Sometimes, the solar system has lain above or below the plane
of the galactic disk.
The local void of gas extends out
of the galactic disk and stretches into the overlying galactic halo region.
It could easily have been caused by a supernova punching through the top and bottom
of the galactic disk, the intense stellar winds from 10 or so hot stars, a powerful gamma - ray burst, or even a large star moving through the area.
If alien lifeforms were to develop on planets orbiting these stars, they would have views of a portion, or all,
of the galactic disk.
However, their gravity has affected our Galaxy as well, distorting the outer parts
of the galactic disk.
Not exact matches
The study appears to vindicate predictions from theorists such as Mark Morris, an astrophysicist at the University
of California, Los Angeles, who in 1993 penned a key paper predicting tens
of thousands
of stellar - mass black holes would form a
disk around the
galactic center.
In Randall and Reece's model
of this dark matter
disk, they found that Earth travels through the
disk on a regular schedule, oscillating above and below the galaxy's equator while orbiting the
galactic center.
The Tadpole galaxy (top left) sports a long tail
of stars and gas pulled out by the gravity
of a
galactic interloper, visible as a small blue clump in the upper part
of the Tadpole's
disk.
Moving out from this central
galactic bulge, the panorama sweeps from the galaxy's central bulge across lanes
of stars and dust to the sparser outer
disk.
Dark atoms and molecules could perhaps clump together into
galactic disks that overlap with the ordinary matter
disks and spiral arms
of galaxies such as Andromeda.
To excite the voorwerp's glow, the black hole and its surrounding accretion
disk, the active
galactic nucleus, or AGN, should have had the brightness
of about 2.5 trillion suns; its radio emission, however, suggested the AGN emitted the equivalent
of a relatively paltry 25,000 suns.
Expanding the size
of the simulation will allow the team to test an alternate theory for the emergence
of galactic wind in
disk galaxies like M82.
Its halo and
disk suggest that the collapse
of a gas cloud, stellar explosions and the capture
of galactic fragments may have all played a role
In the simulations, described in a study published in the September 15 issue
of Nature, Sagittarius stirred up enough ripples to make a smooth, circular, spinning
galactic disk evolve into a spiral much like the Milky Way.
Now, researchers in the nascent field
of galactic seismology have found a possible cause
of at least some
of those ripples: a dwarf galaxy that shot like a bullet through the
galactic disk some half - a-billion years ago.
She shared some
of her first observations
of how these accretion
disks operate in brilliant active
galactic nuclei, or AGNs.
The gas in the
galactic disk will circulate faster and faster as it spirals into the vicinity
of the SMBH.
In some active
galactic nuclei, you have a black hole and accretion
disk and the majority
of the power is associated with these outflowing jets, far more than is associated with the radiant energy that is emitted by the accretion
disk and the hot gas surrounding it.
But in an analysis
of the movements
of some 300 stars located at least 6,000 light - years beyond the
galactic plane, Christian Moni Bidin, an astronomer at the University
of Concepción in Chile, and his colleagues conclude that there is «no compelling evidence» for such a dark
disk.
«These structures are pushed off the plane
of the Milky Way when a massive dwarf galaxy passes through the
galactic disk.
Globular clusters, which are found in the halo
of a galaxy, contain considerably more stars and are much older than the less dense
galactic, or open clusters, which are found in the
disk.
But in a study published today in the journal Nature, astronomers now have compelling evidence showing that some
of these halo structures actually originate from the Milky Way's
disk itself, but were kicked out; this phenomenon is called
galactic eviction.
