关于星际尘埃细丝发现的报告

REPORT ON THE DISCOVERY OF INTERSTELLAR DUST FILAMENTS

哈里·H·里克（Harry H.Ricker）III

翻译：喻园

摘要

所描述的观测证据揭示了以前未知的星际尘埃细丝的存在，这些细丝存在于以下发光背景下：银河星场，球状星团，星系，超新星残留物，银河星团，HII区域，反射星云和行星状星云。

ABSTRACT

Observational evidence described reveals the presence of previously unrecognized interstellar dust filaments against luminous backgrounds provided by: Milky Way starfields, globular clusters, galaxies, supernova remnants, galactic clusters, HII regions, reflection nebulae, and planetary nebulae.

关键词：尘埃，气体和星际介质

简介：

在银河星场，球状星团，星系，超新星残余，银河星团，HII区，反射星云和行星状星云提供的发光背景下，已观察到星际尘埃细丝。尘埃丝中的吸收会产生长而细的条纹，暗带，平行条纹以及模糊背景的斑点。

星际尘埃丝最令人惊讶的方面是它们的极长。在宽视野照片中，观察到长达30度的灰尘丝。它们的外观类似于喷气飞机的蒸气痕迹，表明它们是极长且狭窄的气体和灰尘气瓶。几乎总是发现它们是间隔很近的平行尘埃细丝系统的成员，这给模糊的星空赋予了条纹和条纹的外观。通常，在不同方向上定向的两个或多个平行的尘埃细丝系统会叠加在星空上，使其呈现出斑驳或混乱的外观。这样的星空给人的印象是，许多细小的不规则尘埃云散布在整个区域。

在判断灰尘丝的真实性之前，读者应仔细研究本文引用的照片。细丝几乎不能感知到它们的背景，并且出现在许多细丝以偶然的方式交错的区域中。如果尘埃丝很明显或很容易看到，那么许多年前首次报道它们存在的证据时，它们就会被人们所认识（Minkowski 1955，Roberts 1960和Sandage 1961）。

Interstellar dust filaments have been observed in projection against luminous backgrounds provided by Milky Way starfields, globular clusters, galaxies, supernova remnants, galactic clusters, HII regions, reflection nebulae, and planetary nebulae. Absorption within the dust filaments creates long thin streaks, dark bands, parallel striations, and mottling of the obscured backgrounds.

The most astonishing aspect of the interstellar dust filaments is their extreme length. In wide field photographs, dust filaments up to thirty degrees long have been observed. Their appearance resembles the vapor trails of jet aircraft — suggesting they are extremely long and narrow cylinders of gas and dust. They were almost always found to be members of a system of closely spaced parallel dust filaments, which gives a streaked and striated appearance to obscured starfields. Frequently two or more systems of parallel dust filaments oriented in different directions are superposed on a starfield, imparting a mottled or chaotic appearance to it. Such starfields give the impression of having many tiny irregular dust clouds dispersed throughout the region.

The reader should carefully study the photographs cited herein before rendering a judgment on the reality of the dust filaments. The filaments are barely perceptible against their backgrounds and occur in regions where many filaments crisscross in a haphazard fashion. If the dust filaments were obvious or easily seen, they would have been recognized many years ago when evidence of their existence was first reported (Minkowski 1955, Roberts 1960, and Sandage 1961).

银河星空中的灰尘丝

作者在几乎所有检查过的星空的照片中都认可了平行的尘埃细丝系统，这些系统给被遮盖的星空赋予了条纹和条纹的外观。通过仔细检查长而细的深色细丝的正照片可以识别出它们。旋转照片，直到发现细细的暗丝。然后检查照片中平行于第一根灯丝的细丝。

一旦识别出平行的长丝系统，就旋转照片并检查是否存在其他平行的平行长丝系统。经常发现两个或两个以上的尘埃细丝系统覆盖星空，从而形成复杂的尘埃图案或花丝。发现这些尘埃花丝是造成许多星空斑驳外观的原因。

Scutum中丰富的星云是星空的一个极好的示例，该星空具有前景星际尘埃丝引起的条纹和横纹外观。条纹和条纹的外观可以在Yerkes天文台发布的照片（目录号MW17，MW23和MW106）和银河系中找到（Bok和Bok，1974年，第12页）。

最容易识别的尘埃丝系统是从东向西，与银河赤道成大约60度角。该系统在米尔南部以南很显眼，但可以看到它覆盖了整个星空。将照片旋转90度后，可以在密尔以西识别出第二条平行的尘埃细丝系统，它们平行于北向南，与银河赤道成30度角。还存在第三个由东北向西北，平行于银河赤道的尘埃丝组成的系统。

