OF THE ROGER N. CLARK

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--- -- VISUAL ASTRONOMY OF THE DEEP SKY A VISUAL ATLAS OF DEEP-SKY OBJECTS M8 7 (NGC 4486) NGC 4476, NGC 4478, GALAXIES IN VIRGO NGC 4476: R.A. 12h 30.0m, Dec. 12° 20' NGC 447S: R.A. 12h 30.3m, Dec. 12° 19' MS7: R.A. 12h 30.Sm, Dec. 12° 23 ' (2000.0) T chnical. M87 is a giant elliptical galaxy, he brigh test member of the Virgo Cluster t one of the intrinsically brightest galaxies an . . . the sky. It IS a I so one 0 f t h e most massive. y one estimate, M87 contains 3 trillion stars and dozens of times the mass of our Galaxy! An estimated 10 000 globular clusters surround this galaxy, over 800 of which have been detected by large observatory telescopes. In contrast, our Galaxy has only a couple hundred known gloular clusters. M87 is about 120 000 light-years across, not much more than many spirals. But since it is spherical, while spirals are flattened, M87 may have the largest volume of any known galaxy. M87 also has a very violent nucleus. A high-velocity jet of matter is emerging from the nucleus toward the northwest. It consists of a line of at least six blobs of very hot gas (20 million kelvin) and has a strong magnetic field. The jet extends along the galaxy's axis of rotation. It is estimated to be 5000 lightyears long and only 15 000 years old. A second, fainter jet was recently found emerging from the nucleus in the opposite direction. A third, broad fan also extends to one side. The whole area emits considerable radiation, from radio to X-ray. Near M87's innermost core the stars are orbiting very rapidly, indicating that within 300 light-years of the center there is a very massive object that emits little or no light. This object, with an estimated mass of 5 billion suns, is usually presumed to be a black hole. Gas falling toward it would form an extremely hot and energetic "accretion disk" orbiting just outside the hole as it spiraled in. The accretion disk could be responsible for the creation of the jets. The galaxies to the west of M87 are NGC 4478 and NGC 4476, both ellipticals that are s all only in comparison to their giant nelghbor. Visual. M87 is magnitude 8.6 and about 3 arc-minutes in diameter. In this area the mean surface brightness is high, 19.6 magnitudes per square arc-second. The very faintest outer portions of the galaxy extend to 7 arc-minutes, and the globular clusters to 9 arc-minutes, though these outer parts cannot be detected visually through amateur telescopes. The jet of M87 can be photographed with medium to large amateur telescopes but cannot be detected visually. The jet's total magnitude is 15, and it extends only about 20 arc-seconds from the bright center. Moreover, the jet is superimposed on essentially the brightest part of the galaxy, so the contrast is very low. A telescope a couple of meters in aperture is probably needed to view the jet! The only recorded visuaJ observation of it is by Qtto Struve with the lOO-inch telescope on Mount Wilson, California. In the 8-inch, M87 appears quite bright compared with other ellipticals in the area. It has a bright center and the intensity decreases uniformly to the edge, with no features. NGC 4476 has a visual magnitude of 13.3, an apparent size of 0.7 by 0.4 arc-minutes, and a mean surface brightness of 20.5 magnitudes per square arc-second. NGC 4478 has a visual magnitude of 12.4, a size of 1.0 by 1.8 arc-minutes, and a mean surface brightness of 21. 7 magnitudes per square arc-second. In the 8-inch, NGC 4476 appeared brighter and smaller than NGC 4478, even though the latter is nearly a magnitude brighter. This is because the light of the latter is spread over a larger area. The mean surface brightness values indicate this effect, illustrating their value for detecting objects. Both galaxies appeared as small, faint, fuzzy spots. Medium to high powers are needed to see them. 152 153
-- -- --- VISUAL ASTRONOMY OF THE DEEP SKY A VISUAL ATLAS OF DEEP-SKY OBJECTS ---5' --- Photograph of M87, the large galaxy at right. NeC 4478 is in the upper lift, and NeC 4476 is not shown, being just off the left edge. South is up. (Courtesy Evered Kreimer, The Messier Album.) Drawing of M87 (the large galaxy at right), NeC 4478 (upper left) , and NeC 4476 (near the liftcenter edge) . The positions of Nec 4476 and the star at upper lift are only approximate. Scale: 1.2 arc-min/cm 8-inch f/ l1.5 Cassegrain 20mm Erfle (117 X) 12.4mm Erfle (188X) Viewing Distance (cm) 25X:115 200X:14 50 x: 57 300X:1O 100 X : 29 400x: 7 air mass: 1.46, faintest star: 14 3at zenith 188x· no tracking · " 5/ 1 1/83 10:50--1 1:05 UT at Waianae ranch ' Hawaii; R. Clark 154 155
