The closest Cepheid variable stars

It has long been thought that the two closest Cepheid variable stars were Polaris (Alpha Ursae Minoris) and Delta Cephei, the prototype for this class.  However, recent parallax data from the Gaia Space Observatory suggests that another Cepheid, Eta Aquilae, might actually be slightly closer than Delta Cephei.  Eta Aquilae and Delta Cephei were the first two Cepheid variable stars identified, in 1784, by English astronomers Edward Pigott and John Goodricke, respectively. 

The current status of the closest three Cepheids is summarized in this table: 

Closest Cepheid variables

name	parallax (mas)	distance (ly)	source
Polaris	7.292 ± 0.028	447 ± 2	1
Eta Aquilae	3.711 ± 0.194	879 ± 46	2
Delta Cephei	3.578 ± 0.148	912 ± 38	2
1) Scott G. Engle et al, 2018 Res. Notes AAS 2 126
2) Kayla A. Owens et al., Astrophys.J. 927 (2022)1,8

According to the analysis of the Gaia data in Ref. 2, Eta Aquilae and Delta Cephei are at essentially the same distance, within measurement uncertainty (4–5%).  [note: distance is obtained from the measured parallax by d = 3261 ly/P, where P is the parallax in milliarcsec (mas)]

 Here is a finder chart showing the location of Eta Aquilae (η Aqi):

credit: SkySafariAstronomy.com

On Sunday night (27 July) the sky was remarkably dark, with sqml=21.71 to 21.78. That is almost as good as it gets here in Creede.  These images were obtained with an Olympus E-M1iii + 17mm f/1.8 lens.
 

Eta Aquilae is circled.  Sparkle-6 filter.

The bright star left of center is Altair (Alpha Aquilae, α Aqi).

A closer look.  Softon filter.