Star Brightness worksheet.docx

Star Brightness WORKSHEET These lab activities have evolved over years of use in Clemson University’s Department of Physics and Astronomy general astronomy laboratory. Contributors include Tom Collins, Mark Leising, Neil Miller, Peter Milne, Grant Williams, Donna Mullenax, Jessica Crist, Keith Davis, Amber Porter, Lea Marcotulli, and David Connick. Please direct all questions, complaints, and corrections to David Connick (dconnic@clemson.edu) who is responsible for all errors and omissions. NAME _ Andrew Birchler __________________ Remember to answer all questions with a sentence statement. Single word answers are never acceptable unless filling in a blank number in a table or open space. Support your answers with your data. Table 1 The Twenty Brightest Stars Star M (total) Constellation m Distance (ly) N or S Temp (K) Achernar - 4.67 Eridanus 0.54 139 S 19000 Acrux (alpha1) - 6.86 Crux 1.27 322 S 30000 Aldebaran - 0.56 Taurus .99 66.6 N 4000 Altair 2.25 Aquilae .93 16.7 N 7830 Antares -3.10 Scorpius 5.4 550 S 20900 Arcturus -0.66 Bootes .15 36.7 N 4530 Betelgeuse -6.81 Orion .56 500 N 3500 Canopus -5.80 Carina -0.62 309 S 10100 Capella -0.94 Auriga 0.07 42.8 N 4800 Deneb -7.13 Cygnus 1.33 1400 N 9380 Fomalhaut 1.61 Piscis Austrinus 1.23 25.1 S 8730 Hadar -7.35 Centaurus 0.63 390 S 26200 Pollux 0.64 Gemini 1.22 33.8 N 4660 Procyon 2.53 Canis Minor 0.4 11.4 N 6650 Regulus -1.55 Leo 1.40 79.3 N 12700

Rigel -7.49 Orion 0.28 860 S 11100 Rigil Kent 4.17 Centaurus 0.00 4.36 S 5790 Sirius 1.21 Canis Major -1.44 8.58 S 9400 Spica -5.95 Virgo 1.05 250 S 26200 Vega 0.29 Lyra 0.02 25 N 9790 1) Are there more bright stars in the northern half of the celestial sphere, or in the South? Explain. There are the same number of bright stars in the northern and southern half of the celestial sphere, at least of the stars we tested. In the test 10 of the brightest stars were in the north while 10 of them were in the south. 2) Which star appears to be the brightest star? (most negative m) Sirius (-1.44) 3) Which is intrinsically brightest?(most negative M) Rigel (-7.49) 4) Which star is the closest star? Rigil Kent (4.36 ly) 5) Why are the stars with lowest (brightest) m not those with the lowest M? Explain. Because brightness (m) depends on distance away from earth because it is measured from earths surface, so stars that are further away will tend to have lower brightness because of their distance from earth. 6) Is the North pole star (Polaris) one of the 20 brightest stars? No 7) The Big Dipper is one of the most recognizable figures in the sky. Are any of the twenty brightest stars in the Big Dipper's constellation, Ursa Major? No 8) Which star is the hottest star? Is it in the top 5 of absolute magnitude? Acrux is the hottest star and it is in the top 5 of absolute magnitude 9) Calculate the average temperature, __ 11763 __ in K (Kelvins), and the average distance, _ 253.517 _____ light years. 10) Is Sirius closer to us than the average distance? Yes 11) Display the Milky Way. Are the bright stars noticeably concentrated within the Milky Way? Yes most of the bright stars appear concentrated in the milky way

Mu 3400 249 Nu 4440 421 Xi 6000 24 Omicron 5500 184 Pi 1 5870 46.8 Rho 3490 315 Sigma 1 4200 498 Upsilon 7000 116 Phi 9040 436 16) Name the seven stars that form the Big Dipper. Dubhe, Alkaid, Mizar, Alloth, Megrez, Merek, Phecda 17) Mizar and Alcor are called the horse and rider. For the fainter Alcor to "ride" Mizar, they would need to be close together. Are they close (say, within a few light years)? Yes, they are 4.1 light years apart 18) Are the Ursa Major stars at the same distance from Earth? No they are not all the same distance from earth 19) If the stars aren't close together, why are they part of the same constellation? Because from our perspective on earth they appear close together because we cant perceive how far away they are from us and the depth between the stars. 20) Which group of stars would you expect to be closer on average, the bright ones or the random ones from the big dipper(UMa)? The stars from the big dipper 21) Which group of stars would you expect to be hotter, the bright ones or the random ones from the big dipper (UMa)? The bright stars 22) The average temperature of the Ursa Major stars is ___ 7654.5 _____ °K. The average distance is ___ 175.73 ____ light years.

23) Are the bright stars or UMa stars hotter on average? The bright stars are hotter 24) Are the bright stars or UMa stars closer on average? UMa stars are closer on average