## A Conversation for Parsecs

### Just for the sake of Precision...

A Man In Black Started conversation Apr 15, 2000

For the sake of precision about AUs and Parsecs, here's the exact data:

The Speed of Light ("c") = 299,792.458 Kilometers per second.

1 Astronomical Unit ("AU") = 149,597,870.66 Kilometers.

1 Light Year ("Ly") = 9,460,730,472,580.8 Kilometers, or

63,241.0771 AU.

1 Parsec ("Pc") = 30,856,804,791,684.9 Kilometers, or

206,265.0 AU, or

3.26157 Light Years.

The Speed of Light and the distance of an AU can be pulled from any really good Astronomy Book. The rest can easily be calculated.

Also, the precise parallax to the stars of the Alpha Centauri system, according to the data from the Hipparcos-Tycho satellite, is:

Proxima Centauri (Alpha Centauri C) = 0.77233 so the distance is 1/0.77233 = 1.294783318 parsecs or 4.223026427 light years.

Alpha Centauri A & B = 0.74212 = 1/0.74212 = 1.347490972 parsecs or 4.394936129 light years.

Have a nice day...

### Just for the sake of Precision...

Gnomon - time to move on Posted Jul 10, 2008

While the some of the figures given above are correct, don't rely on them all. The poster doesn't understand the concept of precision. While the speed of light is as 299,792.458 km per second, that is only accurate to 9 figures, so you can't derive a figure with 12-digit accuracy from it.

The astronomical unit is the average distance between the earth and the sun. This is certainly not known to the accuracy stated above.

So please disregard that first posting and make your own calculations.

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