nature.net
December 2007–January 2008
Outward Bound
By Robert Anderson
In November 1958, just a year after Sputnik’s debut, the prolific science fact and fiction writer Issac Asimov published “Our Lonely Planet,” an article in which he reasoned that given the tremendous distances—four light-years even to the nearest star after the Sun, Proxima Centauri—interstellar space travel would take too long to be practical. Nevertheless, the dream of visiting alien worlds is hard to shake.
| ||
|
| |
Google Earth’s Sky feature is the latest Internet application that allows armchair travelers to explore beyond our planet. It is like a planetarium—one that you can explore in three dimensions. You have to download the software to use it, but the link above launches a helpful video clip that shows you how to navigate it. Start by typing in your location on Google Earth, then click the “Sky” button, and you will be looking up instead of down to see the stars and planets currently overhead. You can add or hide information like the artificial lines that connect the stars of the constellations. You can type in any number of celestial destinations—like my favorite, the Sombrero Galaxy—-and you will be pointed in the right direction.
You can then zoom in on objects as if traveling outward from Earth at tremendous speed. Many of the more interesting places are represented by overlain images from the Hubble Space Telescope. You can click on links to get more information about individual stars and nebulae. When viewing the planets, there is a slide bar that allows you move backward and forward in time to track their recent movements across the sky. It claims to have about a hundred million stars and two hundred million galaxies, but, needless to say, I didn’t attempt to check their math.
Another free download that is equally impressive, but launched in 2004 with somewhat less fanfare, is Celestia, created by Chris Laurel, a software designer on sabbatical from Microsoft. Celestia allows you to move freely among 100,000 stars with ability to look back toward the home star or in any other direction. (It’s easy to get disoriented out there.) To get an idea of the voyages this space travel simulator can take you on, download it and click on “run demo” under Celestia in the menu bar. This software has attracted quite a following on the Internet owing to its open code, which allows for “Add-ons” content created by visitors to the site (including imaginary planets such as a terraformed Venus, with appealing oceans of blue water).
A third sky explorer is the Digital Universe Project, created jointly by NASA and the American Museum of Natural History. For a glimpse of what this software allows, go to their science bulletin on “Nearby Stars.” You can watch a short clip made with the program that reveals the fixed stars aren’t so fixed. In a time span of fifty years, the closer ones reveal themselves as they zip across the starry background much like the roaming planets. Astronomers have used those motions to map our neighborhood in the Milky Way Galaxy. An interactive look at how familiar constellations will rearrange themselves in the centuries to come can be found among the simulations at the Department of Physics and Astronomy at the University of British Colombia. Scroll down to “Proper Motion” and you’ll see stars on the move.
If you don’t want to download software, a simple diagram, Stellar Neighbors of the Sun, on a page from the Department of Astronomy and Physics at Georgia State University in Atlanta shows the relative positions of stars out to 3.5 parsecs—units of length equivalent to 3.26 light years. Scroll down this page to learn more about the very closest stars beyond the Sun in the Alpha Centauri group.
Star catalogs of various kinds have multiplied on the Internet. NASA’s Planet Quest: New Worlds Atlas is a good place to go to see where the new extrasolar planets are being found. Scroll down to the “3D New Worlds Atlas” to explore some of the planetary systems that have been discovered nearby. The virtual space can be rotated and individual stars selected for a close up look. This site also helps visitors visualize the small “bubble of space” within our galaxy in which all extrasolar planets have been found.
The Nearby Stars Database, based at Northern Arizona University, aims to have a complete data set of all stars within 25 parsecs of the Sun. Another page, Notable Nearby Stars, is maintained by Solstation.com and gives detailed information on many stars within 100 light-years from Earth.
To see for yourself how astronomers measure the distances to our stellar neighbors, go to the Atlas of Nearby Stars: Projects in Virtual Astronomy by Brian von Konsky, a senior lecturer in the Department of Computing at the Curtin University of Technology in Australia. Here you will find seven experiments you can conduct revealing how parallax (the apparent motion of nearby stars when viewed from different points in Earth’s orbit around the Sun) is used to gauge distance. Another simple demonstration of parallax is hosted by the University of Washington Astronomy Department. For an interesting article on the satellite that mapped an enormous number of stars with great precision, go to From Hipparchus to Hipparcos: Measuring the Universe, One Star at a Time by Catherine Turon, one of the project’s astronomers at the Paris Observatory in France.
Interested in the Big Picture? The Sloan Digital Sky Survey is a project to map the 3D stgructure of the entire Universe, seemingly down to the last galaxy. Reading one of the Survey’s press releases, I learned about their innovative idea to enlist amateur astronomers to help classify—via the Internet—a million or so galaxies in their image bank. Launched last summer, the Galaxy Zoo gives a tutorial on sorting galaxies by their shape and then lets the visitors loose. At its peak, 60,000 galaxies were being served up per hour. When I checked, the project was still going—a great way to advance science without a degree.
Robert Anderson is a freelance science writer who lives in Los Angeles.
Copyright © Natural History Magazine, Inc., 2007