M31 - NGC 224
DSS image of M31
Overlaid DSS image of M31, 120' x 120' with north at top and west to the right

Aladin viewer for the region around M31
Andromeda Galaxy
Hevelius 32, Bode 3, h 50, GC 116, HOLM 017A, MCG +07-02-016, UGC 454, PGC 2557

Type  Galaxy
Magnitude  3.5
Size  190' x 60' @ 35°
Right Ascension  0h 42' 44.4"  (2000)
Declination  41° 16' 9" N
Constellation  Andromeda
Description  !!!eeB, eL, vmE
Classification  SA(s)b
Observing Notes

Andrew Cooper
Nov 23, 2019    Kaʻohe, Mauna Kea, HI (map)
8x42mm Nikon Prostaff 3S Binoculars @ 8x

Large, bright, an oval halo about 3°x1° surrounding a bright large core, a beautiful sight in the binocular field

Andrew Cooper
Oct 21, 2006    TIMPA, Avra Valley, AZ (map)
12x36 Canon Image Stabilized Binoculars

Bright, beautiful, well suited to the 5° field of the binos, flanked by M32 and M110, a bright sharp core with the halo either side extending for about 3°

Andrew Cooper
Aug 28, 2005    TIMPA, Avra Valley, AZ (map)
46cm f/4.5 Deep Violet

Large!! actually make that enormous! The bright core is a large ball of stars at the center with the oval halo reaching past either edge of the field even at the lowest power, extended northeast-southwest, a dark rift separates a spiral arm along the southeastern edge, M32 and M110 flank the core above and below

Rev. T.W. Webb
May 19, 1885    Hardwick, Herefordshire, England (map)

(M31) One of the grandest in the heavens; long, oval, or irregularly triangular, ill-bounded, and brightening to the centre; so plain to the naked eye it seems strange that the ancients scarcely mention it. It is however, referred to as a familiar object by the Persian astronomer, Sûfi, in the tenth century. By moving the telescope rapidly to gain contrast, Bond extended it to the surprising dimensions of 4° in length and 2½° in breadth, of which common instruments show little, and less in proportion to the increase in power. No telescope has been able to deal with its nature. Bonds 14-19/20-in. found no resolution, though it was seen through a rich stratum containing 1500 stars. It detected however two curious dark streaks, like narrow clefts, both beyond any ordinary instruments (but readily shown in photos as dark rings), in which the darker of them forms in reality the boundary of one side of the nebula as seen with a small aperture: both well seen by Se. with 9-9/10-in. achr.: I have caught one with difficulty with 5½-in. achr., '63. Grover has seen both with 6½-in. silvered mirror, and I have traced then through a long extent with 8-in. mirror (With), 1864; but this was after knowledge of the fact, which has a great influence upon the eye; the truth of H.'s remark being often exemplified, that less optical power will show an object than was required for its discovery. Huggins finds spectrum continuous, but cut off at red end.
― Celestial Objects for Common Telescopes, T. W. Webb, 1917

Captain William Henry Smyth
Sep 13, 1833    No. 6 The Crescent, Bedford, England (map)
150mm f/17.6 refractor by Tully 1827

An overpowering nebula, with a companion about 25' in the south vertical. It is of an oval shape, light, brightening towards the sf edge of the general mass, and of a milky irresolvable nebulosity; but though described "in cingulo Andromedae," is between the robes and left arm of the Lady, and certainly below the girdle. There are numerous telescopic stars around; and three minute ones are involved in the glow, but which can have no connection with it, and are doubtless between our system and the nebulosity.

The axis of direction trends sp and nf; and it may be caught by a good eye, on a very fine night, by running a fancied line from Alamak to Mirak, and from thence carrying a rectangular glance to a distance of about 6½°. It can also be struck upon by a ray from γ in the mouth of Cetus, over Sheratan in the head of Aries, and through Mirak, or β Andromedæ, to 6½° beyond.

This is the oldest known nebula; for though it attracted but little notice till the seventeenth century, it was seen, at least, as far back as 905 A.D. Simon Marius re-discovered it, —if such a term can be applied to an object seen with the naked eye: in his rare work —De Mundo Joviali— that astronomer acquaints us, that he first examined it with a telescope on the 15th Dec. 1612; he was astonished at the singularity of the phenomenon, but expressly says, that he leaves to others to judge whether it was a new discovery or not. It was therefore by an oversight, that Halley ascribes the discovery, in 1661, to Bulialdus (Ismaël Boulliaud); who himself mentions its being known as Nebulosa in cingulo Andromedæ, and that it had been noticed 150 years before, by an expert though anonymous astronomer.

The tenuity of its boundary offering no definition for exact comparison, has made the several attempts to figure it so conflicting as to mislead. Marius describes it as resembling the diluted light of the flame of a candle seen through horn, —Halley mentions that it emits a radiant beam, —Cassini calls it à peu-près triangulaire, Le Gentil considered it round for some years, then oval, but always of an uniform light in all its parts, while Messier represents it as resembling two cones, or pyramids of light, opposed by their bases. From such statements, Boulliaud and Kircher thought this wonderful object appeared and disappeared, like Mira; and Le Gentil had no doubt of its undergoing changes in form. But probably this discordance is a consequence of the means employed.

