ASTRO:
     type=galaxy group
     mag=11.15
     const=Leo
     dist=60 M ly
IMAGE:
     location=Emerald Bay community, Lake Palestine, TX
     BrtlCls=4
     exposure=CMOS OSC; 107x180s (5.4h), G100
     palette=LRGB
EQUIPMENT:
​     optics=ES102CF APO / Hyperion 24mmEP (afocal) 1.7x, FL(eff.)=1238mm, f(eff.)/12.1
     camera=ZWO ASI2600MC-Pro
     filter=Optolong L-Pro LPS
     mount=Celestron AVX
     guiding=Orion 60x240mm, ZWO ASi224MC
SOFTWARE:
     acquisition=Stellarium, NINA, PHD2
     processing=PixInsight (RCAstro), Photoshop (APF-R, WebSharp-Pro), LrC

HCG 44 — A Gravitational Conversation in Leo...

Hickson Compact Group 44 (or HCG 44) is a striking assembly of galaxies locked in a slow, gravitational dance about 60 million light‑years away, far beyond the foreground Milky Way stars, in the constellation Leo.  Compact groups like this are among the densest small-scale galaxy environments in the universe, where close encounters are not the exception but the rule.  HCG 44 offers a vivid snapshot of how galaxies influence, and transform one another over cosmic time.

The group contains four (4) principal galaxies, each bearing the marks of past interactions:
    NGC 3190 — The largest of the 4, is a warped, dust‑laden spiral seen at an elegant tilt; its sweeping lanes twisted by gravitational tides.
    NGC 3185 — Toward the lower left of the image, is a barred spiral galaxy with a faint outer ring, showing subtle distortions that hint at earlier encounters.
    NGC 3187 — A dramatically stretched spiral to the lower right, whose arms appear pulled into an "S" curve like taffy, a clear signature of tidal forces at work.
    NGC 3193 — Upper right, a smooth, rounded elliptical galaxy, older and more quietly inactive, yet still part of the group’s shared gravitational story.
Together, these galaxies form a compact configuration where their mutual gravity sculpts their shapes, redistributes their dust & gas, and influences their future evolution.

HCG 44 is a natural laboratory that astronomers study for understanding of how galaxies change when they live in close quarters.  Interactions within the group have stripped dust & gas from several members, leaving behind faint, extended streams detectable only with deep radio imaging. These tenuous structures—invisible to the eye—are the fingerprints of past encounters.  Such environments can trigger bursts of star formation, distort spiral arms, and even cause interactive mergers.  HCG 44 is thought to be in a transitional stage, slowly evolving toward a more tightly bound system that may one day coalesce into a single, massive galaxy.

HCG 44 is part of the Hickson Compact Group catalog, compiled by British Canadian astronomer Paul Hickson while he was Professor of Astronomy at the University of British Columbia.   Hickson identified small, isolated clusters of galaxies exhibiting unusually high densities.  These groups provide rare opportunities to observe galactic interactions on humanly comprehensible scales; close enough to one another for study in detail, yet distant enough to reveal processes unfolding over millions of years.

Dr. Hickson published his study in 1982, consisting of 100 compact galaxy groups scattered throughout the sky.   In his paper "Systematic Properties of Compact Groups of Galaxies", he defined a compact galaxy group as a small, relatively isolated collection of four or five individual systems that are set in close proximity to one another, and that differ in brightness by no more than 3 magnitudes.  Further, so as to avoid confusing the interactions within their central regions, Hickson stipulated an "isolation factor" requiring that there not be a non-member galaxy of similar magnitude within three radii of the group's center.  ...To be otherwise yielded interactions too complex to study, and to produce meaningful outcomes.

Surveying the 1958 Palomar Observatory Sky Survey ("POSS"), Hickson created his inventory of groupings.  The entries in the Hickson Compact Group, or HCG catalog are ordered numerically according to increasing right ascension.  The brightest member of this catalog is HCG 44, nicknamed the "Leo Quartet".

260319 - HCG44 "Leo Quartet" galaxy group