Astronomy 10

Hi everyone,
One final thing. I’d really appreciate your feedback on your experience taking Astronomy 10 this summer. I’d be especially interested in hearing about what you guys liked and didn’t liked about the course, including the level of difficulty with the homeworks and exams. Did you find the projects as useful exercises or wastes of time? Don’t hesitate to let me know what you thought!

I’ve opened the comments section of this post to allow you guys to post the course evaluation. Thanks again and I look forward to hearing you guys have to say.

Hi everyone,
The grades are finally done! The median score in the class was an 88%, so it looks like a majority of you guys did extremely well in the class such that I didn’t feel the need to curve the final grades. I plan on submitted your final grades to Berkeley’s eGrades system later today, so they should be available sometime tomorrow or Sunday, but I’ll contact each of you individually over email with your final score. Thanks again for a great class and best of luck to each of you in the fall semester.

Here are some nice DIY astrophotography taken with a digital Rebel SLR snapped through the eye piece of the Meade LX200. Fun stuff!

Hi guys,
So the Perseid meteor shower peaks tomorrow night and should be visible in the northeastern sky starting around 11pm. The meteor shower is so named because the “shooting stars” will appear to be coming from the Perseus constellation. In fact, the Persieds are actually due to the Earth passing through the debris associated with the comet Swift-Tuttle as the Earth orbits the Sun.

The solutions to homework sets 3 and 4 are now online. You can find them at the link below.

Homework

Sorry guys, the clouds moved in over campus, so the star party has been canceled yet again. Let\\\’s try again on Thursday.

Sorry guys, looks like it\’s cloudy tonight so we\’re going to have to cancel the star party tonight. Let\’s aim to try again on Monday! Enjoy the weekend and good luck on your papers!

Please remember that the class paper is due on Monday, August 3rd! Feel free to contact me if you have any questions about formating, spacing, etc that isn’t covered in the syllabus!

So here’s some more information on the Pioneer 11 plaque that I mentioned today in class. It turns out that the unit used to describe the period of the 14 pulsars displayed on the plaque was the hydrogen spin-flip transition frequency. Quoting Wikipedia:

The Pioneer plaque, attached to the Pioneer 10 and Pioneer 11 spacecraft, portrays the hyperfine transition of neutral hydrogen and used the wavelength as a standard scale of measurement. For example the height of the woman in the image is displayed as eight times 21 cm, or 168 cm. Similarly the frequency of the hydrogen spin-flip transition was used for a unit of time in a map to Earth included on the Pioneer plaques and also the Voyager 1 and Voyager 2 probes. On this map, the position of the Sun is portrayed relative to 14 pulsars whose rotation period circa 1977 is given as a multiple of the frequency of the hydrogen spin-flip transition. It is theorized by the plaque’s creators that an advanced civilization would then be able to use the locations of these pulsars to locate the Solar System at the time the spacecraft were launched.

Hi everyone,
A few of you asked if I could post the stellar evolution movie that I played in class, so here it is in quicktime format.

Stellar Evolution Movie

The process depicted in the movie shows what happens to a star when it runs out of Hydrogen in it’s core. The core pressure decreases causing the core to contract under it’s own gravity. As it contracts, the pressure and temperature of the core increases. Eventually the core gets hot enough that the area immediately surrounding the core star starts to fuse fresh Hydrogen. The increased radiation pressure from the hot core and the Hydrogen burning shell puffs up the outer layer of the star, causing an increase in the luminosity of the star while at the same time decreasing it’s surface temperature. Eventually the core gets hot enough to start fusing He and the core expands due to the pressure from the fusion reactions. When this happens, the core cools slightly, decreasing the radiation pressure felt by the outer layers, causing them to deflate and reduce is size. This has the effect of decreasing the luminosity of the star while increasing it’s temperature. For stars like our sun, the star will eventually use up it’s He and the core will contract once more, get very hot and eventually blow off it’s out layers as a Planetary Nebula. For stars much greater than the mass of the sun, this contraction and expansion of the core will continue for every new element that the star is capable of fusing together until Fe builds up in the core and the star undergoes a supernova.