Virgo Explorer

It's all very well having a 3D view of what a galaxy cluster really looks like (sort of), but what if you want to do actual science ? Sadly we astronomers do not sit around all day gawking at pretty pictures like intergalactic voyeurs. What we actually do is to look for trends in data, to see how one quantity varies with another.

Of course there are plenty of plotting packages that can present data in 3D, but Blender has the advantage of being specifically designed to look at 3D data very easily. Moving the viewpoint, changing what is visible and how it is displayed are extremely easy. Sadly, the basic functions of any graphing tool - like displaying axes - are missing, so these have to be done manually.

Another key feature that's needed is to select and colour the galaxies according to any given parameter. So I wrote a simple Python script that reads in a catalogue file from GOLDMine. You can choose which parameter you're interested in via a drop-down menu, and select (for example) all the galaxies with optical magnitudes brighter than whatever value. You can also display all the available information on a selected galaxy.

Maps of the Virgo Cluster in position-velocity space. Left :early-type galaxies. Right : late-type galaxies.

A slighly more advanced routine lets the user display galaxy properties by colour, rather than just selecting them as discrete variables. So, for example, if you want to look for a trend in galaxy morphology directly, rather than plotting any complicated morphology-density relation, you can do so. Another (less polished) script lets you colour according to one variable minus another (e.g. B-V magnitude - this what astronomers mean when they talk about colour).

Virgo galaxies coloured by morphology. Left - red-blue colour mapping. Right : HSV colour method

Of course, if you want to see that galaxy in the optical, a couple of keystrokes loads the layer with pretty pictures. This is actually the default when you open the file - if you just want to interactively explore the Virgo cluster, all you need is Blender and the Virgo file. However, if you want to use the selection/parameter colour scripts, you'll need (specifically) Blender 2.49 and at least a basic knowledge of Blender.

The file is ~100 MB and contains 781 textures, so it may take a while to load.

I'm currently investigating the possibility of making a web-based version of this that wouldn't require Blender at all.

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