Celestial Atlas
PGC 23000 - 23499 ←     PGC Objects: PGC 23500 - 23999 Link for sharing this page on Facebook     → PGC 24000 - 24499
Click here for Introductory Material
Page last updated Jul 22, 2012

PGC 23935 (with
PGC 23937 = Arp 58)
A 14th-magnitude spiral galaxy (type SAB(rs)c pec) in Cancer (RA 08 31 57.7, Dec +19 12 41)

Based on a recessional velocity of 11160 km/sec, a straightforward calculation indicates that PGC 23935 is about 520 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was just under 500 million light years away at the time the light by which we see it was emitted, a little over 505 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.95 by 0.5 arcmin, the main structure of the galaxy is about 135 thousand light years across, but its outer arms extend 0.4 arcmin to the west and 0.8 arcmin to the east (just past its companion, PGC 23937), giving it an overall span of more than 180 thousand light years.

SDSS image of spiral galaxy PGC 23935 and its compact companion, PGC 23937, which make up Arp 58
Above, a 2.4 arcmin wide closeup of PGC 23935 and its companion, PGC 23937
Below, a 12 arcmin wide region centered on the galaxy
SDSS image of region near spiral galaxy PGC 23935 and its compact companion, PGC 23937, which make up Arp 58

PGC 23937 (with
PGC 23935 = Arp 58)
A 17th-magnitude compact galaxy (type cE0 pec?) in Cancer (RA 08 32 00.6, Dec +19 12 06)

For all practical purposes, the 11255 km/sec recessional velocity of PGC 23937 is the same as that of its larger companion, PGC 23935, which see for a discussion of the effect of Universal expansion on the calculations, and for images of the pair. The result is that both objects must have been just under 500 million light years away at the time the light by which we see them was emitted, just over 505 million years ago. Given that and its apparent size of 0.25 by 0.2 arcmin, PGC 23937 is about 35 thousand light years across.

Celestial Atlas
PGC 23000 - 23499 ←     PGC Objects: PGC 23500 - 23999     → PGC 24000 - 24499