g (acceleration due to gravity) G (gravitational constant) G star G1.9 +0.3 gabbro Gabor, Dennis (1900 — 1979) Gabriel's Horn Gacrux (Gamma Crucis) gadolinium Gagarin, Yuri Alexeyevich (1934 — 1968) Gagarin Cosmonaut Training Center GAIA Gaia Hypothesis
galactic anticenter
galactic bulge
galactic center
Galactic Club
galactic coordinates
galactic disk galactic empire
galactic equator
galactic habitable zone
galactic halo
galactic magnetic field
galactic noise
galactic plane
galactic rotation galactose Galatea GALAXIES galaxy galaxy cannibalism galaxy classification galaxy formation galaxy interaction galaxy merger Galaxy, The Galaxy satellite series Gale Crater Galen (c. AD 129 — c. 216) galena GALEX (Galaxy Evolution Explorer) Galilean satellites Galilean telescope Galileo (Galilei, Galileo)(1564 — 1642) Galileo (spacecraft) Galileo Europa Mission (GEM) Galileo satellite navigation system gall gall bladder Galle, Johann Gottfried (1812 — 1910) gallic acid gallium gallon gallstone Galois, Évariste (1811 — 1832) Galois theory Galton, Francis (1822 — 1911) Galvani, Luigi (1737 — 1798) galvanizing galvanometer game game theory GAMES AND PUZZLES gamete gametophyte Gamma (Soviet orbiting telescope) Gamma Cassiopeiae Gamma Cassiopeiae star gamma function gamma globulin gamma rays Gamma Velorum gamma - ray burst gamma - ray satellites Gamow, George (1904 — 1968) ganglion gangrene Ganswindt, Hermann (1856 — 1934) Ganymede «garbage theory»,
of the origin
of life Gardner, Martin (1914 — 2010) Garneau, Marc (1949 ---RRB- garnet Garnet Star (Mu Cephei) Garnet Star Nebula (IC 1396) garnierite Garriott, Owen K. (1930 ---RRB- Garuda gas gas chromatography gas constant gas giant gas laws gas - bounded nebula gaseous nebula gaseous propellant gaseous - propellant rocket engine gasoline Gaspra (minor planet 951) Gassendi, Pierre (1592 — 1655) gastric juice gastrin gastrocnemius gastroenteritis gastrointestinal tract gastropod gastrulation Gatewood, George D. (1940 ---RRB- Gauer - Henry reflex gauge boson gauge theory gauss (unit) Gauss, Carl Friedrich (1777 — 1855) Gaussian distribution Gay - Lussac, Joseph Louis (1778 — 1850) GCOM (Global Change Observing Mission) Geber (c. 720 — 815) gegenschein Geiger, Hans Wilhelm (1882 — 1945) Geiger - Müller counter Giessler tube gel gelatin Gelfond's theorem Gell - Mann, Murray (1929 ---RRB- GEM «gemination,»
of martian canals Geminga Gemini (constellation) Gemini Observatory Gemini Project Gemini - Titan II gemstone gene gene expression gene mapping gene pool gene therapy gene transfer General Catalogue
of Variable Stars (GCVS) general precession general theory
of relativity generation ship generator Genesis (inflatable orbiting module) Genesis (sample return probe) genetic code genetic counseling genetic disorder genetic drift genetic engineering genetic marker genetic material genetic pool genetic recombination genetics GENETICS AND HEREDITY Geneva Extrasolar Planet Search Program genome genome, interstellar transmission
of genotype gentian violet genus geoboard geode geodesic geodesy geodesy satellites geodetic precession Geographos (minor planet 1620) geography GEOGRAPHY Geo - IK geologic time geology GEOLOGY AND PLANETARY SCIENCE geomagnetic field geomagnetic storm geometric mean geometric sequence geometry GEOMETRY geometry puzzles geophysics GEOS (Geodetic Earth Orbiting Satellite) Geosat geostationary orbit geosynchronous orbit geosynchronous / geostationary transfer orbit (GTO) geosyncline Geotail (satellite) geotropism germ germ cells Germain, Sophie (1776 — 1831) German Rocket Society germanium germination Gesner, Konrad von (1516 — 1565) gestation Get Off the Earth puzzle Gettier problem geyser g - force GFO (Geosat Follow - On) GFZ - 1 (GeoForschungsZentrum) ghost crater Ghost Head Nebula (NGC 2080) ghost image Ghost
of Jupiter (NGC 3242) Giacconi, Riccardo (1931 ---RRB- Giacobini - Zinner, Comet (Comet 21P /) Giaever, Ivar (1929 ---RRB- giant branch Giant Magellan Telescope giant molecular cloud giant planet giant star Giant's Causeway Giauque, William Francis (1895 — 1982) gibberellins Gibbs, Josiah Willard (1839 — 1903) Gibbs free energy Gibson, Edward G. (1936 ---RRB- Gilbert, William (1544 — 1603) gilbert (unit) Gilbreath's conjecture gilding gill gill (unit) Gilruth, Robert R. (1913 — 2000) gilsonite gimbal Ginga ginkgo Giotto (ESA Halley probe) GIRD (Gruppa Isutcheniya Reaktivnovo Dvisheniya) girder glacial drift glacial groove glacier gland Glaser, Donald Arthur (1926 — 2013) Glashow, Sheldon (1932 ---RRB- glass GLAST (Gamma - ray Large Area Space Telescope) Glauber, Johann Rudolf (1607 — 1670) glaucoma glauconite Glenn, John Herschel, Jr. (1921 ---RRB- Glenn Research Center Glennan, T (homas) Keith (1905 — 1995) glenoid cavity glia glial cell glider Gliese 229B Gliese 581 Gliese 67 (HD 10307, HIP 