59* 59* 59* 59* 59* San Diego (33oN) 55 56 57 59 62 64 68 69 67 64 61 57 Assignment The heart of this lab is sorting through your options, which are many and complex. This is where your discussions with your lab partner are of central importance.
Be sure to write up and submit your recommendation independently. There is no right answer, only a reasonable one. We want to see how you added structure to an ambiguous problem in formulating a decision.In a few short paragraphs, state where you would go and why you selected that location. The quality of your answer is much more important than the quantity. Your grade depends on the strength, clarity and conciseness of your arguments. Insofar as your grade is concerned, we're looking for a strong astronomical rationale. This is an astronomy class after all. So state very clearly all of the astronomical criteria you considered, and whether you treated them as primary or secondary in importance. But that isn't all there is to this problem. The non-astronomical considerations are also germane. Mention three issues which you considered. How did these issues affect your decision? (Please be specific as well as brief.)
There are many challenges in identifying the best place to suntan. So before you proceed much further think carefully about what they are. Consider the relevance of such things as the duration of daylight, the height of the Sun, etc. Weather is another issue. And don't forget about skin cancer. Finally, if you select a very remote beach, keep in mind that you'll have to squander a lot of time getting to and from it by helicopter. To make your job a lot easier, here are some average temperatures for cities along the west coast of the Americas at various latitudes.
|Avg Daily Temps (oF)||Jan||Feb||Mar||Apr||May||Jun||Jul||Aug||Sep||Oct||Nov||Dec|
|San Diego (33oN)||55||56||57||59||62||64||68||69||67||64||61||57|
|* Quito is cool owing to its altitude of 12,000 feet. Add 30 degrees for the temperatures at sea level at this latitude.|
Below, you'll find a table with some useful astronomical data for these same cities. If you need it, there's quite a bit of additional data on these cities in various atlases in Suzallo or public libraries. Feel free to use Redshift in Suzallo or the Computer Lab in A214 (first check with your T.A. for access).
Date Rise Time Set Time Noon Altitude Rise Azimuth Set Azimuth Day Length 1/22 -- -- nevero above hor'zn -- -- 00:00 hr:m 2/22 9:37 AM 5:47 PM 9o above S hor'zn 120o=30o S of E(ESE) 240o=30o S of W (WSW) 3/22 6:18 AM 6:24 PM 20o above S hor'zn 85o (E) 275o (W) 4/22 4:34 AM 10:22 PM 31o above S hor'zn 45o=45o N of E (NE) 315o=45o N of W (NW) 5/22 -- -- 39o above S hor'zn -- -- 24:00 6/22 -- -- 42o above S hor'zn -- -- 24:00 7/22 -- -- 39o above S hor'zn -- -- 24:00 8/22 4:44 AM 10:12 PM 30o above S hor'zn 47o=43o N of E (NE) 312o=42o N of W (NW) 9/22 7:06 AM 7:32 PM 19o above S hor'zn 87o= 3o N of E (E) 273o= 3o N of W (W) 10/22 9:20 AM 5:02 PM 8o above S hor'zn 124o=34o S of E (ESE) 236o=34o S of W (WSW) 11/22 -- -- nevero above hor'zn -- -- 00:00 12/22 -- -- nevero above hor'zn -- -- 00:00Location: Seattle Latitude: 48o N
Date Rise Time Set Time Noon Altitude Rise Azimuth Set Azimuth Day Length 1/22 7:48 AM 4:55 PM 23o above S hor'zn 119o=29o S of E(ESE) 241o=29o S of W (WSW) hr:m 2/22 7:03 AM 5:43 PM 32o above S hor'zn 104o=14o S of E (E) 256o=14o S of W (W) 3/22 6:09 AM 6:25 PM 43o above S hor'zn 88o (due E) 272o (due W) 4/22 5:08 AM 7:09 PM 54o above S hor'zn 71o=19o N of E (E) 289o=19o N of W (W) 5/22 4:24 AM 7:48 PM 63o above S hor'zn 57o=33o N of E(ENE) 302o=32o N of W (WNW) 6/22 4:11 AM 8:11 PM 66o above S hor'zn 52o=38o N of E(ENE) 307o=37o N of W (WNW) 7/22 4:34 AM 7:57 PM 63o above S hor'zn 58o=32o N of E(ENE) 302o=32o N of W (WNW) 8/22 5:14 AM 7:10 PM 54o above S hor'zn 71o=19o N of E (E) 288o=18o N of W (W) 9/22 5:56 AM 6:08 PM 43o above S hor'zn 88o (due E) 271o (due W) 10/22 6:38 AM 5:09 PM 31o above S hor'zn 105o=15o S of E (E) 254o=16o S of W (W) 11/22 7:24 AM 4:26 PM 22o above S hor'zn 120o=30o S of E(ESE) 240o=30o S of W (WSW) 12/22 7:55 AM 4:20 PM 19o above S hor'zn 125o=35o S of E(ESE) 235o=35o S of W (WSW)Location: San Diego Latitude: 33o N
