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Quasars
 Radio Astronomy
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 What are Quasars?
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 SDSS Quasars
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SDSS Quasars

The SDSS has found thousands of quasars, including 26 of the 30 most distant quasars ever seen. These quasars have been found in only the first 5% of the sky to be mapped! SDSS could eventually find hundreds of thousands of quasars.

To look at the properties of large numbers of quasars, you are going to use a search tool to retrieve information on a thousand quasars at once. The query tool uses a programming language called Structured Query Language (SQL) to retrieve the data. Don't worry - the next exercise gives you a sample query to get you started.

Exercise 3. Go to SkyServer's SQL Search tool. Copy the query listed below, and paste it into the box (overwrite the default query). Get your results as HTML (the default). Click Submit.


select
w.plate,w.mjd,s.fiberID,s.z as redshift,p.u,p.g,p.r,p.i,p.z,p.ra, p.dec,p.ObjID

from
SpecObj s, PhotoObj p, plate w

where
p.ObjID=s.ObjID and w.plateID=s.plateID and s.zConf>0.95 and s.specClass = 3

You will get a table with information on 1000 quasars. Copy the table and paste it into a spreadsheet in a graphing program such as Microsoft Excel. The first three columns tell you the plate number, MJD, and fiber number that you need to look up the spectrum using the Get Spectra tool. The rest of the columns give you the redshift, magnitudes (u, g, r, i, z), right ascension, declination, and object ID, in that order. Label your columns in the spreadsheet.

When SDSS is unable to find the magnitude of a survey object, it lists the magnitude as 999. Therefore, you may see some of the magnitude columns (u,g,r,i,z) listed as 999. Ignore these, and be sure to set the scales of your graphs so that they do not influence your results.

You can look up the spectra for any of these 1000 quasars with the Get Spectra tool by entering the Plate ID/MJD and the Fiber ID. You can also analyze the quasars in many different ways. The two projects on the next page let you do quasar analysis that was only recently published by the SDSS collaboration. The projects are a little advanced, but they reflect research that professional astronomers are doing right now!