The Internet as a (WorldWide) Telescope

What famous observatory has no lens and no mirror? Such research institutions weren't uncommon in centuries past - Claudius Ptolemy constructed such an observatory at Alexandria in the 2nd century, and in the 16th century, Tycho Brahe built Uraniborg ("the castle of Urania") and Stjerneborg ("star castle") to study the night sky. Now the modern age has its own version: the internet.

The wealth of astronomical data available online grows every day, collected from spacecraft such as Hubble, Spitzer, and Chandra, as well as smaller, groundbased observatories around the globe. And there's a portal through which anyone can access these data to view the universe in its multiwavelength glory: the WorldWide Telescope (WWT).

This software runs on almost any computer or tablet via its web browser. You can also download an application to your Windows desktop. The WorldWide Telescope accesses the internet's amazing treasure-trove to provide beautiful all-sky imagery at dozens of wavelengths, as well as detailed images of many celestial targets. In addition, it offers links to in-depth information about individual objects, using diverse databases ranging from Wikipedia to NASA's Astrophysics Data System, which holds all astronomical literature published since the 1800s. WWT basically functions as an interactive web browser for the sky, a sky browser of sorts. Oh, and it's free.

A Virtual Observatory Is Born

As the internet grew over the decades, astronomers used it mainly as a tool for remote observing, accessing both distant mountaintops and space satellites. But as web browsers became more powerful, and data exchange over the web became commmonplace, astronomers around the globe realized the potential for creating an online set of interconnected astronomical data and research tools that would ultimately offer the best "observatory" the world had ever seen. In 2001 the National Science Foundation awarded a large consortium of institutions an initial grant to create a framework that would eventually evolve into the Virtual Astronomical Observatory. Related virtual observatory efforts appeared around the world, especially in Europe and the UK.

The observatory's backbone was a semi-volunteer organization that created standards for all astronomical data to be entered into the database. The group was invisible to most practicing astronomers but critical for the virtual observatory's operations. For example, most astronomical images come in a FITS (Flexible Image Transport System) format. Virtual observatory standards put in place a decade ago allow astronomers to search, view, and exchange these images.

Today, in spite of funding woes worldwide and particularly in the U.S., the Virtual Observatory has created a set of free astronomical resources that are arguably more accessible and more coordinated than in any other field of science. But how can the public access those resources with an easy-to-use and powerful interface? Enter the WorldWide Telescope.

Building the WorldWide Telescope

Amateur astronomer Curtis Wong grew up in Los Angeles with a deep desire to explore the amazing sky he saw in magazines like Sky & Telescope. But between the city lights and the smog, all he could see with his 60mm refractor were the moon, a few planets, and some nebulae. What he really wanted was a gigantic telescope under a dark sky, and an astronomer by his side to explain what he was seeing.

In 2000 Wong was working at Microsoft Research with big data computer scientist Jim Gray and astronomer Alex Szalay (Johns Hopkins University), who were creating software to make Sloan Digital Sky Survey data available to researchers and the general public. Gray and Szalay wrote a seminal paper envisioning "The World-Wide Telescope, an Archetype for Online Science", and Wong realized that all the elements were there to realize his childhood dream.

At a 2005 conference where Wong presented his vision for what he called the Universe Project, he befriended Alyssa Goodman (Harvard University). They bonded over a shared desire to visualize astronomy and engage the public, and when Wong finally got the go-ahead to make the Universe Project a reality in 2006, Goodman and other professional astronomers advised him on its content and usability. Wong had the good fortune to collaborate with Jonathan Fay, an extraordinary software architect and amateur astronomer himself, and together they built the software between 2006 and 2008 - Wong designed the experience and Fay developed the code.

They renamed the software WorldWide Telescope in honor of Gray, who was lost at sea in 2007. The software received a sneak preview at a 2008 TED conference, and Sky & Telescope featured WWT the same year. S&T editor Stuart Goldman explained that WWT is so feature-laden that you should "watch the introductory tours to learn your way around the program — and then left- and right-click on everything!" This is still good advice -- and there's much more to find now than there was in 2008.

Tour the Universe

Today's amateur astronomers are blessed with a wide variety of tools that show the night sky at any give time or location. The WWT offers the same functions as other planetarium software, but its quality and breadth is unique. WWT features high-resolution images from ground- and space-based telescopes that capture the sky in more than 85 different wavelengths, most of these beyond the spectral window of the human eye.

In its most basic view, WWT features the night sky in visible light, based on Digitized Sky Survey images. This view shows as many as a trillion pixels across, allowing users to zoom from a 60-degree-wide field of view of the Milky Way to a close-up of, say, the wisps of the Veil nebula. Users can also compare two images, either at different resolutions or different wavelengths.

Start playing with WWT controls and a range of options opens up. Simulate eclipses as viewed from the ground or space, or fly to the Moon to see the Lunar Reconnaissance Orbiter's high-resolution images and elevation maps. Travel to Mars and fly through Valles Marinaras, or see each of the 500,000+ asteroids tracked by the NEO center. Then zoom out from the solar system into the Hipparcos catalog and fly through the 100,000+ stars in our neighborhood. Keep zooming out, and you'll pass through the million SDSS galaxies and glimpse the universe's large scale structure. Right-clicking on any star, planet, or galaxy will reveal deeper information on that object from multiple online sources.

But WWT isn't meant just for solo use. Users can create and share guided sky tours, saving their path through the program as if a virtual camera were recording the experience. These tours look like videos and can include musical scores, narration, additional imagery, and hyperlinks. But unlike videos, users can interact with the tour even as they experience it, exploring a particular topic in detail before picking up right where they left off.

Astronomers and educators have already created dozens of sky tours, spanning topics from the very general (such as Astr