گروه محلی
گروهی از کهکشان‌ها که شامل کهکشان راه‌شیری می‌شود
گروه محلی یا خوشه کهکشانی محلی نام یکی از خوشه‌های کهکشانی است که کهکشان راه شیری به همراه تعدادی از کهکشان‌های اطرافش در آن واقع شده‌اند. تعداد دقیق کهکشان های این مجموعه یافت نشده است با این حال تخمین زده می‌شود بیش از 80 کهکشان دیگر که عمدتا کهکشان‌های کوتوله هستند در این گروه وجود داشته باشند. این خوشه کهکشانی خود عضوی از ابرخوشه سنبله که عضوی از ابرخوشه لانیاکیا است؛ می باشد.
مرکز گرانشی گروه محلی کهکشانی جایی میان کهکشان راه شیری و کهکشان آندرومدا قرار دارد. بزرگ‌ترین کهکشان‌های این گروه محلی به ترتیب کهکشان آندرومدا، کهکشان راه شیری و کهکشان مثلث هستند. این دو کهکشان با فاصله 800 کیلو پارسک از نظر گرانشی به یکدیگر مقیدند و با سرعتی حدود 123 کیلومتر بر ثانیه به سمت یکدیگر در حرکتند. علاوه بر آندرومدا و کهکشان راه شیری، دو کهکشان مارپیچی دیگر،یک کهکشان بیضوی،حدود شش(یا کمی بیشتر)کهکشان نامنظم،ودوازده کهکشان کوتوله،از دیگر اعضای گروه محلی اند.بر همکنش بین اعضا،این ساختار را پایدار نگه میدارد. نزدیک ترین کهکشان های اقماری به راه کاهکشان،ابرهای ماژلانی بزرگ و کوچکند،به اختصار(LMC,SMC)
مشخصات
قطر آن ۱۰ میلیون سال نوری است جرم آن 
اعضا
خوشه کهکشانی محلی بیش از ۳۵ عضو دارد
جدول کامل کهکشان های گروه محلی[۱]:
| نام | نوع | صورت فلکی | اطلاعات |
|---|---|---|---|
| Spiral galaxies | |||
| Andromeda Galaxy (M31, NGC 224) | SA(s)b | Andromeda | Largest galaxy in the group[۲] Diameter (D25 isophote): 152,000 light-yearsMass: (۱٫۵±۰٫۵)×۱۰۱۲ M&#x۲۶۰۹;Number of stars: ca. ۱۰۱۲. |
| Milky Way Galaxy | SBbc | Sagittarius (centre) | Second largest galaxy in the group, which may or may not be the most massive galaxy of the group.[۳] Diameter (D25 isophote): 87,400 light-yearsMass: (۱٫۵۴±۰٫۱)×۱۰۱۲ M&#x۲۶۰۹;Number of stars: (۲٫۵±۱٫۵)×۱۰۱۱. |
| Triangulum Galaxy (M33, NGC 598) | SA(s)cd | Triangulum | Third largest, only unbarred spiral galaxy and possible satellite of the Andromeda Galaxy. Diameter (D25 isophote): 60,000 light-yearsMass: ۵×۱۰۱۰ M&#x۲۶۰۹;Number of stars: ۴×۱۰۱۰. |
| Magellanic spiral galaxies | |||
| Large Magellanic Cloud (LMC) | Irr/SB(s)m | Dorado | Fourth largest member of the group, satellite of Milky Way and only Magellanic Spiral Galaxy in the local group Mass: ۱×۱۰۱۰ M&#x۲۶۰۹;Diameter (D25 isophote): 32,200 light-years |
| NGC 3109 | SB(s)m | Hydra | Member of Antlia-Sextans Group |
| Elliptical galaxies | |||
| M32 (NGC 221) | E2 | Andromeda | Satellite of the Andromeda Galaxy, shows signs of a supermassive black hole |
| Irregular galaxies | |||
| Wolf–Lundmark–Melotte (WLM, DDO 221) | Ir+ | Cetus | Possible size between Small Magellanic Cloud and Large Magellanic Cloud |
| IC 10 | KBm or Ir+ | Cassiopeia | |
| Small Magellanic Cloud (SMC, NGC 292) | SB(s)m pec | Tucana | Satellite of Milky Way, 6th largest galaxy in the local group mass: 7 × 109 M☉ |
| Pisces Dwarf (LGS3) | Irr | Pisces | Possible satellite of the Triangulum Galaxy |
| IC 1613 (UGC 668) | IAB(s)m V | Cetus | |
| Phoenix Dwarf | Irr | Phoenix | |
| Leo A (Leo III) | IBm V | Leo | |
| Aquarius Dwarf (DDO 210) | IB(s)m | Aquarius | Distance 3.2 million light years. Quite isolated in space, membership to Local Group established in 1999.[۴] |
| SagDIG (Sagittarius Dwarf Irregular Galaxy) | IB(s)m V | Sagittarius | Most remote from barycenter member thought to be in the Local Group.[۴] |
| NGC 6822 (Barnard's Galaxy) | IB(s)m IV-V | Sagittarius | |
| Pegasus Dwarf (Pegasus Dwarf Irregular, DDO 216) | Irr | Pegasus | |
