Andromeda Galaxy (Messier 31)

Messier 31
Messier 31: Andromeda Galaxy; Celestron RASA 11" f/2.22; ZWO ASI6200 Pro; Tentlingen; © 2020 Peter Kocher

History

The Andromeda galaxy was already mentioned in 905 BC. Mentioned BC by the Persian astronomer Al Sufi and was marked on star maps as a "small cloud" long before the invention of the telescope in 1609.

The first observation with a telescope is usually attributed to the German astronomer Simon Marius in 1611 or 1612. He compared the faint glow to that of a candle shining through a horn. Early astronomers suspected that the «Andromeda Nebula» consisted of glowing gas and that a nearby planetary system was being formed. Spectroscopic analyzes nullified this theory and showed that the light must have come from countless stars.

Messier 31
Messier 31: Image with and without solarisation; 500/2500 mm Newton + SBIG ST-6; Observatory Bülach; © 1996 Stefan Meister

The first indications of the true nature and dimensions of this spiral nebula emerged in late 1923 when several Cepheid variables were found. In a study of these Cepheids using the 100 inch telescope on Mount Wilson, Edwin Hubble finally proved that this must be an extragalactic object and deduced a preliminary distance of 900'000 light years. His publication ended the long controversy about nature this «spiral nebula». Later studies with the newly completed 200 inch telescope showed that the Cepheids in the Andromeda galaxy could be divided into two different populations with different luminosity and that earlier distance measurements were off by a factor of 2-3. [4] Current measurements on Simbad show a distance of 2.5 to 2.6 million light years and that M 31 is moving in our direction at a speed of around 300 km/s. [145]

Physical Properties

M 31 is the largest and closest to us spiral galaxy - apart of course from our own galaxy, the Milky Way with its companions. It owns four small, elliptical companion galaxies, which are located in their gravitational field. Two of them (M 32 and M 110) are in the immediate vicinity. The other two (NGC 147 and NGC 185) lie around 7° to the north in the constellation Cassiopeia. NGC 206 is a bright star cloud within the galaxy M 31. Furthermore, M 31 is home to many globular clusters, of which G 1 is the brightest.

Messier 31
Messier 31: Andromeda Galaxy, while waiting for comet Neowise to rise. Cropped original photo; Nikon D850 with Nikkor 300 mm 2.8D on Vixen GP-DX mount; L: 29*30s + D: 16*30s, ISO 800; Bözberg, Aargau; © 10 July 2020 Bernd Nies
M 31
M 31: Andromeda Galaxy; FSQ 106 on AOK Herkules V12 mount, Moravian G3-16200; R 15x5 min, G 15x5 min, B 16x5 min; Lü-Stailas; © 9. 8. 2021 Stefan Berchten, Hansjörg Wälchli
NGC 206 + M 32
NGC 206 + M 32: Star cloud NGC 206 and companion galaxy M 32; Takahashi Mewlon 250 CR (2500 mm f/10), SBIG STL 11k; 21L x 600 sec 1×1, 10R, 14G, 15B 2×2 x 600sec, 12HA x 1200 sec; Bernese Highlands; © 3.10. 2016 – 14.10. 2017 Bernhard Blank, Dragan Vogel
NGC 206
NGC 206: Star cloud NGC 206 in Andromeda Galaxy M 31; 500 mm Cassegrain 3625 mm f/7.2; SBIG STL11K; 90+30+30+30 min LRGB; Bernese Higlands; © 2011 Radek Chromik
NGC 206
NGC 206: Star cloud in M 31; RC 500 on AOK Herkules V48 mount; SBIG STL-11000M/C2; -30 °C chip temperature, R/G/B unbinned, R 12×5 min, G 10×5 min, B 10×5 min; Observatory Son Bi, Mallorca; © 1.–3. 12. 2016 Beat Kohler, Hansjörg Wälchli
Messier 110 (NGC 205)
Messier 110 (NGC 205): Companion of Andromeda Galaxy; 500 mm Cassegrain 3625 mm f/7.2; SBIG STL11K; 150+40+40+40 min LRGB; Bernese Highlands; © 2011 Radek Chromik
Revised+Historic NGC/IC, Version 22/9, © Dr. Wolfgang Steinicke [277]
NameRADecTypebMagvMagDimDreyer DescriptionIdentification, Remarks
NGC 14700 33 11.7+48 30 26Gx (E5/P)10.59.513.2 × 7.8vF, vL, iR, gsmbM * 11UGC 326, MCG 8-2-5, DDO 3, CGCG 550-6
NGC 18500 38 57.6+48 20 14Gx (E3)10.19.28 × 7pB, vL, iR, vgmbM, rUGC 396, MCG 8-2-10, CGCG 550-9, IRAS 00362+4803
NGC 20500 40 22.1+41 41 07Gx (E5)8.98.119.5 × 11.5vB, vL, mE 165°, vgvmbMM 110, UGC 426, MCG 7-2-14, CGCG 535-14, IRAS 00376+4124
NGC 20600 40 32.3+40 44 18GxyP14.04.2vF, vL, mE 0°part of M 31
NGC 22100 42 41.8+40 51 57Gx (E2)9.08.18.5 × 6.5! vvB, L, R, psmbMNM 32, UGC 452, MCG 7-2-15, IRAS 00399+4035, ARAK 12, Arp 168, CGCG 535-16
NGC 22400 42 44.3+41 16 08Gx (Sb)4.43.4189.1 × 61.7!!! eeB, eL, vmE (Andromeda)M 31, UGC 454, MCG 7-2-16, CGCG 535-17, Andromeda nebula

Finder Chart

M 31 is located in the constellation Andromeda, only 1° 20' from the 4.5 mag bright star ν Andromedae. The best observation time is July to February.

Chart Andromeda Galaxy (Messier 31)
Andromeda Galaxy (Messier 31) in constellation Andromeda. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

Visual Observation

M 31, M 32, M 110
M 31, M 32, M 110: Pencil drawing; Borg 125/800 f/6.4 ED Apo; © Jozef Cukas

Visible to the eye as a blurred star or nebula. The full extent or size can be seen in the binoculars. The companion galaxies M 32 and M 110 can already be seen in a small amateur telescope. M 32 is almost spherical, while M110 appears elliptical. In addition to the bright core of M 31, the two black dust bands are easily perceptible in medium-sized telescopes. In larger telescopes, nodes or blurred globular clusters that belong to the galaxy become visible. [192]

12.5" Ninja-Dobson, F:4.5 / TV-Nagler 31mm, 46x, 1.78°
Eduard von Bergen

More Objects Nearby (±15°)

References

4«Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System» by Robert Burnham; Dover Publications, Inc.; Voume I: ISBN 0-486-23567-X; Volume II: ISBN 0-486-23568-8; Volume III: ISBN 0-486-23673-0
145SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
192Deep-Sky Guide; fernrohr.ch/1d_deep-sky-guide.html (2020-12-25)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)