Astronomy 115-03 Fall 2009

I will use this space to post announcements about the class, scheduling, homework assignments, exam results, etc. If you miss class, check here first to see if you missed anything!

Reading for next Tuesday: Chapter 13 and Section 15-1

11/19/09:
Today's lecture focused on the collection of stars that our solar system resides in, the Milky Way. We went over the basic structure of our galaxy, did the Milky Way Scales lecture tutorial, then looked at why our galaxy looks the way it does. We talked about how star formation is linked to the galaxy's spiral shape, and how we measure the vast distances to other stars in the Milky Way. Parallax turns out to be too limited for this case, so instead we use Cepheid Variable stars (which are a type of standard candle). Next, we looked at how we measure the mass of our galaxy and looked briefly at the properties of the supermassive black hole at the center of our galaxy. I showed a short movie of the orbits of stars near the black hole. I also handed back graded Homework #6. After the holiday, we will start looking at other galaxies and the structure of the Universe as a whole.

Reading for Thursday: Chapter 12

11/17/09:
At the beginning of today's class we did a quick review of the life cycles of stars, then finished up talking about supernovae. Next we talked about what happens to the leftover cores of very massive stars when they die. We discussed neutron stars and pulsars (which are a kind of spinning neutron star with a very strong magnetic field). After that, we moved on to black holes. We discussed how they form, why light cannot escape from them, and how we can indirectly detect them since they give off no light. We also looked at what happens near a black hole's event horizon, and what might happen to someone if they fell into a black hole. At the end of class we did a few voting questions, and a writing activity to tie together the big ideas from stellar evolution.

Furlough Activities and Reading for Tuesday: Finish Chapters 10 and 11, do "Star Formation and Lifetimes" (pp. 111-112) and "Stellar Evolution" (pp. 121-122) lecture tutorials

11/10/09:
Today we began class with a voting question to refresh our memories about how a star's mass is related to its lifetime on the main sequence. Next, we looked at how a star's mass influences what will happen to it after it can no longer fuse Hydrogen into Helium. We discussed the evolutionary paths for low, average, and high-mass stars along the main sequence. We saw how giants, supergiants, and white dwarfs are formed, and also talked about planetary nebulae and supernova remnants. We will finish up a bit more about supernovae next Tuesday, then talk about what happens to the leftover cores of extremely massive stars. Don't forget that class will not be meeting on Thursday, so you will be responsible for the two lecture tutorials listed above.

Reading for Tuesday: Finish Chapter 9, Sections 10-1, 10-2, and 10-4 (10-3 is optional)

11/05/09:
I handed back homework #5 today, and we began our tour through the life cycle of a star. We looked at the origins of stars, and how they form our of the huge clouds of gas and dust scattered throughout the galaxy called nebulae. We looked at the differences between a reflection nebula, an emission nebula, and a dark nebula, and saw several examples of each type. Next, we watched a short movie from a computer simulation of star formation which can be found here. Then we talked about how all stars are on the Main Sequence after the first form, and how they remain stable while they slowly fuse hydrogen into helium. We learned about hydrostatic equilibrium, and saw how stars can self-correct to small changes in thier density or rate of fusion. On Tuesday we will hand in Homework #6 and continue on with the deaths of stars.

Reading for Thursday: Sections 9-1 through 9-3

11/03/09:
Unfortunately, today the projector was broken in class so we had to go through the lecture without slides. I did a quick review of where we left off last Tuesday, then introduced the Hertzsprung-Russel Diagram. We looked at the basic layout of the diagram, its axes, and where stars fall within the diagram. We looked at the differences between Main Sequence stars, Giants, Supergiants, and White Dwarfs, and how their properties compare. We identified several trends in the properties of stars along the Main Sequence, then did the HR Diagram lecture tutorial. Next, we talked about the lifespans of stars and how they are based on the star's mass, and saw how masses of stars are measured through the orbits of binary stars. Finally, we discussed the differences between those stars that appear brightest from Earth and those that are nearby, and learned about the "Potato Chip Rule."

