Lab 07: Stars and spectra: Learning about color, temperature, and spectral class with data from the Sloan Digital Sky Survey In this lab activity you will explore actual spectra for some stars that were measured with the Sloan Digital Sky Survey. RA=236.39139, DEC= 0.40653, MJD=51691, Plate= 342, Fiber=435 5 " Call 300 Refer the lecture "Stars 03" for instructions and 200 examples. Fa [107 erg cm 2 1 X-1] 100 2 0.0003 +/- 0.0001 (1.00), Star 4000 5000 6000 7000 8000 9000 Wavelength [A] Source of these spectra: http://cas.sdss.org/dr6/en/proj/basic/spectraltyp es/studentclasses.aspDefinitions: A spectrum (the plural is spectra) is a graph of the range of wavelengths and intensities emitted by a radiating body. The Sloan Digital Sky Survey (SDSS) measures wavelength in units of Angstroms (symbol A), 1 Angstrom = 10-10 meters = 0.1 nm, or 10-1 nm. The wavelengths of SDSS spectra go from around 4000 A (just into ultraviolet light) to 9000 A (just into infrared light). RA=237.72422, DEC= 0.36614, MJD=51692, Plate= 343, Fiber=341 Continuum peak Lots of light K H. OIll G Mg No OI NIISII Call Helsil NIL Call Noise 100 F, [10-17 erg cm 2 s' A=] ] Absorption line Intensity on the y-axis Very little lighto z= 10,0904 +/- 0.9001 (1.00), Stor 4000 5000 6000 7000 8000 9000 Wavelength [A] Wavelength in Angstroms on the x-axisKnow these definitions: 1) A spectrum (the plural is spectra) is a graph of the amount of light something gives off (how bright the object is) at different wavelengths. The Sloan Digital Sky Survey (SDSS) measures wavelength in units of Angstroms (symbol A), 1 Angstrom = 10-10 meters = 0.1 nm, or 10-1 nm. The wavelengths of SDSS spectra go from around 400 traviolet 9000 A (infrared light). RA=237.72422, DEC= 0.36614, MJD=51692, Plate= 343, Fiber=341 Continuum peak Lots of light K H. OIll Golf How to read the graph: HH G Mg No QI NISI Call Helsil NIL Call Noise Vertical axis: 100 INTENSITY Units are F, [10-17 erg cm-2 s' A"'] Absorption line energy/cm2/sec/wavelengthtensity on the y-axis 50 Horizontal axis: WAVELENGTH Units are Angstroms, 10-10 m Very little light. z= 10,0904 +/- 0.9001 (1.00), Stor 4000 5000 6000 7000 8000 9000 Wavelength [A] Wavelength in Angstroms on the x-axis2) Continuum peak - the top of the broad "hill" in the spectrum 3) Absorption lines - the narrow "valleys" in the spectrum 4) Noise - some small random fluctuation in the spectrum; noise is usually much smaller than the absorption lines RA-237.72+22, DEC- 0.36614. MJD-$1 492. Plots- 343. Fiber-341 OI NIGH Call Call absorption lines noise F, (10717 org em ? "1 1") Intensity An ideal 50 An actual thermal spectrum stellar spectrum 7-10.0004 +/- acca1 (1,an), Ster 4000 6000 7000 8000 9000 4090 4000 GOOD 7000 SOOD 9090 Wavelength (Angstroms) Wavelength [*] 0029 T = for 2 in meters! micron = 106 m nm = 10-9 m max Angstrom = 10-10 mYou can use these example spectra from the SDSS to check your answers; http://classic.sdss.org/dr5/algorithms/spectemplates/ For each spectrum, click on the thumbnail image to see a full sized image. (You can also click on the word "gif" to the right of the thumbnail.) Note: Color can be deceiving! Choose the classification according to the absorption spectrum.An example: Color: blue max: around 4000 A or 400 nm RA=236.39139, DEC= 0.40653, MJD=51691, Plate= 342, Fiber=435 W HK H. OIll Of H SII call G 300 H Mg No IISIN Call HeISII H Oill NIL Call Absorption lines are the dips in the Planck curve. The elements responsible H-a? yes 200 are listed at the top of the graph. H-B? yes F, [10-17 erg cm-2 9-1 1-1] List other elements: G-band H-Y H-8 100 H & K bands of ionized Ca -. . .........". . . ....... He? weak Na Z= 0.0003 +/- 0.0001 (1.00), Star 4000 5000 6000 7000 9000 Approx. Temp.: Wavelength [A] 7,250 K Best Guess Spectral class: A to FRefer to the H-R Diagram: 106 60 Msun 102 Solar Bid 103 Solar Radi 30 Msus Deneb 105 10 Solar Radi B Centauri Riel SUPERGIANTS Betelgeuse Spica Lifetime 10 Msun Canopus Antares 104 107 yrs Polaris 103 1 Solar Radius MAIN 6 Misus Achemar GIANTS Lifetime SEQUENCE Arcturus Aldebaran 102 105 yrs Vega Pollux Sinus 10 0.1 Solar Radius Procyon Altair Lifetime 109 yrs a Centauri A luminosity (solar units) Sur a Centauri B Eridan 61 Cygni A 0.1 10-2 Solar Radius Lifetime 61 Cygni B 1010 yrs Lacaille 9352 0.3 Msun Gliese 725 A 10-2 Sinus B WHITE Gliese 725 8 DWARFS Lifetime Barnard's Star - 0.1 Msun Ross 128 1013 yrs 10-3 10-3 Solar Radius Wolf 359 Procyon B Proxima Centaun DX Cancri 10-4 10-5 O B A F G K M 30.000 10.000 6.000 3,000 increasing surface temperature (Kelvin) decreasing temperature temperatureFor each of the spectra on the following pages: 1. Write down the color of the star. 2. Find and write down the wavelength where the peak in its black body spectrum occurs max). Calculate the surface temperature. Do you see pronounced H-oc and H-B lines? Note the other absorption lines that you see. Based on the absorption spectrum and peak wavelength of the blackbody spectrum, estimate the spectral class is the star. [0 B A F G K M] 991?.