HR Diagram Report 2015 DE(1)(2)

HR Diagram Report Your name: Dylan Sanders For this project we will use real astronomical data gathered by the Hipparcos spacecraft. You will find this project on the “Sloan Digital Sky Surveyor” website: http://skyserver.sdss3.org/dr10/en/proj/advanced/hr/hrhome.aspx The questions in this lab exercise have been adapted from the above mentioned website. The first H-R diagram you should try is a diagram for the brightest stars in the sky. The table below shows the 26 brightest stars in the sky. Instead of plotting their luminosities (which are so large that they're hard to visualize), plot the stars' absolute magnitudes. Absolute magnitude is defined as the magnitude that a star would have if you saw it from a distance of 10 parsecs (about 32 light-years). Stars with higher luminosities put out more light, so they are brighter - they have lower apparent magnitudes. Stars with lower luminosities put out less light, so they are dimmer - they have higher absolute magnitudes. The table below shows the 26 brightest stars, giving their names, apparent magnitudes, absolute magnitudes, and b-v colors. Star Name Apparent Magnitude Absolute Magnitude b-v Sun -26.8 4.8 0.63 Sirius -1.46 1.4 0.0 Canopus -0.72 -2.5 0.15 Arcturus -0.04 0.2 1.23 Alpha Centauri -0.01 4.4 0.71 Vega 0.00 0.6 0.0 Capella 0.08 0.4 0.08 Rigel 0.12 -8.1 -0.03 Procyon 0.38 2.6 0.42 Betelgeuse 0.41 -7.2 1.85 Achernar 0.46 -1.3 -0.16 Hadar 0.63 -4.4 -0.23 Acrux 0.76 -4.6 -0.24 Altair 0.77 2.3 0.22 Aldebaran 0.85 -0.3 1.54 Antares 0.92 -5.2 1.83 Spica 1.00 -3.2 -0.23 Pollux 1.14 0.7 1.0 Formalhaut 1.16 2.0 0.09 Becrux 1.20 -4.7 -0.23 1

Star Name Apparent Magnitude Absolute Magnitude b-v Deneb 1.25 -7.2 0.09 Regulus 1.35 -0.3 -0.11 Adhara 1.50 -4.8 -0.21 Shaula 1.60 -3.5 -0.22 Gacrux 1.63 -1.2 1.59 Castor 1.98 0.5 0.03 Table 1: The 26 brightest stars These data are also available in the Excel Workbook provided with this report. If you want more stars, there is a list of the 314 brightest stars available here ( http://www.astro.utoronto.ca/~garrison/oh.html ) . Exercise 1: [10 pts.] Make an H-R diagram for the brightest stars by graphing b-v (on x- axis) and absolute magnitude (on y-axis) for the 26 stars above. Use the Microsoft Excel workbook named “H-R Diagram Exercise DATA” (Available on Blackboard together with this report) to make your diagram. For help on how to make a graph using Microsoft Excel, see SkyServer's Graphing tutorial . Question 1: [6 pts.] Do you see any groups of stars that appear to have something in common? Sketch a box around those groups in your graph. (Hint: On your Excel Spreadsheet go to: insert – shapes – rectangle. Give the rectangle a certain color so that you can distinguish the different groups. As answer to this questions describe the commonalities for the different groups of stars you have found). 2

The Brightest will have higher values on the x axis. The advantage of looking at the nearest stars is we can talk more about their composition. The diagram for nearest stars will be different because the x-axis values will be lower. Exercise 2 : [10 pts.] Now graph an H-R diagram for the nearest stars . For your convenience the data were copied into the excel workbook (Sheet 2 “Nearest Stars”) Question 6 : [6 pts.] How does this diagram differ from the diagram for the brightest stars? This diagram plot points are different and reflect different variables than the first set of brightest stars. The concentration and data flow are completely different. Question 7 : [4 pts.] How does our Sun compare to the other stars in our neighborhood? It is the largest and one of the hottest suns in our neighborhood. If the hydrogen in its core burns out however it will become a red giant and be much cooler Exercise 3 : [10 pts.] Use the Hipparcos data from Hipparcos Catalog Volume 6 to find the distances to the following stars and record them in table 3. The coordinates given are RA and Dec. Record the Visual magnitudes (V mag) of the stars as well. You will need them later. ( In the Catalog provided the stars have been highlighted in yellow. You need to search for the highlighted objects. The data for each object go over two pages.) the distance d can be determined by calculating 1/parallax. RA Dec Visual Magnitude Parallax (milli-arcsec) Distance (parsecs) 06 42 05.31 -15 12 53.8 4.2 42 300 06 38 35.43 -16 52 24.6 3.7 34 50 parsecs 06 41 33.99 -17 32 01.0 1.5 56 20 parsecs 06 48 48.78 -16 12 41.2 2.2 11 100 parsec Table 3: Distance of stars Now that you know these stars' apparent visual magnitudes and distances, you can find their absolute magnitudes. Absolute magnitude is defined as the magnitude a star would appear to have if it were 10 parsecs away from us. Our Sun's absolute magnitude is 4.84 (compared to its visible magnitude of -26.2!). The relationship between a star's apparent or visible magnitude and absolute magnitude is given by the expression M = m – 5*( log d) + 5, 4

where m is the star's apparent magnitude, M is the star's absolute magnitude, and d is the distance to the star in parsecs. Let's take the star Sirius as an example. It has a visual magnitude (V mag) of -1.44 and it is 2.637 parsecs away. Therefore, its absolute magnitude is M = -1.44 - 5 log (2.637) + 5 = 1.45. Exercise 4 : [10 pts.] Use the visual magnitudes and distances you found earlier to find the absolute magnitudes of these stars and record them in table 4. RA Dec Visual Magnitude Distance Absolute Magnitude 06 42 05.31 -15 12 53.8 1.45 4 parsecs 1 06 38 35.43 -16 52 24.6 -0.4 2 parsecs 6 06 41 33.99 -17 32 01.0 1.3 3 parsecs 4 06 48 48.78 -16 12 41.2 2.2 1 parsec 5 Table 4: Absolute magnitude of stars Now you are ready to make an H-R diagram! The Pleiades Copyright Anglo-Australian Observatory / Royal Observatory, Edinburgh Courtesy AAO Astronomical Images Gallery . Exercise 5 : [14 pts.] You will be making an H-R diagram using data from the Hipparcos Catalog Vol 5 . The Volume 5 of the catalog is provided but you must find the data using the HIP identifier as provided in the Excel workbook sheet 3 “Pleiades”. You will need the visual magnitude, parallax, and b-v color for each star. Graph the HR 5