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

Jordan Raddick

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…

Jordan Raddick

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

Jordan Raddick

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?

Jordan Raddick

DR6 Photometric Coverage

(Both areas, Aitoff projection of equitorial coordinates)

Jordan Raddick

DR6 Spectral Coverage

(Both areas, Aitoff projection of equitorial coordinates)

Jordan Raddick

SkyServer web site

• Entire dataset from the SDSS

• Research-grade science data and tools

• Promotes use of real science data in education

Jordan Raddick

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

Jordan Raddick

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

Jordan Raddick

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

Jordan Raddick

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

Jordan Raddick

Galaxy Zoo

• New project• Classify galaxies

as spiral or elliptical

• Participate in meaningful scientific project