UDF 423

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]

UDF 423
Spiral galaxy UDF 423 in the Hubble Ultra Deep Field
Observation data (J2000 epoch)
Constellation	Fornax
Right ascension	03h 32m 39.16s[1]
Declination	−27° 48′ 44.7″[1]
Redshift	1 (or 0.46)[2]
Distance	7.7 billion light-years (or 4.7 billion light-years) (light travel distance)[3] ~10 billion light-years (or 5.7 billion light-years) (present comoving distance)[3]
Apparent magnitude (V)	20[1]
Characteristics
Type	Sab
Apparent size (V)	0.11' x 5.04"[1] or 0.0027' x 0.0027'

UDF 423 is the spiral galaxy in the lower right quadrant of the Hubble Ultra Deep Field.

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]

See also

• List of Deep Fields