Page last updated Feb 25, 2020|
PGC 62775 (also known as ESO 184-011)
A magnitude 13.5(?) irregular galaxy (type IB(s)m pec?) in Telescopium (RA 19 06 21.4, Dec -56 09 42)
: Based on a galactocentric recessional velocity of about 2605 km/sec (and H0
= 70 km/sec/Mpc), PGC 62775 is about 120 to 125 million light years away. Given that and its apparent size of about 1.5 by 1.3 arcmin (from the images below), it is about 50 to 55 thousand light years across. It is an apparent companion of IC 4817
, and since their recessional velocities only differ by 400 km/sec, it is possible (though not certain) that they are also physical companions, or had a recent close passage which caused their peculiarities.
Above, a 12 arcmin wide DSS image centered on PGC 62775, also showing IC 4817
Below, a 1.8 arcmin wide DSS image of the galaxy
PGC 62946, "The Bird" (also known as ESO 593-008)
A magnitude 14(?) triplet of colliding galaxies in (RA 19 14 31.1, Dec -21 19 09)
Physical Information: Based on a galactocentric recessional velocity of 14675 km/sec (and H0 = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 62946 is about 680 to 685 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 system was about 645 million light years away at the time the light by which we see it was emitted, about 660 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 (including the extended regions cast out of the central galaxies by their interaction) of about 0.8 by 0.7 arcmin (all apparent sizes estimated from the images below), the system is about 150 thousand light years across. The spiral galaxy aligned more or less east-west (left-right in the images) spans about 0.5 by 0.1 arcmin or 90 to 95 thousand light years. The spiral galaxy aligned more or less north-south (top-bottom in the images) spans about 0.45 by 0.1 arcmin or 85 thousand light years. The irregular galaxy spans about 0.15 by 0.12(?) arcmin or 25 to 30 thousand light years.
The system has generally been considered to be two large spiral galaxies in the early stages of a spectacular collision; but the ESO image reveals three apparent cores, interpreted as the centers of the two spiral galaxies and of a third, smaller irregular galaxy. All three should eventually coalesce into a single galaxy, but the process will take hundreds of millions of years, during which the collision of clouds of gas in the three objects will produce huge numbers of new stars, many of which will be bright massive objects whose death throes will fill the 'new' galaxy with supernova remnants whose expanding shells of ejected material will create shock waves in the remaining interstellar medium and give birth to still more stars; so in comparison to the short span of human life, this will remain a spectacular object 'forever'.
Above, a 12 arcmin wide DSS image centered on PGC 62946
Below, a 0.9 by 1.2 arcmin wide image of the trio, using the HST false-color parameters
(Image Credit NASA/ESA/Hubble Heritage Team (STScI/AURA),ESA/Hubble Collaboration
and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University))
Below, a 0.6 by 0.55 arcmin wide false-color image showing the three cores (Image Credit ESO)