A galaxy group or group of galaxies ( GrG ) is an aggregation of galaxies comprising about 50 or fewer gravitationally bound members, each at least as luminous as the Milky Way (about 10 times the luminosity of the Sun ); collections of galaxies larger than groups that are first-order clustering are called galaxy clusters . The groups and clusters of galaxies can themselves be clustered, into superclusters of galaxies.
31-626: The Local Group is the galaxy group that includes the Milky Way , where Earth is located. It has a total diameter of roughly 3 megaparsecs (10 million light-years ; 9 × 10 kilometres ), and a total mass of the order of 2 × 10 solar masses (4 × 10 kg). It consists of two collections of galaxies in a " dumbbell " shape; the Milky Way and its satellites form one lobe, and the Andromeda Galaxy and its satellites constitute
62-410: A diameter of 1 to 2 megaparsecs (Mpc). Their mass is approximately 10 solar masses . The spread of velocities for the individual galaxies is about 150 km/s. However, this definition should be used as a guide only, as larger and more massive galaxy systems are sometimes classified as galaxy groups. Groups are the most common structures of galaxies in the universe, accounting for at least 50% of
93-419: A distance of approximately 180 million light-years located in the constellation of Hercules . Proto-groups are groups that are in the process of formation. They are the smaller form of protoclusters. These contain galaxies and protogalaxies embedded in dark matter haloes that are in the process of fusing into group-formations of singular dark matter halos. Timeline of the far future This
124-646: A mass extinction, by this time most current species will have disappeared through the background extinction rate , with many clades gradually evolving into new forms. Africa's collision with Eurasia will close the Mediterranean Basin and create a mountain range similar to the Himalayas . The Appalachian Mountains peaks will largely wear away, weathering at 5.7 Bubnoff units , although topography will actually rise as regional valleys deepen at twice this rate. Upper estimate for lifespan of
155-513: A normal galaxy group, leaving behind the X-ray halo of the progenitor group. Galaxies within a group interact and merge. The physical process behind this galaxy-galaxy merger is dynamical friction . The time-scales for dynamical friction on luminous (or L*) galaxies suggest that fossil groups are old, undisturbed systems that have seen little infall of L* galaxies since their initial collapse. Fossil groups are thus an important laboratory for studying
186-532: A small number of galaxies, typically around five, in close proximity and relatively isolated from other galaxies and formations. The first compact group to be discovered was Stephan's Quintet , found in 1877. Stephan's Quintet is named for a compact group of four galaxies plus an unassociated foreground galaxy. Astronomer Paul Hickson created a catalogue of such groups in 1982, the Hickson Compact Groups . Compact groups of galaxies readily show
217-610: A timescale of tens of billions of years into a single elliptical galaxy, with the coalescence of Andromeda and the Milky Way being the predominant event in this process. * It is uncertain whether these are companion galaxies of the Andromeda Galaxy Galaxy group The Milky Way galaxy is part of a group of galaxies called the Local Group . Groups of galaxies are the smallest aggregates of galaxies. They typically contain no more than 50 galaxies in
248-476: Is also the time required for a quantum-tunnelled and quantum fluctuation -generated Big Bang to produce a new universe identical to our own, assuming that every new universe contained at least the same number of subatomic particles and obeyed laws of physics within the landscape predicted by string theory .) To date five spacecraft ( Voyager 1 , Voyager 2 , Pioneer 10 , Pioneer 11 and New Horizons ) are on trajectories which will take them out of
279-651: Is an accepted version of this page While the future cannot be predicted with certainty, present understanding in various scientific fields allows for the prediction of some far-future events, if only in the broadest outline. These fields include astrophysics , which studies how planets and stars form, interact and die; particle physics , which has revealed how matter behaves at the smallest scales; evolutionary biology , which studies how life evolves over time; plate tectonics , which shows how continents shift over millennia; and sociology , which examines how human societies and cultures evolve. These timelines begin at
310-753: Is expected to become habitable again Planned lifespan of the Human Document Project being developed at the University of Twente in the Netherlands. Various public monuments composed of hard granite will have eroded one metre, in a moderate climate, assuming a rate of 1 Bubnoff unit (1 mm in 1,000 years, or ≈1 inch in 25,000 years). Without maintenance, the Great Pyramid of Giza will erode into unrecognizability. On
