NASA released a new galactic centre image on 10 November that was supposedly constructed from three previous galactic centre images from Hubble, Spitzer and Chandra. I've now put it into the Milky Way Explorer and you can view it here.

Some of the mysteries around a few of the objects in this image have been discussed on the APOD discussion site. At least one of these objects does not appear on any of the three original images so it is a mystery where it came from.

Gregory Dobler, Douglas Finkbeiner and colleagues have released a set of all-sky gamma ray images based upon the Fermi Large Area Telescope data release back in August. I've put a colour composite of three of these images in the Milky Way Explorer.

Normally I work with the full FITS format data released by astronomers, but in this case, the FITS files use the fairly obscure HEALPix projection which unfortunately is not yet supported by a number of key software tools. For example, Aladin hangs when I try to read these FITS files. So for the moment, I've used the black and white jpeg images also supplied to create the colour composite.

I experimented with a number of data combinations, and ended up using the smoothed versions (with no point sources removed) for these energy ranges: 0.5 to 1 GeV (red), 2 to 5 GeV (green) and 10 to 20 GeV (blue). Higher energy levels up to 300 GeV are available, but the higher energy gamma rays are not particularly constrained to the galactic plane. According to my reading of the accompanying paper, it appears that these higher energy photons are mostly from relatively local objects (within a few thousand parsecs).

The Fermi data is not very high resolution, but nevertheless, it is interesting to see major gamma ray concentrations in the directions of Orion, the Taurus and Ophiuchus dark cloud complexes, and the Large Magellanic Cloud.

I've added the recent Chandra X-ray image of the galactic centre to the Milky Way Explorer.

I've added a BFS overlay map as the BFS catalog corrects the position errors in the Sharpless catalog. The nebula overlays are described here.

Every so often I descend from my austere ivory tower and engage in discussion on various astronomy discussion boards. In this recent exchange, I suspect that the person who posted the original question is not really part of the target group for this site, but the exchange has been entertaining and has attracted about 40 new visitors to Galaxy Map so far. If you are one of them, welcome!

As promised in my last blog entry, I've created overlay maps for the Gum, RCW and Sharpless nebulae. You can find the links and a preliminary analysis, including a description of a surprising error in the Sharpless catalog, here.

As I've been going through my commentary on the RCW catalog, I've come to realise that there are several dubious or erroneous cross identifications in the RCW catalog, especially with regard to objects in the Gum catalog. In several cases, it appears that Colin Gum was actually referring to a different object or only part of the object as later defined by RCW. To deal with this, I'm going to put up a map showing the locations and extents of all the objects in the Sharpless, RCW and Gum catalogs.

My commentary on the Gum catalog currently uses the coordinates for these objects given in SIMBAD. However, these coordinates are often derived by SIMBAD using identifications with other nebulae and do not reflect the actual data given in Gum's original catalog. Unlike the Sharpless and RCW catalogs, Gum's original catalog data is not available through Vizier, so as a first step, I have manually entered Gum's original data for each of the 97 entries in his catalog into an Excel-format spreadsheet.

Gum supplied 1900 epoch RA and Declination data for these objects. I've used the Python ephem library to convert these into current l and b galactic coordinates and added these to the spreadsheet as well. (Note that the galactic coordinates supplied by Gum in his original catalog are based on the old Lund pole system and I have not included these in the spreadsheet.)

You can find the Gum spreadsheet here. I'll post another blog entry when the nebula map is ready.

I've simplified the interface, fixed a few bugs, and most importantly, added several new datasets to the Milky Way Explorer. There is now context-sensitive help, so you can get information on each map you are looking at by clicking the Help button.

I've tested the interface in Internet Explorer 7, Firefox 3.5 and Safari for Windows.

You can go directly to the Milky Way Explorer here but please read the documentation first if you haven't used it before.

Some recent changes to the Google Maps API broke some of the marker and overlay functionality for the Milky Way Explorer (especially for the MSX and Spitzer maps).

I've linked in an older version of the API javascript and now everything is working again.