NAME and DOWNLOAD LINK: Google Earth 4.2 (Sky Edition)

DESCRIPTION: Earth Viewer with New Sky Feature

SIZE: 12.7 MB

MINIMUM REQUIREMENTS: Windows 2000, Windows XP, Windows Vista, Mac OS X 10.4+

COMMENT: "Until now, Google Earth has let you zoom in from outer space to view our planet. With Earth’s new Sky feature, you can turn that perspective around and explore the wonders of the heavens. View images of distant galaxies and nebulae from the Hubble Space Telescope, learn about the movement of the planets and the lifecycle of the stars, and more."

Search the sky for celestial objects such as stars or galaxies by name using the search pane. You'll fly to the most relevant result and can double click other results to view those locations. Finding planets is a little trickier. The search pane doesn't work for planets yet, but if you stumble across one you can view them in motion by enabling the layer option. You can also do a location search by entering right ascension and declination (coordinates used by astronomers similar to latitude and longitude).

Navigate the sky just like you would Earth. Use the control at the upper right of the image to move in any direction or rotate the image. You also can drag the image in direction by holding down the left button of your mouse. You can zoom in and out using the mouse wheel and with left and right clicks. The layers panel, as in the Earth view, lets you select what is displayed. See Backyard Astronomy, the Hubble Showcase, the Planets and more. Click on a layer or sub layer and be taken to that location. It's a great way to explore the universe.

The limits of viewing the sky create a few limits in how Google Earth can view the sky. Obviously no tilting of images, no overview map, you can't make the sky your start location and no atmosphere option. Although you can show a grid of latitude and longitude lines in the sky to orient celestial objects.