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OF THE ROGER N. CLARK
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Published by Sky Publishing Corpora
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CONTENTS M78 (NGC 2068) NGC 207 1,
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PREFACE During research for this bo
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VISUAL ASTRONOMY OF THE DEEP SKY AB
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VISUAL ASTRONOMY OF THE DEEP SKY TH
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.. .. .. .. VISUAL ASTRONOMY OF THE
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e viewed with enough magnification
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lens and a piano-convex eye lens. A
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controlled depends on how many laye
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The Lumicon H-Beta Filter (Figure 3
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every 1 ° in declination and 4 min
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error of only one quarter the field
Page 33 and 34: Table 4.1. Ideal limiting magnitude
Page 35 and 36: 5 Making drawings and keeping recor
Page 37 and 38: more detail in the future. They add
Page 39 and 40: .. .. .. ... Contrast (C) C Log(C)
Page 41 and 42: VISUAL ASTRONOMY OF THE DEEP SKY A
Page 47 and 48: --- VISUAL ASTRONOMY OF THE DEEP SK
Page 49 and 50: --- M76 (NGC 650-651), PLANETARY NE
Page 53 and 54: -- -- M45, THE PLEIADES OPEN CLUSTE
Page 55 and 56: -- Brightest stars of the Pleiades
Page 57 and 58: M42 (NGC 1976), M43 (NGC 1982), THE
Page 59 and 60: --- --- --- VISUAL ASTRONOMY OF THE
Page 61 and 62: -- --- NGC 2023 NGC 2024, IC 434 (T
Page 63 and 64: --- --- M78 (NGC 2068), NGC 2071, D
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Page 67 and 68: --- M67 (NGC 2682), OPEN CLUSTER IN
Page 69 and 70: -- VISUAL ASTRONOMY OF THE DEEP SKY
Page 71 and 72: --- -- M82 (NGC 3034), PECULIAR GAL
Page 73 and 74: -- --- --- MI05 (NGe 3379) NGe 3384
Page 77 and 78: MI09 (NGe 3992), GALAXY IN URSA MAJ
Page 79 and 80: -- --- M99 (NGC 4254), GALAXY IN CO
Page 81 and 82: == -- VISUAL ASTRONOMY OF THE DEEP
Page 83: --- --- -- NGC 4449, GALAXY IN CANE
Page 87 and 88: --- -- M90 (NGC 4569), GALAXY IN VI
Page 89 and 90: --- -- M94 (NGC 4736), GALAXY IN CA
Page 93 and 94: -- VISUAL ASTRON0MY OF THE DEEP SKY
Page 95 and 96: -- --- -- VISUAL ASTRONOMY OF THE D
Page 97 and 98: -- -- VISUAL ASTRONOMY OF THE DEEP
Page 99 and 100: --- -- M83 (NGC 5236), GALAXY IN HY
Page 109 and 110: --- -- VISUAL ASTRONOMY OF THE DEEP
Page 111 and 112: ---------------- 5 / --------______
Page 113 and 114: --- -- VISUAL ASTRONOMY OF THE DEEP
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Page 119 and 120: -- -- VISUAL ASTRONOMY OF THE DEEP
Page 123 and 124: -- MI5 (NGC 7078), GLOBULAR CLUSTER
Page 133 and 134: -- ·rl E I u L ro 5 +J Q) (f) 0 Y
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-- --- VISUAL ASTRONOMY OF THE DEEP
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VISUAL ASTRONOMY OF THE DEEP SKY NG
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'2 5 -rl E I U L CO '---' -t-J ill
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VISUAL ASTRONOMY OF THE DEEP SKY AP
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VISUAL ASTRONOMY OF THE DEEP SKY Ta
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-- Appendix E A catalog of deep-sky
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--- -- VISUAL ASTRONOMY OF THE DEEP
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-- -- --- VISUAL ASTRONOMY OF THE D
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--- --- VISUAL ASTRONOMY OF THE DEE
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-- -- VISUAL ASTRONOMY OF THE DEEP
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-- APPENDIX F: OPTIMUM DETECTION MA
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------- VISUAL ASTRONOMY OF THE DEE
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--- VISUAL ASTRONOMY OF THE DEEP SK
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VISUAL ASTRONOMY OF THE DEEP SKY -
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VISUAL ASTRONOMY OF THE DEEP SKY -
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G VISUAL ASTRONOMY OF THE DEEP SKY
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INDEX INDEX M70 (NGC 6681), 312, 31
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OF THE ROGER N. CLARK

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