天鹅座是另一个表现出平行尘埃丝的区域。广角照片显示至少四个尘埃细丝系统。Yerkes天文台发布的照片（目录号MW6 8，MW69，MW72，MW85）显示该区域被遮盖

由指向东至西，北至南，东南至西北，东北至西南的尘埃丝组成，与银河赤道成六十度，三十度，九十度和零度。R. Minkowski在1953年描述了天鹅绒中存在的细丝（Minkowski，1955年），但并未意识到它们的重要性。

在仙后座中已经发现了四个平行的尘埃细丝系统，其中三个截然不同，而第四个几乎不明显（天文19 78a）。最显着的平行尘埃丝系统在东西方向平行于银河赤道。第二个尘埃丝系统以与赤道成大约三十度的角度从东南向西北定向。该系统最容易在Cepheus边界附近看到，但它覆盖了整个星座。第三个系统的方向是北向南，而几乎看不到的第四个系统的方向是东北向西南。

Systems of parallel dust filaments, which give a streaked and striated appearance to obscured starfields, have been recognized by the author in almost all photographs of starfields examined for their presence. They were recognized by carefully examining positive photographs for long, thin dark filaments. The photographs were rotated until a thin dark filament was recognized. Then the photograph was examined for filaments parallel to the first filament.

Once a system of parallel filaments was recognized, the photograph was rotated and examined for the presence of additional systems of parallel dust filaments. Frequently two or more systems of dust filaments were found to overlie a star-field creating a complex dust pattern or filigree. These dust filigrees were found to be responsible for the mottled appearance of many starfields.

The rich star cloud in Scutum is an excellent example of a starfield having a streaked and striated appearance caused by foreground interstellar dust filaments. The streaked and striated appearance can be recognized in photographs published by the Yerkes Observatory (catalog numbers MW17, MW23, and MW106), and in The Milky Way (Bok and Bok, 1974, page 12).

The most easily recognized system of dust filaments is oriented east to west, at an angle of approximately sixty degrees to the galactic equator. This system is prominent immediately south of Mil, but can be seen to cover the entire starfield. A second system of parallel dust filaments oriented north to south, at an angle of thirty degrees to the galactic equator, can be recognized west of Mil after rotating the photographs by ninety degrees. A third system of dust filaments oriented northeast to northwest, parallel to the galactic equatoris also present.

Cygnus is another region exhibiting parallel dust filaments. Wide field photographs reveal at least four systems of dust filaments. Photographs published by Yerkes Observatory (catalog numbers MW6 8, MW69, MW72, MW85) show the region is obscured

by dust filaments oriented east to west, north to south, southeast to northwest, and northeast to southwest, at angles of sixty, thirty, ninety and zero degrees to the galactic equator. The existence of dust filaments in Cygnus is confirmed by R. Minkowski, who described them in 1953 (Minkowski, 1955), but did not recognize their significance.

Four systems of parallel dust filaments—three distinct and a fourth barely evident—have been recognized in Cassiopeia (Astronomy 19 78a) . The most prominent system of parallel dust filaments is oriented parallel to the galactic equator in the east-to-west direction. A second system of dust filaments is oriented southeast to northwest at an angle of approximately thirty degrees to the equator. This system is most easily seen near the Cepheus border, but it covers the entire Constellation. The third system is oriented north to south, while a fourth system which is barely evident is oriented northeast to southwest.

球团中的灰尘丝

作者检查的所有球状星团照片中都观察到了前景星际尘埃丝。此外，海伦·索耶·霍格（Helen Sawyer Hogg，1959年）在M13，M3和M2中观察到“……明显的暗雾状条纹……”。前景尘埃细丝的存在被径向或切向条纹，平行条纹和斑驳的尘土外观所识别。短时曝光的照片显示出横跨球状星团中心区域的深色条纹和平行条纹。尽管较长的曝光照片使聚类中心区域过度曝光，但在聚类的郊区观察到了径向条纹和条纹。当使用卡片或直尺将条纹和条纹线性延伸至簇的另一侧时，观察到放射状的对应条纹和条纹。因此，这些被证明是灰尘丝的延续，这在过度曝光的簇中心中看不到。垂直于径向方向的切线方向的细丝穿过簇的外围被检测到。在很长的曝光照片中，观察到灰尘丝延伸到周围星空相当长的距离。该观察结果最令人信服地证明了针对球形团簇观察到的尘埃丝的前景特性。被发现跨越集群的郊区。在很长的曝光照片中，观察到灰尘丝延伸到周围星空相当长的距离。该观察结果最令人信服地证明了针对球形团簇观察到的尘埃丝的前景特性。被发现跨越集群的郊区。在很长的曝光照片中，观察到灰尘丝延伸到周围星空相当长的距离。该观察结果最令人信服地证明了针对球形团簇观察到的尘埃丝的前景特性。

