Communications of the ACM
News
The Universe in Your Computer
The telescope, it is often said, is like a time machine in that when you focus on a star, you see that star as it actually appeared tens or even thousands of years in the past. That's how long it takes for lightzipping along at a speed of 300,000 kilometers per secondto cross the vast gulf of space between "there" and "here." These look-back times, as astronomers sometimes call them, can reach astonishing proportions. When you focus your backyard telescope on something like the Andromeda Galaxy, for example, you are looking at light that has been traveling more than two million years to reach your eye. But that's nothing compared with the purview of the world's most powerful telescopes, such as the W.M. Keck, located near the summit of Mauna Kea on the Big Island of Hawaii, or the Hubble Space Telescope, orbiting above the distorting effects of Earth's atmosphere. These time machines have revealed galaxies that appear as they were more than 13 billion years agoor 13 billion light-years awayan epoch in time when the universe was only about 800 million years old.
It boggles the mind, such space and time. There are simply no adequate words to describe the enormity of the universe or its spectacular, never-ending assortment of stars, nebulae, and galaxies. But now, two powerful Web applicationsMicrosoft's Worldwide Telescope (WWT) and Google Skyare providing users with new ways to explore the universe. Both essentially turn a personal computer into a multi-use virtual telescope.
Zooming In
Last May, Microsoft launched the beta version of its Worldwide Telescope, making it the most recent desktop telescope available to the public. At the time, Microsoft chairman Bill Gates called the WWT "a powerful tool for science and education that makes it possible for everyone to explore the universe." The application itself is not a simple browser with links, but an integrated amalgam of data and images from such surveys as the Digitized Sky Survey, the Sloan Digital Sky Survey, the Hubble Space Telescope, the Chandra X-ray Observatory, and the Spitzer Space Telescope. Thus, images are available across multiple wavelengths of the electromagnetic spectrum. The application, which is coded in Microsoft's C# .NET and created with Microsoft's Visual Experience Engine, is a combination of software and Web services that allows users to pan smoothly across the sky while accessing terabytes of images and data from multiple sources. Microsoft likens the result to a "media-rich, immersive experience," with applications for both amateur and professional astronomers.
Microsoft's Worldwide Telescope enables users to pan smoothly across the sky and access terabytes of images and data from multiple sources.
Users can zoom in on the Orion Nebula, for example, and cross-fade from one wavelength view of the nebula to another, revealing hot pockets of gas, which unaided human eyes cannot visually detect, and young stars embedded in obscuring clouds of dust. Cross-fading provides a powerful method of literally looking into the environments and dynamics of celestial objects, thus providing key insights into their nature and why they look the way they do. Menu tabs allow serious researchers to access professional database archives of studies on the objects of their choice. Users can also find the current locations of planets, observe stunning panoramas taken by rovers from the surface of Mars, and zoom in on rotational views of the Moon, Venus, Earth, and Jupiter and its moons Io, Ganymede, and Callisto.
The basic layer of the northern sky in both the WWT and Google Sky is comprised of sky surveys conducted over the years at Palomar Observatory in California, while the southern sky is derived from surveys at the Anglo-Australian Observatory in Australia. A digital version of the photographic plates of the Palomar survey, called the Digital Sky Survey, was produced as a collaborative project between the Space Telescope Science Institute in Baltimore, MD, and the California Institute of Technology. The project's principal investigator, S. George Djorgovski, is excited that the general public can now easily view the science data set that is available in both programs. "I think Google Sky and WWT are great public outreach venues. I really feel positive about them," says Djorgovski. "It is probably too early to gauge any social impact of these [programs], and it will be tricky to measure in any case. But it's got to be good, for obvious reasons."
The WWT has its origins in the pioneering work of Jim Gray, whose many computer science-related accomplishments include developing the SkyServer program for the Sloan Digital Sky Survey, which is considered the most ambitious astronomical survey of the sky ever undertaken. (For more about Gray's astronomical contributions, see the November 2008 Communications article, "Jim Gray, Astronomer," by Alexander S. Szalay.) SkyServer is the forerunner of an information software architecture known as contextual narrative, which seeks to integrate data and stories with interactive contextual exploration in a one-stop shopping environment.
As an integral part of the WWT, contextual narrative both enhances and facilitates the learning experience, giving it new dimensions, says Curtis Wong, principal researcher of the Microsoft Next Media Research group. "It's enabling a new generation of kids who learn through interaction to be inspired to explore the universe in context, guided by astronomers and seamless links to the world's information," Wong says. "I think learning in context has been the original goal for WWT since the beginning, and that has the biggest potential impact for the users."
