Astronomy of the Milky Way: The Observer’s Guide to the Southern Sky

By Mike Inglis

This second edition of Mike Inglis's classic guide to observing the Milky Way in the Southern Hemisphere updates all of the science about the target objects with new findings from the astrophysics field. In addition, the book boasts a larger format with entirely re-drawn maps. Newly laid out for ease of use with an increased number of images in color, it updates and improves the first edition to remain the most comprehensive text on the subject. 

One of the wonders of the universe we live in is the Milky Way, and this book provides a wonderful tour of its highlights for amateur astronomers observing below the equator. In its pages, Southern Hemisphere observers interested in viewing our own galaxy's finest features will find every constellation that the Milky Way passes through with detailed descriptions of the many objects that can be found therein, including stars, double and multiple stars, emission nebulae, planetary nebulae, dark nebulae and supernovae remnants,open and galactic clusters, and galaxies. 

The book also details the one thing that is often left out of observing guides - the amazing star clouds of the Milky Way itself. Accompanying the descriptive text there are many star charts and maps, as well as the latest images made by observatories around the world and in space along with those taken by amateur astronomers. This second edition's updated scientific material and an easy-to-use layout perfect for many nights of fruitful observation.

• Language: English
• Publisher: Springer
• Release date: Apr 5, 2018
• ISBN: 9783319729503

Book preview

© Springer International Publishing AG, part of Springer Nature 2018

Mike InglisAstronomy of the Milky WayThe Patrick Moore Practical Astronomy Serieshttps://doi.org/10.1007/978-3-319-72950-3_1

1. The Milky Way

Mike Inglis¹  

(1)

Patchogue, NY, USA

Mike Inglis

1.1 How to Use This Book

Most of us are familiar with the Milky Way. We may be lucky enough to live in a dark location and can see the misty band of light that stretches across the sky (see Fig. 1.1). Others may live in an urban location and so can only glimpse the Milky Way as a faint hazy patch that envelopes several constellations. But how many of us make a point of observing the Milky Way as a celestial object in its own right? Rather few, it seems, which is a pity as it holds a plethora of wonderful delights, ranging from deeply colored double- and multiple-star systems to immense glowing clouds of gas and mysterious dark nebulae that literally blacken the sky. It also holds quite a few star clusters that literally look like diamonds sprinkled on black velvet, not to mention the occasional neutron star, black hole and possible extrasolar planetary system! In fact, you could spend an entire career observing the Milky Way.

The Milky Way passes through many constellations; some are completely engulfed while others are barely brushed upon. Also, it passes through both the northern and southern parts of the celestial sphere, making it a truly universal object, allowing it to be observed from anywhere in the world (see Star Chart 1).

The object of the book is not to give an introduction to the astrophysics of the galaxy we live in – the Milky Way – there are many books listed in the appendices that can do that, but rather to introduce you to the many objects that can be observed that lie within the Milky Way. It may come as a surprise to you to know that you can observe the Milky Way on any clear night of the year, from any location on Earth. So one could be observing from, say, Australia or Scotland, it wouldn’t matter, as the Milky Way, or rather, particular parts of it, will be visible to you.

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Star Chart 1

The Milky Way in Galactic CoordinatesCompare this star chart that shows the Milky Way superimposed over the constellations, with the image of the Milky Way at the end of the book. Note that the contours of the Milky Way are approximate. (Chart courtesy of Richard Powell.)

We have covered the complete Milky Way in this book, and so that means that there will be areas of it, and thus constellations, that may be unobservable from where you live. For instance, the constellation of Crux is a familiar one to observers living in Australia and New Zealand, but completely unobservable to European observers. Likewise, Camelopardalis and parts of Cepheus may be familiar friends to northern European observers, but are hidden from view of our southern colleagues. What this does mean however is that this is a truly universal book that can be used by any astronomer anywhere in the world.

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Fig. 1.1

The Milky Way (Courtesy of the Lünd Observatory.)