在欧米茄半人马座（NGC5139）的照片中已经观察到所有上述现象。短时间曝光的照片（Sky and Telescope 1963和The Messenger 1979）显示了平行的尘埃丝，它们穿过欧米茄半人马座的中心从东向西，从北向南定向。长时间曝光的照片显示出集束郊区的放射状和切向尘埃细丝。长时间曝光的照片（Kitt.Peak目录号01105； Yerkes目录号SC355）（Shapley和Hodge 1972，第89页； Bok和Bok 1974，第17页）显示了平行的尘埃细丝系统，其方向是东西向，北边是南，延伸到周围的星空。

其他表现出前景星际尘埃细丝迹象的球状星团有：47杜鹃花（NGC104），（基特峰目录01100）；M3（Hale目录号30，Lick目录号DI，Kitt Peak目录号01102），M13（Hale目录号34，Lick目录号U7），M15（Kitt Peak目录号01103）和M92（Lick目录号D6和Kitt Peak目录号01101）。还观察到尘埃丝穿过质量非常低，人口稀少的球状星团NGC5897（Hale目录号62）’和NGC6791（Lick目录号D5），由于它们的恒星密度低而类似于银河星团。

Foreground interstellar dust filaments have been observed in all globular cluster photographs examined by the author. In addition, Helen Sawyer Hogg (1959) has observed, “…obvious streaks of dark nebulosity…” in M13, M3 and M2. The existence of foreground dust filaments was recognized by the presence of radial or tangential streaks, parallel striations, and a mottled dusty appearance. Short exposure photographs revealed dark streaks and parallel striations crossing the central regions of globular clusters. Although longer exposure photographs over-expose the cluster central region, radially directed streaks and striations were observed in.the outskirts of the clusters. When the streaks and striations were linearly extended to the opposite side of the cluster, using a card or ruler, radially directed counterpart streaks and striations were observed. These were thereby proven to be continuations of dust filaments which cannot be seen in the over-exposed cluster center. Tangentially oriented filaments, which are oriented perpendicular to the radial direction, were detected crossing the outskirts of clusters. In very long exposure photographs, dust filaments were observed to extend a considerable distance into the surrounding starfield. This observation was the most convincing demonstration of the foreground nature of the dust filaments seen against globular clusters.

All of the above phenomena have been observed in photographs of Omega Centauri (NGC5139). Short exposure photographs (Sky and Telescope 1963 and The Messenger 1979), show parallel dust filaments oriented east to west and north to south crossing the center of Omega Centauri. Photographs of longer exposure revealed radial and tangential dust filaments in the cluster outskirts. Very long exposure photographs (Kitt .Peak catalog number 01105; Yerkes catalog number SC355) (Shapley and Hodge 1972, p. 89 and Bok and Bok 1974, p. 17) show systems of parallel dust filaments oriented east to west and north to south, extending into the surrounding starfield.

Other globular clusters exhibiting evidence of foreground interstellar dust filaments are: 47 Tucanae (NGC104), (Kitt Peak catalog 01100); M3 (Hale catalog number 30, Lick catalog number DI, Kitt Peak catalog number 01102), M13 (Hale catalog number 34, Lick catalog number U7), M15 (Kitt Peak catalog, number 01103), and M92 (Lick catalog number D6 and Kitt Peak catalog number 01101). Dust filaments have also been observed crossing the very low mass, sparsely populated globular clusters NGC5897 (Hale catalog number 62)’, and NGC6791 (Lick catalog nymber D5) which resemble galactic clusters because of their low stellar density.

