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Andromeda I
Andromeda I by the HST
Observation data (J2000 epoch)
Constellation	Andromeda
Right ascension	00 45 39.8
Declination	+38° 02′ 28″
Redshift	-368 ± 11 km/s
Distance	2.40 ± 0.08 Mly (735 ± 23 kpc)
Apparent magnitude (V)	13.6
Characteristics
Type	dSph
Apparent size (V)	2.5′ × 2.5′
Notable features	satellite galaxy of M31
Other designations
And I, Anon 0043+37, PGC 2666

Andromeda I is a dwarf spheroidal galaxy (dSph) about 2.40 million light-years away in the constellation Andromeda. Andromeda I is part of the local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It is roughly 3.5 degrees south and slightly east of M31. As of 2005, it is the closest known dSph companion to M31 at an estimated projected distance of ~40 kpc or ~150,000 light-years.

Andromeda I was discovered by Sidney van den Bergh in 1970 with the Mount Palomar Observatory 48-inch telescope. Further study of Andromeda I was done by the WFPC2 camera of the Hubble Space Telescope. This found that the horizontal branch stars, like other dwarf spheroidal galaxies were predominantly red. From this, and the abundance of blue horizontal branch stars, along with 99 RR Lyrae stars detected in 2005, lead to the conclusion there was an extended epoch of star formation. The estimated age is approximately 10 Gyr. The Hubble telescope also found a globular cluster in Andromeda I, being the least luminous galaxy where such a cluster was found.

See also

• Andromeda's satellite galaxies

References

1. ^ "NASA/IPAC Extragalactic Database". Results for Andromeda I. Retrieved 2008-01-21.
2. ^ I. D. Karachentsev; V. E. Karachentseva; W. K. Hutchmeier; D. I. Makarov (2004), "A Catalog of Neighboring Galaxies", Astronomical Journal, 127 (4): 2031–2068, Bibcode:2004AJ....127.2031K, doi:10.1086/382905
3. Karachentsev, I. D.; Kashibadze, O. G. (2006), "Masses of the local group and of the M81 group estimated from distortions in the local velocity field", Astrophysics, 49 (1): 3–18, Bibcode:2006Ap.....49....3K, doi:10.1007/s10511-006-0002-6, S2CID 120973010
4. ^ McConnachie, A. W.; Irwin, M. J.; Ferguson, A. M. N.; Ibata, R. A.; et al. (May 2004), "Determining the location of the tip of the red giant branch in old stellar populations: M33, Andromeda I and II", Monthly Notices of the Royal Astronomical Society, 350 (1): 250, arXiv:astro-ph/0401453, Bibcode:2004MNRAS.350..243M, doi:10.1111/j.1365-2966.2004.07637.x, S2CID 18742035
5. ^ van den Bergh, Sydney (January 1972), "Search for Faint Companions to M31", Astrophysical Journal, 171: L31, Bibcode:1972ApJ...171L..31V, doi:10.1086/180861
6. ^ Andromeda I, Students for the Exploration and Development of Space (SEDS), July 25, 2001
7. ^ Pritzl, Barton J.; Armandroff, Taft E.; Jacoby, George H.; Da Costa, G. S. (May 2005), "The Dwarf Spheroidal Companions to M31: Variable Stars in Andromeda I and Andromeda III", The Astronomical Journal, 129 (5): 2232–2256, arXiv:astro-ph/0501083, Bibcode:2005AJ....129.2232P, doi:10.1086/428372, S2CID 9749493
8. McConnachie, A. W.; Irwin, M. J.; Ferguson, A. M. N.; Ibata, R. A.; et al. (2005), "Distances and metallicities for 17 Local Group galaxies", Monthly Notices of the Royal Astronomical Society, 356 (4): 979–997, arXiv:astro-ph/0410489, Bibcode:2005MNRAS.356..979M, doi:10.1111/j.1365-2966.2004.08514.x.
9. Da Costa, G. S.; Armandroff, T. E.; Caldwell, Nelson; Seitzer, Patrick (December 1996), "The Dwarf Spheroidal Companions to M31: WFPC2 Observations of Andromeda I", Astronomical Journal, 112: 2576, arXiv:astro-ph/9610083, Bibcode:1996AJ....112.2576D, doi:10.1086/118204, S2CID 119431084
10. Grebel, E. K.; Dolphin, A. E.; Guhathakurta, P. (September 18–23, 2000). "Discovery of a Globular Cluster in M31's Dwarf Spheroidal Companion Andromeda I". Abstracts of Contributed Talks and Posters presented at the Annual Scientific Meeting of the Astronomische Gesellschaft. Astronomische Gesellschaft Abstract Series. Vol. 17. Bremen. Bibcode:2000AGM....17..P61G. {{cite book}}: |journal= ignored (help)CS1 maint: location missing publisher (link)

