66 ILLUSTRATED GUIDE TO ASTRONOMICAL WONDERS

TABLE 01-1.

Andromeda is a large constellation, ranking 19th in size among the 88 constellations. It covers 722 square degrees of the

celestial sphere, or about 1.8%. Andromeda is one of the ancient constellations. In Greek mythology, Princess Andromeda was the daughter of King Cepheus and Queen Cassiopeia of Æthiopia. The vain Cassiopeia bragged publicly that she was more beautiful than the Nereids, the sea nymph goddesses renowned for their beauty. Bad idea. Poseidon, hearing the angry protests of the proud Nereids, sent floods and Cetus the sea monster to wreak havoc on the land and people of Æthiopia.

In desperation, King Cepheus consulted the oracle of Ammon, which told him that the only way to appease Poseidon was to

volunteer his daughter Andromeda to be devoured by Cetus. Cepheus chained Andromeda to a rock near the sea, to await Cetus. Andromeda, resigned to her fate, watched Cetus approaching. Purely by luck, the Hero Perseus, on his way home after slaying the Gorgon, happened to be sailing past and noticed the sea monster about to devour the pretty girl. Perseus, of course, confronted and slew the sea monster, freed Andromeda from her chains, and married her. All in a day’s work, for a Hero.

Andromeda returned home with Perseus. They went on to have six sons and a daughter and to found the kingdom of Mycenae and the Perseidae dynasty. Upon the death of Andromeda, the goddess Pallas Athena placed her among the stars as the

Featured star clusters, nebulae, and galaxies in Andromeda

object Type Mv Size rA Dec M B u D r notes

TABLE 01-2.

Featured multiple stars in Andromeda

object Pair M1 M2 Sep PA Year rA Dec uo DS notes

57-γ STF 205A-BC 2.3 5.0 9.7 63 2004 02 03.9 +42 20 ◉ ◉ Almach

NGC 205 Gx 8.9 21.9 x 10.9 00 40.4 +41 41 ◉ ◉ M 110; Class E5 pec; SB 13.2

NGC 221 Gx 9.0 8.7 x 6.4 00 42.7 +40 52 ◉ ◉ ◉ M 32; Class cE2; SB 10.1

NGC 224 Gx 4.4 192.4 x 62.2 00 42.7 +41 16 ◉ ◉ ◉ M 31; Class SA(s)b; SB 12.9

NGC 752 OC 5.7 49.0 01 57.8 +37 51 ◉ ◉ Cr 23; Mel 12; Class II 2 r

NGC 891 Gx 10.8 14.3 x 2.4 02 22.6 +42 21 ◉ Class SA(S)b? sp; SB 14.6

NGC 7662 PN 9.2 37.0" 23 25.9 +42 32 ◉ ◉ Blue Snowball Nebula; Class 4+3

andromeda, the Princess

nAME: Andromeda (an-DROM-eh-duh)

SEASon: Autumn

CuLMInATIon: 9:00 p.m., late November

ABBrEVIATIon: And

gEnITIVE: Andromedae (an-DROM-eh-dye)

nEIgHBorS: Ari, Cas, Lac, Peg, Per, Psc

BInoCuLAr oBJECTS: NGC 205 (M 110), NGC 221 (M 32), NGC 224 (M 31), NGC 752

urBAn oBJECTS: NGC 221 (M 32), NGC 224, (M 31), NGC 752, NGC 7662, 57-γ (STF 205)

01

67CONSTELLATION 01 - AND (Andromeda)

constellation Andromeda, with Perseus, Cassiopeia, and Cepheus always nearby.

Andromeda is a mid-northerly constellation that lies far above the plane of our own Milky Way galaxy. When you look toward Andromeda, you are looking through a thinly-populated part of our own galaxy and toward intergalactic space. Accordingly, you won’t find bright nebulae or globular clusters in Andromeda, because those objects are almost exclusively denizens of the galactic plane. You will find numerous galaxies—four of which (look for the Type Gx in Table 01-1) are among our featured objects, including the magnificent Great Andromeda Galaxy—the open cluster NGC 752, and the fine, bluish planetary nebula NGC 7662.

Andromeda is easy to find, located between the prominent W-shape of Cassiopeia to the north and the Great Square of Pegasus to the southwest. The brightest stars in Andromeda form a long, narrow V-shape, with its apex at Alpheratz, the northeastern corner star of the Great Square of Pegasus. For observers at mid-northern latitudes, Andromeda is well-placed for evening viewing from late summer, when it rises after dusk, through mid-winter, when it sets a couple hours after dark. Andromeda culminates at zenith at 9:00 p.m. in late November.

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CHArT 01-1.

