2 ms·

Any chance there will be enough "parallax" in the 6-month period to get a stereo-distancing map for the galaxies? Or do we already have that from red-shift, rel

Any chance there will be enough "parallax" in the 6-month period to get a stereo-distancing map for the galaxies? Or do we already have that from red-shift, relative luminance or some other means?

perihelions 2y ago
Andromeda (the nearest) is 2e19 km away and has a relative motion of 300 km/s in the radial direction. If we assume the tangential motion is similar, that's 5e9 km of tangential displacement over 6 months, for a total angular displacement of 5e-5 arcseconds (50 microarcseconds). That's well below the precision of every telescope. (Admittedly GAIA, the one designed for parallax measurements, comes close, but its techniques only work on very bright point-source objects). I think these articles answer your question: https://en.wikipedia.org/wiki/Cosmic_distance_ladder https://en.wikipedia.org/wiki/Cosmic_distance_ladder https://news.ycombinator.com/item?id=43151943 https://news.ycombinator.com/item?id=43151943 ("Part two of Grant Sanderson's video with Terry Tao on the cosmic distance ladder (mathstodon.xyz)", 99 comments)
- JKCalhoun 2y ago
  Thank you.