Stories of Astronomers and Their Stars

By David E. Falkner

This book recounts the stories of the astronomical pioneers who forever changed our views of the cosmos. The chapters delve into their fascinating lives over the centuries, showing how these pivotal minds built upon the work of their predecessors and unlocked the unique properties of specific stars.

From ancient astronomy to modern imaging and spectroscopy, each tale at once showcases the pace of scientific discovery and the shared passions that drove these starwatchers. Accompanying the stories are a plethora of constellation and finder charts, stellar coordinates and directions, and suggestions for viewing specific stars, all of which are visible to the naked eye or through a small telescope.

In addition, the histories on specific star names and designations are given, along with an overview of the most popular catalogues and online databases that readers can use for reference.

• Language: English
• Publisher: Springer
• Release date: Sep 2, 2021
• ISBN: 9783030803094

Book preview

Part I

The Night Sky

Since this book is about stars, it seems appropriate to begin by talking about the night sky. Unfortunately for many of us, light pollution has robbed our ability to see many of these stars. According to a 2019 National Geographic article, nearly 1/3 of the world’s population are unable to see the Milky Way from where they live, including this author (Drake 2019).

Along with the Sun, Moon, and planets, bright stars are our last lingering hope in an ever-brightening sky. The Sun is a star, of course, and it is discussed in this book. Most of the other stars should be visible to this book’s readers, though it may be necessary to venture away from the big city lights to see some of them.

Chapter 1 discusses the sky as a celestial sphere surrounding the Earth and the coordinate system used to navigate the sky. We will also talk about preparing for an observing session.

Chapters 2–5 discuss the night sky visible at four specific times of the year: the equinoxes and solstices. The star charts for each of these dates and times depict the night sky at 9 p.m. at two latitudes: 45° north and 45° south. For each location and time, there is a chart for the northern view and a chart for the southern view. The star chart projections provide for some overlap, so the four charts easily show all the constellations visible in the sky on that date, time, and location. A complete list of all the constellations along with any named stars they contain can be found in Appendix 1.

Since most of the world’s population is affected by some amount of light pollution, I tried not to overwhelm the charts with myriad fainter stars that probably would not be visible. If you need more detailed star charts, check out Part VII, which contains catalogs for stars and deep-sky objects.

Reference

Drake, N. Our nights are getting brighter, and Earth is paying the price. National Geographic. 2019. https://​www.​nationalgeograph​ic.​com/​science/​2019/​04/​nights-are-getting-brighter-earth-paying-the-price-light-pollution-dark-skies/​

© Springer Nature Switzerland AG 2021

D. E. FalknerStories of Astronomers and Their StarsThe Patrick Moore Practical Astronomy Serieshttps://doi.org/10.1007/978-3-030-80309-4_1

1. Observing the Night Sky and the Celestial Sphere

David E. Falkner¹  

(1)

Blaine, MN, USA

Most of the stars discussed in this book can be seen in the night sky with the unaided eye or a small telescope. It helps, however, to have some understanding of the night sky so you can find your way around and locate the star in question.

To ancient astronomers, the night sky was viewed as a sphere that surrounded the Earth. All the fixed stars were pinpricks of light on this celestial sphere. As such, stars were the same distance affixed to this celestial sphere, but no one knew how far that was. Having a celestial sphere enabled the astronomers to assign a coordinate system on the sphere so stars could be located in the same way that latitude and longitude can locate any place on Earth. The celestial equator is located above the Earth’s equator. The north and south celestial poles are located above the corresponding Earth poles.

Parallel lines corresponding to Earth’s latitude were projected onto the celestial sphere. These were called lines of declination, or just declination (dec).

Longitude on Earth consists of meridian lines running from the north pole to the south pole. The Greenwich meridian is the reference line, and longitude increases from 0 to 180 degrees east and west from that point. However, projecting this longitude system onto the celestial sphere did not work since the celestial sphere was constantly moving. The ancient astronomers noticed the sky revolved around the Earth about once every 24 h. So, using meridians from the north celestial pole (NCP ) to the south celestial pole (SCP ), they divided the sky into 24 h. They decided the zero-reference point would be where the path of the Sun, called the ecliptic , crossed the celestial equator on its way northward, a point in Aries called the vernal equinox . As one faces north, the hours increase as they move to the right around the celestial sphere, and so, the term right ascension (RA) was given to these meridian lines.

With this coordinate system in the sky, every fixed object could be located by its right ascension and declination.

As a point of note, each of the planets, the Moon, and the Sun seemed to move independently from the celestial sphere. The ancients believed each was attached to their own crystal spheres. Today, even though we know the sky is not a sphere around the Earth, it is still convenient to look at it that way, and we still use the celestial coordinate system to locate stars and other objects in the sky (Fig. 1.1).