External links

• Andromeda I on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

v t e Andromeda Galaxy
Location	Andromeda Galaxy → Andromeda subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Local Hole → Observable universe → Universe Each  → may be read as "within" or "part of".
Satellite galaxies	M32 M110 NGC 185 NGC 147 Andromeda I Andromeda II Andromeda III Andromeda IV* Andromeda V Andromeda VI Andromeda VII Andromeda VIII Andromeda IX Andromeda X Andromeda XI Andromeda XII Andromeda XIII Andromeda XIV Andromeda XV Andromeda XVI Andromeda XVII Andromeda XVIII Andromeda XIX Andromeda XX Andromeda XXI Andromeda XXII Andromeda XXIII Andromeda XXIV Andromeda XXV Andromeda XXVI Andromeda XXVII Andromeda XXVIII Andromeda XXIX Triangulum subgroup* *It is uncertain whether these are companion galaxies of the Andromeda Galaxy
Catalogued stars	AE Andromedae AF Andromedae M31-RV
Other	Andromeda–Milky Way collision S Andromedae Mayall II M32p NGC 206 3XMM J004232.1+411314
Category

v t e Constellation of Andromeda
Adhil Andromeda in Chinese astronomy List of Andromeda's satellite galaxies List of stars in Andromeda
Stars	Bayer α (Alpheratz) β (Mirach) γ (Almach) δ ε ζ η θ ι κ λ μ ν ξ (Adhil) ο π ρ σ τ υ (Titawin) φ χ ψ ω A b c υ Per (Nembus) Flamsteed 2 3 4 5 6 7 8 9 10 11 12 13 14 (Veritate) 15 18 22 23 26 28 32 36 39 41 44 45 47 55 56 58 59 63 64 65 66 6 Per Variable R T U W Z RT RV RX SU SW TU TW WZ XZ AB AC AD AE AF AR BM BX CC CG CN DS DX EG ET EU FF GO GP GQ GX GR GY HH HN IW KK KX KZ LL LN LP LQ OP OS OU PX PY QR QV QX V385 V428 V439 V455 V529 V807 HR 1 40 56 78 104 122 134 178 275 282 283 289 379 410 483 687 746 748 8884 8925 8950 8962 8973 9011 9074 9075 9105 HD 16175 (Buna) 222155 Other 3XMM J004232.1+411314 ADS 48 HAT-P-6 (Sterrennacht) HAT-P-16 HAT-P-19 HAT-P-28 M31-RV KELT-1 NGC 44 NGC 82 NGC 84 NGC 91 NGC 162 NGC 464 Qatar-3 Qatar-4 Qatar-5 PA-99-N2 WASP-1 WISE 0146+4234 WISE J0005+3737 WISE J004945.61+215120.0
Exoplanets 14 Andromedae b κ Andromedae b υ Andromedae b c d Gliese 15 Ab c HD 13931 b HD 16175 b HAT-P-6b HAT-P-32b WASP-1b WASP-33b Qatar-4b Qatar-5b
Star clusters	NGC 206 272 752 956 7686 Other Mayall II RBC EXT8
Nebulae	NGC 7662
Galaxies	Messier 32 110 NGC 5 11 13 19 20 21 27 39 43 48 49 51 67 68 69 70 71 72 74 76 79 80 81 83 85 86 90 93 94 96 97 108 109 112 140 149 160 169 181 183 184 214 218 226 228 229 233 243 252 258 260 262 280 304 317 389 393 404 425 431 477 512 513 523 528 529 531 536 542 561 605 620 668 679 687 700 703 704 705 708 709 710 712 714 717 721 732 753 759 801 812 834 891 906 910 911 912 913 920 937 980 995 996 999 1000 7640 7836 Numbered I II III IV V VIII IX X XI XVIII XIX XXI Other 3C 66A 3C 66B Andromeda Galaxy Arp 273 Donatiello I UGC 1840
Galaxy clusters Abell 262 NGC 68 group
Astronomical events GRB 101225A SN 1885A (S)
Category

• Dwarf galaxies
• Dwarf spheroidal galaxies
• Peculiar galaxies
• Local Group
• Andromeda Subgroup
• Andromeda (constellation)
• Principal Galaxies Catalogue objects
• Astronomical objects discovered in 1970