Cepheid Variable Lab Write-Up

Problem: Graph the apparent magnitude and the log of the period of a set of stars and use that information to determine a relationship between the two variables and use that information to calculate the apparent magnitude and distance of a star in SMC with the same period.

Hypothesis: I could tell from looking at the table of data that the relationship between apparent magnitude and the log(Period) would be fairly linear. I did not think, however, that using one set of data and the graph drawn from that set could give accurate results for the apparent magnitude and distance of a completely different star.

Procedure: 1) I plotted the table of values. 2) I drew a line of best-fit for the scatter plot. 3) I used that graph and line of best fit to determine the relationship between a Cepheid variable’s period and luminosity or apparent magnitude. 4) I used my line of best-fit to estimate the apparent magnitude of a star located in SMC (which has a period equal to that of delta-ceph). 5) I used the given equation to find the absolute magnitude of delta-cephei. 6) I then used that information and the given equation to find the distance of the star in SMC and expressed that answer in both parsecs and light years.

Data and Calculations: Can be found on the sheet and graph that will be handed in tomorrow.

Conclusion: From this lab I learned that the relationship between a star’s period and apparent magnitude is inverse and fairly linear. I also learned, to my surprise, that the apparent magnitude can be used to find the distance of a star that has the same period. The distance that I eventually determined for SMC was not too far off from the given answer but there was still a fair amount of error in my calculations. The error primarily came from my graph. I plotted my points by hand and the line of best-fit is always a total estimation. This is was a problem in this particular lab because a large part of my calculations were based on a number (the apparent magnitude of SMC) that was estimated using the line of best-fit on my graph so naturally you can see how a less-than-perfect line of best-fit would result in inaccuracy in determining the apparent magnitude. Another possible reason is the imprecision of my numbers as the rules for significant digits allows for a limited amount of precision.

Age of Stars Lab Write-Up

Problem: To find the ages of two clusters of stars by plotting stellar data on a color-magnitude diagram.

Hypothesis: I believe that the age of M45 will be significantly younger than that of 47 Tuc as 47 Tuc is a globular cluster and those tend to contain older stars.

Procedure: 1) I plotted both sets of data in the form of a scatter plot. 2) I identified the red giant stars on the graph and circled them. 3) I determined which of the two clusters is close to Earth. 4) I estimated the lifetimes of each of the clusters using the table provided that indicates lifetime as it relates to spectral type.

Data and Calculations: Can be found on the worksheet and graph that will be turned in tomorrow.

Conclusions: From this lab I learned how color and magnitude can be used to determine the rough age of a star or star cluster. My hypothesis was correct in that the stars in 47 Tuc are in fact older than the stars in M45. Possible error in this lab is found in the inaccuracy of the graph and the age estimate is only rough as we can only guess as to the spectral classification.

Spectral Classification Lab Write-Up

Problem: To understand the Morgan-Keenan system of spectral classification, find behavior of absorption lines and the relationship between wavelength, temperature, Balmer lines and spectral classification.

Hypothesis: Prior to doing the lab I thought that stronger Balmer lines would indicate a higher temperature.

Procedure: 1) I described the spectra in terms of flux pattern. 2) I estimated the Balmer line strength of each panel and ordered them from strongest to weakest lines. 3) I estimated the peak wavelength of each panel. 4) I used the estimated wavelengths to determine that temperature of each panel using Wein’s Law. 5) I used those temperatures to identify the hottest and coolest stars and ordered all panels from hottest to coolest. 6) I compared the order of temperature to the order of Balmer line strength to see if there was any relationship between the two.

Data and Calculations: Can be found on the lab worksheet that will be turned in tomorrow.

Conclusions: The lab helped me determine that there is somewhat of a relationship between Balmer line strength and temperature but the relationship isn’t entirely direct. I found that temperature was greatest in those stars with a Balmer strength that was neither low nor high. I was also reminded that peak wavelength is always a good indication of temperature and was given a greater understanding of how spectral classification can be used when you know the temperature of a given object (in this case, each panel of stars).

Sky Journel #7

Date: November 4, 2010
Time: 11:00 PM
Location: Crestview Lane, Mount Vernon, WA

The picture below is a replica I made of the sky as I saw it last night. The points have been drawn fairly large so that they’re able to be seen.
            a. Capricornus: Azimuth: 70⁰ Altitude: 300⁰ NW. I wasn’t able to see the head of Capricornus but I was able to make out the box-like body.
            b. Jupiter: Azimuth: 80⁰. Altitude: 40⁰ NE. I thought it was interesting to see how much Jupiter moved from when I viewed it last week whether that is due to the change of date or the time I went out.
            c. Fomalhaut: Azimuth: 10⁰. Altitude: 110⁰ SE. This star was fairly noticeable but I was really unsuccessful in trying to find the entire constellation, Piscis.

