RD1

RD1 (0140+326 RD1)
RD1 as viewed by the W. M. Keck Observatory
Observation data (J2000 epoch)
Constellation	Triangulum
Right ascension	01^h 43^m 42.8^s
Declination	+32° 54′ 00.0″
Redshift	5.34[1]
Distance	around 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

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]

References

1. arXiv, "A Galaxy at z = 5.34". (209 KB), 11 March 1998
2. 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