In recent months, my colleagues and I have been working very hard on compiling a massive catalogue which details the position and brightness of roughly 200 million stars located in the northern part of the Milky Way. The catalogue is based on a huge set of images which we collected as part of the IPHAS survey using the Isaac Newton Telescope in La Palma. The data set contains 1.6 TB of compressed FITS images!
Although the paper which describes the new catalogue is still under peer-review, our first major result already appeared on the arXiv today. Using a probabilistic graphical model, Stuart Sale (Oxford) and collaborators used the catalogue to estimate the distance and extinction towards 38 million stars. The result of this effort is a 3D map of extinction (i.e. interstellar dust) across the Northern Galactic Plane:
The new IPHAS catalogue is particularly well suited for this task, because it provides narrow-band H-alpha photometry for stars down to ~20th magnitude. When this data is combined with the IPHAS broad-band magnitudes (Sloan r/i), it yields a good proxy for the intrinsic brightness and colour of each star (which in turn is key to obtaining distance and extinction estimates). In effect, H-alpha photometry is the cheapest-imaginable method to carry out a spectroscopic survey.
To learn more about the project, visit the fancy new website for the IPHAS survey which I created recently.