Date Rise Time Set Time Noon Altitude Rise Azimuth Set Azimuth Day Length 1/22 6:49 AM 5:11 PM 38o above S hor'zn 113o=23o S of E(ESE) 247o=23o S of W (WSW) hr:m 2/22 6:24 AM 5:40 PM 47o above S hor'zn 102o=12o S of E (E) 259o=11o S of W (W) 3/22 5:50 AM 6:01 PM 58o above S hor'zn 89o (due E) 271o (due W) 4/22 5:11 AM 6:23 PM 69o above S hor'zn 75o=15o N of E (E) 285o=15o N of W (W) 5/22 4:45 AM 6:45 PM 78o above S hor'zn 65o=25o N of E(ENE) 295o=25o N of W (WNW) 6/22 4:41 AM 7:00 PM 81o above S hor'zn 61o=29o N of E(ENE) 299o=29o N of W (WNW) 7/22 4:55 AM 6:54 PM 77o above S hor'zn 65o=25o N of E(ENE) 295o=25o N of W (WNW) 8/22 5:16 AM 6:26 PM 69o above S hor'zn 75o=15o N of E (E) 284o=14o N of W (W) 9/22 5:36 AM 5:45 PM 57o above S hor'zn 89o (due E) 271o (due W) 10/22 5:58 AM 5:08 PM 46o above S hor'zn 103o=13o S of E (E) 257o=13o S of W (W) 11/22 6:25 AM 4:44 PM 37o above S hor'zn 114o=24o S of E(ESE) 246o=24o S of W (WSW) 12/22 6:47 AM 4:47 PM 34o above S hor'zn 118o=28o S of E(ESE) 242o=28o S of W (WSW)Location: Quito Latitude: 0o S (note: alt=12,000 feet)
Date Rise Time Set Time Noon Altitude Rise Azimuth Set Azimuth Day Length 1/22 6:22 AM 6:29 PM 71o above S hor'zn 110o=20o S of E(ESE) 250o=20o S of W (WSW) 12:07 hr:m 2/22 6:24 AM 6:31 PM 80o above S hor'zn 100o=10o S of E (E) 260o=10o S of W (W) 12:07 3/22 6:18 AM 6:24 PM 90o=overhead 89o (due E) 271o (due W) 12:06 4/22 6:09 AM 6:16 PM 78o above N hor'zn 78o=12o N of E (E) 282o=12o N of W (W) 12:07 5/22 6:07 AM 6:14 PM 69o above N hor'zn 70o=20o N of E(ENE) 290o=20o N of W (WNW) 12:07 6/22 6:13 AM 6:19 PM 66o above N hor'zn 66o=24o N of E(ENE) 294o=24o N of W (WNW) 12:06 7/22 6:17 AM 6:24 PM 69o above N hor'zn 70o=20o N of E(ENE) 290o=20o N of W (WNW) 8/22 6:14 AM 6:20 PM 78o above N hor'zn 78o=12o N of E (E) 282o=12o N of W (W) 9/22 6:04 AM 6:10 PM 90o=overhead 89o (due E) 270o (due W) 10/22 5:55 AM 6:02 PM 79o above S hor'zn 101o=11o S of E (E) 259o=11o S of W (W) 11/22 5:56 AM 6:04 PM 70o above S hor'zn 110o=20o S of E(ESE) 250o=20o S of W (WSW) 12/22 6:08 AM 6:17 PM 67o above S hor'zn 113o=23o S of E(ESE) 247o=23o S of W (WSW)Location: Valparaiso Latitude: 33o S (note: on Pacific Coast due West of Santiago)
Date Rise Time Set Time Noon Altitude Rise Azimuth Set Azimuth Day Length 1/22 6:01 AM 7:59 PM 76o above N hor'zn 114o=24o S of E(ESE) 246o=24o S of W (WSW) hr:m 2/22 6:31 AM 7:53 PM 67o above N hor'zn 103o=13o S of E (E) 257o=13o S of W (W) 3/22 6:53 AM 6:58 PM 56o above N hor'zn 90o (due E) 270o (due W) 4/22 7:16 AM 6:18 PM 44o above N hor'zn 76o=14o N of E (E) 284o=14o N of W (W) 5/22 7:37 AM 5:53 PM 36o above N hor'zn 66o=24o N of E(ENE) 294o=24o N of W (WNW) 6/22 7:52 AM 5:49 PM 33o above N hor'zn 62o=28o N of E(ENE) 298o=28o N of W (WNW) 7/22 7:47 AM 6:03 PM 36o above N hor'zn 66o=24o N of E(ENE) 294o=24o N of W (WNW) 8/22 7:19 AM 6:24 PM 45o above N hor'zn 76o=14o N of E (E) 284o=14o N of W (W) 9/22 6:39 AM 6:45 PM 56o above N hor'zn 90o (due E) 270o (due W) 10/22 6:00 AM 7:07 PM 68o above N hor'zn 104o=14o S of E (E) 256o=14o S of W (W) 11/22 5:34 AM 7:35 PM 76o above N hor'zn 115o=25o S of E(ESE) 256o=26o S of W (WSW) 12/22 5:36 AM 7:58 PM 80o above N hor'zn 119o=29o S of E(ESE) 241o=29o S of W (WSW)Notes:
The asteroid would be a brightness of 1.
