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Location of Earth

From Wikipedia, the free encyclopedia
Location of the Earth in the Universe
Earth Location

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Logarithmic representation of the universe centered on theSolar System. Celestial bodies on this graphic are clickableThe image above contains clickable links and shown with their sizes enlarged.

Knowledge of thelocation of Earth has been shaped by 400 years of telescopic observations, and has expanded radically since the start of the 20th century. Initially,Earth was believed to be thecenter of the Universe,which consisted only of those planets visible with thenaked eye and an outlying sphere offixed stars.[1] After the acceptance of theheliocentric model in the 17th century, observations byWilliam Herschel and others showed that the Sun lay within a vast, disc-shapedgalaxy of stars.[2] By the 20th century, observations ofspiral nebulae revealed that theMilky Way galaxy was one of billions in anexpanding universe,[3][4] grouped into clusters andsuperclusters. By the end of the 20th century, theoverall structure of the visible universe was becoming clearer, with superclusters forming into a vast web offilaments andvoids.[5] Superclusters, filaments and voids are the largest coherent structures in the Universe that we can observe.[6] At still larger scales (over 1000megaparsecs[a]) the Universe becomes homogeneous, meaning that all its parts have on average the same density, composition and structure.[7]

Since there is believed to be no "center" or "edge" of the Universe, there is no particular reference point with which to plot the overall location of the Earth in the universe.[8] Because theobservable universe is defined as that region of the Universe visible to terrestrial observers, Earth is, because of the constancy of the speed of light, the center of Earth's observable universe. Reference can be made to the Earth's position with respect to specific structures, which exist at various scales. It is still undetermined whether the Universe isinfinite. There have been numerous hypotheses that the known universe may be only one such example within a highermultiverse; however, no direct evidence of any sort of multiverse has been observed, and some have argued that the hypothesis is notfalsifiable.[9][10]

Details

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Earth is the third planet from the Sun with an approximate distance of 149.6 million kilometres (93.0 million miles), and is traveling nearly 2.1 million kilometres per hour (1.3 million miles per hour) throughouter space.[11]

