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Announcing the Velocity Explorer

Submitted by Kevin Jardine on 3 June, 2013 - 17:58

About a year ago, the Harvard astronomer Thomas Dame suggested that I might consider experimenting with the 3D visualisation of velocity data. As mentioned in the Velocity section of this site, in the 1950s there was tremendous excitement about the idea of using a rotational model of the Milky Way combined with velocity data to produce a map of the galaxy.

This effort ran into various problems and by the 1970s had been largely abandoned for a number of reasons, some scientific and some cultural (even astronomy has its fashions).

However, recently mapping the galaxy has come back into fashion, partly because of improved and new sources of data, and partly because increased computing power has made much more sophisticated data analysis possible.

Today I'm announcing the Velocity Explorer, an interactive tool for exploring gas velocity in the galactic plane. The Velocity Explorer images were created using a marching cubes algorithm that is more typically used by medical researchers analysing MRI data to visualise tissue structures in the brain and other parts of the body.

It turns out that isosurfaces of constant gas temperature in the Milky Way are a bit like human tissue structures and can be analysed by similar tools.

There is a detailed introduction to the Velocity Explorer here:

I'm pretty sure that the Velocity Explorer is not really what Dame had in mind (I think he was more interested in rotating and otherwise manipulating individual cloud complexes). However, it does fit closely with the overall goal of this site, which is to present research on mapping the Milky Way.

I've used the Velocity Explorer to derive a model for the Milky Way, described here:

and even a partial map:

The model and map were fun to produce and the process I used to create them is described in detail, but they should not be treated too seriously. The problems astronomers faced in the 1950s when using velocity data to map the galaxy are still around. The only reliable way to map the galaxy is radio parallax.

Still, I think that the Velocity Explorer may be a useful tool for professional astronomers and may even suggest good parallax targets for radio astronomers. And the new model of the galaxy described on this site might spark some interesting debate, which can only be good.