UDF 423

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UDF 423
UDF 423
Observation data (J2000 epoch)
Constellation Fornax
Right ascension 03h 32m 39.16s[1]
Declination −27° 48′ 44.7″[1]
Redshift 1[2]
Distance 7.7 billion light-years
(light travel distance)[3]
~10 billion light-years
(present comoving distance)[3]
Apparent magnitude (V) 20[1]
Apparent size (V) 0.11' x 5.04"[1]
See also: Galaxy, List of galaxies
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[edit]

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 5.9 billion years old.[3]


  1. ^ a b c d e f "UDF 423". Wikisky. Retrieved 2010-11-03. 
  2. ^ a b Sangeeta Malhotra. "As far as the Hubble can see" (PDF). Arizona State University. Retrieved 2010-10-28. 
  3. ^ a b c d e Edward L. (Ned) Wright. "Cosmology Calculator I". Astronomy @ UCLA. Retrieved 2010-10-22.