星系中的灰尘丝

在从无尘椭圆形到富尘不规则星系的银河系中，已经观察到星际尘埃细丝。由于椭圆形星系几乎没有内部尘埃，因此在这些星系的照片中观察到的尘埃很可能是投影中看到的前景尘埃丝。在从椭圆形支配星系团的巨型椭圆形体到局部小矮星的所有椭圆形星系的投影中都观察到了尘埃丝。

NGC205，NGC185和NGC147等局部群矮椭圆形星系的外观与球状星团的相似性表明存在前景尘埃细丝。在这些星系的照片中，前景尘埃细丝的存在通过平行条纹，深色条纹，尘埃带，尘埃斑和斑驳的外观表示。NGC185的外观（Sandage 1961和Shapley and Hodge 1972）类似于由平行的粉尘细丝系统覆盖的球状星团。外部区域呈斑点状，这是因为灰尘丝的系统从东到西，从北到南，从东北到西南以及从东南到西北方向排列。在NGC205（Hale目录号2，Sandage 1961）和NGC147（Hale目录号1，NGC205）的照片中也观察到平行条纹

在巨型椭圆星系的投影中已观察到尘埃细丝：M87（NGC4486），M59（NGC1621），M49（NGC4472和M85（NGC4362）），M87是最好的例子。

在长时间和短期曝光的照片中都检测到了灯丝。在M87短射流的短曝光照片中（Sandage 1961，Lick目录号S4），在核区域观察到平行的尘埃细丝，并与射流成直角交叉。从北到南，从东到西排列的尘埃细丝使核区域呈斑驳的外观，使其类似于球状星团的外观。在M87的长时间曝光照片中（Sandage 1961，Evans 1968，Hale目录号24，Lick目录号S5和Kitt Peak目录号02120），在微弱的外壳中已发现灰尘丝。

观察到尘埃细丝的晚型不规则星系包括麦哲伦星云，IC1613和NGC6822。麦哲伦星云的大小与众不同，因为它们类似于银河系的分离部分。麦哲伦星云上投射的前景尘埃丝的外观类似于银河系星空上的外观。观察到长长的深色条纹，平行条纹和斑点。大麦哲伦星云中部30-多拉多斯附近的照片（第Page和Page 1969； Sandage 1961； Alter，Cleminshaw和Phillips 1974； Hodge 1966；和Goldberg 1966）显示了两个相互垂直的，平行的尘埃细丝系统从北到南。在较暗的外部区域也检测到平行的尘埃细丝系统（Dickson 1968）。在长时间曝光下 在麦哲伦星云大条的西北端看到了宽视野的照片，宽细丝或条带。麦哲伦小云（Dickson 1968; Menzel 1964，and

哥德堡（1966）。确定了从东到西和从北到南的两个突出的平行尘埃丝系统。

IC1613是另一个I型不规则星系，它是本地组的成员。照片（Sandage 1961和Hubble 1936）显示，在NGC6822的照片中也观察到星际尘埃细丝从东到西，从东北到西南，从东南到西北穿过星系（Menzel 1964； Hodge和Shapley 1972）。

这里给出的描述用作具有可观察到的前景尘埃细丝的星系的示例。作者检查了许多其他星系的照片，并观察了在高和低银河纬度的大量星系中的前景尘埃丝。这表明尘埃丝并不局限于银河赤道区域，而是在其上方和下方广泛分布。哈勃地图集（Sandage 1961）中对星系的描述证实了星系前尘埃丝的存在，其中描述了大量不符合其基本星系形式的放射状尘埃带和条纹。

Interstellar dust filaments have been observed in projection against galaxies ranging from dust-free elliptical to dust-rich irregular galaxies. Because elliptical galaxies contain little internal dust, the dust observed in photographs of these galaxies is likely to be foreground dust filaments seen in projection. Dust filaments have been observed in projection against all types of elliptical galaxies from the giant ellipticals, which dominate galactic clusters, to local group dwarfs.

The similarity of the appearance of local group dwarf elliptical galaxies, such as NGC205, NGC185, and NGC147, to the appearance of globular clusters suggested the presence of foreground dust filaments. In photographs of these galaxies, the presence of foreground dust filaments was indicated by parallel striations, dark streaks, dust lanes, dust patches, and a mottled appearance. The appearance of NGC185 (Sandage 1961 and Shapley and Hodge 1972) resembles the appearance of a globular cluster overlain by systems of parallel dust filaments. The outer region has a mottled appearance due to systems of dust filaments oriented east to west, north to south, northeast to southwest, and southeast to northwest. Parallel striatic were also observed in photographs of NGC205 (Hale catalog number 2, and Sandage 1961) and NGC147 (Hale catalog number 1, and Sandage 1961).