341-514: Is isolated in the general field" and delineated, by decreasing luminosity, its members to be M31 , Milky Way , M33 , Large Magellanic Cloud , Small Magellanic Cloud , M32 , NGC 205 , NGC 6822 , NGC 185 , IC 1613 and NGC 147 . He also identified IC 10 as a possible part of the Local Group. mass: 7 × 10 M ☉ The galaxies of the Local Group are likely to merge together under their own mutual gravitational attractions over
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#1732764881793372-474: The Antlia Dwarf Galaxy as well as Sextans B , Leo P , Antlia B and possibly Leo A , is uncertain due to extreme distances from the center of the Local Group. The Antlia-Sextans Group is unlikely to be gravitationally bound to the Local Group due to probably lying outside the Local Group's Zero-velocity surface —which would make it a true galaxy group of its own rather than a subgroup within
403-582: The Dark Era is on these timescales instantaneous. This is also the highest estimated possible time for the Black Hole Era (and subsequent Dark Era) to commence. Beyond this point, it is almost certain that the universe will be an almost pure vacuum, with all baryonic matter having decayed into subatomic particles, gradually winding down their energy level until it reaches its final energy state , assuming it does not happen before this time. (Because
434-546: The Moon , Neil Armstrong 's "one small step" footprint at Tranquility Base will erode by this time, along with those left by all twelve Apollo moonwalkers , due to the accumulated effects of space weathering . (Normal erosion processes active on Earth are not present due to the Moon's almost complete lack of atmosphere .) The LAGEOS satellites' orbits will decay, and they will re-enter Earth's atmosphere, carrying with them
465-483: The future of Earth , the Solar System and the universe must account for the second law of thermodynamics , which states that entropy , or a loss of the energy available to do work, must rise over time. Stars will eventually exhaust their supply of hydrogen fuel via fusion and burn out. The Sun will likely expand sufficiently to overwhelm most of the inner planets (Mercury, Venus, and possibly Earth), but not
496-495: The rings of Saturn in their current state. During this era, Saturn's moon Titan may reach surface temperatures necessary to support life. The Universe's expansion, assuming a constant dark energy density, multiplies the wavelength of the cosmic microwave background by 10 , exceeding the scale of the cosmic light horizon and rendering its evidence of the Big Bang undetectable. However, it may still be possible to determine
527-838: The Andromeda Galaxy; the two galaxies are 750,000 light years apart, and experienced a close passage 2–4 billion years ago which triggered star formation across Andromeda's disk. The Pisces Dwarf Galaxy is equidistant from the Andromeda Galaxy and the Triangulum Galaxy, so it may be a satellite of either. The other members of the group are likely gravitationally secluded from these large subgroups: IC 10 , IC 1613 , Phoenix Dwarf Galaxy, Leo A , Tucana Dwarf Galaxy, Cetus Dwarf Galaxy, Pegasus Dwarf Irregular Galaxy , Wolf–Lundmark–Melotte , Aquarius Dwarf Galaxy, and Sagittarius Dwarf Irregular Galaxy . The membership of NGC 3109 , with its companions Sextans A and
558-461: The Andromeda and the Milky Way galaxies, are both spiral galaxies with masses of about 10 solar masses each. Each has its own system of satellite galaxies : The Triangulum Galaxy (M33) is the third-largest member of the Local Group, with a mass of approximately 5 × 10 M ☉ (1 × 10 kg), and is the third spiral galaxy. It is unclear whether the Triangulum Galaxy is a companion of
589-602: The Local Group. This possible independence may, however, disappear as the Milky Way continues coalescing with Andromeda due to the increased mass, and density thereof, plausibly widening the radius of the zero-velocity surface of the Local Group. The term "The Local Group" was introduced by Edwin Hubble in Chapter VI of his 1936 book The Realm of the Nebulae . There, he described it as "a typical small group of nebulae which
620-584: The Solar System and into interstellar space . Barring an extremely unlikely collision with some object, the craft should persist indefinitely. Estimated lifespan of the HD-Rosetta analog disc, an ion beam-etched writing medium on nickel plate, a technology developed at Los Alamos National Laboratory and later commercialized. (The Rosetta Project uses this technology, named after the Rosetta Stone .) According to scientific predictions, Chernobyl