Sky Journel #6

Date: October 28, 2010
Time: 8:30 PM
Location: Crestview Lane, Mount Vernon, WA

The picture below is a replica I made of the sky as I saw it last night. The points have been drawn fairly large so that they’re able to be seen. With the help of Stellarium I was able to actually see full constellations because I had a better idea of what I was looking for but I’m still not convinced that they look like the shape that they’re supposed to look like.
            a. Piscis. Azimuth: 30⁰. Altitude: 190⁰ SW. This one was fairly hard to see because it was so low on the horizon.
            b. Capricornus: Azimuth: 75⁰. Altitude: 45⁰ NE. The connection of the stars looks a lot more like a bull to me but Stellarium lets you see the image over the constellation which is cool.
            c. Jupiter: Altitude: Azimuth: 90⁰. 230⁰ NW. I think this was Jupiter. It could have been a star but it stood out slightly in color.

Weekly Reflection 11/8-11/12

The most difficult part for me this week was the labs. I had to skip one of them to go to a corporate meeting and I had difficulty understand the math concepts for both. I think that the actual plotting of the data was time consuming and I realize it can be done on excel but I couldn’t figure out how to overlap both sets of data on the same scatter plot. Aside from the labs I found the lectures to be informative and it was awesome to have a holiday this week! As for the test, I think I did okay on it and I’m sooooo glad that we are able to have notes, it takes away a lot of the stress of memorizing and I think it allows us to think about concepts more when we aren’t worried about memorizing formulas and information. I did think that the test included a lot of writing but with a two hour block that isn’t too much of a big deal. Lastly, I liked seeing how different groups presented the same information on stellar evolution and seeing how a couple groups displayed the information helped me understand the stage-to-stage process.

Weekly Reflection 11/1-11/5

I didn’t have any trouble with the lab on Monday and the concepts this week were pretty easy to understand. The mythology on my constellation research was pretty interesting and I liked hearing about the mythology of everyone else’s in my group. At this point I don’t feel prepared for the test next week but there are a few things I can do to change that so I’m not too worried about it. My aha moment this week was learning about black holes as I’ve always heard about them but never really understood what they are and I think the evolution of stars is cool to see in picture form.

Weekly Reflection 10/25-10/29

The test this week went okay. I felt like I pretty much knew what would be on the test. I find Chapter 10 pretty easy to grasp as math is always easier for me to understand rather than concepts. I think it would have made more sense to study stars in this depth at the beginning of the quarter when we began looking at constellations and the celestial sphere. I unfortunately had to miss the lab on Friday but I have done it myself and didn’t have any difficulty with it.

Stellar Evolution APOD: Methuselah Nebula MWP1

        This picture features a planetary nebula at a distance of 4,500 light years away. Planetary nebula is one of the final stages of stellar evolution as the central star is shrugging off its outer layers to advance to a white dwarf and eventually cease of the life of the star. This particular nebula is one of the largest known with a diameter of nearly 15 light years and can be found in the constellation Cygnus the Swan. The average planetary nebulae typically last 10 to 20 thousand years but Methuselah Nebula has an age of 150 thousand years which has given astronomers great insight into the evolution of its central star. This star type is unique as you can physically see the star’s outside layers being shed in the pink and blue colored debris surrounding the central star.

Constellation Project:

         Scorpius is one of the twelve constellations of the zodiac and is most visible in Washington in July and throughout the rest of the summer, can be seen by viewers located at latitudes of 42⁰ and above and is usually seen just above the horizon. Some of the five brightest stars of Scorpius are Antares, Graffias, Dschubba, Sargas and Shaula. The brightest star is Antares which is a red supergiant with an M1 spectral classification, an apparent magnitude of 0.9 and a distance from the earth of 520 light years. Graffias is the actually the sixth brightest star in this constellation though it is given the title of beta because of its position in the constellation and is actually the combination of two stars, Beta-1 and Beta-2. Beta-1 has a magnitude of 2.62 and Beta-2 has a magnitude of 4.92. Both stars in Graffias are 530 light years away which 2200 astronomical units apart, are class B stars and appear bluish-white to the eye.
        The third star in Scorpius is Dschubba which is a spectral type B0.2 IV star, has an apparent magnitude of 2.29 and a distance of 400 light years. The fourth star is Sargas which can be found 270 light years away from Earth and has an apparent magnitude of 1.86 and is a spectral type F1II star. Shaula is the fifth brightest star in Scorpius and is a bluish-white star of spectral class B1 V, has an apparent magnitude of 1.62 and is 300 light years away from Earth. Some other objects contained in Scorpius include open clusters Messier 6 and 7 and globular clusters Messier 4 and 80 and the star U Scorpii which is the fastest nova with a period of around 10 years.