Dust filaments have been observed in projection against the giant elliptical galaxies: M87 (NGC4486), M59 (NGC1621), M49 (NGC4472, and M85 (NGC4362). M87 is the best example. Dust

filaments have been detected in both long- and short-exposure photographs. In short-exposure photographs (Sandage 1961, and Lick catalog number S4) of the M87 jet, parallel dust filaments were observed in the nuclear region, and crossing the jet at right angles. The dust filaments, which are oriented north to south and east to west, impart a mottled appearance to the nuclear region causing it to resemble the appearance of globular clusters. In long exposure photographs of M87 (Sandage 1961, Evans 1968, Hale catalog number 24, Lick catalog number S5, and Kitt Peak catalog number 02120), dust filaments have been recognized in the faint outer envelope.

Late type irregular galaxies in which dust filaments were observed include the Magellanic Clouds, IC1613, and NGC6822. The Large and Small Magellanic Clouds are unique because they resemble detached portions of the Milky Way. The appearance of foreground dust filaments in projection against the Magellanic Clouds resembles their appearance against Milky Way starfields. Long dark streaks, parallel striations, and mottling have been observed. Photographs (Page and Page 1969; Sandage 1961; Alter, Cleminshaw and Phillips 1974; Hodge 1966; and Goldberg 1966) of the Central region of the Large Magellanic Cloud near 30-Doradus show two mutually perpendicular systems of parallel dust filaments oriented east to west and north to south. Systems of parallel dust filaments were also detected in the fainter outer regions (Dickson 1968). In long-exposure, wide-field photographs, wide filaments or bands were seen crossing the northwestern end of the bar of the Large Magellanic Cloud. Dust filaments were also recognized in photographs of the Small Magellanic Cloud (Dickson 1968; Menzel 1964, and

Goldberg 1966). Two prominent systems of parallel dust filaments oriented east to west and north to south were identified.

IC1613 is another Type I irregular galaxy, which is a member of the local group. Photographs (Sandage 1961 and Hubble 1936) show interstellar dust filaments crossing this galaxy from east to west, northeast to southwest, and southeast to northwest have also been observed in photographs of NGC6822 (Menzel 1964; Hodge and Shapley 1972).

The descriptions presented here serve as examples of galaxies having observable foreground dust filaments. The author has examined photographs of many other galaxies and observed foreground dust filaments in a large number of galaxies at both high and low galactic latitudes. This indicates that the dust filaments are not confined to the region of the galactic equator, but that they are widely distributed both above and below it. The existence of dust filaments in front of galaxies was confirmed by descriptions of galaxies in The Hubble Atlas (Sandage 1961), where a large number of instances of radial dust lanes and streaks which do not conform to the underlying galactic form are described.

行星状星云和反射星云

本节介绍在超新星遗迹，HII区域，银河星团，行星状星云和反射星云提供的发光背景下，对投射的星际尘埃丝的观测结果。这些观察扩大了观察到灰尘丝的物体的范围。加强星际尘埃丝存在的证据，并证明其普遍存在。

This section describes observations of interstellar dust filaments observed in projection against the luminous backgrounds provided by supernova remnants, HII regions, galactic clusters, planetary nebulae, and reflection nebulae. These observations expand the list of objects against which dust filaments have been observed; strengthening the evidence for the existence of interstellar dust filaments, and demonstrating their ubiquity.

超新星遗迹

在天鹅座环（NGC6992-6995，6990），IC443，蟹状星云（Ml），维拉残留物和沙恩147的照片中，观察到超新星残留物发光背景下的尘埃细丝。尽管需要仔细检查才能看到，已经观察到穿过包括天鹅绒环的发光灯丝的网络穿过尘埃灯丝（Hale目录号108、109、159和S-20； Lick目录号N3a，N3b和N3c，以及Kitt Peak目录号01010）。宽视场照片（Dufay 1957和Struve 1962）显示天鹅座环被大量尘埃丝覆盖，这些尘埃丝纵横交错地环绕着周围的星空和残余物的发光网络。在一些短时间曝光的照片中，残留物的发光弧中明显存在间隙。更长的曝光照片显示这些间隙是前景尘埃丝使区域变暗的区域。在长时间曝光的照片中，已观察到灰尘丝穿过NGC6992-6985，然后穿过同一灰尘丝穿过残留物另一侧的NGC6990。

尽管观察到灰尘丝穿过天鹅绒环的狭窄发光弧，但是很难跟随灰尘丝任何距离。IC443提供了更均匀的发光背景，在黑尔天文台的照片（目录编号56）中发现了灰尘丝。宽尘丝和窄尘丝均被识别。它们的长丝状性质是显而易见的，因为可以在整个发光背景上跟踪它们一段距离。连续照片（海尔天文台目录编号102、57和S-22；里克目录编号N5a）中蟹状星云的斑驳外观表明存在前景尘埃。在紧凑的超新星残余物上纵横交错地发现了黑暗的车道，条纹和条纹。

