Cancer Cluster
A Compact Galaxy Cluster in the Cosmic North
Quick Reader
| Attribute | Details |
|---|---|
| Name | Cancer Cluster (Abell 1367) |
| Type | Galaxy cluster |
| Constellation | Cancer |
| Distance from Earth | ~330 million light‑years (~100 Mpc) |
| Number of Galaxies | 70+ bright members (hundreds including dwarfs) |
| Dominant Galaxies | NGC 3842, NGC 3862, NGC 3841 |
| Cluster Type | Rich, moderately evolved, spiral‑rich |
| Supercluster Association | Part of the Leo Supercluster, connected to Coma Supercluster |
| Scientific Importance | A key site for studying galaxy infall, stripping, and cluster–cluster interactions |
| Observation | Located in the northern sky, visible in spring; accessible to mid‑sized amateur telescopes |
Introduction – A Cluster Caught in Motion
The Cancer Cluster, officially cataloged as Abell 1367, is a rich galaxy cluster located in the constellation Cancer. At a distance of around 330 million light-years, it lies near the intersection of major cosmic filaments and acts as a gateway into the Coma Supercluster complex.
What makes Abell 1367 stand out is its ongoing assembly — it’s a young, unrelaxed cluster, currently accumulating galaxies and groups along multiple axes. Unlike more mature clusters like Coma or Virgo, Cancer Cluster retains a high fraction of spiral galaxies and exhibits multiple infall fronts, making it a laboratory for studying:
Star formation triggering and suppression
Ram-pressure stripping
Shock heating and ICM dynamics
Environmental pre-processing
Cluster Composition and Dynamics
Abell 1367 contains a mixed population of ellipticals, spirals, and lenticulars. The cluster core is elliptical-dominated, while the outskirts still host actively star-forming spirals — many of which are undergoing transformation as they fall into the hot intracluster medium (ICM).
Key Member Galaxies
| Galaxy | Type | Features |
|---|---|---|
| NGC 3842 | Giant elliptical | Brightest cluster galaxy (BCG); X-ray center |
| NGC 3862 | Elliptical | Hosts radio source 3C 264 with optical jet |
| NGC 3841 | Elliptical | Passive, cluster core resident |
| NGC 3860 | Spiral | Signs of gas stripping and trailing HI |
| UGC 6697 | Spiral/irregular | Starburst galaxy with intense Hα tail |
The presence of galaxies like UGC 6697, undergoing ram-pressure stripping, shows that the cluster is still accreting from surrounding filaments.
General Properties
| Property | Value |
|---|---|
| Distance | ~100 Mpc (~330 million light‑years) |
| Redshift (cz) | ~6500–7500 km/s |
| Velocity Dispersion | ~800–900 km/s |
| X-ray Emission | Moderate, centered on NGC 3842 |
| Morphology Mix | ~50% spirals (unusual for a cluster) |
| Binding State | Not fully virialized; active assembly underway |
Hot Gas, Ram-Pressure Stripping, and Starburst Signatures
The Cancer Cluster (Abell 1367) is a powerful case study for observing ram-pressure stripping, shock heating, and starburst activity—all signatures of galaxies entering a dynamically active, gas-rich environment.
Unlike older clusters that are fully virialized, the Cancer Cluster shows signs of recent and ongoing infall, making it ideal for understanding how galaxies are transformed by their environment.
X-ray Observations and Intracluster Medium (ICM)
The cluster emits moderate X-ray radiation, primarily observed by ROSAT, XMM-Newton, and Chandra:
The X-ray emission is centered on the elliptical galaxy NGC 3842, but lacks the strong cool core seen in relaxed clusters like Hydra.
The ICM temperature is estimated at ~3–4 keV, typical for medium-mass clusters.
The gas is not uniformly distributed—suggesting active merging substructures and turbulence.
This provides evidence that the cluster is still in the process of assembling, with multiple accretion axes feeding gas and galaxies from surrounding filaments.
Ram-Pressure Stripping in Action
Several spirals and irregulars in Abell 1367 show clear signs of gas removal due to their motion through the hot ICM. Key examples include:
UGC 6697
A highly disturbed, edge-on spiral or irregular galaxy.
Features an extended H-alpha emission tail, several tens of kiloparsecs long.
Starburst activity is concentrated at the leading edge, triggered by ram-pressure compression.
NGC 3860
Displays a trailing HI tail, suggestive of gas being stripped as it moves through the cluster.
Star formation is suppressed in the leading disk but persists in shielded regions.
These galaxies are part of the cluster’s outskirts, where gas-rich members are beginning to interact with the hot halo, initiating stripping and morphological change.
AGN Feedback: The Case of NGC 3862 (3C 264)
NGC 3862 is an elliptical galaxy with an active nucleus that hosts the radio source 3C 264, a well-known AGN jet emitter.