AssignmentDesign a scale model of the solar system and its nearest neighbor. Your model should include the following:
My model is *Sun *Earth *Moon *Mars *Jupiter *Pluto * Alpha Centauri Object Distance (km) Angular size (") Sun 1.5 X 10 8 1800 Mars distance from the sun is 1.5237 a.u. 2.279 x 10 8 km. Jupiter 5.2028 a.u. 7.783 x 10 8 km. Pluto 6.3 x 10 9 0.06 All of the relevant numbers for the sizes and distances for these objects can be found in the appendices (1) of the text book. To convert them to your scale, simply divide them by your chosen scale factor. For example: If you choose to make a 1/10th scale model, you would then make the Earth (with a real radius of 6378 km) have a radius of 637.8 km in your model. Obviously, picking the correct scale is important. Making a 1/10th scale model of the Earth isn't very useful, but making a 1/1000th scale model of a doll house isn't going to be much good either. So choosing the right scale to display your information is important. If you are having trouble choosing a scale (or with any other part of this assignment) talk to your TA.
What to turn in:
(1) - The Appendices: The back of astronomy textbooks are full of data tables of useful information. For this project, the most useful parts are unit conversions, the information on the sun, and the information on the planets. The semi-major axis is the average distance from the planet to the sun. Alpha-Centauri is just like the sun in size.
The exercise is much harder than it looks. You may work with a partner, but everyone must turn in their own version.
Assignment Sizes will be measured in light-seconds, light-hours, light-years, etc. A light-unit is the distance travelled by light in the indicated time. For example, since light travels at a speed of 300,000 km/sec, a light-second is 300,000 km. A light year (l-y) is the distance travelled by light in one year, or:
Your job is to fill the empty parts of the table below with examples of objects or distances of the appropriate size. You may not be able to fill all of the entries (feel free to leave any two boxes empty). Your entries in the table should follow the examples shown below. The words "distance" or "size" should appear in each entry along with a corresponding number rounded to the nearest power of 10.
Be as complete as you can. You may need to browse through the entire text to find the answers. Even better is the videotape "Powers of 10" available at the media center of the Oedegaard undergraduate library (mezzanine level). For faster service mention Astronomy 101 when requesting the tape.
There is no value in being highly precise in your answers. That's why the range of powers of ten is shown in each box. We're just looking for scale sizes. Its like saying that people are larger than rain drops (a few millimeters) and smaller than cars (a few meters).
|Approx Size||Example of object size or distance from Earth|
|10-18 - 10-15 l-s||size of atom = about 10-19 light-sec|
|10-15 - 10-12 l-s|| |
|10-12 - 10-9 l-s|| |
|10-9 - 10-6 l-s||size of person = few x 10-9 light-sec|
|10-6 - 10-3 l-s|| |
|10-3 - 100 l-s|| |
|100 - 103 l-s||distance to Moon = about 1 light-sec|
|103 -106 l-s|| |
|106 - 109 l-s
note: 107.5 l-s = 1 l-y
|distance to nearest stars = a few light years
(Switch to the more reasonable units of light years hereafter...)
|103 - 106 l-y|| |
|106 - 109 l-y|| |
|109 - 1012 l-y|| |
|1012 - 1015 l-y|| |
Assignment This is a little exercise on "global warming". You will be given a month of the year. For your month you are to go and look up the year which had the highest high temperature and the lowest low temperature on EACH day of that month. You can find this information by looking up old local newspapers (the weather page should have the information you need) or in an almanac.
