Hundreds of Galaxies in the Coma Cluster
The Coma Cluster is a large galaxy cluster containing over a thousand galaxies. The cluster is located approximately 330 million light years away in the constellation Coma Berenices. This means that the light captured in this image left the cluster 330 million years ago; here on earth, this was around the time when humans shared a common ancestor with amphibians and plants had just evolved the ability to produce seeds!
All of the objects that are labeled on the annotated image above are galaxies within the NGC/IC and PGC catalogs. Each label contains millions to billions of stars with at least as many planets. No individual stars have been labeled.
Something Hidden in the Coma Cluster
Galaxy clusters are the result of the attractive force of gravity on an intergalactic scale. Since Newton, we’ve known anything with mass will attract any other massive object. Einstein refined this idea in 1915 with the publication of his general theory of relativity. General relativity states that mass and energy sculpt the very fabric of space and time, resulting in what we know as gravity.
The Coma Cluster would play a role in further redefining our conception of matter, eventually leading to the current belief that the familiar matter we interact with daily is greatly outnumbered by some sort of invisible matter.
In 1933, Swiss astronomer Fritz Zwicky was studying galaxy clusters. Drawing upon Edwin Hubble’s prior observations of the Coma Cluster, Zwicky made a striking discovery: the galaxies within the cluster have such high velocities that gravity would be insufficient to keep them bound together. This discovery suggested one of two things: either the observed clustering of hundreds of galaxies was a chance alignment as they went on their separate ways, or there existed an invisible form of matter that was keeping them together. Zwicky determined that a chance alignment was implausible and hypothesized the existence of dunkle Materie or dark matter which contributed mass and held the galaxies together.
It wasn’t until the 1960’s and 70’s when dark matter was re-discovered and taken more seriously. Vera Rubin and Kent Ford were observing how quickly stars rotated in galaxies and noticed a parallel to Zwicky’s findings: the stars were moving too fast to stay bound within the galaxies. There must be some invisible matter which kept them from being ejected out into intergalactic space.
Since the 70’s, there have been numerous observations pointing to the existence of dark matter. Dark matter is a necessary ingredient to explain how quickly galaxies spin, the temperature of gasses within galaxy clusters, the movement of individual galaxies within clusters, gravitational lensing seen in images taken by telescopes like Hubble and JWST, temperature differences in the cosmic microwave background, and the overall large-scale structure of the universe. The current “standard model” of cosmology best describing our experimental observations even has dark matter in its name: Lambda - Cold Dark Matter (ΛCDM). Despite our reliance on dark matter to explain the universe, direct detection remains elusive and its fundamental properties are a mystery.
Current estimates suggest that roughly 90% of the mass within the Coma Cluster is dark matter and that a staggering 85% of the universe's total matter takes this invisible form. Dark matter vastly outnumbers conventional matter by more than fivefold and challenges our fundamental understanding of the cosmos.
Deep & Wide Field of the Coma Galaxy Cluster
Constellation: Coma Berenices
Coordinates: RA: 12h 59m 49s Dec: +27° 58’ 50”
Dates Acquired: Feb. 6, Feb. 12, Feb. 14, Mar. 3, Mar. 7 2024
Bortle Class: 6
Latitude: +43°
Equipment Info:
Telescope: William Optics Grand Tourismo 71 with 6AIII Flattener/Reducer
Focal Length: 335.2mm
f/4.2
Main Camera: ZWO 533MM-Pro
Guide Camera: ZWO 290MM-mini
Mount: Sky Watcher EQ6Ri-Pro
Filters: Astrodon 31mm (LRGB)
Integration:
Lum: 106 x 180s
Red: 46 x 180s
Green: 36 x 180s
Blue: 35 x 180s
Calibrated with flats & dark flats
Total Integration: 11h 9m
Processing Techniques - PixInsight Workflow:
WBPP & GraXpert - LRGB
RGB - RGBCombination, SPCC
L - BlurXTerminator
GeneralizedHyperbolicStretch on L and RBG
StarXTerminator on L & RGB
SCNR-Green , CorrectMagentaStars, Curves on RGB-Stars
Curves on RGB-Starless
PixelMath to recombine stars & starless:
RGBK = combine(stars, starless, op_screen())
Apply L to RGB via LRBGCombination
Crurves on LRGB
NoiseXTerminator
Plate solved and annotated in PixInsight
