I understand that astronomers use right ascension and declination for the position of stars. However both these values strike me as very anthropocentric and, more importantly, unreliable over time as I understand that the Earth wobbles a bit over time so the celestial equator shifts and I guess Sun's rotation around the galaxy and Milky Way's own trajectory should play a role in depreciating the accuracy of those values over time.

So my questions are:

[1] how steady are right ascension and declination values for distant stars over time?

[2] is there a more stable coordinate system or do we lack an absolutely fixed frame of reference?

  • 1
    $\begingroup$ If you use a fixed epoch date, such J2000.0, right ascension and declination values are a lot more stable. The ICRF reference frame that NASA uses is a mostly fixed coordinate system that does not precess or nutate over time. However, it uses our solar system's barycenter as its central point, so it's not 100% fixed. Note that NASA uses ICRF even for data +-15000 years from now. $\endgroup$ – user21 Oct 14 '14 at 0:09

The values are more steady for objects close to Ecliptic poles, but in genenral, they change by a few arcseconds every year.

Yes, we lack an absolutely fixed frame of reference.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.