Interacting galaxy

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NGC 3169 (left) and NGC 3166 (right) display some curious features, showing that each is close enough to feel the distorting gravitational influence of the other. Image from the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory. NGC 3169 NGC 3166.jpg
NGC 3169 (left) and NGC 3166 (right) display some curious features, showing that each is close enough to feel the distorting gravitational influence of the other. Image from the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory.

Interacting galaxies (colliding galaxies) are galaxies whose gravitational fields result in a disturbance of one another. An example of a minor interaction is a satellite galaxy disturbing the primary galaxy's spiral arms. An example of a major interaction is a galactic collision, which may lead to a galaxy merger.

Contents

Satellite interaction

A giant galaxy interacting with its satellites is common. A satellite's gravity could attract one of the primary's spiral arms. Alternatively, the secondary satellite can dive into the primary galaxy, as in the Sagittarius Dwarf Elliptical Galaxy diving into the Milky Way. That can possibly trigger a small amount of star formation. Such orphaned clusters of stars were sometimes referred to as "blue blobs" before they were recognized as stars. [1]

Animation of Galaxy Collision

Galaxy collision

Merging galaxies in the distant Universe through a gravitational magnifying glass. Merging galaxies in the distant Universe through a gravitational magnifying glass.jpg
Merging galaxies in the distant Universe through a gravitational magnifying glass.

Colliding galaxies are common during galaxy evolution. [3] The extremely tenuous distribution of matter in galaxies means these are not collisions in the traditional sense of the word, but rather gravitational interactions.

Colliding may lead to merging if two galaxies collide and do not have enough momentum to continue traveling after the collision. As with other galaxy collisions, the merging of two galaxies may create a starburst region of new stars. [4] In that case, they fall back into each other and eventually merge into one galaxy after many passes through each other. If one of the colliding galaxies is much larger than the other, it will remain largely intact after the merger. The larger galaxy will look much the same, while the smaller galaxy will be stripped apart and become part of the larger galaxy. When galaxies pass through each other, unlike during mergers, they largely retain their material and shape after the pass.

Galactic collisions are now frequently simulated on computers, which use realistic physics principles, including the simulation of gravitational forces, gas dissipation phenomena, star formation, and feedback. Dynamical friction slows the relative motion of galaxy pairs, which may possibly merge at some point, according to the initial relative energy of the orbits. A library of simulated galaxy collisions can be found at the Paris Observatory website GALMER. [5]

Galactic cannibalism

2MASX J16270254+4328340 galaxy has merged with another galaxy leaving a fine mist, made of millions of stars, spewing from it in long trails. The last waltz.jpg
2MASX J16270254+4328340 galaxy has merged with another galaxy leaving a fine mist, made of millions of stars, spewing from it in long trails.

Galactic cannibalism is a common phenomenon. [14] It refers to the process in which a large galaxy, through tidal gravitational interactions with a companion, merges with that companion. The most common result of the gravitational merger between two or more galaxies is a larger irregular galaxy, but elliptical galaxies may also result.

It has been suggested that galactic cannibalism is currently occurring between the Milky Way and the Large and Small Magellanic Clouds. Streams of gravitationally-attracted hydrogen arcing from these dwarf galaxies to the Milky Way is taken as evidence for the theory.

Galaxy harassment

Galaxy harassment is a type of interaction between a low-luminosity galaxy and a brighter one that takes place within rich galaxy clusters, such as Virgo and Coma, where galaxies are moving at high relative speeds and suffering frequent encounters with other systems of the cluster due to the high galactic density.

According to computer simulations, the interactions convert the affected galaxy disks into disturbed barred spiral galaxies and produces starbursts followed by, if more encounters occur, loss of angular momentum and heating of their gas. The result would be the conversion of (late type) low-luminosity spiral galaxies into dwarf spheroidals and dwarf ellipticals. [15]

Evidence for the hypothesis had been claimed by studying early-type dwarf galaxies in the Virgo Cluster and finding structures, such as disks and spiral arms, which suggest they are former disc systems transformed by the above-mentioned interactions. [16] However, the existence of similar structures in isolated early-type dwarf galaxies, such as LEDA 2108986, has undermined this hypothesis [17] [18]

Notable interacting galaxies

Montage of some well known interacting galaxies Galaxies Gone Wild!.jpg
Montage of some well known interacting galaxies
Name Type Distance
(million ly)
Magnitude Notes
Milky Way Galaxy, LMC and SMC SBc/SB(s)m/SB(s)m pec0Satellites interacting with their primary
Whirlpool Galaxy (M51)SAc (SB0-a)37+8.4Satellite interacting with its primary
NGC 1097 SB(s)bc (E6)45+9.5Satellite interacting with its primary
Butterfly galaxies NGC 4567/8 SA(rs)bc / SA(rs)bc60+10.9Early phase of interaction
NGC 2207 and IC 2163 SAc/SAbc114+11galaxies going through the first phase in galactic collision
Mice Galaxies (NGC 4676A and NGC 4676B)S0/SB(s)ab300+13.5galaxies going through the second phase in galactic collision
Antennae Galaxies (NGC 4038/9)SAc/SBm45+10.3galaxies going through the third phase in galactic collision
NGC 520 S100+11.3galaxies going through the third phase in galactic collision
NGC 2936 Irr352+12.9?

