Reach for the stars

Posted on 7 Dec 2007 at 11:25

With the release of Google Earth 4.2, Google decided that organising the world's information wasn't enough - it was time to have a crack at the rest of the universe. The Sky mode, or Google Sky as it's often known, is a boon to amateur and professional astronomers - a sort of mirror of Google Earth stitched together from space imagery created by NASA, The Space Telescope Science Institute, The Sloan Digital Sky Survey, the Digital Sky Survey Consortium and the UK Astronomy Technology Centre, among others.

To find Sky mode, load Google Earth and select View | Switch to Sky. You can navigate using the mouse in exactly the same way as you do in the Earth application, and the pop-in navigation tools in the right-hand corner of the screen work identically, bar the Tilt function, which is irrelevant here. As in Earth view, the Layers palette also plays a crucial role, enabling you to switch in and out of tiers of overlaid imagery and data.
Using KML, third parties are already adding their own layers of imagery, information and animation to Google Sky.
The Hubble Showcase, for example, gives you easy access to spectacular imagery from the Hubble Space Telescope. Clicking on the blue crescent moon icons in the Sky view takes you to the image and an explanatory description, while zooming in on the general area will show the image in its stellar context. Alternatively, you can page through the Hubble imagery using the Layers palette. Expand the tree view, and you'll see the images divided into different categories, such as Black Holes and Quasars or Clusters of Galaxies, with links to the various Hubble placemarks. Clicking once will bring up the photo and explanation. Double-clicking will take you to the right location. Other layers, such as the Planets in Motion or the Moon in Motion, track the movements of the named body over a specific time period, controlled by a time slider at the top-right of the screen.

Finding a particular planet, nebula or constellation is simple; use the Search box in the Search palette on the left of the screen, and Sky mode will cheerfully pan and zoom to your chosen object just like the regular Earth app. Sky mode works with common names or the standard astronomical catalogues, so typing in M82, NGC3034 or Cigar Galaxy will all take you to the same place. It will also find locations if you enter co-ordinates using the standard Right Ascension/Declination celestial scheme.

All of this makes Google Earth a great tool for simple amateur astronomy. You can find your current location on Google Earth, switch to Sky View and see a map of the stars above you. Sky mode even has a layer called Backyard Astronomy, which focuses on objects that can either be seen with the naked eye, binoculars or a basic telescope, covering the Messier Catalog (Mxx), the New General Catalog (NGC) or the Yale Bright Star Catalog.
Imagery from the Hubble Space Telescope has been directly integrated into the main Sky texture layer.
However, in some respects, Sky mode falls down at this point. On Earth, geographical points of interest remain pretty much where they're put, but in the sky everything moves, as does your point of view as the earth rotates. Sky mode gives you a flat, unanimated display and doesn't move or update the stars or planetary positions in real-time. What's more, there's no horizon indicator and no easy way to set the display to a different time, making it a blunt tool if you want to make a map in the morning to go stargazing that night. Such features are provided by the free, open-source Planetarium applications such as Stellarium or Celestia, which also feature more dynamic 3D animated views of the stars and planets.