The constellation Andromeda (field width 50°)

andromeda, the Princess

68 ILLUSTRATED GUIDE TO ASTRONOMICAL WONDERS

M 32 (ngC 221) ★★ ••• gx MBuDr

Chart 01-2 Figure 01-1 m9.0, 8.7' x 6.4' 00h 42.7m +40° 52'

Clusters, Nebulae, and Galaxies

Along with our own Milky Way galaxy, the galaxies M 31, M 32, and M 110 are members of the Local Group of galaxies. M 31, the famous Great Andromeda Galaxy, is the nearest major galaxy to our own Milky Way galaxy, and is in many respects a twin sister to it. Recent data suggest that M 31 is somewhat larger than our Milky Way, but is much less densely populated, with only about half the mass. At a distance of about 2.9 million light years, M 31 has the distinction of being the most distant object that is easily visible without optical assistance.

M 31 stands out to the naked eye from a moderately dark site, and is clearly visible with the slightest optical aid even from light-polluted urban sites. Although M 32 is a much more difficult binocular object than M 31, its relatively high surface brightness (10.1) makes it visible with a 50mm or larger binocular from a dark site as a fuzzy star about 25’ S of the bright core of M 31. M 110, located about 37’ NW of the core of M 31 and with lower surface brightness of 13.2, is extremely challenging but may be possible with a tripod-mounted 60mm or larger binocular from a dark site.

M 31 begins to reveal detail in a 3.5" or larger telescope, and shows nuanced detail in typical amateur instruments of 6", 8", or 10" aperture. All three galaxies are visible in the field of a 1° eyepiece, although M 32 and M 110 show little detail. M 31 shows a mottled appearance, with two dark lanes clearly visible. At 90X to 125X, the core of M 31 takes on the grainy appearance of a globular cluster that is not quite resolvable into individual stars. M 32 is visible with direct vision as a prominent circular nebulosity with gradual brightening to a star-like core, located just S of the core of M 31, but embedded within the nebulosity of M 31. M 110 is visible as a faint, oval nebulosity on the NW side of M 31, opposite M 32, and near the edge of the visible extent of M 31.

M 31 (ngC 224) ★★★★ ••• gx MBuDr

Chart 01-2 Figure 01-1 m4.4, 192.4’ x 62.2’ 00h 42.7m +41° 16’

Image reproduced from Digitized Sky Survey courtesy Palomar Observatory and Space Telescope Science Institute

FIgurE 01-1.

Figure 01-1. NGC 224 (M 31), NGC 221 (M 32, bottom center), and NGC 205 (M 110, top right) (60' field width)

M 110 (ngC 205) ★★ ••• gx MBuDr

Chart 01-2 Figure 01-1 m8.9, 21.9' x 10.9' 00h 40.4m +41° 41'

69CONSTELLATION 01 - AND (Andromeda)

CHArT 01-2.

M 31, M 32, and M 110 (15° field width; 5° finder circles; LM 9.0)

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The Andromeda Galaxy cluster is easy to find. From m2 Alpheratz (21-α), which is the NE star in the Great Square of Pegasus, hop 6.9° ENE (east northeast) to m3 31-δ and then 7.9° NE to m2 Mirach (43-β). Alternatively, you can locate Mirach directly by using the westernmost triangle of Cassiopeia—of which m2 Shedir is the apex—as a pointer to Mirach. Follow that pointer 21.4° SSE (about two fists south southeast) to Mirach, which is the brightest star in the near vicinity.

Once you have located Mirach, move the finder NW, placing Mirach on the edge of the field. The m4 star 37-μ will be prominent in the finder. Continue moving the finder on the same line until 37-μ reaches the edge of the field, and M 31 will be visible in the finder with the m5 star 35-ν prominent about 1.5° E.

70 ILLUSTRATED GUIDE TO ASTRONOMICAL WONDERS

CHArT 01-3.

NGC 752 (10° field width; 5° finder circle; LM 9.0)

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NGC 752 is a moderately rich, detached, loosely scattered open cluster that is best viewed with a large binocular or at low magnification in a telescope. The cluster is easy to locate with a 50mm binocular or finder. With Almach and m4 50-υ, it forms nearly an equilateral triangle with 5° sides, with the center of the cluster located about 2.1° dead W of m5 58-Andromedae and 40’ NE of the prominent m6 pair 57-Andromedae. In a 50mm binocular or finder, the cluster is visible as a dozen or so m9 stars, with a very faint nebulosity of unresolved dimmer stars. In our 10" scope at 42X, 60+ stars are visible, most m10 and m11.

ngC 752 ★★★ ••• oC MBuDr

Chart 01-3 Figure 01-2 m5.7, 49.0' 01h 57.8m +37° 51'

Image reproduced from Digitized Sky Survey courtesy Palomar Observatory and Space Telescope Science Institute

FIgurE 01-2.

NGC 752 (60' field width)