| UGC 4879 (VV124) | IAm | Ursa Major | One of the most isolated galaxies in Local Group. Situated at the edge of the Local Group. |
| Sextans A (UGCA 205) | Ir+V | Sextans | Member of Antlia-Sextans Group |
| Sextans B (UGC 5373) | Ir+IV-V | Sextans | Member of Antlia-Sextans Group |
| Leo P | Irr | Leo | Member of Antlia-Sextans Group, extraordinarily low metallicity (Z = 0.03ZMW) |
| AGC 198606 | Irr? | Leo | Gas-rich ultra-faint dwarf galaxy |
| AGC 215417 | Irr? | Leo | Gas-rich ultra-faint dwarf galaxy |
| AGC 219656 | Irr? | Leo | Gas-rich ultra-faint dwarf galaxy |
| AGC 249525 | Irr? | Boötes | Gas-rich ultra-faint dwarf galaxy, Situated at the edge of the Local Group |
| AGC 268069 | Irr? | Serpens | Gas-rich ultra-faint dwarf galaxy |
| Dwarf elliptical galaxies | |||
| M110 (NGC 205) | dE6p | Andromeda | Satellite of the Andromeda Galaxy and 5th largest galaxy with the mass of 9.3 billion solar masses. |
| NGC 147 (DDO 3) | dE5 pec | Cassiopeia | Satellite of the Andromeda Galaxy |
| Dwarf spheroidal galaxies | |||
| Boötes I | dSph | Boötes | |
| Cetus Dwarf | dSph/E4 | Cetus | |
| Canes Venatici I Dwarf and Canes Venatici II Dwarf | dSph | Canes Venatici | Satellites of the Milky Way[۵][۶] |
| Andromeda III | dE2 | Andromeda | Satellite of the Andromeda Galaxy |
| NGC 185 | dE3 pec | Cassiopeia | Satellite of the Andromeda Galaxy |
| Andromeda I | dE3 pec | Andromeda | Satellite of the Andromeda Galaxy |
| Sculptor Dwarf (E351-G30) | dE3 | Sculptor | Satellite of Milky Way |
| Andromeda V | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda II | dE0 | Andromeda | Satellite of the Andromeda Galaxy |
| Fornax Dwarf (E356-G04) | dSph/E2 | Fornax | Satellite of Milky Way |
| Carina Dwarf (E206-G220) | dE3 | Carina | Satellite of Milky Way |
| Leo I (DDO 74) | dE3 | Leo | Satellite of Milky Way |
| Sextans Dwarf | dE3 | Sextans | Satellite of Milky Way |
| Leo II (Leo B) | dE0 pec | Leo | Satellite of Milky Way |
| Ursa Minor Dwarf | dE4 | Ursa Minor | Satellite of Milky Way |
| Draco Dwarf (DDO 208) | dE0 pec | Draco | Satellite of Milky Way |
| SagDSG (Sagittarius Dwarf Spheroidal Galaxy) | dSph/E7 | Sagittarius | Satellite of Milky Way |
| Tucana Dwarf | dE5 | Tucana | |
| Cassiopeia Dwarf (Andromeda VII) | dSph | Cassiopeia | Satellite of the Andromeda Galaxy |
| Pegasus Dwarf Spheroidal Galaxy (Andromeda VI) | dSph | Pegasus | Satellite of the Andromeda Galaxy |
| Ursa Major I Dwarf and Ursa Major II Dwarf | dSph | Ursa Major | Satellite of Milky Way |
| Leo IV | dSph | Leo | Satellite of the Milky Way |
| Leo V | dSph | Leo | Satellite of the Milky Way |
| Leo T | dSph/Irr | Leo | Satellite of the Milky Way |
| Boötes II | dSph | Boötes | Satellite of the Milky Way |
| Boötes III | dSph | Boötes | Satellite of the Milky Way |
| Boötes IV | dSph | Boötes | Satellite of the Milky Way |
| Coma Berenices | dSph | Coma Berenices | Satellite of the Milky Way |
| Segue 2 | dSph | Aries | Satellite of the Milky Way |
| Hercules | dSph | Hercules | Satellite of the Milky Way |
| Pisces II | dSph | Pisces | Satellite of the Milky Way |
| Reticulum II | dSph | Reticulum | Satellite of the Milky Way |
| Reticulum III | dSph | Reticulum | Satellite of the Milky Way |
| Eridanus II | dSph | Eridanus | Probable satellite of the Milky Way |
| Grus I | dSph | Grus | Satellite of the Milky Way |
| Grus II | dSph | Grus | Satellite of the Milky Way |
| Tucana II | dSph | Tucana | Satellite of the Milky Way |
| Hydrus I | dSph | Hydrus | Satellite of the Milky Way |
