|- Hubble Diagram|
|- Spectral Types|
|- H-R Diagram|
|- Sky Surveys|
|- Image Processing|
|Spiele & Wettbewerbe|
|VLA FIRST Survey|
|What are Quasars?|
Take another look at the query you used to get your first 1,000 quasars:
The query you used limits the objects it returns by applying one "constraint" - the query returns only objects with zconf > .35. Zconf is a measure of the statistical confidence level in the redshift measurement. The query only returns quasars for which we are more than 35% certain that the measured redshift is correct.
Try modifying the query. A couple of ideas would be to change or eliminate the confidence level zconf, or to add a statement in the "where" clause to search for quasars less than a certain magnitude (such as u < 20). Or you could try searching for various lines in the quasars' spectra.
To learn more about how to work with SQL, see SkyServer's Searching for Data how-to tutorial.
When you are dealing with a large database such as the SDSS (over 150 million objects in Data Release 3, and probably hundreds of millions when the survey is finished), you need to use tools such as the SQL Search tool to find the data you want.
Project designed by Robert Sparks
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