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RD1 (0140+326 RD1)
0140+326 RD1
RD1 as viewed by the W. M. Keck Observatory
Observation data (J2000 epoch)
Right ascension 01h 43m 42.8s
Declination+32° 54′ 00.0″
Distancearound 12.5 billion light-years
(light travel distance)[2]
~26 billion light-years
(present comoving distance)[2]

RD1 or 0140+326 RD1 is a distant galaxy, it once held the title of most distant galaxy known.[3] RD1 was discovered in March 1998, and is at z = 5.34,[1] and was the first object found to exceed redshift 5.[4] It bested the previous recordholders, a pair of galaxies at z=4.92 lensed by the galaxy cluster CL 1358+62 (CL 1358+62 G1 & CL 1358+62 G2). It was the most distant object known to mankind for a few months in 1998, until BR1202-0725 LAE was discovered at z = 5.64.

Distance measurements[edit]

The "distance" of a far away galaxy depends on what distance measurement you use. With a redshift of 5.34,[1] light from this galaxy is estimated to have taken around 12.5 billion years to reach us.[2] But since this galaxy is receding from Earth, the present comoving distance is estimated to be around 26 billion light-years.[2]


  1. ^ a b c arXiv, Dey, Arjun; Spinrad, Hyron; Stern, Daniel; Graham, James R.; Chaffee, Frederic H. (1998). "A Galaxy at z = 5.34". The Astrophysical Journal. 498 (2): L93–L97. arXiv:astro-ph/9803137. doi:10.1086/311331. (209 KB), 11 March 1998
  2. ^ a b c d Edward L. (Ned) Wright. "Cosmology Calculator I". Astronomy @ UCLA. Retrieved 2010-10-22.
  3. ^ Astronomy Picture of the Day, A Baby Galaxy, March 24, 1998
  4. ^ New York Times, Peering Back in Time, Astronomers Glimpse Galaxies Aborning, October 20, 1998
Preceded by
ClG 1358+62 G1+G2
Most distant galaxy
2011 — 
Succeeded by
BR 1202-0725 LAE