\" See the list of possible absorption lines and their respective wavelengths on the next page, and also in Stars 03. How to submit your work: Type your answers directly onto the power point slides with the spectra, save as a separate file, and upload to Canvas. 0r, print out the pdf file and write your answers on the pages with the spectra, photograph those slides, and upload to Canvas. Absorption bands listed on the SDSS spectra: H = Hydrogen (H-a, H-B, H-y, H-8) Refer to these tables of He = Helium symbols and wavelengths Ca = Calcium where the absorption bands Na = Sodium are found. Mg = Magnesium O = Oxygen Ti = Titanium N = Nitrogen Si = Silicon G = "G-band" a complex of molecules, mainly due to CH molecule H&K = bands of ionized Ca Spectral Lines Wavelengths (Angstroms) Wavelengths, in How HB, Hy 6600, 4800, 4350 Angstroms of Ionized Calcium H and K Lines 3800 - 4000 spectral lines: lots of lines from 4900 - 5200, 5400 - 5700, 6200 - Titanium Oxide 6300, 6700 - 6900 G Band (CH complex) 4250 Sodium 5800 Helium (neutral) 4200 Helium (ionized) 4400Refer to this table to help you classify each star: Temperature (Kelvin) 28,000 - 50,000 Ionized helium 10,000 - 28,000 Helium, some hydrogen 7500 - 10,000 Strong hydrogen, some ionized metals Spectral Type Spectral Lines Hydrogen, ionized calcium (labeled H and K on spectra) and iron 6000 - 7500 Neutral and ionized metals, especially calcium; strong G band 3500 - 5000 Neutral metals, sodium 2500 - 3500 Strong titanium oxide, very strong sodium 5000 - 6000 Color: max: 1 Surface temperature: RA=236.39139, DEC= 0.40653, MJD=51691, Plate= 342, Fiber=435 OIll OIll Of H. SII call 300 H Mg Na OI NISHI Call ISII Oill NII Call H-a? 200 H-B? F, [10- erg cm-2 s-1 1-1] List other elements: 100 ....... : ::: O 2= 0.0003 +/- 0.0001 (1.00), Star 4000 5000 6000 7000 8000 9000 Wavelength [A] Spectral class:Color: 5" 2 max: 2 Surface temperature: RA=237.17385, DEC=-0.00098, MJD=51691, Plate= 342, Fiber=141 H. OIll Of H SII call G: He Mg Na OI NIISII Call Helsil H. Oill NILL Call 150 m H-a? 100 H-B? F, [10717 erg cm-2 9-1 1-1] List other elements: - . . . . . .. ... .........5-.. . . . . . . . . ......" . . . . . ... O Z=x0.0002 +/- 0.0001 (1.00), Star 4000 5000 6000 7000 8000 9000 Wavelength [A] Spectral class:\fColor: 5" Amax: 4 Surface temperature: RA=202.53563, DEC= 0.15610, MJD=51955, Plate= 298, Fiber=400 OIll H SI call G No IISIN 10: Call 600 Helsil Call H-a? 400 H-B? F, [10-17 erg cm-2 9-1 A-1 ] List other elements: 200 . ......" -. . . Z=-0.0001 +/- 0.0001 (1.00), Star 4000 5000 6000 7000 8000 9000 Wavelength [A] Spectral class:Color: max: 5 Surface temperature: RA=237.72422, DEC= 0.36614, MJD=51692, Plate= 343, Fiber=341 HK H. Oil Of H SII call Me Mg Na QI NIISII Call NIL Call 100 H-a? H-B? F, [10- erg cm 2 8-1 1-1] List other elements: :: :::::::: :: - . . .. Z=10.0904 +/- 0.0001 (1.00), Star 4000 5000 6000 7000 8000 9000 Wavelength [A] Spectral class:Color: 5" max: 6 Surface temperature: RA=186.91480, DEC=-1.90127, MJD=51993, Plate= 334, Fiber=461 150 HAH He Mg Na OI NISI call Helsil Oill NIIL Call K H. OIll OIll Call: H-a? 100 H-B? F, [10-17 erg cm-2 9-1 1-1 ] List other elements: -.. .. . . . . Z= 0.0001+/- 0.0001 (1.00), Star 4000 5000 6000 7000 8000 9000 Wavelength [A] Spectral class:Color: 5" 7 ~max : Surface temperature: RA=237.61973, DEC= 0.63370, MJD=51691, Plate= 342, Fiber=586 H & OIll Of H SII call G H Mg Na QI NIISII Call ISII Oill Call R..... 100 H-a? H-B? F [10 erg cm 2 s-1 A-1] List other elements: - .. . . ...... ........ .......".............".":" O Z=+0.0002 +/- 0.0001 (1.00), Star 4000 5000 6000 7000 8000 9000 Wavelength [A] Spectral class:Further questions: Comparing luminosities: Go back and compare stars 1 and 2. They are both blue, and their peak wavelengths are in the violet range, so they are most likely O-type stars, or blue giants. BUT: Star #lappears brighter than star #2 in the image, yes? Look at the numbers on the y-axis. These numbers tell you the amount of light emitted per unit area for each star. Note the top numbers: Star #1: Star #2: 1. Given that they are both hot O-type stars, probably blue giants, and assuming that the measured light is related to apparent magnitude (m) which star is closer to us? 2. How can you tell, from the amount of light measured