It took University of Hertfordshire astronomers 10 years to do it, but their meticulous efforts have resulted in a mindboggingly detailed catalogue of the visible part of the northern section of the Milky Way — a vast swath of space that contains new fewer than 219 million stars.

Looking below, the axes show galactic latitude and longitude (coordinates that relate to the position of the center of the galaxy). The mapped data contain the counts of stars detected in i, the longer (redder) wavelength broad band of the survey, down to a faint limit of 19th magnitude. This is just a small section of the full map, but it portrays in exquisite detail the complex patterns of obscuration due to interstellar dust.

The astronomers used the Isaac Newton Telescope (INT) on La Palama in the Canary Islands to compile the map. You can find a higher resolution image here, which I used to create this zoomed-in image showing a small portion of the map:


From the Royal Astronomical Society's press release:

From dark sky sites on Earth, the Milky Way appears as a glowing band stretching across the sky. To astronomers, it is the disk of our own galaxy, a system stretching across 100,000 light-years, seen edge-on from our vantage point orbiting the Sun. The disk contains the majority of the stars in the galaxy, including the Sun, and the densest concentrations of dust and gas.

The unaided human eye struggles to distinguish individual objects in this crowded region of the sky, but the 2.5-metre mirror of the INT enabled the scientists to resolve and chart 219 million separate stars. The INT programme charted all the stars brighter than 20th magnitude – or 1 million times fainter than can be seen with the human eye.

Using the catalogue, the scientists have put together an extraordinarily detailed map of the disk of the Galaxy that shows how the density of stars varies, giving them a new and vivid insight into the structure of this vast system of stars, gas and dust.

The image included here, a cut-out from a stellar density map mined directly from the released catalogue, illustrates the new view obtained. The Turner-like brush strokes of dust shadows would grace the wall of any art gallery. Maps like these also stand as useful tests of new-generation models for the Milky Way.


The study will appear in an upcoming edition of The Royal Astronomical Society.

Image: Hywel Farnill, University of Hertfordshire.

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