global hands-on universe meeting july 15, 2007 authentic data in the classroom with the sloan...

Global Hands-On Universe meeting

July 15, 2007

Authentic Data in the Classroom with the Sloan Digital Sky Survey

Jordan Raddick (Johns Hopkins University)

Jordan Raddick

The Sloan Digital Sky Survey

• Map of the universe• 2.5 m telescope in

New Mexico• CCD imaging• Follow-up spectra

Jordan Raddick

The Data of the SDSS

Photometric Data

Spectral Data

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Photometric Data

• Tri-color images • Single-color FITS files

– ultraviolet (u)– green (g)– red (r)– infrared (i, z)

• Magnitudes through each filter

• Object type• More…

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Spectral Data

• 3800 to 9200 Ångstroms• GIF files with prominent

lines marked• FITS files available

– SpecView Java applet(STScI)

• Object type and redshift• Detailed line widths and strengths

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Introduction to DR6

• ~9,600 square degrees– (Full moon is 0.25 square degrees)

• Images of ~280 million objects– ~90 million stars, ~140 million galaxies

• ~1 million spectra– ~60,000 stars, 600,000 galaxies, 75,000 quasars

• Science quality data• Where in the sky?

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DR6 Photometric Coverage

(Both areas, Aitoff projection of equitorial coordinates)

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DR6 Spectral Coverage

(Both areas, Aitoff projection of equitorial coordinates)

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SkyServer web site

• Entire dataset from the SDSS

• Research-grade science data and tools

• Promotes use of real science data in education

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Example: H-R Diagram

• Strategy:– Get data for a lot of stars in a star cluster– Need magnitudes– Plot color vs. magnitude– Interpret

• Palomar 5– RA = 229.013, Dec = -0.123, Radius = 3 arcmin

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Get Data

• Search Form• Tools -> Search ->

Search Form• Form is a sentence

where you fill in words• “Show me stars

at RA = 229.013, dec = -0.1083, radius = 3. Show me 1,000. Get object ID, RA, Dec, and magnitudes.

• Click Generate Query

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Get Data

• Your request is translated into SQL code:select top 1000 p.objid, p.ra, p.dec, p.u, p.g, p.r, p.i, p.zfrom star p

• Switch Output Format to CSV• Click Submit Query to SkyServer or Submit

Query to Image List• Download or save file

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View and Analyze Data

• Open CSV file in a graphing program

• Note bug with Object IDs• Add new columns for

u-g, g-r, r-i, i-z

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Plot Data

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Interpret Plot

• Interpret plot to learn stellar evolution

• See SkyServer’s “Project” on H-RDiagram

• Projects -> Advanced ->H-R Diagram

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Galaxy Zoo

• New project• Classify galaxies

as spiral or elliptical

• Participate in meaningful scientific project