651-429: The effect of dark matter , as the visible mass is greatly less than that needed to gravitationally hold the galaxies together in a bound group. Compact galaxy groups are also not dynamically stable over Hubble time , thus showing that galaxies evolve by merger, over the timescale of the age of the universe. Fossil galaxy groups, fossil groups, or fossil clusters are believed to be the end-result of galaxy merging within
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#1732764881793682-605: The expansion of the universe through the study of hypervelocity stars . Collisions between brown dwarfs will create new red dwarfs on a marginal level: on average, about 100 stars will be shining in what was once "Milkomeda". Collisions between stellar remnants will create occasional supernovae. By this point, the black dwarf that was once the Sun will have cooled to 5 K (−268.15 °C; −450.67 °F). On this vast timescale, even ultra-stable iron stars will have been destroyed by quantum-tunnelling events. At this lower end of
713-412: The formation and evolution of galaxies and the intragroup medium in an isolated system. Fossil groups may still contain unmerged dwarf galaxies , but the more massive members of the group have condensed into the central galaxy. This hypothesis is supported by studies of computer simulations of cosmological volumes. The closest fossil group to the Milky Way is NGC 6482 , an elliptical galaxy at
744-517: The galaxies in the local universe. Groups have a mass range between those of the very large elliptical galaxies and clusters of galaxies. In the local universe, about half of the groups exhibit diffuse X-ray emissions from their intracluster media . Those that emit X-rays appear to have early-type galaxies as members. The diffuse X-ray emissions come from zones within the inner 10–50% of the groups' virial radius, generally 50–500 kpc. There are several subtypes of groups. A compact group consists of
775-520: The giant planets, including Jupiter and Saturn. Afterwards, the Sun would be reduced to the size of a white dwarf , and the outer planets and their moons would continue orbiting this diminutive solar remnant. This future situation may be similar to the white dwarf star MOA-2010-BLG-477L and the Jupiter-sized exoplanet orbiting it. Long after the death of the solar system, physicists expect that matter itself will eventually disintegrate under
806-659: The influence of radioactive decay , as even the most stable materials break apart into subatomic particles. Current data suggests that the universe has a flat geometry (or very close to flat), and thus will not collapse in on itself after a finite time. This infinite future could allow for the occurrence of even massively improbable events, such as the formation of Boltzmann brains . However, according to more recent studies in 2016, anthropogenic climate change, if left unchecked, may delay this otherwise expected glacial period by as much as an additional 50,000 years, potentially skipping it entirely. Niagara Falls will have eroded
837-567: The other. The two collections are separated by about 800 kiloparsecs (3 × 10 ^ ly; 2 × 10 km) and are moving toward one another with a velocity of 123 km/s . The group itself is a part of the larger Virgo Supercluster , which may be a part of the Laniakea Supercluster . The exact number of galaxies in the Local Group is unknown as some are occluded by the Milky Way; however, at least 80 members are known, most of which are dwarf galaxies . The two largest members,
868-528: The remaining 32 km to Lake Erie , and will therefore cease to exist. The many glacial lakes of the Canadian Shield will have been erased by post-glacial rebound and erosion. The Indian Plate will advance into Tibet by 180 km (110 mi). Nepali territory, whose boundaries are defined by the Himalayan peaks and on the plains of India , will cease to exist. Even without
899-485: The start of the 4th millennium in 3001 CE, and continue until the furthest and most remote reaches of future time. They include alternative future events that address unresolved scientific questions, such as whether humans will become extinct , whether the Earth survives when the Sun expands to become a red giant and whether proton decay will be the eventual end of all matter in the universe. Keys All projections of
930-448: The timescale, iron stars decay directly to black holes, as this decay mode is much more favourable than decaying into a neutron star (which has an expected timescale of 10 10 76 {\displaystyle 10^{10^{76}}} years), and later decaying into a black hole. The subsequent evaporation of each resulting black hole into subatomic particles (a process lasting roughly 10 years), and subsequent shift to
961-453: The total number of ways in which all the subatomic particles in the observable universe can be combined is 10 10 115 {\displaystyle 10^{10^{115}}} , a number which, when multiplied by 10 10 10 56 {\displaystyle 10^{10^{10^{56}}}} , is 10 10 10 56 {\displaystyle 10^{10^{10^{56}}}} , this