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Ring galaxy
A ring galaxy is a type of galaxy that includes a large annular structure. The galactic center may be relatively separate from the ring structure, or present a continuous disc shape. Hoag's Object, discovered by Arthur Hoag in 1950, is an example of a ring galaxy. The ring contains many massive, relatively young blue stars, which are extremely bright. The central region contains relatively little luminous matter. Some astronomers believe that ring galaxies are formed when a smaller galaxy passes through the center of a larger galaxy. Because most of a galaxy consists of empty space, this "collision" rarely results in any actual collisions between stars. However, the gravitational disruptions caused by such an event could cause a wave of star formation to move through the larger galaxy. Other astronomers think that rings are formed around some galaxies when external accretion takes place. Star formation would then take place in the accreted material because of the shocks and compressions of the accreted material.
All of the processes that form ring galaxies appear to cause significant effects on stellar populations. Based on observations of the spectrum of the ring structures, there appears to be very high star formation rates caused by the outwards pressure wave. The regions also have very high metallicities, supporting the idea of a significant amount of evolution of the stellar population within the ring. The methods ring galaxies are theorized to be formed through include, but are not limited to, the scenarios listed below:
A phenomenon where the rotational velocity of the bar in a barred spiral galaxy increases to the point of spiral spin-out. Under typical conditions, gravitational density waves would favor the creation of spiral arms. When the bar is unstable, these density waves are instead migrated out into a ring-structure by the pressure, force, and gravitational influence of the baryonic and dark matter furiously orbiting about the bar. This migration forces the stars, gas and dust found within the former arms into a torus-like region, forming a ring, and often igniting star formation.
Galaxies with this structure have been found where the bar dominates, and essentially "carves out" the ring of the disc as it rotates. Oppositely, ring galaxies have been found where the bar has collapsed or disintegrated into a highly-flattened bulge.
Other instabilities have been predicted due to asymmetries caused by spiral arms, which creates a net torque depending on the pattern of the bar. This torque creates a resonance instability that drives matter from the arms both outwards and inwards towards the core, creating the distinct ring and core structure.
Despite this, observations suggest that bars, rings and spiral arms have the ability to fall apart and reform over the span of hundreds of millions of years, particularly in dense intergalactic environments, such as galaxy groups and clusters, where gravitational influences are more likely to play a role in the morphological and physical evolution of a galaxy without the influence of collisions and mergers.
Another observed way that ring galaxies can form is through the process of two or more galaxies colliding. The Cartwheel Galaxy, galaxy pair AM 2026-424, and Arp 147 are all examples of ring galaxies thought to be formed by this process.
In pass-through galactic collisions, or bullseye collisions, an often smaller donor galaxy will pass directly through the disc of an often larger spiral, causing an outward push of the arms from the gravity of the smaller galaxy, as if dropping a rock into a pond of still water. These collisions can either launch the bulge and core away from the main disk, creating an almost empty ring appearance as the shockwave pushes the spiral arms out, or shove the core out towards the disk, often creating an oval-shaped ring with the bulge still somewhat intact. In side-swipe and head-on collisions, the appearance of a perfect ring are less likely, with chaotic and warped appearances dominating. In these collisional galaxy systems, the individual galaxies that made up the ring system are often still observable.
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Ring galaxy AI simulator
(@Ring galaxy_simulator)
Ring galaxy
A ring galaxy is a type of galaxy that includes a large annular structure. The galactic center may be relatively separate from the ring structure, or present a continuous disc shape. Hoag's Object, discovered by Arthur Hoag in 1950, is an example of a ring galaxy. The ring contains many massive, relatively young blue stars, which are extremely bright. The central region contains relatively little luminous matter. Some astronomers believe that ring galaxies are formed when a smaller galaxy passes through the center of a larger galaxy. Because most of a galaxy consists of empty space, this "collision" rarely results in any actual collisions between stars. However, the gravitational disruptions caused by such an event could cause a wave of star formation to move through the larger galaxy. Other astronomers think that rings are formed around some galaxies when external accretion takes place. Star formation would then take place in the accreted material because of the shocks and compressions of the accreted material.
All of the processes that form ring galaxies appear to cause significant effects on stellar populations. Based on observations of the spectrum of the ring structures, there appears to be very high star formation rates caused by the outwards pressure wave. The regions also have very high metallicities, supporting the idea of a significant amount of evolution of the stellar population within the ring. The methods ring galaxies are theorized to be formed through include, but are not limited to, the scenarios listed below:
A phenomenon where the rotational velocity of the bar in a barred spiral galaxy increases to the point of spiral spin-out. Under typical conditions, gravitational density waves would favor the creation of spiral arms. When the bar is unstable, these density waves are instead migrated out into a ring-structure by the pressure, force, and gravitational influence of the baryonic and dark matter furiously orbiting about the bar. This migration forces the stars, gas and dust found within the former arms into a torus-like region, forming a ring, and often igniting star formation.
Galaxies with this structure have been found where the bar dominates, and essentially "carves out" the ring of the disc as it rotates. Oppositely, ring galaxies have been found where the bar has collapsed or disintegrated into a highly-flattened bulge.
Other instabilities have been predicted due to asymmetries caused by spiral arms, which creates a net torque depending on the pattern of the bar. This torque creates a resonance instability that drives matter from the arms both outwards and inwards towards the core, creating the distinct ring and core structure.
Despite this, observations suggest that bars, rings and spiral arms have the ability to fall apart and reform over the span of hundreds of millions of years, particularly in dense intergalactic environments, such as galaxy groups and clusters, where gravitational influences are more likely to play a role in the morphological and physical evolution of a galaxy without the influence of collisions and mergers.
Another observed way that ring galaxies can form is through the process of two or more galaxies colliding. The Cartwheel Galaxy, galaxy pair AM 2026-424, and Arp 147 are all examples of ring galaxies thought to be formed by this process.
In pass-through galactic collisions, or bullseye collisions, an often smaller donor galaxy will pass directly through the disc of an often larger spiral, causing an outward push of the arms from the gravity of the smaller galaxy, as if dropping a rock into a pond of still water. These collisions can either launch the bulge and core away from the main disk, creating an almost empty ring appearance as the shockwave pushes the spiral arms out, or shove the core out towards the disk, often creating an oval-shaped ring with the bulge still somewhat intact. In side-swipe and head-on collisions, the appearance of a perfect ring are less likely, with chaotic and warped appearances dominating. In these collisional galaxy systems, the individual galaxies that made up the ring system are often still observable.