Reading for Tuesday: Finish Chapter 8, section 9-1

10/29/09:
Today we took the second midterm during class. I will be posting scores here on the website by the last four digits of your Student ID number. Results will probably be available here by Friday afternoon, and I will post a physical list outside my office on Tuesday. Update 5PM: Scores are up!

Midterm #2 is on Thursday! (No Reading)

10/27/09:
Today we picked up with a quick review of parallax, and did some voting questions to make sure everyone had the basics before moving on. Although we won't have time to do the Parallax and Distance lecture tutorial in class, I would recommend it as part of your studying for the midterm on Thursday (see above for a review sheet). We learned about the difference between apparent magnitude and absolute magnitude, and how brightness is related to distance (although luminosity is not). Next, we looked at the range of luminosities and sizes that a star can have through a series of artists' drawings, and learned about the relationships between luminosity, temperature, and radius. We did the Luminosity, Temperature, and Size lecture tutorial, then answered some voting questions and midterm review questions at the end of class.

Reading for Tuesday: Sections 8-1 through 8-3

10/22/09:
Today we began with a quick recap from Tuesday's lecture on the difference between nuclear fusion and nuclear fission, and then looked at how the Sun uses the proton-proton chain to fuse hydrogren nuclei into helium nuclei. I showed this video of the individual steps of the proton-proton chain, and then we looked at the time scales of each step individually. We also made some predictions about how fusion works and tested them with this demo. Next, we started Chapter 8, which begins with parallax and the method of measuring a star's distance using its parallax angle. At the end of class we got started on the Parsec lecture tutorial, which we will finish up on Tuesday.

Reading for Thursday: Sections 7-2 and 8-1

10/20/09:
Today we started off by looking at the basic properties of the Sun, then looked more closely at the Sun's outermost layers. We also covered the different forms of solar activity, and spent some time with sunspots in particular. We saw how solar activity is connected to the Sun's magnetic field. I showed a movie of granulation that can be found here and you can see a vidio of the rotation of the Sun here via the website spaceweather.com. We talked then about solar flares and prominences, then looked at a movie of a coronal mass ejection from the Solar and Heliospheric Observatory (SOHO). Since we were running ahead of schedule, I started the next set of slides which deal with the Sun's interior: the core, the radiation zone, and the convection zone. We looked at other unsuccessful attempts to explain the Sun's lifetime and luminosity, and on Thursday we will delve deeper into the process of fusion.

Reading for Tuesday: Sections 7-1 and 7-3

10/15/09:
We began today's class by looking at the spectral classification system (OBAFGKM), which is how astronomers tell different types of stars apart according to their temperature and their spectral features. Next we moved on to the Doppler Effect and how it can shift the wavelengths of absorption lines in the spectra of stars. We also did the Doppler Shift lecture tutorial. This demo is a nice graphical display of the Doppler Effect. Next week we will start Chapter 7, which deals with the Sun.

Reading for Thursday: Sections 6-3 and 7-1

10/13/09:
I'll be collecting Homework #4 today until 4PM, so if you didn't hand it in during class make sure you stop by my office. We started class off with a brief review of how atoms can abosrb or emit light, and I showed the hydrogen atom demo before we got to our voting questions. Next, we looked at the basics of a blackbody spectrum, which is a way for us to model the spectra of stars. We saw that the area under the blackbody curve is related to the total energy output of the star, while the wavelength of the peak tells us the temperature and color of the star. We did the Blackbody Radiation lecture tutorial, then I did a recap of the rules concerning blackbodies, temperatures, colors, and total energy outputs.

Reading for Tuesday: Sections 6-2 and 6-3

10/08/09:
We began Chapter 6 today, which deals with how light interacts with matter. We looked at the structure of an atom, and how electrons in an atom can absorb or emit energy. I also explained how this absorption or emission can be read in the spectrum of the light. You can check out how this works using this demo of the hydrogen atom. Next, we did the Light and Atoms lecture tutorial, andon Tuesday we will go over some of the trickier questions relating light, color, and energy. I also handed back graded homework #3, which you can pick up in my office if you didn't get it before or after class.

