The SH0ES Project: Observations of Cepheids in NGC 4258 and Type Ia SN Hosts

NGC 4258 plays a crucial role in the Extragalactic Distance Scale because it is the only

nearby galaxy

with a very accurate and precise distance measurement (3% total

uncertainty).

We present results from recent

HST

observations of

Cepheids

in this galaxy, obtained as part of the SH0ES project. By combining ACS and WFPC2 observations from Cycles 12, 13 and 15, we have been able to discover long‐period

Cepheids

with periods up to 130 days.

We also summarize the results nd future plans of the SH0ES project to characterize the properties of

Cepheids

in NGC 4258 and hosts of “ideal” type Ia SNe, with the aim of estimating the

Hubble constant

with a total

uncertainty

below 5%.