### aggregation:

Galaxy
* All galaxies attract each other via gravity
  - emit radio waves as well as light
  - exist inside the universe
* All galaxies have a faint outer region or envelope and a mysterious dark matter halo
  - the same shape
* Every galaxy contains hundreds of billions of stars, each, perhaps, with planets
  - is in the universe
* Galaxies Look with binoculars for the Beehive star cluster, faintly visible to the naked eye
  - almost outnumber all other types of objects combined
* Galaxies also appear in larger clusters
  - conjoin
  - contain vast clouds of gas and dust, which are the raw materials for new stars
* Galaxies also have different ages and move at different speeds
  - extra motions
  - appear as spirals because of a close gravitational interaction with neighboring galaxies
* Galaxies are also part of space
  - big
  - cities of stars
  - clouds of hundreds of billions of stars like our own Milky Way
* Galaxies are clusters of stars that typically rotate about some center of mass point
  - which typically rotate about some center of mass point
  - collections of billions of stars orbiting together as islands in the universe
  - complex objects, showing many different faces, forms, and sizes
  - everywhere in the sky
  - familiar as very large groupings of stars
  - found in a variety of sizes and shapes
  - huge groups of stars, gas, dust and space materials
  - immense systems containing billions of stars
  - inherently dynamic systems that change with time
  - irregular, elliptical, and spiral
* Galaxies are large assemblies of stars, nebulae, and star clusters that are bound by gravity
  - but are actually a much smaller pack of galaxies
  - groupings of millions to hundreds of billions of stars
  - groups of stars nebulae and other objects that orbit the galactic center
  - lens-shaped collections of billions of stars
  - likely to encounter other galaxies a few times over their histories
  - massive collections of stars, gas, and dust
  - more dense near the nucleus and become sparser the further out from the nucleus
  - mostly empty space
* Galaxies are much denser than the intergalactic medium
  - larger systems of stars and usually include clouds of gas and dust
  - often found in pairs or in clusters, Planets have satellites
  - predominantly responsible for multiple imaging
  - separated from each other by enormous stretches of empty space
  - some of the most treasured objects for visual and photographic studies
  - stationary but time continues to change, giving the appearance of motion
* Galaxies are the basic units of mass in the universe and are visible from very great distances
  - birth place of stars
  - titanic swarms of tens of millions to trillions of stars
* Galaxies are very large aggregations of stars, gas, dust, and physical matter
  - and distinct communities of stars
  - large, with typical diameters of tens to hundreds of thousands of light years
  - massive, too, so their gravity is strong
* Galaxies can also have a rounded look and some are more irregular in shape
  - even collide
  - have various shapes , from elliptical to spiral
* Galaxies come in a great range of shapes and sizes
  - all sizes and types
* Galaxies come in different shapes and sizes
  - sizes, shapes, colors and chemical compositions
  - diverse shapes and sizes
  - many different shapes and sizes
  - several forms
  - various shapes and sizes
  - consist largely of dark matter
* Galaxies consist of numerous stars and are held together by gravity
  - stars and interstellar gas
* Galaxies contain billions of stars like our Sun
  - tens to hundreds of billions of stars
  - continue to separate from one another, although more slowly as time passes
  - do fall into groups and groups of groups
* Galaxies emit all kinds of light, from visible to infrared
  - in the blue because of the large amounts of dust
* Galaxies exist in a variety of sizes with regular and irregular shapes
  - many different forms, with vastly different properties
  - two basic forms, with variations
  - expand and populate the universe
  - gather together to form clusters, which, in turn, clump into superclusters
  - gather, form, and interact
  - generally don t escape collision
* Galaxies have a variety of types
  - certain features in common
  - gravitational fields
  - low surface brightness and except for the brightest and biggest, can be easy to miss
  - magnetic fields of their own
  - several different shapes
  - live in great clusters, like swarms of bees
  - look the same whether viewed in visible or X-ray wavelengths
* Galaxies never appear to occur singly
  - crash into each other
* Galaxies often appear to be distinct but fuzzy patches of light
  - crash into one another
* Galaxies orbit each on in clusters
  - radiate a continuous spectrum of energy
  - represent directories, planets represent files, and wormholes represent symlinks
* Galaxies rotate and move in clusters as if a tremendous amount of unseen matter is present
  - every which way
* Galaxies seem to be grouped on the outside edges of the voids
  - together in what appears to be a very complex sponge-like arrangement
  - go through a massive burst of star creation early in their lives
  - show position angle, morphology and size
* Galaxies tend to be found in groupings throughout the universe
  - groups and clusters
  - grouped into clusters
* Galaxies tend to clump together in the universe, forming clusters of galaxies
  - thus have a mixture of stars and diffuse interstellar medium
  - too are immense vortex fields in space
* Galaxies travel through space at speeds approaching two million miles per hour
  - typically have billions of stars
  - undergoing such rapid star formation are known as starburst galaxies
  - vary in size from a few thousand to a million light years in diameter
  - wind themselves up much too fast to be billions of years old
* Many galaxies also continue to form new generations of stars
  - appear to be undergoing recent, enhanced star formation
  - contain dust and molecular gas, which can be studied in the submillimeter
  - form clusters of stars, and many clusters form superclusters
* Many galaxies have extremely small but very energetic and luminous nuclei
  - regions in their cores that resemble very weak quasars
  - unusual activity in their cores
  - lie in thin sheet-like structures
  - possess both inner and outer rings simultaneously
* Most galaxies are believed to have a supermassive black hole at their center
  - members of groups
  - millions of light-years away
  - spiral, like our own Milky Way, or they're round
  - thought to have a black hole in their heart
* Most galaxies are too far away to see their X-rays sources
  - small and dim for young eyes and bright lights
  - harbor a quiescent black hole, a black hole that presently accretes little
* Most galaxies have black holes at their centers
  - spectra dominated by the combined light of all their stars
  - lie in clusters, groupings of several to many thousands of galaxies
  - live in groups or clusters
  - occur in large clusters or groups, and interact with each other gravitationally
  - probably undergo at least one significant collision in their lifetime
  - reside in groups
* Some galaxies are disk shaped with pinwheel arms, called spirals
  - elliptical in shape, while others look like single or multiple spirals
  - neither ellipsoidal nor are they spirals
  - so distant the their light takes millions of years to reach the Earth
  - very bright in radio waves compared to normal galaxies
  - contain emission nebula that are brighter than the brightest stars in the galaxy
  - have extremely luminous nuclei, often outshining the rest of the galaxy
* Some galaxies have spiral arms about that tightly wrapped
  - or pinwheel arms
  - produce lots of infant stars
  - seem to release prodigious amounts of energy
  - then acquire a flattened disk, such as the one the sun lives in.
  * Then there are irregular galaxies. All galaxies exist inside the universe
* belong to a globular cluster.
* counts with magnitude and colour.
* is astronomical objects.
* is located in space
  - universes
  - part of universes
+ Galaxy, Description
  * Many galaxies also continue to form new generations of stars. Globular star clusters, on the other hand, are not currently forming stars because this activity happened billions of years ago and then stopped once all of the gas and dust clouds were used up.
+ Milky Way, Galactic center: Spiral galaxies :: Local galaxies
  * Movement of material around the galactic center shows that it has a compact object of very large mass. Most galaxies are believed to have a supermassive black hole at their center. Blandford R.D. 1999. Origin and evolution of massive black holes in galactic nuclei. In 'Galaxy Dynamics', ASP Conference Series vol.