An interesting feature in Stellarium is that as time passes, the virtual star system will evolve, with the sun setting and the various constellations becoming more prominent in the dark night sky. You have a selection of visual effects that you can switch on or off such as the atmosphere, or trace lines for the star systems. Impressive stuff for a few minutes, but once you’ve got the general gist of what Stellarium entails, you’ll quickly tire of zooming out to distant stars and watching as they slowly move across the screen.

While Google Earth brings you detailed photos of our planet’s surface, Stellarium can only achieve a much lower resolution representation of the solar system’s planets, without mentioning the fact that stars are limited to simple white dots zipping through the sky. With over 120,000 stars accurately plotted out in this virtual planetarium, it’s obvious that a lot of work has gone in to its creation. However, Stellarium's excruciating level of detail is likely only to appeal to the real die-hard star gazers.

The idea behind Stellarium is a good one in theory, but when it comes down to it most people will see it as little more than a smart, interactive screensaver. That said, if you have an affinity for astronomy, would like to learn the constellations, or simply enjoy watching beautiful sunsets, then Stellarium is for you.

Download Stellarium 0.11.2 in Softonic

World Wind's real selling point is the quality of its satellite imagery. World Wind reveals Earth in many different perspectives thanks to the large variety of maps. Blue Marble exposes Earth in its true colors, Landsat 7 gives you high resolution imagery, and MODIS can display time relevant data such as earthquakes, fires or floods. Browse over mountains and observe the snowy peaks, the clouds, and the different colors of the rock, with incredible precision. Be aware though that the lower you go, the more detail will appear, and World Wind will take more time to process the image.

A digital globe wouldn't be complete without its own search option. Find a destination by typing its name in the search tool located on the top bar. Landmarks are particularly well catalogued. If you select the landmark finder tool from the top section, World Wind will exhibit small tags for all locations it considers of significance. Click on the tag and you will be directed to the Wikipedia page for that particular landmark, where you'll be able to read all about it. It is important to point out however that the search function in World Wind is not as good at finding cities as it is with landmarks.

Another of World Wind's assets is its usability. Zoom in over the map using the rollover button of your mouse and skim to parts of the screen with your mouse. The more you focus down on a place the more names of cities and significant locations pop up. These can clog up your screen however, so you'd be wise to configure World Wind to only show the information you need, like country borders and urban areas.

To set itself apart from Google Earth, World Wind provides two original tools. Capitalizing on its lunar explorations, the aeronautics administration lets you view the Moon in extremely high definition. Focus in on its craters, deserts and plains and search for Apollo 11's landing site. Additionally, World Wind recreates the infamous Oregon trail mapped out by American adventurers Lewis and Clark at the beginning of the 19th century, stretching out from Independece, Missouri to the Pacific state of Oregon. World Wind points to significant landmarks which should be of interest to students or history amateurs.

World Wind is as good a digital imagery program as Google Earth. While the image resolution process can be sluggish, World Wind manages to set itself apart thanks to its landmark finder and fun tools like the Moon visualizer and the Lewis & Clark trail.

Download NASA World Wind 1.4.0.0 in Softonic

Celestia is a real-time, 3D space simulator that lets you fly around galaxies, checking out all the fascinating things they contain - from planets and stars to asteroids and space stations. It may only be a simulation, but, unless you win the lottery, it is probably the closest you're going to get to the real thing.

For free software, Celestia is extremely complete. It has a wealth of demos, online and offline user guides, a wiki, a forum and even a Wikipedia entry! It is just as well that all this help is available, however, because it is not a particularly easy program to use. In theory, you navigate around the universe by using the mouse or the keyboard. Right-clicking on an object (such as a planet) will bring up various options, while in the tool bar you can perform more complex tasks, such as searching for Bayer designations, taking videos, tracking objects and configuring options. Although all that sounds pretty normal, it is not as easy as it seems.

I found the controls to be jerky and non-intuitive, and despite spending a fair amount of time playing around with it, didn't manage to get it working as well as I suspect it can. Briefly reading the manuals didn't help either, and I think that to get the most out of Celestia, you would have to put some serious research in.

Astronomy fans and those with a burning interest in our galaxy will surely make the effort that is needed to really get the most out of Celestia. The program definitely encourages serious dedication and obviously has been created by a person - Chris Laurel - who loves what he does. Celestia is meticulously researched and put together, and there is a multitude of extra resources on the website.

Celestia: a beautiful and fascinating program for those willing to make the effort.

Download Celestia 1.6.1 in Softonic

WWT does contain space imagery that enables you to observe starts, planets, constellations and other celestial elements without having to buy an expensive telescope, that's true. In that sense, it's similar to Google's space browsing tool. But in my opinion, this app is much more intended for professional astronomers – or at least serious astronomy fans – rather than for people who just want to take a sneak peek at our planet as if they were taking a ride on a NASA shuttle.

Don't get me wrong here: there's nothing wrong with being a serious astronomy app. I'm just warning you in case you expect something else. Other than that, WorldWide Telescope is a great tool that all astronomy fans are going to love. It includes loads of information and also lets you download guided tours from the program itself to learn more about a certain topic.

You can freely move around the sky with your mouse, but I found this a bit confusing and soon preferred to use the image galleries under the Explore menu. These galleries were a bit disappointing though, because you can perfectly see the boundaries of the image you're viewing and so it doesn't feel like a real telescope anymore.

Worldwide Telescope is not a space browser like Google Sky; rather than that, it's a comprehensive astronomy atlas with loads of data, photo galleries and freely downloadable guided tours.

Download WorldWide Telescope Beta in Softonic