Then you should plot two histograms of the distribution of "hot" years and "cold" years, and comment on what you find. Do you see a trend? Is it significant? What does this data suggest about the possibility of global warming? Are there problems with the data?
Comment briefly (1-2 paragraph), on your results. Also, mention where you got your information from, the name of the almanac or newspaper. You may work in pairs to collect your data, but you must each turn in your own write-up.
Life on Europa?
Given information about life living under extreme conditions on Earth and the evidence for a liquid ocean on Europa, the students will summarize their position in the "Life on Europa" debate and judge whether or not further exploration is warranted.
This is a web-research activity. Your first goal is to find and read enough information to be able to present, in a few paragraphs, the arguments for and against the possibility of primitive life in the liquid oceans underlying Europa's icy surface. Your second goal is to judge whether or not we should be funding future probes to Europa.
Because this is an essay and not a lab, some initial guidance is definitely warranted. First, because we are looking for life that can live under hostile and exceptional conditions, we need to formally define some terms. As you review the following "definitions," be sure to read the supporting links for needed information.
The term exobiology means is the study of life beyond the Earth. But since there's no known life beyond the Earth people say its a subject with no subject matter. It refers to the search for life elsewhere, Mars, the satellites of Jupiter and in other solar systems. It is also used to describe studies of the origin of life on Earth, that is, the study of pre-biotic Earth and what chemical reactions might have taken place as the setting for life's origin. From An interview with exobiology pioneer, Dr. Stanley L. Miller, UCSD
Life on Earth is remarkably adaptable. Organisms are able to survive under conditions previously thought impossible. Specific examples of extreme environments that harbor life are sea ice, sub-seafloor hydrothermal systems, and subterranean basalt. From University of Washington astrobiology research pages.
This is a term you will be coming across frequently in your reading. "Archaeans don't look that different from most bacteria under the microscope; since most of them are extremely difficult to culture, their unique place among living organisms long went unrecognized. However, biochemically and genetically, they are as different from bacteria as you are. Although many books and articles refer to them as 'Archaebacteria,' they aren't bacteria - they're archaea."
Archaeans include inhabitants of some of the most extreme environments on the planet. For further information, see Introduction to the Archaea from UC Berkeley.
Type up your responses for the following topics. Your essay should be in narrative form, having good paper structure, and not simply rote answering of the questions. Put in a good opening paragraph that will let the reader know what is to follow. You do not need to go into great detail in any of the areas, but you must show you have read the material and are "qualified" to enter into the scientific debate. Nicely constructed two-three paragraphs for each should do. Be sure to bring in information from the above readings and what you have learned during this quarter.
Start by describing the evidence suggesting Europa may have a subsurface ocean of liquid water. Besides your text, check out Cracks Best Evidence Yet for Europan Ocean.
Summarize the arguments supporting the likelihood of life on Europa. See Could Life Exist Near Europa's Surface? from Space Views.
We may wish for little phosphorescent aliens with swollen heads, big eyes, and long limbs, but we probably aren't going to get them. What are the arguments against complex life on Europa? See Complex Europan Life Unlikely from Space Views.
The above two articles give some ideas about how to answer some of our questions. Describe two space programs, present or future, for the exploration of Europa. Additional information can be had at NASA's Europa Orbiter mission.
Should we go there? Here is an article about possible contamination by life hitch-hiking on Earth probes. Summarize a couple of NASA's concerns.
Give your overall evaluation of the "Possible Life on Europa," and judge whether or not funds should be spent on sending probes to Europa in the future. That is, enter into this debate on a preliminary basis. You may take any approach or stance of your choosing. Points awarded for a convincing argument, for evidence of having carefully considered the alternatives, for bringing in knowledge gained from the past weeks spent in Astronomy 150u.
|The total essay should be about 2-3 pages long (12 pt, space-and-a-half, 1" margins -- or single spaced with double spaces between paragraphs). Your essay will be graded upon the clarity of your writing, indication that you have reviewed the material, and overall good writing techniques.|
So, now you want to become an astrobiologist. You can, you know. Study hard and then apply to become a graduate student in the first astrobiology PhD program in the States. Check out the University of Washington Astrobiology Program, a cross-disciplinary study in the possibility of life beyond Earth.
catalog of Europan links
A different approach to the debate of liquid water and life on Europa
Europa Web Sites
Extremophiles Scientific American, April 1997.
Some very serious considerations about
Preventing the Forward Contamination of Europa
from The National Academies.
a. What is the angle between the traffic light and the sun for the driver?
You may wish to draw a diagram to help you visualize this. I will also describe the situation if asked.
b. Will the angle between the traffic light and the sun increase or decrease as the car moves closer to the light?
