Slice of 37,859-star tour

kj37859 data


Kevin Jardine has put together a list of 37,859 bright stars from the Gaia DR2, StarHorse, and Hipparcos databases, going out to 3,000 parsecs from Earth. He describes his collection as follows.

"Several of the maps contain overlays of luminous stars. These are determined by taking Gaia DR2 stars with low astrometry errors (err/plx< 0.2, G > 5 and RUWE < 1.4). If these stars are in the 2MASS and StarHorse catalogs and the StarHorse quality flags are (SH_GAIAFLAG == '000') and (SH_OUTFLAG == '00000') and the 2MASS quality flag is 'AAA', then we use the StarHorse dereddened absolute magnitude, otherwise we calculate the absolute magnitude using Gaia G and the parallax with a zero point correction of -0.029. We've also supplemented this data set with Hipparcos 2007 re-analysis stars with err/plx < 0.2 if they are not in our list."

The collection is available for download as an xlsx spreadsheet at all_3kpc_luminous_merged.zip. Jardine discusses the collection in an interesting thread on his @galaxy_map Twitter account.

The spreadsheet contains xyz-coordinates in the "xg, yg, zg" fields. The description for xg is "galactic x coordinate using the distance associated with the catalog in the catalog field (origin at Sun)", and similarly for yg and zg.

To build the TSP instance, we scaled Jardine's coordinates by 10 to put them into units of 1/10th parsecs. The resulting xyz triples are listed in each of the following two files, one star per per line.

  • kj37859.xyz, list of coordinates
  • kj37859.tsp, the coordinates in TSPLIB format.

To match the points in the TSP data to the original astronomy databases, in the following file we list for each entry the first three fields in Jardine's spreadsheet, containing (1) the data source (StarHorse, Gaia DR2, or Hipparcos), (2) Gaia DR2 source ID, and (3) the Hipparcos ID.

  • kj37859_names.csv

An optimal tour for kj37859 is given in the following files.

  • kj37859_tour.txt, a list of integers from 1 up to 37,859, giving the order the stars appear in the tour,
  • kj37859_order.txt, the points for kj37859 permuted in the tour order,
  • kj37859.tour, the tour in TSPLIB format.

Log files for the LKH and Concorde runs to solve the kj37859 TSP can be found on the compute page.

Computing Distances

To create an instance of the TSP, we need to specify precisely the point-to-point distances we use. For this we adopt the standard TSPLIB norm for 3D Euclidean data. This norm takes the straight-line distance between two points and rounds the resulting value to the nearest integer. In our case, the star-to-star distance is therefore measured to the nearest 1/10th parsec. Here is a simplified version of the computer code used in Concorde for the distance calculation.

Interactive View

Rotating -- See the point set rotating in 3-space. Stars are represented by twinkling points.