7918) Gliese 710 (HD 168442, HIP 89825) Gliese 86 Gliese 876 Gliese Catalogue glioma glissette glitch Global Astrometric Interferometer for Astrophysics (GAIA) Global Oscillation Network Group (GONG) Globalstar globe Globigerina globular cluster globular proteins globule globulin globus pallidus GLOMR (Global Low Orbiting Message Relay) GLONASS (Global Navigation Satellite System) glossopharyngeal nerve Gloster E. 28/39 glottis glow - worm glucagon glucocorticoid glucose glucoside gluon Glushko, Valentin Petrovitch (1908 — 1989) glutamic acid glutamine gluten gluteus maximus glycerol glycine glycogen glycol glycolysis glycoprotein glycosidic bond glycosuria glyoxysome GMS (Geosynchronous Meteorological Satellite) GMT (Greenwich Mean Time) Gnathostomata gneiss Go Go, No - go goblet cell GOCE (Gravity field and steady - state Ocean Circulation Explorer) God Goddard, Robert Hutchings (1882 — 1945) Goddard Institute for Space Studies Goddard Space Flight Center Gödel, Kurt (1906 — 1978) Gödel universe Godwin, Francis (1562 — 1633) GOES (Geostationary Operational Environmental Satellite) goethite goiter gold Gold, Thomas (1920 — 2004) Goldbach conjecture golden ratio (phi) Goldin, Daniel Saul (1940 ---RRB- gold - leaf electroscope Goldstone Tracking Facility Golgi, Camillo (1844 — 1926) Golgi apparatus Golomb, Solomon W. (1932 — 2016) golygon GOMS (Geostationary Operational Meteorological Satellite) gonad gonadotrophin - releasing hormone gonadotrophins Gondwanaland Gonets goniatite goniometer gonorrhea Goodricke, John (1764 — 1786) googol Gordian Knot Gordon, Richard Francis, Jr. (1929 — 2017) Gore, John Ellard (1845 — 1910) gorge gorilla Gorizont Gott loop Goudsmit, Samuel Abraham (1902 — 1978) Gould, Benjamin Apthorp (1824 — 1896) Gould, Stephen Jay (1941 — 2002) Gould Belt gout governor GPS (Global Positioning System) Graaf, Regnier de (1641 — 1673) Graafian follicle GRAB graben GRACE (Gravity Recovery and Climate Experiment) graceful graph gradient Graham, Ronald (1935 ---RRB- Graham, Thomas (1805 — 1869) Graham's law
of diffusion Graham's number GRAIL (Gravity Recovery and Interior Laboratory) grain (cereal) grain (unit) gram gram - atom Gramme, Zénobe Théophile (1826 — 1901) gramophone Gram's stain Gran Telescopio Canarias (GTC) Granat Grand Tour grand unified theory (GUT) Grandfather Paradox Granit, Ragnar Arthur (1900 — 1991) granite granulation granule granulocyte graph graph theory graphene graphite GRAPHS AND GRAPH THEORY graptolite grass grassland gravel graveyard orbit gravimeter gravimetric analysis Gravitational Biology Facility gravitational collapse gravitational constant (G) gravitational instability gravitational lens gravitational life gravitational lock gravitational microlensing GRAVITATIONAL PHYSICS gravitational slingshot effect gravitational waves graviton gravity gravity gradient gravity gradient stabilization Gravity Probe A Gravity Probe B gravity - assist gray (Gy) gray goo gray matter grazing - incidence telescope Great Annihilator Great Attractor great circle Great Comets Great Hercules Cluster (M13, NGC 6205) Great Monad Great Observatories Great Red Spot Great Rift (in Milky Way) Great Rift Valley Great Square
of Pegasus Great Wall greater omentum greatest elongation Green, George (1793 — 1841) Green, Nathaniel E. Green, Thomas Hill (1836 — 1882) green algae Green Bank Green Bank conference (1961) Green Bank Telescope green flash greenhouse effect greenhouse gases Green's theorem Greg, Percy (1836 — 1889) Gregorian calendar Grelling's paradox Griffith, George (1857 — 1906) Griffith Observatory Grignard, François Auguste Victor (1871 — 1935) Grignard reagent grike Grimaldi, Francesco Maria (1618 — 1663) Grissom, Virgil (1926 — 1967) grit gritstone Groom Lake Groombridge 34 Groombridge Catalogue gross ground, electrical ground state ground - track group group theory GROUPS AND GROUP THEORY growing season growth growth hormone growth hormone - releasing hormone growth plate Grudge, Project Gruithuisen, Franz von Paula (1774 — 1852) Grus (constellation) Grus Quartet (NGC 7552, NGC 7582, NGC 7590, and NGC 7599) GSLV (Geosynchronous Satellite Launch Vehicle) g - suit G - type asteroid Guericke, Otto von (1602 — 1686) guanine Guiana Space Centre guidance, inertial Guide Star Catalog (GSC) guided missile guided missiles, postwar development Guillaume, Charles Édouard (1861 — 1938) Gulf Stream (ocean current) Gulfstream (jet plane) Gullstrand, Allvar (1862 — 1930) gum Gum Nebula gun metal gunpowder Gurwin Gusev Crater gut Gutenberg, Johann (c. 1400 — 1468) Guy, Richard Kenneth (1916 ---RRB- guyot Guzman Prize gymnosperm gynecology gynoecium gypsum gyrocompass gyrofrequency gyropilot gyroscope gyrostabilizer Gyulbudagian's Nebula (HH215)
The rotation curve is flat in the outer parts
of most
galactic disks (dark matter!).