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Fig. 1.1

Celestial sphere (Review of the Universe–Stars–Celestial Sphere , https://​universe-review.​ca/​F08-star01.​htm, accessed on March 27, 2021, Figure 08-01e)

Another way of locating objects on the celestial sphere is by using a coordinate system based on your current location. This is called the horizon or altitude–azimuth (abbreviated Alt-Az) coordinate system. In this coordinate system, the distance the object is above the horizon is its altitude and is measured in degrees from 0° at the horizon to 90° at the zenith (the point directly overhead). The object also must be located with respect to where on the horizon the altitude was measured, which is called its azimuth. Azimuth is measured as degrees along the horizon starting at due north and moving to the right: North is 0°, east is 90°, south is 180°, and west is 270°. Now the object can be located based on its altitude and azimuth. Instead of degrees of azimuth, many people find it easier to use compass directions. This way of identifying celestial objects is fine for a casual setting, keeping in mind that the Alt-Az method of locating objects only works for that location and time (Fig. 1.2).

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Fig. 1.2

Horizon or altitude–azimuth coordinate system (Review of the Universe–Stars–Celestial Sphere , https://​universe-review.​ca/​F08-star01.​htm, accessed on March 27, 2021, Figure 08-01g)

To help get oriented to the sky and aid in finding the stars discussed in the following parts of the book, the next four chapters will briefly introduce the reader to the night sky. Each chapter shows the night sky as visible at 9 PM near the March equinox, the June solstice, the September equinox, and the December solstice. The charts show the sky in both the Northern and Southern Hemispheres, and some of the major stars and constellations will be discussed.

Before venturing out to observe stars or other objects, it is a good idea to do some preparation. Decide ahead of time on what stars or objects you want to observe. Check star charts or planetarium programs to ensure the object will be in a part of the sky you can physically see during the time you will be observing. Do some simple research on the size and brightness of the objects and ensure you have the right equipment to observe them. Also, study the meteorological conditions for the time you plan to observe. Websites such as Clear Dark Sky or Clear Outside provide hour-by-hour forecasts for temperature , cloud cover, transparency (how clear the air is), seeing (how calm the air is), wind, and humidity. These factors not only affect your success at finding and viewing an object but are also key for how to protect your equipment and charts and how to dress. High humidity may mean you will need dew protection to keep your optics from fogging up. Dew can also settle on any unprotected electronics you may be using, such as a computer or tablet, as well as any charts. If the temperature drops to around freezing, then frost could form on these same items.

Your ability to dress for the weather conditions can mean the difference between observing long hours in comfort and feeling miserable while observing. You do not move around much when observing, so you are not generating heat for your body. Dress for temperatures from 20 to 30 degrees colder than forecasted, especially if it will be humid or breezy. Wear waterproof shoes or boots so your feet will stay dry. Bring a hat that will cover your ears. If possible, bring hand warmers and toe warmers as the extremities are the first to feel the cold. It may seem like overkill, but you can always peel off a layer if you get too warm. Remember: It is easier to stay warm than it is to get warm.

I encourage you to venture out and observe the stars that are talked about in this book, perhaps with renewed interest and deeper understanding once you learn about the astronomers who first did the same.

© Springer Nature Switzerland AG 2021

D. E. FalknerStories of Astronomers and Their StarsThe Patrick Moore Practical Astronomy Serieshttps://doi.org/10.1007/978-3-030-80309-4_2

2. The Spring/Fall Sky

David E. Falkner¹  

(1)

Blaine, MN, USA

The star charts in this chapter depict the evening sky on March 20, which is near the equinox. The charts contain sufficient stars to determine constellations without overwhelming the charts with all the stars visible from a dark location. The stars visible from a given location will depend on the amount of light pollution in the area. Remember the Moon can also be a huge light polluter and you can expect fewer stars to be seen under the full Moon versus no Moon. I will discuss the view from each hemisphere separately.

There are four charts in this chapter. Figures 2.1 and 2.2 depict the night sky looking north and looking south, respectively, from an imaginary observatory located at 45° north latitude. Likewise, Figs. 2.3 and 2.4 have north and south views of the sky from an imaginary observatory at 45° south latitude. Depending on your location, you may need to shift the view a bit, but between all four figures, all the constellations discussed in this chapter will be visible.

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Fig. 2.1

Star chart of the northern sky from 45° north latitude on March 20

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Fig. 2.2

Star chart of the southern sky from 45° north latitude on March 20

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Fig. 2.3

Path of the north celestial pole as a result of the Earth’s precession (Public Domain/Wikimedia Commons—Tauʻolunga, June 2006)

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Fig. 2.4

Star chart of the northern sky from 45° south latitude on March 20

These next four chapters focus on constellations and stars, but there are also references to asterisms. An asterism is a group of stars that depicts a familiar object but is not a constellation. For observers of the northern sky, the most famous asterism is the Big Dipper, also known as the Plough. Other notable naked-eye asterisms are the Teapot in Sagittarius, the Great Square of Pegasus, and the Winter Triangle. There are dozens, perhaps hundreds of asterisms. Some can be seen with the naked eye, but others may require binoculars or a telescope to view. Despite the large number of asterisms and their familiarity in amateur astronomy, they have no official designation by the International Astronomical Union (IAU).