Le Gentil, by his paper of 1749, seems to have used telescopes of various sizes, in order to see it very clearly "non seulement pour servir à la reconnoitre, mais encore pour voir si dans la suite elle ne seroit point sujetle à quelque variation, soit dans la figure, soit dans la position;" yet fifteen years afterwards Messier differs from him, by assigning a greater brilliance to the centre than to the edges, which latter accords better with my views of it, than do our apparent mean places. It is, however, remarkable that Messier examined this giant nebula with a 4½ foot Newtonian, and then turned the instrument upon γ Andromedæ "qui en étoit fort près" to compare its light with that of the star, on a beautiful night of August, 1764; but he makes no mention of the duplicity, or contrasted colours, of that lovely star.

Sir William Herschel, the Præses of all the examiners into the construction of the heavens, gave this phenomenon a rigid scrutiny, and concluded it to be the nearest of all the great nebulæ. "The brightest part of it," he says, "approaches to the resolvable nebulosity, and begins to show a faint red colour; which, from many observations on the magnitude and colour of nebulæ, I believe to be an indication that its distance in the coloured part does not exceed 2000 times the distance of Sirius." Does not exceed that distance! That is, so far from us, that light, which is endowed with the swiftest degree of motion yet known, flying along at the rate of 190,000 miles in a second of time, or nearly twelve millions of miles in a minute, would require upwards of 6000 years to traverse the awful interval: as to that type of terrestrial velocity, so often cited, the cannon-ball, with its 500-miles-an-hour pace, it would have no chance of passing the same space under nine or ten thousand millions of years. What an overwhelming idea does such an astonishing conclusion give of the All-wise and Omnipotent Intelligence!

Halley considered the light of this object as depending quite on a particular cause. In reality, he says, the spot is "nothing else but the light coming from an extraordinary great space in the ether, through which a lucid medium is diffused that shines with its own proper lustre." Other philosophers have advanced similar opinions, or at least, opinions not remotely different; and there is still a wide field for conjecture and speculation. The causes and arrangement of so astonishing a mass of nebulous matter, if not quite inscrutable, are still so unapproachable that it will probably occupy ages to detect them; but we must hesitate in the conclusion of a contemporaneous lecturer, of its being composed of the united lustre of a vast system of stars.

The companion was discovered in November, 1749, by Le Gentil, and was described by him as being about an eighth of the size of the principal one; he adds, " m'a paru exactement de la même densité que l'ancienne." The light is certainly more feeble than here assigned. Messier whose No. 32 it is observed it closely in 1764, and remarked, that no change had taken place since the time of its being first recorded. In form it is nearly circular. The powerful telescope of Lord Rosse* has been applied to this, after finding that no actual re-solution in the large nebulae could be seen, though its edge had stellar symptoms; and it proved to be clearly resolvable into stars the which directly interferes with Le Gentil's remark.
* This telescope is a reflector of three feet in diameter, of performance hitherto unequalled. It was executed by the Earl of Rosse, under a rare union of skill, assiduity, perseverance, and munificence. The years of application required to accomplish this, have not worn his Lordship's zeal and spirit; like a giant refreshed, he has returned to his task, and is now occupied upon a metallic disc of no less than six feet in diameter. Should the figure of this prove as perfect as the present one, we may soon over-leap what many absurdly look upon as the boundaries of the creation.
― A Cycle of Celestial Objects Vol II, The Bedford Catalogue, William Henry Smyth, 1844

Charles Messier
Jan 3, 1764    

The beautiful nebula of the belt of Andromeda, shaped like a spindle; M. Messier has investigated it with different instruments, & he didn't recognize a star: it resembles two cones or pyramids of light, opposed at their bases, the axes of which are in direction NW-SE; the two points of light or the apisces are about 40 arc minutes apart; the common base of the pyramids is about 15'. This nebula was discovered by Simon Marius, & consequently observed by different astronomers. M. le Gentil has given a drawing in the Memoirs of the Academy for 1759, page 453. It is reported on the English atlas.
― Connaissance des Temps, 1781

William Herschel

The ninth is that in the girdle of Andromeda, which is undoubtedly the nearest of all the great nebulae; its extent is above a degree and a half in length and, in even one of the narrowest places, not less than 16' in breadth. The brightest part of it approaches to the resolvable nebulosity, and begins to shew a faint red colour; which, from many observations on the colour of and magnitude of nebulae, I believe to be an indication that its distance in this coloured part does not exceed 2000 times the distance of Sirius.

There is a very considerable, broad, pretty faint, small nebula [M110] near it; my Sister discovered it August 27, 1783, with a Newtonian 2-feet sweeper. It shews the same faint colour with the great one, and is, no doubt, in the neighborhood of it. It is not the 32d of the Connoissance des Temps [M32]; which is a pretty large round nebula, much condensed in the middle, and south following the great one; but this is about two-thirds of a degree north preceding it, in a line parallel to Beta and Nu Andromedae.
Other Data Sources for M31
Nearby objects for M31

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