Galaxy

1.

2.

3.

galaxy - галактика
[ˈgæləksɪ]
Milky Way - Млечный
[ˈmɪlkɪ weɪ]
Путь
elliptical galaxy эллиптическая
галактика
[ɪˈlɪptɪkəl ˈgæləksɪ]

4.

shell galaxy -
[ʃel ˈgæləksɪ]
эллиптическая
галактика с оболочкой
spiral galaxy -
[ˈspaɪərəl ˈgæləksɪ]
спиральная галактика
barred spiral galaxy пересеченная
спиральная галактика
[bɑːd ˈspaɪərəl ˈgæləksɪ]

5.

peculiar galaxy -
[pɪˈkjuːlɪə ˈgæləksɪ]
пекулярная галактика
ring galaxy - кольцевая
[rɪŋ ˈgæləksɪ]
галактика
lenticular galaxy линзовидная галактика
[lenˈtɪkjʊlə ˈgæləksɪ]

6.

irregular galaxy –
[ɪˈregjʊlə ˈgæləksɪ]
несимметричная
галактика
Magellanic Clouds -
[mæʤɪˈlæntɪk klaʊdz]
Магеллановы облака
ultra diffuse galaxy ультра диффузная
галактика
[ˈʌltrə dɪˈfjuːs ˈgæləksɪ]

7.

Galaxy

8.

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas,
dust, and dark matter. The word galaxy is derived from the Greek galaxias (γαλαξίας),
literally "milky", a reference to the Milky Way. Galaxies range in size from dwarfs
with just a few hundred million (108) stars to giants with one hundred trillion (1014)
stars, each orbiting its galaxy's center of mass.
Galaxies are categorized according to their visual morphology as elliptical, spiral, or
irregular. Many galaxies are thought to have supermassive black holes at their
centers. The Milky Way's central black hole, known as Sagittarius A*, has a mass four
million times greater than the Sun. As of March 2016, GN-z11 is the oldest and most
distant galaxy observed. It has a comoving distance of 32 billion light-years from
Earth, and is seen as it existed just 400 million years after the Big Bang.
In 2021, data from NASA's New Horizons space probe was used to revise the previous
estimate of 2 trillion galaxies down to roughly 200 billion galaxies. This followed a
2016 estimate that there were two trillion or more galaxies in the observable universe,
overall, as many as an estimated stars (more stars than all the grains of sand on planet
Earth). Most of the galaxies are 1,000 to 100,000 parsecs in diameter (approximately
3,000 to 300,000 light years) and are separated by distances on the order of millions of
parsecs (or megaparsecs). For comparison, the Milky Way has a diameter of at least
30,000 parsecs and is separated from the Andromeda Galaxy, its nearest large
neighbor, by 780,000 parsecs.

9.

The space between galaxies is filled with a tenuous gas (the intergalactic medium)
having an average density of less than one atom per cubic meter. The majority of
galaxies are gravitationally organized into groups, clusters, and superclusters. The
Milky Way is part of the Local Group, which it dominates along with Andromeda
Galaxy. The group is part of the Virgo Supercluster. At the largest scale, these
associations are generally arranged into sheets and filaments surrounded by immense
voids. Both the Local Group and the Virgo Supercluster are contained in a much
larger cosmic structure named Laniakea.

10.

Milky Way

11.

The Milky Way is the galaxy that includes our Solar System, with the name
describing the galaxy's appearance from Earth: a hazy band of light seen in the night
sky formed from stars that cannot be individually distinguished by the naked eye.
The term Milky Way is a translation of the Latin via lactea, from the Greek
γαλακτικός κύκλος (galaktikos kýklos), meaning "milky circle."From Earth, the
Milky Way appears as a band because its disk-shaped structure is viewed from
within. Galileo Galilei first resolved the band of light into individual stars with his
telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way
contained all the stars in the Universe. Following the 1920 Great Debate between the
astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble
showed that the Milky Way is just one of many galaxies.
The Milky Way is a barred spiral galaxy with an estimated visible diameter of
100,000–200,000 light-years. Recent simulations suggest that a dark matter disk, also
containing some visible stars, may extend up to a diameter of almost 2 million lightyears. The Milky Way has several satellite galaxies and is part of the Local Group of
galaxies, which form part of the Virgo Supercluster, which is itself a component of
the Laniakea Supercluster.
It is estimated to contain 100–400 billion stars and at least that number of planets. The
Solar System is located at a radius of about 27,000 light-years from the Galactic
Center, on the inner edge of the Orion Arm, one of the spiral-shaped concentrations
of gas and dust.

