Searching the NVO Registry
In Exercises 1 and 2, you made H-R diagrams for the 26 brightest and 26
nearest stars. In Exercise 3, you combined the two diagrams (unscientifically) into
a single schematic diagram. In Exercise 4, you calculated distances and absolute
magnitudes for 5 stars, then used your knowledge to understand the stars.
Every diagram you have made so far has relatively few stars on it. Astronomers have
measured magnitudes, colors, and parallax angles for many, many more stars than you
have already seen. But these data are sitting in data archives, and it can be
hard to figure out how to access them.
Part of the purpose of the NVO is to allow people - both astronomers and students
like you - to quickly and easily access astronomy data from all over the world.
The tool you will use to search for H-R diagram data is the
NVO Registry.
The Registry collects metadata, information that describes what data a
dataset contains, and how that data is structured.
Try it now. Open the
Registry (it will open in a new window). You will see a screen like this:
The registry holds metadata for thousands of astronomy projects. You can't look
at every entry in the registry to find the ones that would help you make an
H-R diagram; that would take months. So enter a keyword in the search box. To make
a good H-R diagram, you need to find a project that measures parallax angles of stars.
So enter "parallax" in the search box and press the "Go!" button.
The screen changes to look like this:
Notice the resource type display near the top of the page. The table
below the Resource Type label shows the different types of resources that match
the your search. Here, it helps to know a little about the resource types in the
registry. Cone resources have data described by location - so you can search
for data around a specific location if you know the RA and dec. TabularSkyService
resources have data described through a link to a specific table, such as a table
published in an astronomy paper.
For the purpose of making an H-R diagram, the Cone search is the most useful
resource type. Click the Cone label to show only the cone resources.
Click Next to learn more about what the different resources in the registry mean.
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