Page last updated Sep 18, 2021
PGC 50640 (= HCG 71C)
(A member of Hickson Compact Group 71)
A magnitude 16(?) spiral galaxy (type SB(rs)cd?) in Boötes (RA 14 11 05.1, Dec +25 28 58)
Physical Information: As discussed in the entry for NGC 5008, the group that it is a member of (NGC 5008, IC 4382 and PGC 50640) was about 420 to 425 million light-years away at the time the light by which we see it was emitted, about 430 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 about 0.55 by 0.35 arcmin (from the images below), PGC 40640 is about 65 to 70 thousand light-years across.
Above, a 4.8 arcmin wide labeled SDSS image of Hickson Compact Group 71
Below, a 0.6 arcmin wide SDSS image of PGC 50640
For other images see Hickson Compact Group 71
PGC 50641 (= HCG 71D)
(A member of Hickson Compact Group 71)
(but not a physical member of the Group)
A magnitude 16.5(?) lenticular galaxy (type (R?)S0?) in Boötes (RA 14 11 08.3, Dec +25 27 28)
Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 20545 km/sec (and H0 = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 50641 is about 955 to 960 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 about 880 to 885 million light-years away at the time the light by which we see it was emitted, about 910 to 915 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 about 0.4 by 0.25 arcmin (from the images below), the galaxy is about 100 to 105 thousand light-years across.
Membership In HCG 71: Although listed as a member of HCG 71, PGC 50641 is a much more distant background galaxy, and has no actual relationship to the other members of the group, save for being in the same part of the sky.
Above, a 4.8 arcmin wide labeled SDSS image of Hickson Compact Group 71
Below, a 0.75 arcmin wide SDSS image of PGC 50641
For other images see Hickson Compact Group 71
PGC 50984
(= MCG +07-29-058)
A magnitude 15.5(?) spiral galaxy (type Sc?) in Boötes (RA 14 16 26.0, Dec +39 39 04)
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 7775 km/sec (and H0 = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 50984 is about 360 to 365 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 about 350 to 355 million light years away at the time the light by which we see it was emitted, about 355 to 360 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 about 0.8 by 0.35 arcmin (from the images below), the galaxy is about 80 thousand light years across.
Relationship To NGC 5541: PGC 50984 has nearly the same recessional velocity as peculiar spiral galaxy NGC 5541, so there is a very good chance that they are physical companions. However, the peculiar appearance of NGC 5541 is not due to PGC 50984, but to the galaxy it is colliding with, as discussed in the entry for the NGC object.
Above, a 12 arcmin wide SDSS image of PGC 50984, also showing NGC 5541
Below, a 1 arcmin wide SDSS image of the galaxy
|