Optical observations reveal a bright relativistic jet, similar to M87.
The AGN injects energy into the local environment, disturbing the surrounding ICM.
The jet is aligned with X-ray cavities, suggesting it is heating the intracluster gas.
This makes Abell 1367 one of the few nearby clusters where both AGN feedback and ram-pressure stripping can be observed in the same system.
Star Formation and Transformation Gradient
The cluster shows a spatial gradient of galaxy properties:
| Zone | Dominant Galaxy Types | Star Formation | Gas Content |
|---|---|---|---|
| Core | Ellipticals, S0s | Quenched | HI-deficient |
| Intermediate | Lenticulars, spirals | Patchy or reduced | Partial stripping |
| Outskirts | Spirals, irregulars | Active | HI-rich, extended halos |
This progression reflects the environmental quenching mechanisms at work:
- Ram-pressure stripping removes gas from infalling spirals.
- Galaxy harassment—repeated fast encounters—disturbs morphologies.
- Tidal interactions with group cores reshape dwarfs and late-type galaxies.
Galaxy Mergers and Infall Structures
Spectroscopic studies show that:
The cluster contains subgroups with coherent motion vectors.
Velocity dispersion (~800–900 km/s) suggests ongoing mergers.
Some galaxies have elongated orbits, consistent with recent infall trajectories.
This supports the idea that Abell 1367 is young by cluster standards and will evolve further over the next few billion years.
Scientific Importance and Cosmological Relevance
The Cancer Cluster (Abell 1367) is not just another galaxy cluster — it’s a vital system for understanding how galaxy clusters grow, how galaxies are transformed during infall, and how large-scale structure connects group-sized nodes into massive clusters.
Its intermediate state — not yet fully virialized, yet already active — makes it ideal for studying:
The onset of environmental quenching
The role of the intracluster medium (ICM) in stripping and heating
The balance between secular evolution and dynamical disruption
It serves as a key component of the Coma Supercluster’s growth edge, feeding into larger structures while still preserving observable star-forming galaxies, disturbed spirals, and AGN-hosting ellipticals.
Frequently Asked Questions (FAQ)
What is the Cancer Cluster?
A: Also known as Abell 1367, it’s a galaxy cluster located about 330 million light-years away in the constellation Cancer. It contains a mix of ellipticals, spirals, and lenticulars, and is notable for its ongoing cluster assembly and galaxy transformation processes.
Is the Cancer Cluster part of a larger structure?
A: Yes. It is a major component of the Coma Supercluster, connected by filaments to:
The Coma Cluster (Abell 1656)
The NGC 4065 Group
The Leo Cluster
It sits at the confluence of cosmic filaments, making it a gateway node in large-scale structure.
What kinds of galaxies are found in it?
A: The cluster hosts:
Massive ellipticals in the core (e.g., NGC 3842, NGC 3862)
Ram-pressure stripped spirals (e.g., NGC 3860, UGC 6697)
Star-forming dwarfs and irregulars in the outskirts
This makes it rich in observational diversity, especially for galaxy evolution studies.
What makes Abell 1367 scientifically interesting?
A: It offers a combination of:
Active galaxy infall
Environmental transformation in real time
Coexisting AGN feedback and ram-pressure stripping
Subcluster merging
These phenomena are rarely observed together in such clarity.
Can the Cancer Cluster be observed with amateur telescopes?
A: Some of its brightest galaxies (like NGC 3842 and NGC 3862) are visible in medium-to-large amateur telescopes under dark skies. The cluster is best viewed during northern spring months, particularly in March and April.
Comparison with Nearby Galaxy Clusters
| Cluster | Distance (Mly) | State | Spiral Fraction | AGN Activity | Notes |
|---|---|---|---|---|---|
| Cancer (Abell 1367) | ~330 | Semi-relaxed | Moderate (~50%) | Yes (e.g., 3C 264) | Cluster in active assembly |
| Coma (Abell 1656) | ~320 | Fully evolved | Low (~10%) | Low/moderate | Massive, virialized |
| Virgo | ~65 | Dynamically young | High (~60%) | High (M87 jet) | Nearest large cluster |
| Hydra (Abell 1060) | ~190 | Relaxed | Low (~20%) | Yes (cool-core) | Southern benchmark cluster |
Final Thoughts – A Cluster in Transition
The Cancer Cluster is a snapshot of a cosmic ecosystem in motion — not yet finished, but no longer primitive. It shows us how:
Spirals become lenticulars
Gas is lost to the environment
Galaxies get reshaped by large-scale forces
Its role in the Coma Supercluster’s development, coupled with its observable multi-phase galaxy population, makes it a powerful tool for both theoretical modeling and deep-sky observational astronomy.