Solids and dense gases give off a continuous spectrum of electromagnetic radiation simply due to the thermal motion of the atoms and molecules jostling each other about. For example, a chunk of lead is heated to 1,000 degrees Kelvin, then 2,000 degrees Kelvin, then 3,000 degrees Kelvin. The amount of electromagnetic radiation given off at each wavelength of the spectrum is measured, using a light meter. The following results are obtained:
|AMOUNT OF EM RADIATION EMITTED|
|at 1,000 K||at 2,000 K||at 3,000 K|
|4,000||8.7 X 10-7||56||23,000|
|5,000||3.8 X 10-4||675||82,000|
a) Graph the amount of EM radiation emitted versus wavelength for each temperature all on one plot. (So you should have 3 curves, one for each temperature, on your graph. Put wavelengths on the horizontal axis (from 4,000 to 40,000 angstroms), and amount of radiation emitted on the vertical axis (from 0 to 350,000 ergs/cm2/s/angstrom).
b) Referring to Figure 4-3 on p. 48 of your text, label the type of electromagnetic radiation that corresponds with the wavelengths on your horizontal axis (for example, "x-rays", "blue visible light", "radio").
c) The peak of the curve shows the wavelength at which most of the radiation is being emitted. At which temperature would you most likely be able to see radiation with your naked eye? Explain your answer.
d) From the three curves you plotted, at which temperature does the lead give off the most radiation at ALL wavelengths?
e) Describe how your graph would be different if a chunk of aluminum were heated instead of a chunk of lead. Note that aluminum has 13 protons and lead has 82 protons.
a) The above section described radiation from a solid chunk of material. The spectrum of a thin gas (many examples of which are in the spectroscopy lab) is very different from the thermal radiation spectrum of a solid or dense gas. How is the spectrum different?
b) Describe how a photon would interact with the atom drawn at right to create:
i) an absorption line
ii) an emission line
c) The above hydrogen atom absorbs a photon which has just the right amount of energy to kick the electron from the 2nd energy level to the 3rd. When this energized atom relaxes, how will the wavelength of the emitted photon compare with the wavelength of the photon which was absorbed?
d) The spectrum from a star has continuous thermal radiation with absorption lines. Explain how this could be (a drawing may be helpful).
a) Suppose you observe three stars with both a red and a blue filter. Star A is brighter in the blue than in the red. Star B is brighter in the red than in the blue and Star C is equally bright in both the red and the blue. With this information, put the three stars in order of increasing temperature. Explain briefly how you got your answer.
b) Suppose you see two stars with the same color--the peak of the thermal radiation curve is at the same wavelength. Yet one star appears 100 times brighter than the other. What can you conclude?
The sun gives off energy all of the time. This is the energy that all life
uses to grow and live; whether directly (as photosynthesis by plants) or
indirectly (as herbivores and carnivores that consume the energy stored in
living things). Without that energy source, the Earth would be a dark,
cold, lifeless place. So, it is certainly of interest to ask "Will the
Sun be there tomorrow?", or, more usefully, to ask when the sun will stop
shining. In other words, how long will the sun last?
The goal of this homework assignment is to answer that question. > The Sun formed from a spinning cloud of gas through gravitational collapse. The planets formed at the same time. So the ages of the planets provide a good estimate of the age of the Sun: 4.5 billion years. The Sun has been shining brightly, at almost exactly the same rate (a constant luminosity), for 4.5 billion years. This implies that it has been producing energy at a constant rate for those 4.5 billion years.
Mass of 1 Hydrogen atom: 1.673 x 10-24 grams Mass of 1 Helium atom: 6.644 x 10-24 grams
- Luminosity - energy per second; usually the total energy given off by an object per second.
- 1 Watt = 107 ergs/sec
- 1 Solar Luminosity = 3.89 x 1033 ergs/sec
- Energy - Bah. Try and define that. Usually measured in ergs; an erg is about the energy of one flea jump.
- 1 erg = 1 gm*cm2/sec2 = 10-7 joules
- [if you use E=mc2 with the mass in grams, the speed in cm/sec, then you get E in gm*(cm/sec)2, which is gm*cm2/sec2 = ergs]
- Mass - the amount of matter. Usually measured in grams, or solar masses.
- 1 solar mass = 1.989 x 1033 gm
- 1 hydrogen atom = 1 proton = 1.67352 x 10-24 gm
- Speed - velocity; distance traveled per time unit. Measured in lots of units; We'll use cm/sec because of the definition energy in ergs
- Speed of light = c = 3.00 x 1010 cm/sec = 300,000 km/sec
- Time - measured in seconds, days, months, years.
- 1 year = 3.15 x 107 seconds