Future collision of the Milky Way with Andromeda

Astronomers have estimated the Milky Way Galaxy will collide with the Andromeda Galaxy in about 4.5 billion years. It is thought that the two spiral galaxies will eventually merge to become an elliptical galaxy [19] [20] or perhaps a large disc galaxy. [21]

See also

Related Research Articles

The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby galaxies. Galaxy formation is hypothesized to occur from structure formation theories, as a result of tiny quantum fluctuations in the aftermath of the Big Bang. The simplest model in general agreement with observed phenomena is the Lambda-CDM model—that is, that clustering and merging allows galaxies to accumulate mass, determining both their shape and structure. Hydrodynamics simulation, which simulates both baryons and dark matter, is widely used to study galaxy formation and evolution.

<span class="mw-page-title-main">Galaxy</span> Large gravitationally bound system of stars and interstellar matter

A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek galaxias (γαλαξίας), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 billion stars, range in size from dwarfs with less than a hundred million stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies.

<span class="mw-page-title-main">Globular cluster</span> Spherical collection of stars

A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of member stars, all orbiting in a stable, compact formation. Globular clusters are similar in form to dwarf spheroidal galaxies, and the distinction between the two is not always clear. Their name is derived from Latin globulus. Globular clusters are occasionally known simply as "globulars".

<span class="mw-page-title-main">Irregular galaxy</span> Class of galaxy

An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy. Irregular galaxies do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure.

<span class="mw-page-title-main">Hydra (constellation)</span> Constellation straddling the celestial equator

Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees, and also the longest at over 100 degrees. Its southern end borders Libra and Centaurus and its northern end borders Cancer. It was included among the 48 constellations listed by the 2nd century astronomer Ptolemy. Commonly represented as a water snake, it straddles the celestial equator.

<span class="mw-page-title-main">Lenticular galaxy</span> Class of galaxy between an elliptical galaxy and a spiral galaxy

A lenticular galaxy is a type of galaxy intermediate between an elliptical and a spiral galaxy in galaxy morphological classification schemes. It contains a large-scale disc but does not have large-scale spiral arms. Lenticular galaxies are disc galaxies that have used up or lost most of their interstellar matter and therefore have very little ongoing star formation. They may, however, retain significant dust in their disks. As a result, they consist mainly of aging stars. Despite the morphological differences, lenticular and elliptical galaxies share common properties like spectral features and scaling relations. Both can be considered early-type galaxies that are passively evolving, at least in the local part of the Universe. Connecting the E galaxies with the S0 galaxies are the ES galaxies with intermediate-scale discs.

<span class="mw-page-title-main">Galactic bulge</span> Tightly packed group of stars within a larger formation

In astronomy, a galactic bulge is a tightly packed group of stars within a larger star formation. The term almost exclusively refers to the central group of stars found in most spiral galaxies. Bulges were historically thought to be elliptical galaxies that happened to have a disk of stars around them, but high-resolution images using the Hubble Space Telescope have revealed that many bulges lie at the heart of a spiral galaxy. It is now thought that there are at least two types of bulges: bulges that are like ellipticals and bulges that are like spiral galaxies.

<span class="mw-page-title-main">Starburst galaxy</span> Galaxy undergoing an exceptionally high rate of star formation

A starburst galaxy is one undergoing an exceptionally high rate of star formation, as compared to the long-term average rate of star formation in the galaxy or the star formation rate observed in most other galaxies. For example, the star formation rate of the Milky Way galaxy is approximately 3 M/yr, while starburst galaxies can experience star formation rates of 100 M/yr or more. In a starburst galaxy, the rate of star formation is so large that the galaxy consumes all of its gas reservoir, from which the stars are forming, on a timescale much shorter than the age of the galaxy. As such, the starburst nature of a galaxy is a phase, and one that typically occupies a brief period of a galaxy's evolution. The majority of starburst galaxies are in the midst of a merger or close encounter with another galaxy. Starburst galaxies include M82, NGC 4038/NGC 4039, and IC 10.

