UDF 423 is the spiral galaxy in the lower right quadrant of the Hubble Ultra Deep Field.
UDF 423 is the Hubble Ultra Deep Field (UDF) identifier for a distant spiral galaxy. With an apparent magnitude of 20,[1] UDF 423 is one of the brightest galaxies in the HUDF and also has one of the largest apparent sizes in the HUDF.[1]
Distance measurements
The "distance" of a far away galaxy depends on how it is measured. With a redshift of 1,[2] light from this galaxy is estimated to have taken around 7.7 billion years to reach Earth.[3] However, since this galaxy is receding from Earth, the present comoving distance is estimated to be around 10 billion light-years away.[3] In context, Hubble is observing this galaxy as it appeared when the Universe was around 4.9 billion years old.[3]