12.

The stars in the innermost 10,000 light-years form a bulge and one or more bars that
radiate from the bulge. The galactic center is an intense radio source known as
Sagittarius A*, a supermassive black hole of 4.100 million solar masses. Stars and
gases at a wide range of distances from the Galactic Center orbit at approximately 220
kilometers per second. The constant rotation speed contradicts the laws of Keplerian
dynamics and suggests that much (about 90%) of the mass of the Milky Way is
invisible to telescopes, neither emitting nor absorbing electromagnetic radiation. This
conjectural mass has been termed "dark matter". The rotational period is about 240
million years at the radius of the Sun. The Milky Way as a whole is moving at a
velocity of approximately 600 km per second with respect to extragalactic frames of
reference. The oldest stars in the Milky Way are nearly as old as the Universe itself
and thus probably formed shortly after the Dark Ages of the Big Bang.

13.

Elliptical galaxy

14.

An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a
smooth, nearly featureless image. They are one of the three main classes of galaxy
described by Edwin Hubble in his Hubble sequence and 1936 work The Realm of the
Nebulae, along with spiral and lenticular galaxies. Elliptical (E) galaxies are, together
with lenticular galaxies (S0) with their large-scale disks, and ES galaxies with their
intermediate scale disks, a subset of the "early-type" galaxy population.
Most elliptical galaxies are composed of older, low-mass stars, with a sparse
interstellar medium and minimal star formation activity, and they tend to be
surrounded by large numbers of globular clusters. Elliptical galaxies are believed to
make up approximately 10–15% of galaxies in the Virgo Supercluster, and they are
not the dominant type of galaxy in the universe overall. They are preferentially found
close to the centers of galaxy clusters.
Elliptical galaxies range in size from tens of millions to over one hundred trillion
stars. Originally, Edwin Hubble hypothesized that elliptical galaxies evolved into
spiral galaxies, which was later discovered to be false, although the accretion of gas
and smaller galaxies may build a disk around a pre-existing ellipsoidal structure.
Stars found inside of elliptical galaxies are on average much older than stars found in
spiral galaxies.

15.

Shell galaxy

16.

A shell galaxy is a type of elliptical galaxy where the stars in the galaxy's halo are
arranged in concentric shells. About one-tenth of elliptical galaxies have a shell-like
structure, which has never been observed in spiral galaxies. The shell-like structures
are thought to develop when a larger galaxy absorbs a smaller companion galaxy. As
the two galaxy centers approach, the centers start to oscillate around a center point,
the oscillation creates gravitational ripples forming the shells of stars, similar to
ripples spreading on water. For example, galaxy NGC 3923 has over twenty shells.

17.

Spiral galaxy

18.

Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his
1936 work The Realm of the Nebulae and, as such, form part of the Hubble sequence.
Most spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and
a central concentration of stars known as the bulge. These are often surrounded by a
much fainter halo of stars, many of which reside in globular clusters.
Spiral galaxies are named by their spiral structures that extend from the center into
the galactic disc. The spiral arms are sites of ongoing star formation and are brighter
than the surrounding disc because of the young, hot OB stars that inhabit them.
Roughly two-thirds of all spirals are observed to have an additional component in the
form of a bar-like structure, extending from the central bulge, at the ends of which the
spiral arms begin. The proportion of barred spirals relative to barless spirals has
likely changed over the history of the universe, with only about 10% containing bars
about 8 billion years ago, to roughly a quarter 2.5 billion years ago, until present,
where over two-thirds of the galaxies in the visible universe (Hubble volume) have
bars.
The Milky Way is a barred spiral, although the bar itself is difficult to observe from
Earth's current position within the galactic disc. The most convincing evidence for the
stars forming a bar in the galactic center comes from several recent surveys, including
the Spitzer Space Telescope. Together with irregular galaxies, spiral galaxies make up
approximately 60% of galaxies in today's universe. They are mostly found in lowdensity regions and are rare in the centers of galaxy clusters.

19.

Barred spiral galaxy

20.

