How old is Polaris?

[LondonNeil]

https://www.scientificamerican.com/article/how-old-is-the-north-star-the-answer-could-change-our-maps-of-the-cosmos/

Intriguing!

[Nik271]

Interesting. The previous estimate  for the distance to Polaris was about 400 ly and this has been revised up by 25%. I wonder how it will affect the cosmic ladder calculations further up and potentially even the Hubble tension. It is looking more and more likely this is due to measurement uncertainty of cosmic distances rather than a gap in the model. 

[LondonNeil]

Yes.  I won't pretend to know all the consequences but it does seem to me that the distance uncertainty is a pretty big issue!

[lunator]

Interesting article. I have looked at Polaris AB many times. I am notbsure how confident astronomers are about their status. If they are physically linked then this could be a major change in the distance ladder.

Cheers

Ian

[Highburymark]

Interesting article. For some reason Polaris B isn’t marked on Sky Safari - the companion is only named as SAO 305 - it’s inconsistent on a number of double stars. 

[lunator]

Had a quick dig around. The AB proper motion is similar and there are quite extensive notes in the Washington Double Star Catalogue. The parallax's come from Hipparchus  7.54 mas for A and 6.16 for B. The GAIA number for B is 7.27 mas no data for A ( too bright I guess). GAIA parallax can be iffy as I have found out working with Robin and Andreas on the double STF216.

It will be interesting to see how this plays out.

Cheers

Ian

[lunator]

Here are the notes in the WDS.
02318+8916 STF  93     alp Umi = 1 UMi = Polaris. Cepheid variable and spectroscopic binary,   .       
                       P = 30y. A close companion has been suspected. The close pair,          .       
                       measured three time from 1937-1939 by R.H. Wilson using an eyepiece     WRH1941b
                       interferometer, was not seen again until Evans et al. (2006) resolved   Evs2006 
                       it with HST.  Wilson's measures agree with the combined astrometric/    .       
                       spectroscopic solution by Gerasimovic (1936), although both orbit and   Ger1936 
                       measures are called into dispute by the more recent orbit of Wielan et  Wln2000 
                       al. (2000), whose solution includes mass estimates, etc.                .       
                       NPOI Limb-darkened diameter 3.28 +/- 0.02 mas,                          NOI1999 
                       R = 46. +/- 3. \rsun.                                                   .       
                       An earlier orbit by Wyller (1957) was rejected from Fourth Orbit        Wye1957 
                       Catalog ("amplitude below noise level")                                 Wor1983 
                       Component B = BD+88@@@7. See discussion of this system by Roemer.       Re_1965 
                     

 While Hipparcos parallax of A 7.56 +/- 0.48 from the original mission   HIP1997a
                       and 7.54 +/- 0.011 mas from the re-reduction, the HST-FGS parallax of   VlF2007 
                       B = 6.26 +/- 0.24 mas implies that that A is high luminosity and        BdH2018 
                       pulsating in the second overtone if AB is physical, i.e., the distance  .       
                       to B is the same as A.                                                  .       
                       

The C component was observed by Burnham in the late 19th century, then  Bu_1894 
                       not seen again until the early 21st century by Daley and Ashcroft.      Dal2006a
                       The extremely large magnitude makes the pair too close for most large   .       
                       astrometric surveys.                                                    .       
                       The D component has also been recently recovered in 2MASS data.         TMA2003 
                       According to Jim Daley, the R-I color for C is 0.56 and for D it is     .       
                       0.67. The V-I color for D is 1.08.                                      Dal2006b
                       AB: H 4   1.

[jjohnson3803]

On 02/06/2024 at 03:42, Nik271 said:

 I wonder how it will affect the cosmic ladder calculations further up and potentially even the Hubble tension. 

I've been wondering about our "conventional wisdom" re: Cepheids for awhile.  Actually, I've been wondering about Type Ia supernovae as an accurate distance measure at high z too.  Ah well, time will tell...