<span class="mw-page-title-main">Dwarf galaxy</span> Small galaxy composed of up to several billion stars

A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is sometimes classified as a dwarf galaxy; others consider it a full-fledged galaxy. Dwarf galaxies' formation and activity are thought to be heavily influenced by interactions with larger galaxies. Astronomers identify numerous types of dwarf galaxies, based on their shape and composition.

<span class="mw-page-title-main">Antennae Galaxies</span> Interacting galaxies in the constellation Corvus

The Antennae Galaxies are a pair of interacting galaxies in the constellation Corvus. They are currently going through a starburst phase, in which the collision of clouds of gas and dust, with entangled magnetic fields, causes rapid star formation. They were discovered by William Herschel in 1785.

<span class="mw-page-title-main">Satellite galaxy</span> Galaxy that orbits a larger galaxy due to gravitational attraction

A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy. Satellite galaxies and their constituents are bound to their host galaxy, in the same way that planets within our own solar system are gravitationally bound to the Sun. While most satellite galaxies are dwarf galaxies, satellite galaxies of large galaxy clusters can be much more massive. The Milky Way is orbited by about fifty satellite galaxies, the largest of which is the Large Magellanic Cloud.

<span class="mw-page-title-main">NGC 1512</span> Galaxy in the constellation Horologium

NGC 1512 is a barred spiral galaxy approximately 38 million light-years away from Earth in the constellation Horologium. The galaxy displays a double ring structure, with a (nuclear) ring around the galactic nucleus and an (inner) further out in the main disk. The galaxy hosts an extended UV disc with at least 200 clusters with recent star formation activity. NGC 1512 is a member of the Dorado Group.

<span class="mw-page-title-main">Eyes Galaxies</span> Pair of galaxies in the constellation Virgo

The Eyes Galaxies are a pair of galaxies about 52 million light-years away in the constellation Virgo. The pair are members of the string of galaxies known as Markarian's Chain.

<span class="mw-page-title-main">Andromeda–Milky Way collision</span> Predicted galactic collision

The Andromeda–Milky Way collision is a galactic collision predicted to occur in about 4.5 billion years between the two largest galaxies in the Local Group—the Milky Way and the Andromeda Galaxy. The stars involved are sufficiently far apart that it is improbable that any of them will individually collide, though some stars will be ejected.

<span class="mw-page-title-main">Galaxy merger</span> Merger whereby at least two galaxies collide

Galaxy mergers can occur when two galaxies collide. They are the most violent type of galaxy interaction. The gravitational interactions between galaxies and the friction between the gas and dust have major effects on the galaxies involved. The exact effects of such mergers depend on a wide variety of parameters such as collision angles, speeds, and relative size/composition, and are currently an extremely active area of research. Galaxy mergers are important because the merger rate is a fundamental measurement of galaxy evolution. The merger rate also provides astronomers with clues about how galaxies bulked up over time.

<span class="mw-page-title-main">NGC 7727</span> Peculiar galaxy in the constellation Aquarius

NGC 7727 is a peculiar galaxy in the constellation Aquarius. It harbors two galactic nuclei, each containing a supermassive black hole, separated 1,600 light years apart.

The following outline is provided as an overview of and topical guide to galaxies:

<span class="mw-page-title-main">NGC 4660</span> Galaxy in the constellation Virgo

NGC 4660 is an elliptical galaxy located about 63 million light-years away in the constellation Virgo. The galaxy was discovered by astronomer William Herschel on March 15, 1784 and is a member of the Virgo Cluster.

<span class="mw-page-title-main">NGC 2936</span> Interacting spiral galaxy in the constellation Hydra

NGC 2936 is an interacting spiral galaxy located at a distance of 326 million light years, in the constellation Hydra. NGC 2936 is interacting with elliptical galaxy NGC 2937, located just beneath it. They were both discovered by Albert Marth on Mar 3, 1864. To some astronomers, the galaxy looks like a penguin or a porpoise. NGC 2936, NGC 2937, and PGC 1237172 are included in the Atlas of Peculiar Galaxies as Arp 142 in the category "Galaxy triplet".

<span class="mw-page-title-main">IC 4710</span> Irregular galaxy in the constellation Pavo

IC 4710 is a galaxy in southern constellation of Pavo, roughly 34 million light-years away.

References

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  19. whose gravitational interactions will fling various celestial bodies outward, evicting them from the resulting elliptical galaxy.Hazel Muir (2007-05-14). "Galactic merger to 'evict' Sun and Earth". New Scientist. Archived from the original on 20 April 2014. Retrieved 2014-10-07.
  20. Astronomy, June 2008, page 28, by Abraham Loeb and T.J.Cox
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