This is a pannable and zoomable face-on map of the Milky Way galaxy within about 650 pc (2100 ly) of the Sun. It is derived from density isosurfaces of subsets of the 1069480 stars that had relatively low error measurements (error/parallax < 0.2) in the Tycho-Gaia Astrometric Solution (TGAS) star parallax catalog released as part of Gaia DR1. TGAS is supplemented with the older Hipparcos dataset to add missing brighter stars.
As Tycho-2 is very uncomplete beyond relative magnitude 11, I have restricted the star selection to only stars with relative magnitude < 11. I used a subset of these stars that should be visible throughout the 650 parsec radius (ignoring dust). This implies an absolute magnitude of approximately 1.5, so I have restricted the stars used for mapping to those with an absolute magnitude of 1.5 or brighter.
The green "bright" 70% density isosurface shown in these images is computed using about 140 thousand stars and a gaussian normal with a sigma of 8 parsecs. It shows the major dense clumps of stars. The blue "hot" star density isosurfaces are computed using the 5800 star subset of the bright stars with 2MASS J-H colour index <= -0.032 (O and B class stars) and a gaussian normal with a sigma of 8 parsecs.
The isosurfaces are filtered to remove small connected regions with less than 5 stars, revealing the larger regions.
The stars actually displayed on the map are not the complete set used for mapping, but are the stars found within the 70% density bright star isosurface or the selected bright star isosurface(s). In effect, the map shows the denser concentrations of stars in the solar neigbourhood and the brightest stars within those denser concentrations.
In addition I have added all the stars with absolute magnitude brighter than -1 (green labels). I have also provided yellow labels for stars in the hot isosurfaces with absolute magnitude brighter than -1 and white labels for stars in the bright isosurfaces with absolute magnitude brighter than -1. You can see these if you set the labels to isosurface or stars.
Check the Galaxy Map blog for more details on how these isosurfaces were constructed.
The dust overlay in red is taken from figure 3 (top) in this preprint: Three-dimensional mapping of the local interstellar medium with composite data, Capitanio, Letizia; Lallement, Rosine; Vergely, Jean Luc; Elyajouri, Meriem; Monreal-Ibero, Ana eprint arXiv:1706.07711
The direction of the centre of the galaxy is towards the top of the map.
You can use the controls at the upper right to choose the hot isosurfaces to display and select general map and/or more detailed isosurface labels. Beneath the search box are two options:
At the upper left are controls to zoom in and out and return to the home view.
You can also move left, right, up and down by dragging your mouse, using the arrow keys, or using the WASD keys. You can zoom in and out using the + and - keys or your mouse wheel.
Clicking or tapping will zoom into the current position. Double clicking/tapping will move the map to the current location of the tap or mouse pointer.
Individual star data is activated at the highest zoom level. Hovering over a star will give its name and distance above and below the galactic plane. Clicking on a star will bring up a box that describes the star in more detail, including the isosurface regions it appears in, links to the Tycho star map, SIMBAD, and various Vizier star catalogs.
The galactic longitude and distance from the Sun along the galactic plane of the current mouse pointer location appear at the lower left.
The isosurface labels list the identifier, a name, the distance of the centre of the isosurface in parsecs from the galactic plane, and the number of hot stars / bright stars / all stars located within the isosurface.
The names given to the isosurfaces and other map regions are purely my own invention but are derived where ever possible from the names of star clusters or the brightest star found within the region.
Kevin Jardine
Galaxy Map