National Aeronautics and Space Administration

Object Names/Coordinates Help

Coordinates may be entered in the Equatorial, Galactic, and Ecliptic coordinate systems. The coordinates may be either decimal degrees or in sexagesimal format. A comma is recommended for delimiting the coordinates; however, this is not required for most coordinate formats.

Examples of possible input formats:


• Object name: Cyg X-1
  
  
• Object name: NGC 5195
  
  Note: Object names are resolved by name resolvers and should conform to IAU-assigned abbreviations and standard astronomical nomenclature.
  
  
• Equatorial (decimal degrees): 101.295, -16.699
  
  
• Equatorial (sexagesimal): 6 45 10.8, -16 41 58 (RA in hours)
  
  
• Equatorial (sexagesimal): 6 45.18, -16 42.0 (RA in hours)
  
  
• Equatorial (sexagesimal): 6h45m10.8s, -16d41m58s (explicit sexagesimal units)
  
  
• Equatorial (sexagesimal): 6H45'10.8", -16D41'58" (case insensitive)
  
  
• Equatorial (sexagesimal): 6:45:10.8, -16:41:58 (colon separators)
  
  
• Equatorial (sexagesimal): 6h 45m 10.8s, -16d 41m 58s (spaces are allowed after the sexagesimal units)
  
  
• Equatorial (sexagesimal degrees): 101d17m42.0s, -16d41m58s (RA in degrees)
  
  
• Equatorial (sexagesimal degrees): 101d17:42.0, -16:41:58
  
  
• Equatorial (sexagesimal degrees): 101°17'42.0" -16°41'58"
  
  
• Galactic (decimal degrees): 227.218, -8.876
  
  
• Galactic (sexagesismal degrees): 227d13m04.8s, -08d52m33.9s
  
  
• Galactic (sexagesismal degrees): 227°13'04.8", -08°52'33.9"
  
  
• Galactic (sexagesismal degrees): 227:13:04.8, -08:52:33.9
  
  
• Ecliptic (decimal degrees): 104.089, -39.587
  
  
• Ecliptic (sexagesimal degrees): 104 05 20.8, -39 35 14.9
  
  
• Ecliptic (sexagesimal degrees): 104d05'20.8", -39d35'14.9"
  
  
• Ecliptic (sexagesimal degrees): 104:05:20.8, -39:35:14.9
  
  

As shown above, many of the above formats may be used in any coordinate system; however, the units of the longitude coordinate may depend upon the coordinate system if the syntax does not explicitly identify the units. Equatorial coordinates given in non-explicit sexagesimal formats assume hours of right ascension. For Galactic and Ecliptic sexagesimal formats, the longitude must be given in degrees. All coordinates in any coordinate system given in decimal format are assumed to be degrees.

Some HEASARC Web services (like the X-Ray Background Tool and Browse) allow the user to enter multiple object names and/or coordinate pairs if they are separated by a semicolon.

Example input with multiple object names and coordinates:


• Cyg X-1; Cyg X-2; 16 19 55.07, -15 38 24.8; Eta Car; 19.27, -73.44; Ar Lac

If an astronomical object identifer is ambiguously resolved by the specified name resolver(s) (SIMBAD and/or NED), most HEASARC Tools will display a list of astronomical objects returned by the name resolver(s) that match the entered name. This list is sorted by offset relative to the first match returned by the name resovler(s). No particular merit to the first entry is implied. When this occurs, the user can select one of the identifiers listed by clicking on the object name link. The tool then proceeds to use the coordinates for the selected identifier.