# Counting Nearby Stars

In my previous post, I casually stated that there are 61 stars in the region within 5 parsecs of the Sun -- at least according to the Gliese Catalog of Nearby Stars. I did not state where you could get that information for yourself. This short post describes how to figure this out for yourself. Here is my approach:

• Get a copy of the Gliese Catalog here.
• Look in the readme file here to understand the document format.
• Many of these stars have common names that you can find .
• Analyze the text file for the nearby stars in Excel like I did here.

My quick and dirty analysis shows that there are 61 stars within 5 parsecs of the Sun. I put together an Excel table but it is my second favorite software tool -- Mathcad is my favorite. I did add a couple of columns to the original Gliese columns: (1) a column of common names, and (2) the distances to the stars in light-years. The Gliese catalog just gives the milliarcseconds of parallax and I needed to convert the milliarcseconds to light-years using the following formula.

 $\displaystyle d[\text{light-years }\!\!]\!\!\text{ =}\frac{{{d}_{AU}}[\text{km }\!\!]\!\!\text{ }}{\frac{\pi \left[ \text{radians} \right]}{180{}^\circ }\cdot \frac{\theta [\text{milliarcseconds }\!\!]\!\!\text{ }\cdot \text{0}\text{.001}\left[ \frac{\text{arcseconds}}{\text{milliarcseconds}} \right]}{3600\left[ \frac{\text{arcseconds}}{\text{degree}} \right]}\cdot {{d}_{LightYear}}[\text{km }\!\!]\!\!\text{ }}$

Here is the table I put together. I should note that new stars have been discovered since the Gliese table was put together (example). This is just a rough order of magnitude calculation (Fermi problem) and the results are good enough for what I am doing here.

 Gliese Reference Common Name Distance (Light-Years) Sun Sun 0.00 GL551C Proxima 4.24 GL559A αCentauriA 4.37 GL559B αCentauriB 4.37 GL699 Barnard's 6.00 GL406 Wolf359 7.82 GL411 Lalande21185 8.23 GL65A BLCeti 8.59 GL65B UVCeti 8.59 GL244A SiriusA 8.60 GL244B SiriusB 8.60 GL729 Ross154 9.59 GL905 Ross248 10.36 GL144 εEridani 10.70 GL447 Ross128 10.86 GL866A Luyten789-6A 11.11 GL15A Groombridge34A 11.30 GL15B Groombridge34B 11.30 GL845A εIndiA 11.32 GL820A 61CygniA 11.33 GL820B 61CygniB 11.33 GL725A Struve2398A 11.43 GL725B Struve2398B 11.43 GL71 tauCeti 11.44 GL280A ProcyonA 11.44 GL280B ProcyonB 11.44 GL887 Lacaille9352 11.50 GJ1111 DXCancri 11.86 GL54.1 YZCeti 12.23 GL273 Luyten's 12.37 GL825 Lacaille8760 12.65 GL191 Kapteyn's 12.66 GL860A Kruger60A 12.98 GL860B Kruger60B 12.98 GL628 Wolf1061 13.37 GL234A Ross614A 13.51 GL234B Ross614B 13.51 GJ1061 L372-58 14.04 GL473A Wolf424A 14.09 GL473B Wolf424B 14.09 GL35 VanMaanen's 14.16 NN3522 Gliese3522 14.60 GL83.1 TZAri 14.61 NN3618 Luyten143-23 14.68 GL1 Gliese1 14.75 NN3622 Gliese3622 14.80 GL674 Gliese674 14.89 GL440 Gliese440 14.97 GL832 Gliese832 15.21 GL380 Groombridge1618 15.34 GJ1002 Gleise1002 15.37 GL687 Gliese687 15.38 GJ1245A Gliese1245A 15.43 GJ1245B Gliese1245B 15.43 GL682 Gliese682 15.46 GL876 Gliese876 15.48 GL166A 40EridaniA 15.79 GL166B 40EridaniB 15.79 GL166C 40EridaniC 15.79 GL388 ADLeo 16.04 GL768 Altair 16.27
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