Many of the objects mentioned will, of course, need some sort of optical equipment, but a significant number are naked-eye objects, which is appropriate, as the Milky Way itself is a naked-eye object and the biggest one at that! But there are also quite a considerable number that only require small telescopes or binoculars, and by small we mean, say, 6-cm to 10-cm aperture. There are also those objects that will require a somewhat larger aperture, say, 10-cm to 25-cm, and the majority of the faint objects are in this aperture range. But not to exclude those observers with large telescopes we have also mentioned a few objects where very large apertures will be needed. Thus there is something for all amateur astronomers to see.

But remember that the pre-eminent types of objects that are just perfect to view with binoculars, and are truly impressive, are the many rich and awe-inspiring star fields or star clouds. This is what makes the Milky Way so spectacular. On a clear evening, one can observe Cygnus or Vulpecula or Sagittarius or Centaurus, and literally be transported to other realms. The sights that fill the field of view cannot really be described, and once seen are never forgotten.

It goes without saying that a good star atlas is an essential part of every amateur astronomer’s arsenal, and fortunately there are many fine atlases to be had. A fine example of an atlas that is perfect for naked-eye observing is the redoubtable Norton’s Star Atlas. Armed with this and perhaps a pair of binoculars will give a lifetime of opportunity. For those that need a more-detailed atlas, there are two that warrant attention, SkyAtlas 2000.0 and Uranometria 2000. Both of these cover most, if not all, of the objects mentioned in the book, and will allow you to locate and find most of the fainter and not easily recognizable objects. It is also possible these days to have planetarium software on a computer, and these, too, are fine tools to have, many allowing detailed star charts to be printed.

An astute observer will notice that the boundary of the Milky Way that we have adopted may not be the same as that in, say, Norton’s, or an older star atlas. We have in fact taken the boundary to be that identified by the Dutch Astronomer Antonie Pannekoek, who measured the density of stars in the sky and ascribed a limiting factor to the star density that enabled a boundary to be placed on the visible Milky Way. We are of course completely immersed in the Milky Way and most stars, nebulae and clusters that we observe are in fact within the Milky Way.¹ Thus the misty band of light that we call the Milky Way is just a region of the sky where the number of stars is so large so as to make a distinct and visible impression.²

However, there is a downside to adopting this boundary, as many of the favorite objects are left out if they do not lie within the Milky Way. Examples of such passed-over showpieces are the Pleiades and the Andromeda Galaxy, to name just a few.

The layout of the book is straightforward. The constellations that lie within the Milky Way are more-or-less³ grouped in order of the month in which they transit at midnight. This means that the constellation will be at its highest point above your horizon at midnight. The reason for this is quite simple; if we were to describe in detail all the Milky Way constellations that can be seen at any one particular time of the year, not only would we be repeating a substantial amount of information but the book would probably be about 900 pages long! Thus, for January and February, we discuss the Milky Way in Monoceros and Canis Major, to name but a few. However, seasoned amateurs will know that there are other constellations besides these that are in the Milky Way that can be seen during these months, and this is perfectly true, but they do not transit at midnight during these months! The other constellations may be rising at midnight, or setting, or something in between, but they will not be at their best position for observation at midnight! It is just a convenient means of presenting the data in a reasonable manner. You can of course view other parts of the sky during these months, such as Cygnus, but it may not necessarily be at its optimum observing position. In fact, for the example given, it will be so low down as to be nearly unobservable. Nevertheless, it will be there for you to look at.⁴

For the sake of completeness, however, at the end of each chapter we have listed, for both northern and southern observers, those Milky Way constellations that are also visible but with the above caveat in mind! Armed with this knowledge, you can go out and observe quite a large proportion of the Milky Way on any clear night of the year, from anywhere in the world.

In addition, we do not structure each chapter in any formal way, but rather in a manner that seemed appropriate. For instance, in Orion, we start of by describing the many wonderful double and multiple stars that the constellation has, whereas in Cassiopeia, we begin with detailed descriptions of its many glorious star clusters.