The Northern Hemisphere

The stars and constellations worth reviewing are in the central part of the charts. Stars in the eastern and western quarters of the charts are better positioned at other times in the year and are found in those charts. Figures 2.1 and 2.2 show the stars in the northern sky.

Looking at Fig. 2.1, Polaris can be seen halfway from the horizon to the zenith, which provides a perspective on the star chart projection. Between Polaris and the horizon are the circumpolar constellations of Cassiopeia, the Queen; Cepheus, the King; and tiny Lacerta, the Lizard. They will be much easier to see in 6 months, so we will revisit those constellations in Chap. 4.

Polaris is the end star in the handle of the Little Dipper or Ursa Minor, the Lesser Bear. It can be found rather easily by locating the bright stars of the Big Dipper asterism and following the two stars at the end of the bowl (Merak and Dubhe). Following a line connecting Merak to Dubhe, continue to the first bright star. Also known as the North Star because of its position within a ½ degree of the north celestial pole, Polaris is the brightest in its immediate area of the sky.

Its location near the north celestial pole means that Polaris remains nearly stationary in the night sky providing a reliable means of determining true north. Its stationary position in the night sky has made it the subject of numerous references. In Hymn to the North Star , a song by Kate Harper and William Cullen Bryant, they refer to the star in its more traditional sense as a guide for mariners. Other references emphasize its singular location in the night sky. In her poem Later Life, Christina Rossetti compares Sirius and Polaris referring to the latter as

…one unchangeable upon a throne

Broods o’er the frozen heart of Earth alone

Content to reign the bright particular star

Of some who wander or of some who groan.

John Keats in his work Last Sonnet writes of the pole star:

Bright star! Would I were steadfast as thou art –

Not in the lone splendour hung aloft the night… [1].

There are other references to Polaris as a bright star which were probably figurative references to its stationary position in the night sky. It is not a stretch to believe that references to Polaris as a bright star and a beacon of the North may have prompted some to believe that Polaris is the brightest star in the sky. In 1978, singer/songwriter Gerry Rafferty had the hit song Right Down the Line with the lyrics:

You’ve been as constant as a Northern Star

The brightest light that shines

Such instances have perpetuated the misconception that the North Star is the brightest star in the night sky. In fact, Sirius is the brightest, with Polaris coming in a distant 49th place in brightness (see Appendix 2).

In the twenty-first century, we are fortunate to have a fairly prominent star so close to the north celestial pole (NCP). Yet, Polaris has not always been the pole star and will lose that distinction in the future. As the Earth spins on its axis, it also wobbles much like a top. This wobbling is called precession, and it causes the celestial sphere to move in a circular motion once every 25,772 years. Currently, Polaris lies about 0.5° from the NCP and will remain so into the twenty-second century. After its closest approach to the NCP in 2102, it will gradually move away and not return as the pole star another 25,777 years. Figure 2.3 shows the path of the NCP as a result of precession.

Directly above Ursa Minor is Ursa Major, the Great Bear very near the zenith. It contains the familiar seven-star asterism known by different names around the world, including the Big Dipper, the Plough, and the Wagon. Every star in the Big Dipper is named and is bright enough to make the list of stars brighter than magnitude 2.5 (see Appendix 2). The center star of the handle is named Mizar, with its faint companion Alcor. These stars are the subject of further study in Chaps. 11 and 15.

Starting between the two dippers, and then wrapping around Ursa Minor and meandering to the northeast, is Draco, the Dragon. This constellation will be better placed high in the sky in June.

Taking the three stars in the Big Dipper handle (Alioth, Mizar, and Alkaid), follow the curve to bright star Arcturus in the southeast. The pneumonic to remember is Arc to Arcturus. Arcturus is in the constellation Boötes, the Herdsman, which we will talk more about in Chap. 3. To the southeast of the Big Dipper handle is the small constellation Canes Venatici, the Hunting Dogs with its main star Cor Caroli. The globular cluster Messier 3 (M3) is found in Canes Venatici, and its stars are the subject of Chap. 19.

To the west of Ursa Major is the faint constellation Lynx, the Lynx. At the northern end of Lynx is the very faint constellation Camelopardalis, the Giraffe. The unusual name Camelopardalis originates from early European explorers in Africa. They had never seen a giraffe and thought the animal had the characteristics of both the camel and the leopard—hence the name Camelopardalis. Both Lynx and Camelopardalis have faint stars and will be tough to find in the light-polluted skies of large cities and their suburbs.