Google Sky offers multiple information layers, including constellation figures and the current positions of planets.
Information Rich
In August 2007, Google launched its universal Sky browser by making it available as a free download at Google Earth. Like the WWT, it also provides a seamless view of the night sky using images from the Digital Sky Survey, the Hubble Space Telescope, and other professional observatories. Google Sky also uses multiple information layers that can be selected under its sky database, including constellation figures, the current positions of the planets, and a backyard astronomy layer that labels stars, constellations, and celestial objects. When the "education center" and "current sky events" options are selected, users can click for Hubble-cast videos, virtual tours of stars and galaxies, and detailed descriptions of celestial objects provided by other sources, such as NASA's Hubble site and Wikipedia. When all layers are selected, though, the screen can become crowded, but the numerous choices make Google Sky undeniably information rich.
Google Earth was created to project imagery onto the surface of a sphere. For Google Sky, that perspective is reversed by using the same infrastructure to project images of the sky onto the inside of a sphere, creating a realistic representation of the celestial vault. There is, however, a small tradeoff (which some users argue is not so small). Because Google Sky uses a latitude and longitude projection, the stars in the original images were significantly distorted between seven and eight degrees of both celestial poles. Hence, these regions were replaced with a lower-resolution view of the sky derived from the Tycho II star catalog. The stars in those polar regions are obviously not as sharp as the other parts of Google Sky's sky (they exhibit a decided radial stretch from the pole outward), but they are properly scaled and their colors are based on real color data.
Like Google Earth, Google Sky utilizes Keyhole Markup Language (KML), which is an XML-based language for displaying geographic data and visualizations for Web-based 3Dbrowsers. In this case, KML files display not mountains and cities, but celestial objects as well as annotated data files. Users can add their own content by converting it into a KML file and posting it at either Google Sky or on the Web so that others can add it, if they choose. One such example is an orrery that shows the positions of the planets in the solar system with respect to each other on a particular night.
"I'm coming across this problem that the kids are way ahead of teachers," says Carol Christian.
Lior Ron, a product manager for Google Sky, says the program encourages users to see Earth in perspective with the vastness of the universe. "We hope that Google Sky will bring about a fundamental change in the way we perceive our place in the universe, just as Google Earth changed how we look at our planet," he says. "A number of [theorists] have talked to us about how looking at things like the IRAS [infrared astronomical satellite] infrared map in the Web version of Google Sky really brought a physical reality to their mental model of the sky that they hadn't had previously," says Ron.
One of the most fascinating aspects of WWT and Google Sky is how they allow you to view celestial objects in context with their surroundings in the immensity of space. For example, when you zoom in on the region of sky known as Hubble Ultra Deep Field, you'll discover it is just one-tenth the diameter of the full Moon, small enough to cover with a pencil tip held at arm's length. But when you follow the clickable links, you'll discover this tiny bit of celestial real estate contains more than 10,000 galaxies.
Field of Dreams
The advent of these virtual telescope programs is being celebrated by astronomers, but as Djorgovski notes, measuring their impact on education is tricky. Carol Christian, an astronomer at the Space Telescope Science Institute, home of the Hubble Space Telescope, agrees. "It's something that's going to take years," she says. "This isn't something you can do in a couple of months. Right now it's a field of dreams. We built it. Will they come?"
Christian believes the key to Google Sky's success will be innovative educators. "I'm coming across this problem that the kids are way ahead of teachers," she says. "We need to get teachers... to understand that the student of the future and the worker of the future needs to be facile with finding information, analyzing it, applying critical thinking, making decisions, and finding the data they need to answer a question."
To date, both the WWT and Google Sky claim millions of active users. If these numbers are any indication, both applications will soon be an essential part of the science classroom and museum, as well as a powerful tool that will enable researchers to access, publish, and update data in context with the very universe they study. The virtual telescope is a field of dreams with unlimited possibilities, all of which will be explored and augmented by users in ways we can only speculate about now. In the not-too-distant future, computer scientists may look back on the rise of applications such as the WWT and Google Sky as forerunners of the much ballyhooed Web 3.0 era, which would be fitting since it promises to be light-years ahead of today's Internet.
Figures
Figure. Microsoft's Worldwide Telescope contains a wealth of data and images, such as this partial view of the Orion Nebula from Sloan Digital Sky Survey.
Figure. A view of the Andromeda Galaxy, a spiral galaxy located more than two million light-years away, as it appears in Google Sky.
©2009 ACM 0001-0782/09/0100 $5.00
Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee.
The Digital Library is published by the Association for Computing Machinery. Copyright © 2009 ACM, Inc.
No entries found