| Draco II | dSph | Draco | Satellite of the Milky Way |
| Carina III | dSph | Carina | Satellite of the Milky Way |
| Triangulum II (Laevens 2) | dSph | Triangulum | Satellite of the Milky Way |
| Carina II | dSph | Carina | Satellite of the Milky Way |
| Pictor II | dSph | Pictor | Satellite of the Milky Way |
| Horologium II | dSph | Horologium | Satellite of the Milky Way |
| Virgo I | dSph | Virgo | Satellite of the Milky Way |
| Aquarius II | dSph | Aquarius | Satellite of the Milky Way |
| Crater II | dSph | Crater | Satellite of the Milky Way |
| Hydra II | dSph | Hydra | Satellite of the Milky Way |
| Antlia II | dSph | Antlia | Satellite of the Milky Way |
| Pegasus III | dSph | Pegasus | Satellite of the Milky Way |
| Pegasus IV | dSph | Pegasus | Satellite of the Milky Way[۷] |
| Pegasus W | dSph | Pegasus | Recent star formation, could still be starforming |
| Cetus III | dSph | Cetus | Satellite of the Milky Way |
| Tucana B | dSph | Tucana | [۸] |
| Perseus I Dwarf Galaxy (Andromeda XXXIII) | dE | Perseus | Satellite of Andromeda |
| Antlia Dwarf | dE3/dSph/Irr? | Antlia | Member of Antlia-Sextans Group |
| Andromeda IX | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda X | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XI | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XII | dSph | Andromeda | Possible satellite of the Andromeda Galaxy |
| Andromeda XIII (Pisces III) | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XIV (Pisces IV) | dSph | Pisces | Possible satellite of the Andromeda Galaxy |
| Andromeda XV | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XVII | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XIX | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XX | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XXI | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XXII | dSph | Pisces | Possible satellite of the Triangulum Galaxy |
| Andromeda XXIII | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XXIV | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XXV | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XXVI | dSph | Andromeda | Satellite of the Andromeda Galaxy |
| Andromeda XXVII | dSph | Andromeda | Satellite of the Andromeda Galaxy, tidally disrupted[۹] |
| Andromeda XXIX | dSph | Pegasus | Satellite of the Andromeda Galaxy |
| Andromeda XXX (Cassiopeia II) | dSph? | Cassiopeia | Satellite of the Andromeda Galaxy |
| Andromeda XXXI (Lacerta I) | dSph? | Lacerta | Satellite of the Andromeda Galaxy |
| Andromeda XXXII (Cassiopeia III) | dSph? | Cassiopeia | Satellite of the Andromeda Galaxy |
| Andromeda XXXIV (Pegasus V) | dSph | Pegasus | Satellite of the Andromeda Galaxy[۱۰] |
| Andromeda XVI (Pisces V) | dSph | Pisces | Possible satellite of the Andromeda Galaxy |
| Andromeda XXVIII | dSph? | Pegasus | Possible satellite of the Andromeda Galaxy |
| Andromeda XXXIII (Perseus I) | dSph? | Perseus | Possible satellite of the Andromeda Galaxy |
| Andromeda XVIII | dSph | Andromeda | |
| Centaurus I | dSph | Centaurus | Satellite of the Milky Way[۱۱] |
| Pisces VII (Triangulum III) | dSph? | Pisces | Candidate, possible satellite of the Triangulum Galaxy[۱۲] |
| Identification unclear | |||
| Virgo Stellar Stream | dSph (remnant)? | Virgo | In the process of merging with the Milky Way |
| Canis Major Dwarf | Irr? | Canis Major | Possibly a dwarf galaxy in the process of merging with the Milky Way |
| Hydra 1 | Hydra | Possibly a dwarf galaxy in the process of merging with the Milky Way | |
