Where is the center of the Milky Way located? I have downloaded a star database from this page (The HYG Database):
http://astronexus.com/node/34  

And all the stars have (among other parameters) their XYZ coordinates in parsecs according to this definition:  


  X,Y,Z: The Cartesian coordinates of the star, in a system based on the
  equatorial coordinates as seen from Earth. +X is in the direction of
  the vernal equinox (at epoch 2000), +Z towards the north celestial
  pole, and +Y in the direction of R.A. 6 hours, declination 0 degrees


The problem is: I cannot figure out how to calculate the XYZ coordinates of the center of the galaxy (the Milky Way). So the question is: What are the coordinates of the Milky Way center? (Or is it not possible to calculate it just with that information?). This is an example of the data:
Distance estimates to the center of our galaxy vary around $r \approx$ 8000 $\pm$ 200 parsecs.
Its spherical equatorial coordinates are $\alpha$ = 17h45m40s, $\delta$ = -29$^\circ$00'28" (J2000).
Converting those to rectangular form, we have:
$$\begin{align}
X &amp;= r \cos \delta \cos \alpha \approx -437 \pm 11 \ \mathrm{pc} \\
Y &amp;= r \cos \delta \sin \alpha \approx -6983 \pm 175 \ \mathrm{pc} \\
Z &amp;= r \sin \delta \approx -3879 \pm 97 \ \mathrm{pc}
\end{align}$$
As with most celestial objects, its direction is known much more precisely than its distance.
We can't pinpoint its 3D position, but we can narrow it down to a long, fuzzy ellipsoid pointing away from the Sun.