Reading for Thursday: Sections 6-1 and 6-2

10/06/09:
Today in class we moved our focus to telescopes. We learned about the basic functions of a telescope and how lenses can bend or refract light, allowing us to see faint, distant objects. We learned about how light-gathering power and angular resolution are connected to the size of the objective lens or mirror, and that magnification is usually the least important function of a telescope. Next, we looked more closely at how telescopes work within the context of Earth's atmosphere, and reviewed how the atmosphere absorbs or transmits different parts of the EM spectrum. We did the Telescopes and Earth's Atmosphere lecture tutorial, and then had some discussion about the real-world scenarios of government funding agencies choosing between astronomy projects.

Reading for Tuesday: Sections 5-2 through 5-5

10/01/09:
We began chapter 5 today, which looks at the basics of observing astronomical objects. Before we can talk about telescopes, we have to understand what we're looking at: light. Today's lecture focused on understanding light and the properties that astronomers use to characterize light. We looked at how light can have a wavelength and frequency (like a wave on the ocean), and how it can also carry energy. We also learned that all light travels at the same speed, regardless of how much energy it carries. This demo has a nice interactive version of the entire EM spectrum. We looked at the different properties of gamma rays, x-rays, ultraviolet, visible, infrared, and radio waves and did the EM Spectrum lecture tutorial. At the end of class we did a few voting questions, and talked about the differences between red light and blue light.

Reading for Thursday: Section 5-1

09/29/09:
Today we handed in Homework #3 and took the first midterm during class. I will compile the scores and post them both here and outside my door according to the last four digits of your Student ID number. They should be up by tomorrow afternoon at the latest. Update: Midterm scores are posted above!

09/24/09:
Today's lecture centered on Newton's laws of motion and gravity. We learned that mass and distance both affect the strength of the gravitational force, and how gravity governs the motions of planets as they orbit around the Sun. We also looked in depth at Newton's three laws of motion and how they are connected to the force of gravity. We did the Newton's Laws and Gravity lecture tutorial near the end of class, but ran out of time for our voting question. When reviewing for our midterm on Tuesday, it will be very helpful to have already completed the gravity questions on Homework #3. Additionally, questions 4 through 9 from today's lecture tutorial will be important for the exam. More details on the midterm can be found in the review sheet posted above. I also handed back the second homework assignment, so if you did not pick it up in class you can come get it in my office.

Reading for Thursday: Section 4-5

09/22/09:
At the beginning of today's class we refreshed our memories about Copernicus and Galileo, then moved along by talking about the relationship between Tycho Brahe and Johannes Kepler. We spent the rest of class breaking down Kepler's laws and doing the lecture tutorial on Kepler's Third Law. This demo is a good way to look at Kepler's laws in action, and I showed it several times in class. At the end of class we did a few voting questions, and we will finish up Chapter 4 on Thursday. Additionally, the first midterm is coming up in one week. You can find a review sheet posted in the above section; it contains a list of topics and lecture tutorials that will be covered on the exam along with the general structure of the exam and the type of scantron you'll need to provide.

Reading for Tuesday: Sections 4-3 and 4-4

09/17/09:
Today we started Chapter 4, which focuses on the astronomical community's shift from a geocentric (Earth-centered) universe model to a heliocentric (Sun-centered) universe model. We started out by looking at the basic greek model of the universe, and how it had to be modified to accomodate the prograde and retrograde motion of the planets across the night sky. We looked at Ptolemy's model, and saw how the deferents and epicycles work together to explain planetary motion in this demo. Next, we looked at Copernicus's model and how it can also explain planetary motion. We didn't get to this demo in class, but it nicely displays the Copernican model along with retrograde motion. Finally, we saw how Galileo's telescopic observations contradicted the basic ideas on which the geocentric model was based. Next time we will continue by looking at Tycho and Kepler.