| Tucana III | dSph or cluster? | Tucana | Satellite of the Milky Way, tidally disrupting |
| Tucana IV | dSph or cluster? | Tucana | Satellite of the Milky Way |
| Tucana V | dSph or cluster? | Tucana | Possibly non-existent |
| Columba I | dSph or cluster? | Columba | Satellite of the Milky Way |
| Segue 1 | dSph or Globular Cluster | Leo | Satellite of the Milky Way |
| Cetus II | Cetus | Likely part of Sagittarius tidal stream | |
| Willman 1 | dSph or Globular Cluster | Ursa Major | 147,000 light-years away |
| Horologium I | dSph or Globular Cluster | Horologium | Satellite of the Milky Way. Not to be confused with the Horologium Supercluster. |
| Pictoris | dSph or Globular Cluster | Pictor | Satellite of the Milky Way |
| Phoenix II | dSph or Globular Cluster | Phoenix | Satellite of the Milky Way |
| Indus I (Kim 2) | dSph or Globular Cluster | Indus | Satellite of the Milky Way |
| Eridanus III | dSph or Globular Cluster | Eridanus | Satellite of the Milky Way or SMC[۱۳] |
| Sagittarius II | dSph or Globular Cluster | Sagittarius | Satellite of the Milky Way |
| Andromeda VIII | dSph? | Andromeda | Satellite of the Andromeda Galaxy, tidally disrupting |
| Antlia B | Antlia | Member of Antlia-Sextans Group | |
| Probable non-members | |||
| Andromeda IV | Irr | Andromeda | Once considered to be associated with M31. Its distance is now known to be 22 to 24 million light years (not close to the Andromeda Galaxy at all).[۱۴] |
| GR 8 (DDO 155) | Im V | Virgo | Distance 7.9 million light years[۱۵] |
| IC 5152 | IAB(s)m IV | Indus | Distance 5.8 million light years, possibly an outlying member of the local group[۱۶] |
| NGC 300 | SA(s)d | Sculptor | Distance 6.07 million light years |
| NGC 55 | SB(s)m | Sculptor | Distance 6.5 million light years[۱۷] |
| NGC 404 | E0 or SA(s)0− | Andromeda | Distance 10 million light years[۱۸] |
| NGC 1569 | Irp+ III-IV | Camelopardalis | In IC 342 group of galaxies. Distance 11 million light years[۱۹] |
| NGC 1560 (IC 2062) | Sd | Camelopardalis | Distance 8-12 million light years |
| Camelopardalis A | Irr | Camelopardalis | Distance 12 million light years[۱۷] |
| Argo Dwarf | Irr | Carina | |
| ESO 347-8 (2318–42) | Irr | Grus | |
| UKS 2323-326 (ESO 407-18) | Irr | Sculptor | Distance 7.2 million light-years[۱۷] |
| UGC 9128 (DDO 187) | Irp+ | Boötes | |
| KKs 3 | dSph | Hydrus | |
| Objects in the Local Group no longer recognised as galaxies | |||
| Palomar 12 (Capricornus Dwarf) | Capricornus | Globular cluster formerly classified as a dwarf spheroidal galaxy | |
| Palomar 4 (Ursa Major Dwarf) | Ursa Major | Globular cluster formerly classified as a dwarf spheroidal galaxy | |
| Palomar 5 (Serpens Dwarf) | Serpens | Globular cluster formerly classified as a dwarf spheroidal galaxy | |
| Palomar 3 (Sextans C) | Sculptor | Globular cluster formerly classified as a dwarf spheroidal galaxy[۲۰] | |
| Segue 3 | Pegasus | Globular cluster formerly classified as a dwarf spheroidal galaxy[۲۱] | |
| Laevens 1 (Crater Dwarf) | Crater | Globular cluster formerly classified as a dwarf spheroidal galaxy[۲۲] | |
| DES J2038-4609 (Indus II) | Indus | Likely a chance alignment of stars[۲۳] | |
جایگاه گروه محلی در جهان قابل مشاهده
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منابع
مشارکت‌کنندگان ویکی‌پدیا. «Local Group». در دانشنامهٔ ویکی‌پدیای انگلیسی، بازبینی‌شده در ۲۱ می ۲۰۲۰.
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