Timeline for How can we be sure that we have identified very distant stars correctly?
Current License: CC BY-SA 3.0
6 events
| when toggle format | what | by | license | comment | |
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| Oct 7, 2015 at 9:08 | vote | accept | Rory Alsop | ||
| Nov 18, 2013 at 10:48 | comment | added | Moriarty | @Arne Parallax is generally most accurate, though all other measurements I can think of should work too (except using redshifts). It's just the fact that galaxies in a cluster tend to move about relative to each other that means we can't use Hubble's constant for nearby objects. The relative movement of these nearby objects (i.e., Andromeda is actually moving towards us) "overpowers" the comparatively small effects due to the expansion of space. | |
| Nov 18, 2013 at 6:50 | comment | added | Arne | Interesting. So basically we are mostly stuck with parallax measurements in our own galaxy? | |
| Nov 17, 2013 at 22:37 | comment | added | Moriarty | This is not generally true for stars. At the distances where Hubble's constant is our most effective measurement of distance, individual stars are too dim to resolve - we just see whole galaxies. We can really only resolve stars like Cepheids within our Local Group of galaxies - and within our galactic neighbourhood, the other galaxies move independently from Hubble's constant. | |
| Nov 17, 2013 at 22:03 | comment | added | Arne | I would say that the redshift in the spectrum plays a big role. The absorption lines are kind of like a fingerprint for the elements in the star. If those are shifted, we can calculate the redshift, and hence the distance. | |
| Nov 17, 2013 at 8:49 | history | answered | Moriarty | CC BY-SA 3.0 |