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Calculating Distance
Between Alien Suns


Astronomy Space Software - Space Stars in the NeighborHood: Viewing Cube with an interesting knot of stars around 61 UMa.
Viewing Cube showing several stars near 61 Ursae Majoris (61 UMa).

Select a Starting Point

First, you need to select your starting point for calculating a distance. Merely point and click the desired star. In this example, we have chosen 61 Ursae Majoris (61 UMa). Nearby are an unusually high number of mid-dwarfs very close by.

Sometimes it is helpful to click on the "Center On" button (see below) and to reduce the scale of the Viewing Cube to minimize the clutter of stars and to make it easier to find that for which you are looking. Then you merely click on the "Calc Distance" button, then select the star to which you want to calculate. This second star is your "distance target."

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Astronomy Space Software - Space Stars in the NeighborHood: Star Data and Hood Tools panels.
Star Data panel and Hood Tools with "Center On" and "Calc Distance" buttons.
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Astronomy Space Software - Space Stars in the NeighborHood: Viewing Cube and the last step in calculating distance.
The magenta (pink) marker surrounds the "distance target" star. Viewing Cube set to 8 parsec scale.

Select a Target Star

After clicking the "Calc Distance" button, you merely select the other star in the distance calculation. This is shown in the Viewing Cube by a magenta (hot pink) marker.

The "Calc Distance" button now becomes a "Done" button, and below it, the distance in either parsecs or light years. Switch between the two units by selecting or deselecting View, Light Years from the main menu, or by using CTRL-Y to toggle between the two.

In our example, we find that the target star (Groombridge 1830) is far closer to 61 UMa than Alpha Centauri is to Sol (our sun) and Earth. But astronomical science tells us that Groombridge 1830 is one of the galactic halo stars—an underluminous sub-dwarf (G8 VI). So, the two stars are not part of a family, but merely a serendipitous pair which will soon pass each other. The luminosity class (VI) frequently gives this away.

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Astronomy Space Software - Space Stars in the NeighborHood: Hood Tools with the distance calculated.
Hood Tools "Calc Distance" button now says "Done." Below it resides the calculated distance.
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Sometimes a system contains more than one star, and sometimes, because of chance alignment in the Viewing Cube, you click on more than one star at a time. The following dialog box appears when you need to decide which star is to be the distance target.

Stars in the NeighborHood: 'Select Target Star' dialog box.
Dialog box for selecting the distance target star from two or more stars.
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Astronomy Space Software - Space Stars in the NeighborHood: Viewing Cube showing more stars around 61 UMa including some with planets.
Viewing Cube scale set at 16 parsecs. More stars visible, including several know to have planets.

More Calculating
by Point-and-Click

This view shows the Viewing Cube scale expanded to 16 parsecs (from 8 pc shown earlier). Natually, this includes more stars even though we've omitted all types but mid-dwarfs and hot dwarfs. Here we find the distance between 61 UMa and the closest system known to have planets, 70 Virginis (70 Vir).

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