Dust filaments have been observed against the luminous backgrounds of supernova remnants in photographs of the Cygnus Loop (NGC6992-6995, 6990), IC443, Crab Nebula (Ml), Vela Remnant, and Shajn 147. Although they require careful scrutiny to be seen, dust filaments have been observed crossing the network of luminous filaments comprising the Cygnus Loop (Hale catalog numbers 108, 109, 159 and S-20; Lick catalog numbers N3a, N3b, and N3c,\ and Kitt Peak catalog number 01010) . Wide-field photographs (Dufay 1957 and Struve 1962) show the Cygnus Loop is overlain by.a profusion of dust filaments criss-crossing the surrounding starfield and the luminous network of the remnant. In some short-exposure photographs, obvious gaps in the luminous arcs of the remnant were evident. Longer exposure photographs revealed that these gaps were regions darkened by foreground dust filaments. In very long-exposure photographs, dust filaments have been observed crossing NGC6992-6985 and followed to where the same dust filament crosses NGC6990 on the opposite side of the remnant.

While dust filaments have been observed crossing the narrow luminous arcs of the Cygnus Loop, it is difficult to follow the dust filaments for any distance. IC443 provides a more uniform luminous background against which dust filaments have been identified in the Hale Observatory’s photograph (catalog number 56). Both wide and narrow dust filaments were recognized. Their long filamentary nature is evident, since they can be followed for a distance across the luminous background. The mottled appearance of the Crab Nebula in continuum photographs (Hale Observatory’s catalog numbers 102, 57 and S-22; Lick catalog number N5a) indicates the presence of foreground dust. Dark lanes, streaks and striations were detected criss-crossing this compact supernova remnant.

HII地区

尽管难以识别，但在北美星云（NGC7000），IC434（环绕马头星云），玫瑰花状星云（NGC2237），IC1396，IC2944（环绕Lambda Centauri）和Eta Carina星云（NGC3372）。有两个因素导致难以观察到针对HII区域的灰尘丝。首先，很难将前景尘埃与星云内部的尘埃区分开，其次，过度暴露会使吸收较弱的尘埃丝变得模糊。

北美星云是HII区域的最好例子，在周围的星空中和星云的背景下都观察到了星际尘埃丝。NGC7000（Hale目录号S-.19，Lick目录号Nil，Yerkes目录号N21，Dufay’1957）的照片中已识别出平行的尘埃细丝系统，这些照片显示了尘埃细丝从东到西，从北到南，从东北到西南，东南到西北。

Although difficult to recognize, interstellar dust filaments have been observed in projection against the luminous backgrounds provided by the North American Nebulae (NGC7000), IC434 .(surrounding Horsehead Nebula), Rosette Nebula (NGC2237), IC1396, IC2944 (surrounding Lambda Centauri) and the Eta Carina Nebula (NGC3372). Two factors contribute to the difficulty in observing dust filaments against HII regions. First, it is difficult to differentiate foreground dust from dust internal to the nebula, and, second, over-exposure obscures the weakly absorbing dust filaments.

The North American Nebula is the best example of an HII region, for which interstellar dust filaments have been observed in the surrounding starfield and against the background of the nebulae. Systems of parallel dust filaments have been recognized in photographs of NGC7000 (Hale catalog number S-.19, Lick catalog number Nil, Yerkes catalog number N21, Dufay’1957) which show dust filaments oriented east to west, north to south, northeast to southwest, and southeast to northwest.

银河星团

银河星团类似于球状星团，因为它们是恒星密度增加的区域。但是，它们包含的恒星较少，密度较小且质量较小。由于恒星密度低，很难观察到投射到银河星团上的前景尘埃丝。银河星团Mil是一个相对丰富，紧凑的星团的例子，在星团上发现了星际尘埃丝。Mil位于Scutum星云内，先前显示该星云被尘埃丝遮盖了。在米尔的照片中已经观察到类似于在球状星团中观察到的暗线，细丝和条纹（Mallas and Kreimer 1978）。在一些照片中，可以看到穿过米尔的尘埃细丝延伸到周围的星空中。在米尔照片中看到的黑暗车道和灯丝也可以通过小型望远镜观察到。作者已经使用八英寸望远镜看到了这些功能。

梅西埃专辑（Mallas and Kreimer 1978）展示了梅西埃目录中所有星系团的照片。研究了这些照片以寻找前景尘埃细丝的证据。在以下照片中检测到星际尘埃细丝：NGC6603（M24的一部分），M26，M35及其伴随的NGC2158，M37 ；M46，M50和M93。

