Telescope : SW Esprit 100ED
Mount : SW Wave 150i
Camera : ZWO 533mc
Guiding :Zwo 120mono with Touptek oag
Filters: Total exposure time :8 hours & 40minutes from 2 nights with SVBONY 260 2"
Programs I have used : ZWO AsiAir & PixInsight 1.9.4
NGC 7331 (also cataloged as Caldwell 30) is an unbarred spiral galaxy located approximately 40 to 45 million light-years away in the constellation Pegasus. Discovered by William Herschel in 1784, it is famously known as the brightest galaxy in the night sky that was not included in Charles Messier's iconic 18th-century catalog.
The Milky Way's "Twin"
NGC 7331 is frequently referred to as the Milky Way's twin, as it shares a remarkably similar size, mass, star count, and star-formation rate with our own galaxy. However, it holds two major differences:
- No Central Bar: Unlike the Milky Way, which is a barred spiral, NGC 7331 is an unbarred spiral galaxy. It lacks the elongated central bar structure of stars.
- Counter-Rotating Core: In a bizarre cosmic anomaly, the central bulge of the galaxy rotates in the opposite direction of the surrounding galactic disk.
The "Deer Lick" Group
NGC 7331 is the dominant member of a visual grouping of galaxies known as the Deer Lick Group. While NGC 7331 sits in the foreground, four smaller, distant galaxies (NGC 7335, 7336, 7337, and 7340) can be seen in the background. These background galaxies sit nearly ten times farther away—about 300 to 350 million light-years—and are affectionately nicknamed the "fleas" of the galaxy.
Recent Supernova Activity
The galaxy has a history of hosting powerful supernovae. Several notable stellar explosions have occurred here, including:
- SN 2026aaiv: A Type Ia supernova discovered in September 2026 by the ATLAS survey, caused by the thermonuclear explosion of a white dwarf.
- SN 2025rbs: Another Type Ia supernova that flared up during the summer of 2025.
- SN 2014C: A highly studied "chameleon" supernova that unexpectedly transformed from a Type Ib into a Type IIn within a year, shedding light on the final life stages of massive stars.
Stephan's Quintet (also designated as Hickson Compact Group 92) is a visually stunning group of five galaxies in the constellation Pegasus. Discovered by French astronomer Édouard Stephan in 1877, it holds the historic title of being the very first compact galaxy group ever discovered. It gained global fame in 2022 when it was featured as one of the first target images released by the James Webb Space Telescope (JWST).
A Cosmic Illusion: Quintet or Quartet?
Despite being called a "Quintet" (a group of five), it is physically a quartet of interacting galaxies, with one cosmic intruder just passing through the foreground:
- The Interloper (NGC 7320): The prominent bluish spiral galaxy on the upper left is located only 40 million light-years away from Earth. It is a close neighbor of NGC 7331 and just happens to sit along our line of sight.
- The True Members (NGC 7317, 7318A, 7318B, and 7319): These four galaxies are gravitationally locked together in a violent dance, located much deeper in space at roughly 290 to 340 million light-years away.
A High-Speed Galactic Collision
The true members are undergoing a chaotic, slow-motion smashup. One of the galaxies, NGC 7318B, is currently barreling through the group at a staggering speed of nearly 2 million miles per hour (~3.2 million km/h). This extreme movement has triggered one of the largest interstellar shockwaves ever observed, comparable to a sonic boom on a galactic scale.
This collision causes:
- Giant Tidal Tails: Massive streams of gas, dust, and stars are being ripped out of the galaxies.
- Starbust Star Formation: The intense compression of hydrogen gas is actively sparking the birth of millions of new stars.
Proximity to NGC 7331
In the night sky, Stephan's Quintet is located less than half a degree away from the large spiral galaxy NGC 7331. Because they are so close together visually, astrophotographers frequently capture both NGC 7331 and the Quintet in a single wide-field frame, showcasing an incredible sense of depth in the universe.
Would you like to know what the James Webb Space Telescope discovered hidden inside the supermassive black hole at the center of NGC 7319, or are you looking for telescope coordinates to observe them?