Throughout the book are many simple star charts, and they are just that – simple! They are not meant to take the place of a star atlas but are rather a pointer in the right direction. Also, I have had the opportunity to include quite a few wonderful photographs and CCD images of many of the objects described. These were taken by gifted and talented astrophotographers and astro-CCD imagers and to include them in the book is a privilege. You may notice, by their conspicuous absence, there are no drawings of any of the objects in the book. The reason for this is simple. Not only can the author not draw but drawings or sketches, particularly of astronomical objects, are very personal constructs and more often than not do not resemble the generally recognized shape or form of an object. Rather they describe what you, the observer, can see at that particular moment. It is no exaggeration to say that one can take two observers, show them the same object through two identical telescopes at the same time, and ask them to draw it, and you will end up with two quite different and distinct drawings. Furthermore, as the astronomer David Ratledge says in his book on the Caldwell objects, how can one really sketch something in detail when you are using averted vision?

Finally, at the end of each chapter is a list of the main objects mentioned in the text, giving their positions in right ascension and declination. This will allow you to use a star atlas, the GOTO facility of your telescope or the setting circles on your telescope in order to locate and observe the objects. Also included where appropriate is the object’s magnitude, and for double stars, their separation and position angles.

We have tried to include not only the well-known Messier, Caldwell and NGC objects that we are all familiar with but also those that are perhaps less familiar to you. They may be faint and/or small, but they are all definitely worth observing. If we have left out an object that may be a particular favorite of yours, then we apologize, as we tried to include as much as we could.

So, enough of the words, but before we begin a year round voyage of the Milky Way, let’s discuss a topic that is central to the subject matter of this book, and that every astronomer should be aware of.

1.2 Star Charts

Throughout each section on any constellation are many simple star charts, and they are just that – simple! They are not meant to take the place of a detailed star chart, but rather act as pointers to the right direction. Many, if not most, astronomers have access to planetarium software on their phones, tablets, and desktop computers, and let’s not forget that most telescopes now come with huge databases and GOTO facilities, so detailed star charts, which go down to 10th magnitude with thousands of deep sky objects on them, are redundant in a book of this type. Just use the charts as a signpost to the locations of the objects, rather than detailed finder charts. They are not, and never were, intended for that purpose.

1.3 A Plea to the Faithful

We live in a world where science and especially astronomy is making great leaps forward in our knowledge and understanding of the universe. Every day there is a news article on some new discovery either from an Earthbound telescope or satellite in space, or a new image is published of some magnificent and mysterious object deep in outer space.

At the same time more and more people are becoming interested in amateur astronomy. Telescopes are getting cheaper, better, and packed with additional extras such as thousand-object databases and equatorial mounts. And of course, the Internet is a vast resource of information on everything astronomical.

But one thing is worrisome – the ever increasing plague that is light pollution and especially when it concerns the topic of this book – the Milky Way. How many of us can remember a time when we could go out into our gardens or a nearby park, and see the wonderful swathe of the Milky Way cut a path across the sky. Nowadays one needs to be deep in a sparsely populated rural landscape or high in the lonely mountains in order to see this wonder of nature.

We are told constantly that the resources and animals of the world we live in need to be conserved and protected. In the same vein, we should keep the seas clean, the landscapes natural and the atmosphere breathable. Yet, in all this, it seems that conservation of nature and the appreciation of our world stops when it gets dark. Surely, the most wonderful spectacle in all of nature is the night sky, blazing forth in all its glory. Yet the majority of the world seems unaware that we are losing this resource. In a recent study published in the Monthly Notices of The Royal Astronomical Journal, it stated about one fifth of the World population, more than two thirds of the US population and more than one half of the EU population have already lost naked eye visibility of the Milky Way….and about two thirds of the World population and 99% of the population in US (excluding Alaska and Hawaii) and EU live in areas where the night sky is above the threshold set for polluted status. ⁵ This is a truly appalling statistic! And if you think we are being overly dramatic, just think back to your own experience in this regard. How much of the night sky have you seen literally disappear in just a few years?

Will it be possible to take our children or grandchildren out into the garden and show them the Milky Way, and how splendid it looks hoping to inspire the awe and wonder that it should? If we do not try to curb the energy and wasteful spread of light pollution, this will not happen. But what can we do?