Reading for Thursday: Sections 4-1 through 4-3

09/15/09:
The first homework assignment is graded, you may pick up your assignment at my office. The second homework is due today by 4PM. Please stop by my office to drop it off if you did not hand it in during class. Today we did a quick review of why the moon shows different phases, then did the Cause of the Moon Phases lecture tutorial. I also some more examples with the lunar phases demo linked in Thursday's entry. We also talked about how the position of the moon in its orbit determines the time of day it will appear in the sky. Next, we talked about how lunar and solar eclipses happen, and what they look like from Earth. To get updates on future eclipses, NASA has a good information page here. We are running about one lecture behind what is printed on the syllabus schedule, so we will start covering material from Chapter 4 on Thursday.

Reading for Tuesday: Sections 4-1 and 4-2

09/10/09:
I started off by doing a recap of the seasons from last week, and we looked at two more demos relating to our seasons. We also saw that the seasons are only connected to Earth's tilted axis, not by our distance from the Sun. Next, we started talking about the phases of the moon. I went over the different names of all the phases, and showed some diagrams explaining why we see different phases throughout the moon's orbit (which takes about one month). We looked at one more demo of the Earth, Sun, and moon. We are running a bit behind the lecture schedule, so we will finish up moon phases and eclipses on Tuesday before starting Chapter 4. I will post slides for the Chapter 4 material, but we will only barely be starting them on Tuesday.

Reading/furlough activities: Finish Chapter 3, do "Path of the Sun" and "Seasons" lecture tutorials (pp. 87-96)

09/03/09:
Today we covered more about observing the night sky. We learned how one's location on Earth or the time of year (determined by Earth's position in its orbit) both change what is visible on a given night. We did the Seasonal Stars lecture tutorial, and then did some quick introduction to how the Sun's path through the sky changes with the seasons. We saw that the Sun reaches its highest noontime height above the horizon on June 21 (the summer solstice) and its lowest noontime height on December 21 (the winter solstics). We also saw that this causes us to get longer days and more intense heat from the Sun in summer, and shorter days and less intense heat from the Sun in winter. I didn't get a chance to show this demo before the end of class, but it might be helpful in demonstrating some of these topics. Between now and next Thursday, I expect everyone to at least attempt the two lecture tutorials listed above, and we will begin our next class with more discussion of the seasons. I also collected the first homework assignment today; the second homework assignment will be posted above.

Reading for Thursday: Chapter 3

09/01/09:
We started off class with a short writing prompt dealing with the reading, and connected last week's lecture tutorial with the material being covered today. After a short review of positions on the sky, we learned how to measure distances on the sky using angles. Next, we looked more closely at the apparent motion of stars over the course of an evening and played around with the Rotating Sky Demo. We did the Motion lecture tutorial, and then answered some questions to make sure everyone understood the main points from the tutorial. On Thursday we will continue with more on the night sky and start looking at how the sky changes over a year rather than just over a day.

Reading for Tuesday: Finish Chapter 2

08/27/09:
Today we picked up with more units systems again, and had a quick review of scientific notation. We talked about the metric system for measuring lengths, and also covered the definition of Astronomical Units and the light-year. Next, we shifted our focus to finding our way around the night sky and making simple, naked-eye observations. We learned about the differences between constellations and asterisms, and how to find the North Star more easily. Next, we talked about the Celestial Sphere model and how it relates to our normal perspective of the night sky, as shown in this demo. We also did the Position lecture tutorial and had time for one voting question at the end of class. As for enrollment, we have been able to add the first four students on the wait list, and it looks very unlikely that we will be able to add anyone who is not on the wait list.

Reading for Thursday: Chapter 1 and Section 2-1

08/25/09:
Welcome to Astro 115! I collected a short questionnaire from everyone in class today to keep track of enrollment. We had about 200 students in the room today, so we are extremely full. I was able to add the first four students on the wait list due to no-shows, and will continue to make announcements about the enrollment status at the beginning of class. I spent some time going over the structure of our class and the policies outlined in the syllabus above, and on how this class is designed to help you learn. Next, we had a short introduction to astronomy and how it is influenced (both in broad and specific ways) by the scientific method. On Thursday we will pick up with systems of units. If you'd like to see the video "Powers of Ten" I showed in class, here's the YouTube link. I've also posted notes for today's lecture, and Thursday's class as well. You can also take a look at the first homework assignment.