Sun-Centered Coordinate Grids
Sun-Centered Coordinate Grids
| Group Name | 1lmo, 1ly, 10ly, 100ly, 1kly, 10kly |
| Reference | -- |
| Prepared by | Brian Abbott (AMNH/Hayden) |
| Labels | Yes |
| Files | target1lweek.speck, target1lmonth.speck, grid1lmonth.speck; target1ly.speck, grid1ly.speck; target10ly.speck, grid10ly.speck; target100ly.speck, grid100ly.speck; target1kly.speck, grid1kly.speck; target10kly.speck, grid10kly.speck |
| Dependencies | none |
The Sun-centered coordinate grids consist of two superimposed meshes. One mesh is a square coordinate grid with lines through the origin and lines appearing halfway along the grid's length. For example, if the grid is 1 light-year, then grid lines would cross the origin, mark the 0.5-light-year (6-light-month) point, and mark the edge of the grid. The other mesh forms lines of constant radius. These are rings around the Sun (not to be confused with orbits) that mark where these distances lie in space.
The grids in each of these data groups are nested within one another and range from the light-day scale (in 1lmo) to the 10,000-light-year scale (in 10kly). The grids are placed in the Galactic plane.
Using the Grids
Each grid is centered on the Sun and covers a size scale that is well suited for particular data sets in the Atlas. The units are in light-travel time and appear as “lw” for light-weeks, “ly” for light-years, and “kly” for kilo-light-years (1,000-light-year units).
| 1lmo | The light-month grid extends to 4 light-weeks, or 1 light-month. Lines of constant radius are drawn for the first 7 light-days, after which lines are drawn each light-week. The overlying grid has increments every two light-weeks.
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| 1ly | Beyond the light-month grid is the light-year grid. It consists of lines of constant radius for each light-month and an overlying grid in increments of 6 light-months. Displaying the Oort cloud along with this grid provides a good measure for the Oort cloud sphere (about 10.5 light-months).
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| 10ly | A 10-light-year grid with lines of constant radius every year. Viewing the grid face-on along with the stars, one is able to see the locations of those nearby stars close to the plane. While this is not an exact measuring tool, it's easy to see that Alpha Centauri (Proxima) is just more than 4 light-years and Sirius is between 8 and 9 light-years.
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| 100ly | A 100-light-year grid with lines of constant radius every 10 light-years. Here we can see the radio sphere at about 65 light-years and many of the exoplanets.
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| 1kly | A 1,000-light-year (1-kilo-light-year) grid with lines every 500 light-years and lines of constant radius every 100 light-years. On this scale we see several of the local OB associations that lie in the Orion Arm (the Sun is located on the inner edge of the Orion Arm, sometimes called a spur), as well as a few of the nearest open clusters.
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| 10kly | The 10 kly (10,000-light-year) grid is large enough to view those nearby data sets that are confined to the plane of the Galaxy, more or less. All the OB associations are found within the grid, as are data from the open clusters, supernova remnants, and HII regions. |
© 2002-2005 American Museum of Natural History
Last Modified: 2007-12-19 by Brian Abbott