|
The actual orbit of the Earth around the Sun (ecliptic) is tilted at about 60 degrees to the galactic plane.
The Earth's axis remains essentially tilted in the same direction relative to the galaxy (ignoring precession of course). Thus, the Earth's axis stays pointed to the north and south celestial poles and that is why objects generally can be given fixed celestial co-ordinates. The cycle of axial precession for the Earth takes about 26000 years, the orbit of the Sun around the galaxy takes some 225 million years. Precession will require noticeable change of celestial coordinates (one degree about every 72 years), while the coordinates of extra galactic objects will change minutely over time relative to galactic objects (one arcsecond about every 174 years).
Regards Rob
Last edited by Robh; 04-12-2011 at 07:06 PM.
Reason: Grammar.
|