As a result, many specific structural features
of the spiral arms are not well known, especially when compared with other spirals observed outside the Milky Way such as Andromeda (which is located a few million ly above the
galactic plane
of obscuring dust in the Milky Way's
disk.
At that time, however,
galactic disks were generally clumpy and irregular, so other processes likely overwhelmed the formation
of similar eyelid features.
From this perspective, astronomers have been actively working on the starburst regions
of galaxies (* 1) and the active
galactic nuclei (AGN) at the center
of galaxies, which are called circumnuclear
disks (CND)(* 2).
These
galactic types are all characterized by violent activity at their cores, usually explained as arising from an accretion
disk of hot gases that surrounds a central black hole having a mass
of about 1,000,000,000 Suns.
Some are found in globular clusters, but most move in a huge cloud around the
disk called the
galactic halo, which has a luminous inner component defined by globular star clusters and other easily observable stars (with coronae
of hot gas possibly expelled by supernovae and
of high - velocity neutron stars) and an outer dark - matter component inferred from its gravitational impact on the Milky Way's spiral
disk.
Mature
galactic disks form later, composed
of many star - forming regions at 50 — 100 parsec in size.
In addition, tidal forces affecting the Oort Cloud come from the differential gravitational forces exerted by stars in the Milky Way's
galactic disk and by the
galactic core on the Sun and comets as a result
of their relative location in the Solar System, which have been modelled with numerical simulations (Duncan et al, 1987).
Because gravity depends upon mass, you might think that most
of a galaxy's mass would lie in the
galactic disk or near the center
of the
disk.
The thick
disk is generally formed
of old stars that may lie several thousand light - years (ly) above or below the
galactic plane, unlike thin
disk stars such as Sol which typically lie within a thousand ly.
We have clearly detected FIR dust emission extended in the halo
of the galaxy; there are two filamentary emission structures extending from the
galactic disk up to 9 kpc in the northern and 6 kpc in the northwestern direct... ▽ More We present new far - infrared (FIR) images
of the edge - on starburst galaxy NGC253 obtained with the Far - Infrared Surveyor (FIS) onboard AKARI at wavelengths
of 90 um and 140 um.
Using several methods, we re-consider whether some or even all
of the candidates may be associated with unrelated
galactic or extragalactic emission and conclude that it is highly unlikely that none
of the candidates represents a true circumstellar
disk.
The «Local Bubble»
of low - density, hot and ionized gas, is actually part
of a tube - like chimney that extends through the local region
of the spiral
disk into the surrounding
galactic halo, and so may can act as a vent for the energetic hot gas produced by supernovae (more).
The central region
of the Milky Way is dominated by a bar - like structure, which stirs up the material in the outer
galactic disk as it rotates over millions
of years and may be responsible for its spiral structure.
Globular clusters orbit the Milky Way galaxy outside the
galactic disk at tens
of thousands
of light - years away.
Previously, astronomers thought that the Milky Way's spiral thin
disk petered out at its furthest hypothesized extent
of as much as 50,000 ly from the
galactic center.
Due to Kapteyn's proximity to Sol and its deduced ancient origin from outside the
galactic disk, the system has been an object
of high interest among astronomers.