Galactic clusters resemble the globular star clusters because they are regions of increased star density. However, they contain fewer stars, are less dense, and less massive. Because of the low star density, it is difficult to observe foreground dust filaments projected onto galactic clusters. The galactic cluster Mil is an example of a relatively rich, compact cluster against which interstellar dust filaments have been observed. Mil is located within the Scutum star cloud which was previously shown to be obscured by dust filaments. Dark lanes, filaments, and striations similar to those observed in globular clusters have been observed in photographs of Mil (Mallas and Kreimer 1978). In some photographs, dust filaments crossing Mil can be seen extending into the surrounding star-field. The dark lanes and filaments seen in Mil photographs can also be observed through small telescopes. The author has seen these’features using an eight-inch telescope.

The Messier Album (Mallas and Kreimer 1978) presents photographs of all galactic clusters in Messier’s catalog. These photographs were studied for evidence of foreground dust filaments. Interstellar dust filaments were detected in photographs of: NGC6603 (part of M24), M26, M35 and its companion NGC2158, M37,; M46, M50 and M93.

行星状星云

很难确定地确定投射到行星状星云上的尘埃丝。然而，照片显示它们经常具有粉尘细丝存在的斑驳的粉尘外观特征。观察到尘埃丝对着哑铃形星云（M27），水瓶座的NGC6781，螺旋星云（NGC7293）和环形星云（M57）。

哑铃形星云是行星状星云最好的例子，由于尘埃细丝，星云呈斑点状。在Hale（产品目录编号106和S-26）和Lick（产品目录编号N40和X16）照片中容易识别出斑驳的灰尘外观。在这些照片中，M27的脸部有斑点。仔细检查后发现，出现斑点或斑点的原因是由于M27的表面上有灰尘通道，细丝和深色斑点。沙漏的西北端和西南端明显有明显的尘埃带。

由于前景尘埃细丝的存在而呈现出斑驳的外观的第二行星状星云是NGC6781。在黑尔天文台的照片（目录号S-39）中观察到了从东向西的细条纹和条纹。螺旋星云的照片（Hale目录号48）显示穿过发光环的细细平行尘埃细丝，在发光环的内部呈斑点状并显示出灰尘的迹象。LH Aller（1970）在对螺旋星云的描述中证实了这一点：“这颗巨大的附近行星的高度复杂的结构还表现为环的斑驳和条纹。” 最后，环形星云的黑尔天文台照片（目录编号66）表明存在平行于M57主轴排列的平行尘埃细丝。

It is difficult to identify, with certainty, dust filaments projected onto planetary nebulae. However, photographs show they frequently have a mottled dusty appearance characteristic of the presence of dust filaments. Dust filaments have been observed against the Dumbell Nebula (M27), NGC6781 in Aquarius, the Helix Nebula (NGC7293), and the Ring Nebula (M57).

The Dumbell Nebula is the best example of a planetary nebula having a mottled appearance due to dust filaments. The mottled dusty appearance is easily recognizable in the Hale (catalog numbers 106 and S-26) and Lick (catalog numbers N40 and X16) photographs. In these photographs, the face of M27 has a blotched appearance. Closer examination shows the blotched or mottled appearance is due to dust lanes, thin filaments, and dark patches on the face of M27. Prominent dust lanes are obvious at the northwestern and southwestern ends of the luminous hourglass.

A second planetary nebula having a mottled appearance due to the presence of foreground dust filaments is NGC6781. Thin streaks and striations oriented east to west have been observed in the Hale Observatory’s photograph (catalog number S-39). Photographs of the Helix Nebula (Hale catalog number 48) show thin parallel dust filaments crossing the luminous rings, which have a mottled appearance and exhibit evidence of dust, on the inside of the rings. L. H. Aller (1970) confirmed this in a description of the Helix Nebula as follows: “The highly complex structure of this large, nearby planetary is also shown by the mottlings and striations of the ring.” Finally, Hale Observatory photographs (catalog number 66) of the Ring Nebula suggest the presence of parallel dust filaments aligned parallel to the major axis of M57. The luminous ring also has a mottled dusty appearance in a Lick Observatory color photograph (catalog number X14) .

