Searching for Data

You can see that searching the data by hand is tedious and time consuming. To make a good H-R diagram for a globular cluster, you might need a couple of hundred stars or more. To make a diagram with hundreds of stars, you would need some tool to search through SDSS data automatically.

Fortunately, SkyServer includes several tools to search through SDSS data. The simplest is the Radial Search tool, which finds all objects in a region of sky. You can search more precisely with the SQL Search form below, which uses a programming language called SQL to make requests, or queries, from the SDSS database.

Searching for Stars in Palomar 5

You can use either of the search tools to find stars near Palomar 5. You can use the radial search tool to find all objects, then use Excel to pare the list down to the stars. Or you can use the SQL Search form to look for stars, and only stars.

Click one of the links below to learn one of the two methods for finding stars. Your teacher might tell you which one he or she wants you to use. Either link will bring up a new page in this window.

Use the Radial Search tool and Excel

Use the SQL Search tool

Regardless of which method you chose, you should now have a table of data for all stars in the region around Palomar 5.

Exercise 7. Using the data from your search, create an H-R diagram for Pal 5. Graph r on the y-axis and g-r on the x-axis. Remember to reverse the values on the y-axis so brighter stars are at the top. You may also want to adjust the min and max values of the axes to give a better view of the H-R diagram.

Question 12. Can you see the main sequence on this diagram? Can you see any of the giants and supergiants? If so, identify these groups of stars on your diagram.