Google Sky Lab Development

Our lab development efforts are focused on making astronomy more accessible and inspiring for students by introducing the subject through the wonderfully intuitive framework of the Sky layer in the Google Earth application. This layer is automatically included in Google Earth (download) and can be accessed by clicking the Saturn Icon at the top of the Google Earth window, or by going to view->sky in the drop-down menu.

For our labs, the Sky layer has be supplemented by user-generated plugins written in a simple markup language called KML. The plugins can add interactive features and images to the Sky environment. Plugin development has become central to our lab creation efforts because plugins allow Sky to draw on external databases, like the SDSS, so that students can easily engage the data.


To load a given plugin the user should start Google Earth, load the sky layer and then go to file->open in the drop down menu and browse for the file. Most plugins are only activated when the viewport stops so, after loading, you have to pan and stop again before the plugin will become active.

SDSS Galaxy or Star Query Plugin -- Based on Simon Krughoff's SDSS plugin (available here), it queries for galaxies or stars in the field of view from the SDSS spectroscopic and photometric database, circles them and provides information in a pop-up window, including a link to spectrum if available. (Note: the Galaxy Spectrum Query in the "Galaxy Query Plugin" is currently set to return spectra for all objects in the SDSS because object identification is unreliable. From the image context it is usually clear what the spectrum pertrains to.)

SDSS Galaxy Color-Magnitude or Stellar HR Diagram Plugin -- Queries galaxies in the field of view from the SDSS database and displays their color-magnitude diagram.

Note: popup and circled galaxies are from the Query plugin graph in left is from the HR/CMD plugins .

Undergraduate Labs

The following table contains a number of undergraduate labs.

Topics Covered
Files Used (right click links to download)
Introduction to Google Sky (PDF/TeX)
Basics of Sky: The surveys included and a quick reference.
some coordinates
The HR Diagram (PDF/TeX, Image)
Stellar Populations: Explore the HR Diagram of Open Clusters, Dwarf Spheroidals, and Globular Clusters in the SDSS, and of field stars in Hipparchos.
SDSS Star Query, SDSS Stellar HR Diagram, Hipparcos Star Query and Hipparcos-HR (thanks to James Stafford). Locations: Open Clusters, Dwarf Spheroidals, and Globular Clusters.
Hubble Lab: Morphological Types, Spectra of Galaxies, and the Hubble Expansion Law (PDF/TeX, Image)
Constructing the Hubble Diagram: Measure distance from Brightest Cluster Galaxy photometry, and redshifts from galaxy spectrum.
Homogeneity of Space: Show that Galaxy counts are a Poisson distribution on large enough scales. Scales listed in the lab are too small for Poisson statistics. See next lab below for an extension.
Understanding Spectra: Explore the general shape of spectra for various morphological types.
SDSS Galaxy Query w/o redshifts displayed and SDSS QSO/Star Spectra Query
Locations: BCGs and random fields
Homogeneity with Magnitude Limits (PDF/TeX)
Extension of the homogeneity exploration in the Hubble lab above.

SDSS Galaxy Query by R-Magnitude Bins
Galaxy Environments, Clusters of Galaxies, and Dark Matter (PDF/TeX)
Galaxy Environments: Field galaxies, colors and luminosities
Clusters: Properties and cluster finding
Dark Matter: Cluster masses from the virial theorem
SDSS Galaxy Query and Galaxy Color-Magnitude Diagram. Locations: Clusters, Groups, and Fields (same fields as hubble lab),
*Labs were assembled by Sam Leitner collaboration with Andrey Kravtsov and Mike Gladders.


Since KML markup can be lengthy and repetitive most plugins are generated by scripts. Rather than making peers reverse engineer our plugins in order to modify them for their own purposes, we are happy to provide the relevant scripts to anyone who is interested. For now, we ask that you email me at, but in the future we will probably provide links to those scripts and a manual for plugin development. (Note that *.kmz files are just zipped versions of kml files and are activated the same way). Notes on Error Checking
Sometimes KML will be interpretted properly in sky, but still be unstable. It's worth checking that your code complies with kml standards because Earth upgrades can alter GE's interpretation of your markup. contains a program that will check that your kml is strictly compliant.

To check that your perl output is what you should expect you'll need the "west,south,east,north" (which correspond to the Dec and the RA-180) position arguments that Sky passes to your scripts. The following is a sample script call for a FOV that is within the SDSS footprint, you can easily expand the "FOV" it as needed:,25.00,-33.00,25.05
View Page Source to see the original output markup.

Links -- A KML tutorial for Google Earth -- A number of layer examples for Sky.

These efforts are funded by the University of Chicago and the Kavli Institute for Cosmological Physics (KICP).
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