In order to try to come to an equitable balance between conservation and common sense, we need to be aware and appreciative to the wishes of the non-astronomer. It may be necessary to show them how beautiful and, more importantly, how special the night sky, and the Milky Way, really is. Fortunately, there are many conservation societies throughout the world that share this agenda, not forgetting the very important Dark Sky societies, specifically aimed at reducing light pollution, and we as astronomers must promote their aims and agendas.

The night sky and the Milky Way are truly wonders of the universe we reside in and are part of the place we call home, Earth. They have been companions with us since humans first looked up towards the stars many thousand and perhaps millions of years ago, and yet in just a few generations, we may lose them. We need, nay must, keep these wonders, not just for us but for all people of all time. So please, become aware that we are losing, slowly but surely, our access to the night sky. Join the conservation societies that actively promote safe and efficient nighttime lighting, and become an active member of the Dark Sky association. Show your family and friends how amazing the night sky is and how necessary it is that it remain visible.

As was once sung in a song, we are star stuff, and we as astronomers, and in fact all people, would do well to remember this.

Footnotes

1

There are a few objects that can be observed that are actually located outside of the Milky Way (and I don’t mean galaxies!).

2

The boundary used is also the one adopted by the International Astronomical Union.

3

There are exceptions to this, as described in the text.

4

I had quite a detailed correspondence with several amateur astronomers from the UK, Australia and the USA about how to present the data, and this method was the one that most of them preferred.

5

P. Cinzano, F. Falchi, C.D. Elvidge. Monthly Notices of the Royal Astronomical Society, 328, 689-707 (2001).

© Springer International Publishing AG, part of Springer Nature 2018

Mike InglisAstronomy of the Milky WayThe Patrick Moore Practical Astronomy Serieshttps://doi.org/10.1007/978-3-319-72950-3_2

2. The Milky Way: January – February

Mike Inglis¹  

(1)

Patchogue, NY, USA

Mike Inglis

Monoceros, Canis Minor, Hydra, Canis Major, Puppis, Lepus, Columba, Pyxis, Antlia, Vela.

R.A 6h ↔ 11h Dec. 12° ↔ –28°: Galactic Longitude¹ 200° – 290°: (Star Chart 2i , Fig.  2 )

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Star Chart 2i

The Milky Way – January to February

2.1 Monoceros

The Milky Way at the start of a new year runs diagonally through the constellation Monoceros and in fact the galactic equator runs more-or-less straight along this path (see Star Chart 2). In the early part of January the constellation transits and is at its best for both northern and southern hemisphere observers. When we look out at Monoceros, we are actually peering deep into the Orion Arm of the galaxy, in the opposite direction to the galactic center in Sagittarius. Many beginner observers are surprised to learn this, as the area is not ablaze with the star fields and dark dust clouds that one normally associates with the Milky Way. Indeed, at first glance the area seems quite empty and barren. However, this is a misconception, as there are several open clusters, nebulae and stars that warrant our attention.

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Star Chart 2

Monoceros

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Fig. 2

The southern Milky Way. Note the enormous Vela SNR on the right of the image. (Image courtesy of Matt BenDaniel; http://​starmatt.​com.)

Probably the most famous, and certainly one of the most photographed, objects [or, as in these days, CCD imaged] is the area surrounding the star cluster NGC 2244 (Caldwell 50), that lies about 2.5° east of Epsilon (ε) Monocerotis. The cluster itself contains about 100 stars and has a combined magnitude² of around 4.8, so that on a dark night, it will appear to the naked eye as a fuzzy star.

When observed through a small telescope, the field is filled with a sprinkling of stars set against the faint glow of the Milky Way. The brightest stars in the cluster are two giant stars; a blue-white O5 type star and a distinctly yellow K0 type star,³ known as 12 Monocerotis. ⁴ A larger telescope, of say, 15-cm aperture, will show dozens of stars with the brighter members forming nice paired arrangements. However, surrounding the cluster is an object that can, and should, impress the observer. It is the enormous cloud of glowing gas known as the Rosette Nebula, NGC