反射星云

在反射星云的照片中，前景尘埃细丝的存在通过在反射星云的投影中看到的长而细的条纹，条带和条纹来表明。褶ia（M15）是前景星尘细丝遮盖的反射星云的最佳示例。仔细检查照片（Hale目录号112、128和S-30； Lick目录号D4，Kitt Peak目录号01106和01107； Yerkes目录号N71和N72）显示出星云上的暗条纹，条带和条纹。le宿星云反射星云的一个有趣特征是存在细长而直的发光细丝。这些发光的灯丝可能是由le宿星团附近的星际尘埃丝引起的，这些星际尘埃丝被星团的明亮恒星照亮。在Rho Ophiuchi（Yerkes目录号MW的照片）中也观察到前景尘埃丝的证据

The presence of foreground dust filaments in photographs of reflection nebulae is indicated by long thin streaks, bands, and striations seen in projection against reflection nebulae. The pleiades (M15) is the best example of a reflection nebula obscured by foreground dust filaments. Careful examination of Pleiades photographs (Hale catalog number 112, 128 and S-30; Lick catalog number D4, Kitt Peak catalog numbers 01106 and 01107; and Yerkes catalog numbers N71 and N72) revealed dark streaks, bands, and striations superposed onto the nebulae. An interesting feature of the Pleiades reflection nebula is the presence of long thin and straight luminous filaments. These luminous filaments may be caused by interstellar dust filaments in the vicinity of the Pleiades cluster, which are illuminated by the bright stars of the cluster. Evidence of foreground-dust filaments has also been observed in photographs of Rho Ophiuchi (Yerkes catalog number MW

总结，结论和问题

本文已经证明，长而细的尘埃丝遍布星际介质。它们的特点是吸收率低，宽度窄，笔直和极长。发现它们排列在间隔很近的尘埃细丝系统中，这些尘埃细丝赋予模糊的背景以条纹和斑驳的外观。通常，两个或多个平行的尘埃细丝系统沿视线重叠。

先前无法识别的尘埃丝的存在将需要对星际介质的结构和动力学理论进行修订。它们的存在为星际介质的研究增添了新的维度，并为将尘埃细丝的观测用作星际空间物理学的探究提供了机会。前景的尘埃丝存在于针对球状星团，星系，HII区域的投影中，反射星云和行星状星云将需要修改这些物体的外观解释，因为这些物体中显然存在的许多尘埃必须是前景尘埃丝。

星际尘埃丝的存在对恒星形成理论具有重要意义，因为无限长的气瓶不会因重力坍塌而变得不稳定（Kaplan and Pikelner 1970）。如果这是正确的，那么恒星就不可能由星际尘埃丝形成。这给我们留下了一个问题：灰尘丝是如何产生的？它们在恒星形成中发挥作用吗？它们在星际介质的结构和动力学中扮演什么角色？

This paper has demonstrated that long, thin and straight dust filaments populate the interstellar medium. They are characterize by low absorption, narrow width, straightness, and extreme length. They are found to be lined up in systems of closely spaced dust filaments which impart a striated and mottled appearance to obscured backgrounds. Frequently, two or more systems of parallel dust filaments are superposed along the line of sight.

The existence of previously unrecognized dust filaments will require revision of theories for the structure and dynamics of the interstellar medium. Their existence adds a new dimension to studies of the intersteller medium and provides the opportunity to use observations of dust filaments as probes of the physics of interstellar space. The presence of foreground dust filaments in projection against globular clusters, galaxies, HII regions,reflection nebulae, and planetary nebulae will require revision of how the appearance of these objects is interpreted, because much of the dust apparently within these objects must be foreground dust filaments.

The existence of interstellar dust filaments has significant implications for theories of star formation because infinitely long cylinders of gas cannot become unstable to gravitational collapse (Kaplan and Pikelner 1970). If this is correct, then stars cannot form out of interstellar dust filaments. This leaves us with the questions: How were the dust filaments created? Do they play a role in star formation? What role do they play in the structure and dynamics of the interstellar medium?

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参考资料

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Astronomy 1978a, November, p. 76

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Dickson, F. P. 1968, The Bowl of Night (Cambridge, Ma.: The MIT Press)

Dufay, J. 1957, Galactic Nebula and Interstellar Matter (London: Hutchinson’s)

Evans, D. S. 1968, Observation in Modern Astronomy (New York: American Elsevier)

参考（续）

Goldberg, L. 1966, Annual Review of Astronomy and Astrophysics, (Palo Alto: Annual Reviews, Inc.) v. 4

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Hubble, E. 1936, The Realm of the Nebulae (New Haven: Yale)

Kaplan, S. A. and Pikelner, S. B. 1970, The Interstellar Medium (Cambridge, Ma.: Harvard)

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