Table

[edit]
FeatureDiameterNotesSources
(most suitable unit)(km, withscientific notation)
Earth12,756.2km
(equatorial)		1.28×104Measurement comprises just the solid part of the Earth; there is no agreed upper boundary forEarth's atmosphere.
Thegeocorona, a layer of UV-luminescent hydrogen atoms, lies at 100,000 km.
TheKármán line, defined as the boundary of spacefor astronautics, lies at 100 km.		[12][13][14][15]
Orbit of the Moon768,210 km[b]7.68×105The average diameter of the orbit of the Moon relative to the Earth.[16]
Geospace6,363,000–12,663,000 km
(110–210 Earth radii)		6.36×106–1.27×107The space dominated byEarth's magnetic field and itsmagnetotail, shaped by thesolar wind.[17]
Earth's orbit299.2 million km[b]
2 AU[c]		2.99×108The average diameter of the orbit of the Earth relative to the Sun.
Encompasses theSun,Mercury andVenus.		[18]
Inner Solar System~6.54 AU9.78×108Encompasses the Sun, theinner planets (Mercury, Venus, Earth,Mars) and theasteroid belt.
Cited distance is the 2:1resonance with Jupiter, which marks the outer limit of the asteroid belt.		[19][20][21]
Outer Solar System60.14 AU9.00×109Includes theouter planets (Jupiter,Saturn,Uranus,Neptune).
Cited distance is the orbital diameter of Neptune.		[22]
Kuiper belt~96 AU1.44×1010Belt of icy objects surrounding theouter Solar System. Encompasses thedwarf planetsPluto,Haumea andMakemake.
Cited distance is the 2:1resonance with Neptune, generally regarded as the outer edge of the main Kuiper belt.		[23]
Heliosphere160 AU2.39×1010Maximum extent of thesolar wind and theinterplanetary medium.[24][25]
Scattered disc195.3 AU2.92×1010Region of sparsely scattered icy objects surrounding the Kuiper belt. Encompasses the dwarf planetEris.
Cited distance is derived by doubling theaphelion of Eris, the farthest known scattered disc object.
As of now, Eris's aphelion marks the farthest known point in the scattered disc.		[26]
Oort cloud100,000–200,000 AU
0.613–1.23pc[a]		1.89×1013–3.80×1013Spherical shell of over a trillion (1012)comets. Existence is currently hypothetical, but inferred from the orbits oflong-period comets.[27]
Solar System1.23 pc3.80×1013The Sun and itsplanetary system. Cited diameter is that of the Sun'sHill sphere; the region of its gravitational influence.[28]
Local Interstellar Cloud9.2 pc2.84×1014Interstellar cloud of gas through which the Sun and a number of other stars are currently travelling.[29]
Local Bubble2.82–250 pc8.70×1013–7.71×1015Cavity in theinterstellar medium in which the Sun and a number of other stars are currently travelling.
Caused by a pastsupernova.		[30][31]
Gould Belt1,000 pc3.09×1016Projection effect of theRadcliffe wave andSplit linear structures (Gould Belt),[32] between which the Sun is currently travelling.[33]
Orion Arm3000 pc
(length)		9.26×1016Thespiral arm of the Milky Way Galaxy through which the Sun is currently travelling.
Orbit of the Solar System17,200 pc5.31×1017The average diameter of the orbit of the Solar System relative to theGalactic Center.
The Sun's orbital radius is roughly 8,600 parsecs, or slightly over halfway to the galactic edge.
One orbital period of the Solar System lasts between 225 and 250 million years.		[34][35]
Milky Way Galaxy30,000 pc9.26×1017Our homegalaxy, composed of 200 billion to 400 billion stars and filled with theinterstellar medium.[36][37]
Milky Way subgroup840,500 pc2.59×1019The Milky Way and those satellitedwarf galaxies gravitationally bound to it.
Examples include theSagittarius Dwarf, theUrsa Minor Dwarf and theCanis Major Dwarf.
Cited distance is the orbital diameter of theLeo T Dwarf galaxy, the most distant galaxy in the Milky Way subgroup. Currently 59 satellite galaxies are part of the subgroup.		[38]
Local Group3Mpc[a]9.26×1019Group of at least 80 galaxies of which the Milky Way is a part.
Dominated byAndromeda (the largest), the Milky Way andTriangulum; the remainder aredwarf galaxies.		[39]
Local Sheet7 Mpc2.16×1020Group of galaxies including the Local Group moving at the same relative velocity towards theVirgo Cluster and away from theLocal Void.[40][41]
Virgo Supercluster30 Mpc9.26×1020Thesupercluster of which the Local Group is a part.
It comprises roughly 100galaxy groups and clusters, centred on theVirgo Cluster.
The Local Group is located on the outer edge of the Virgo Supercluster.		[42][43]
Laniakea Supercluster160 Mpc4.94×1021A group connected with thesuperclusters of which the Local Group is a part.
Comprises roughly 300 to 500galaxy groups and clusters, centred on theGreat Attractor in theHydra–Centaurus Supercluster.		[44][45][46][47]
Pisces–Cetus Supercluster Complex330 Mpc1×1022Galaxy filament that includes thePisces-Cetus Superclusters,Perseus–Pisces Supercluster,Sculptor Supercluster and associated smaller filamentary chains.[48][49]
Observable Universe28,500 Mpc8.79×1023At least 2 trillion galaxies in the observable universe, arranged in millions of superclusters,galactic filaments, andvoids, creating afoam-like superstructure.[50][51][52][53]
Universe≥28,500 Mpc
(possibly infinite)		≥8.79×1023Beyond the observable universe lie the unobservable regionsfrom which no light has yet reached the Earth.
No information is available, as light is the fastest travelling medium of information.
However,uniformitarianism argues that the Universe is likely to contain more galaxies in the same foam-like superstructure.		[54]

Gallery

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Logarithmic depiction of Earth's location
Location of Earth in theUniverse
Star associations and interstellar medium map of theLocal Bubble
Molecular clouds around the Sun inside theOrion-Cygnus Arm
Orion-Cygnus Arm and neighbouring arms
Orion-Cygnus Arm inside theMilky Way
The Sun within the structure of the Milky Way
LocationOfEarth
The image above contains clickable linksClickable image of theLocation of Earth.Place your mouse cursor over an area in the image to see the relatedarea name;click to link to an article about the area.
A logarithmic map of the observable universe. From left to right, spacecraft and celestial bodies are arranged according to their proximity to the Earth.
Stereoscopic view of the universe (805 x 416) for cross-eyed viewing

See also

[edit]

Notes

[edit]
  1. ^abcA parsec (pc) is the distance at which a star'sparallax as viewed from Earth is equal to onesecond of arc, equal to roughly 206,000 AU or 3.0857×1013 km. Onemegaparsec (Mpc) is equivalent to one millionparsecs.
  2. ^abSemi-major andsemi-minor axes.
  3. ^1 AU orastronomical unit is the distance between the Earth and the Sun, or 150 million km. Earth's orbital diameter is twice its orbital radius, or 2 AU.

References

[edit]
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  2. ^"1781: William Herschel Reveals the Shape of our Galaxy".Carnegie Institution for Science. Archived fromthe original on 26 March 2014. Retrieved19 March 2014.
  3. ^"The Spiral Nebulae and the Great Debate".Eberly College of Science. Retrieved22 April 2015.
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    NOTE: Estimated velocity of the Earth traveling through outer space may be between 1.3–3.1 million kilometres per hour (0.8–1.9 million miles per hour) – see discussion at "Wikipedia:Reference desk/Archives/Science/2019 July 20#How fast are we moving through space?"
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