Galaxy Trios Catalog

While many people are familiar with the "Leo Triplet," the Galaxy Trios catalog used by serious observers is actually a specific subset of the Miles Paul "Atlas of Compact Galaxy Trios." This database is a modern favorite because it focuses on the "social" aspect of galaxies—those that are grouped in threes within a single field of view. It is one of the pillars of the Astronomical League’s *Galaxy Groups & Clusters* program.

History & Who Made It

The database was compiled by Miles Paul, an avid deep-sky observer and astrophotographer. In the late 1990s and early 2000s, he curated a list of 50 compact galaxy trios.

Paul noticed that while "groups" (like Hicksons) were well-cataloged, many observers loved the specific aesthetic of a "triplet"—three distinct galaxies arranged in a geometric pattern that fits comfortably in a standard wide-field eyepiece. His work was eventually adopted as a formal observing challenge to provide a "middle ground" between looking at single galaxies and massive, overwhelming galaxy clusters.

The Purpose: The "Eyepiece Aesthetic"

Unlike professional catalogs that focus on dark matter or redshift, the Miles Paul Trios were chosen for their visual impact.

• Compactness: The trios must be close enough to be seen together, creating a unique "neighborhood" feel.

• Variety: The list ensures you aren't just looking at three identical smudges; many trios feature a mix of spirals, ellipticals, or edge-on galaxies.

• Interaction Study: Many of these trios are physically interacting, showing "tidal tails" or warped shapes that provide a real-time look at galactic evolution.

What Objects Can Be Found In It?

The catalog is composed of 50 primary trios. While some are famous Messier objects, many are obscure NGC and IC groupings that most observers would otherwise overlook.

The Galaxy Trios Database

Catalog Name: Atlas of Compact Galaxy Trios

Creator: Miles Paul

Total Trios: 50 (150 total galaxies)

Primary Gear: 8-inch to 12.5-inch telescopes

Source Catalogs: NGC, IC, and UGC

Object Category: General Features

• Interacting Trios: Groups physically pulling on each other (e.g., Arp targets).

• Optical Trios: Galaxies that look like a trio from Earth but are actually at different distances.

• Mixed Morphology: Trios containing different galaxy types (Spiral + Elliptical).

Top 5 "Must-See" Trios from the Catalog:

1. The Leo Triplet: M65, M66, and NGC 3628 (The most famous trio in the sky)

2. The Draco Trio: NGC 5981, NGC 5982, and NGC 5985 (A perfect line of three different galaxy types).

3. The Wild's Triplet (Arp 248): Three interacting galaxies in Virgo. 

4. The NGC 7331 Group: While part of a larger group, the "Deer Lick" core is often observed as a tight trio. 

5. The NGC 5985 Group: Known for having an edge-on, an elliptical, and a face-on spiral all in one row. 

The Challenge for the Observer

Chasing the Galaxy Trios is a test of patience and averted vision. In many trios, one galaxy is a "showpiece" (bright and easy), while the other two are "ghosts" that require a dark sky and high magnification to reveal.

Because of this, the Miles Paul catalog is often the favorite second step for observers who have finished the "200 Brightest Galaxies" and want to see how these "island universes" interact with their neighbors.

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