A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed
of stars. Bars are found in about half of all spiral galaxies. Bars generally affect both
the motions of stars and interstellar gas within spiral galaxies and can affect spiral
arms as well. The Milky Way Galaxy, where the Solar System is located, is classified
as a barred spiral galaxy.
Edwin Hubble classified spiral galaxies of this type as "SB" (spiral, barred) in his
Hubble sequence and arranged them into sub-categories based on how open the arms
of the spiral are. SBa types feature tightly bound arms, while SBc types are at the
other extreme and have loosely bound arms. SBb-type galaxies lie in between the two.
SB0 is a barred lenticular galaxy. A new type, SBm, was subsequently created to
describe somewhat irregular barred spirals, such as the Magellanic Clouds, which
were once classified as irregular galaxies, but have since been found to contain barred
spiral structures. Among other types in Hubble's classifications for the galaxies are
the spiral galaxy, elliptical galaxy and irregular galaxy.

21.

Peculiar galaxy

22.

A peculiar galaxy is a galaxy of unusual size, shape, or composition. Between five and
ten percent of known galaxies are categorized as peculiar. Astronomers have
identified two types of peculiar galaxies: interacting galaxies and active galactic
nuclei (AGN).
When two galaxies come close to each other, their mutual gravitational forces can
cause them to acquire highly irregular shapes. The terms 'peculiar galaxy' and
'interacting galaxy' have now become synonymous because the majority of peculiar
galaxies attribute their forms to such gravitational forces.

23.

Ring galaxy

24.

A ring galaxy is a galaxy with a circle-like appearance. Hoag's Object, discovered by
Art 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.

25.

Lenticular galaxy

26.

A lenticular galaxy (denoted S0) is a type of galaxy intermediate between an elliptical
(denoted E) 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 (like
elliptical galaxies). 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.

27.

Irregular galaxy

28.

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.
Collectively they are thought to make up about a quarter of all galaxies. Some
irregular galaxies were once spiral or elliptical galaxies but were deformed by an
uneven external gravitational force. Irregular galaxies may contain abundant amounts
of gas and dust. This is not necessarily true for dwarf irregulars.
Irregular galaxies are commonly small, about one tenth the mass of the Milky Way
galaxy. Due to their small sizes, they are prone to environmental effects like crashing
with large galaxies and intergalactic clouds.

29.

Magellanic Clouds

30.

The Magellanic Clouds (or Nubeculae Magellani are two irregular dwarf galaxies
visible in the Southern Celestial Hemisphere; they are members of the Local Group
and are orbiting the Milky Way galaxy. Because both show signs of a bar structure,
they are often reclassified as Magellanic spiral galaxies.
The Large Magellanic Cloud and its neighbour and relative, the Small Magellanic
Cloud, are conspicuous objects in the southern hemisphere, looking like separated
pieces of the Milky Way to the naked eye. Roughly 21° apart in the night sky, the true
distance between them is roughly 75,000 light-years. Until the discovery of the
Sagittarius Dwarf Elliptical Galaxy in 1994, they were the closest known galaxies to
our own (since 2003, the Canis Major Dwarf Galaxy was discovered to be closer still,
and is now considered the actual nearest neighbor). The LMC lies about 160,000 light
years away, while the SMC is around 200,000. The LMC is about twice the diameter of
the SMC (14,000 ly and 7,000 ly respectively). For comparison, the Milky Way is about
100,000 ly across.
The total mass of these two galaxies is uncertain. Only a fraction of their gas seems to
have coalesced into stars and they probably both have large dark matter halos. One
recent estimate of the total mass of the LMC is about 1/10 that of the Milky Way. That
would make the LMC rather a large galaxy in the current observable universe. Since
the sizes of relatively nearby galaxies are highly skewed, the average mass can be a
misleading statistic. In terms of rank, the LMC appears to be the fourth most massive
member of over 50 galaxies in the local group.

31.

Ultra diffuse galaxy

32.

An ultra diffuse galaxy (UDG) is an extremely low luminosity galaxy, the first
example of which was discovered in the nearby Virgo Cluster by Allan Sandage and
Bruno Binggeli in 1984. These galaxies have been studied for many years prior to
their renaming in 2015. Their lack of luminosity is due to the lack of star-forming gas,
which results in these galaxies being reservoirs of very old stellar populations.
Based on discoveries confirmed in 2018, this class of galaxies includes both extremes
of dark matter content: Some UDGs consist almost entirely of dark matter (such a
galaxy may have the same size and mass as the Milky Way but a visible star count of
only 1%), while other UDGs appear to be almost entirely free of dark matter