Next phase in the Microsoft-Google rivalry: Star Wars?

Maybe not, but Microsoft Corp. is expanding its galactic footprint with a program for zooming around a virtual universe consisting of images from some of the top telescopes and cameras on Earth and in space.

Microsoft's free WorldWide Telescope program was to be released in preliminary form Monday night by the company's research unit. The company says the intent is educational, not commercial.

But the release of the software will give techies, astronomy buffs and anyone else a chance to see if a piece of Microsoft technology can outshine one of the Internet's biggest stars.

That would be Google Inc., which already has a similar offering called Google Sky, a companion to its Google Earth program.

Features of WorldWide Telescope include virtual tours of different parts of space, led by expert educators and astronomers. People will be able to use the Microsoft program to create their own space tours, to share with their friends.

The program is also notable for its high level of detail, its large volume of data and the ability to fine-tune the views, said Curtis Wong, principal researcher in Microsoft's Next Media Research Group.

"I expect that there are going to be a lot of people learning so much more about the sky, because we've taken away the limitations of light pollution and smog and bad weather," Wong said. "Those of us in Seattle, it's our chance to finally see the sky."

WorldWide Telescope was announced and demonstrated in February, but Microsoft researchers have long had an interest in the field. The program builds on the work of people including Jim Gray, a Microsoft researcher missing at sea since last year.

The program runs on the PC desktop but pulls data and images from the Internet. Google Sky can run in a standard Web browser or in the downloadable Google Earth program. But the system requirements for Microsoft's WorldWide Telescope program come with a catch: It works only in Windows XP or Windows Vista.