Northwest of Lynx is Auriga, the Charioteer, with its bright star Capella. At a declination of nearly +46°, Capella is almost circumpolar at latitude 45°. As a result, it is visible most of the year. West and a little north of Lynx are the stars Castor and Pollux, the two brightest stars in the constellation Gemini, the Twins.

Looking south, we see the sky as depicted in Fig. 2.2. High in the sky is the Sickle or backward question mark of Leo, the Lion, with bright Regulus at the southern end of the Sickle. The Sickle marks the head of Leo lying down in the sky and stretched toward the east, with Denebola marking its tail. Two other bright stars in Leo include Algieba embedded in the Sickle and Zosma marking the rear haunches of the Lion.

Directly north of Leo is Leo Minor, the Lesser Lion, another faint constellation that will be tough to find in light-polluted skies. Leo is one of the constellations of the zodiac and to its west are two more: Cancer, the Crab, and Gemini, the Twins. At the northern end of Gemini are the two bright stars that mark the twins, Castor and Pollux. The remainder of the constellation extends to the west and includes the stars Alhena and Tejat before encountering the setting Orion, the Hunter. Between Gemini and Leo lies the faint zodiac constellation of Cancer. This is another constellation hard to find in light-polluted skies.

Southwest of Cancer and Gemini is the small constellation of Canis Minor, the Lesser Dog with its bright star Procyon. Just south of Cancer is the start of Hydra, the Serpent, a lengthy yet faint constellation that extends to the southeast. Hydra will be better placed for viewing when we turn our attention to the Southern Hemisphere. Just east of Hydra’s brightest star, Alphard, is the very faint constellation Sextans, the Sextant.

Between Denebola in Leo and Arcturus in Boötes lies the faint constellation Coma Berenices, Berenices Hair. To the southeast of Leo lies the next constellation in the zodiac, Virgo, the Virgin with its bright star Spica. Another way to find Spica is by returning to the mnemonic for finding Arcturus. From there, continue following the Big Dipper handle’s curve to Spica—Arc to Arcturus and speed to Spica. Two other named stars in Virgo are Porrima and Vindemiatrix. Much of the Virgo cluster of galaxies can be found in the region of the sky bounded by Denebola, Vindemiatrix, and Porrima.

Southern Hemisphere

Moving to the Southern Hemisphere, where autumn is beginning, the view of the night sky from the southern observatory located at 45° south latitude is depicted in Figs. 2.4 and 2.5.

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Fig. 2.5

Star chart of the southern sky from 45° south latitude on March 20

Facing north about 30° above the horizon is Leo, the Lion lying on his back. The backward question mark is upside down with the star Regulus at the top. Between Leo and the horizon is the faint constellation Leo Minor, the Lesser Lion. Flanking Leo are two more constellations of the zodiac. Faint Cancer, the Crab, lies to the northwest. To the east beyond Denebola, the Lion’s tail, lies Virgo, the Virgin, extending to the east. Along with Virgo’s bright star Spica are the less prominent stars Porrima and Vindemiatrix.

Above these three constellations of the zodiac is the long but faint constellation of Hydra, the Serpent. Between its brightest stars, Alphard and Regulus, lies the faint constellation Sextans, the Sextant. The constellations of Crater, the Cup, and Corvus, the Crow, lie between Hydra and Virgo. Corvus has two named stars: Glenah and Algorab. To the south of Hydra and very near the zenith is the faint constellation Antlia, the Air Pump.

There are several bright stars in the western sky, but they will be better located in the December sky.

The view to the south is riddled with constellations, many of which are faint and will be difficult to see in light-polluted skies. There are several constellations near the southern horizon that will be better placed in the sky for viewing in September. Due south and on the horizon is Grus, the Crane. Staying on the horizon and working west, we find Phoenix, the fabled bird that rises from the ashes, with its main star Ankaa. Looking southwest is the diminutive constellation Fornax, the Furnace. Meandering above Phoenix and Fornax is Eridanus, the River, with the bright star Achernar marking the end of the river, and farther west the star Acamar.

Moving eastward from Grus just above the horizon is the faint constellation Indus, the Indian. Looking southeast, the faint constellations of Telescopium, the Telescope, and Corona Australis, the Southern Crown, are on the rise, along with the Sagittarian asterism, the Teapot, which is right on the southeastern horizon. Above Telescopium is the constellation Ara, the Altar. The tail of Scorpius, the Scorpion, is east of Ara, while the diminutive constellation Norma, the Level, lies to the northeast.

North of Grus and west of Indus lies Tucana, the Toucan, while directly north of Indus lies Pavo, the Peacock, with the main star named for the colorful bird. North of Eridanus is the faint constellation Horologium, the Clock, and farther west Caelum, the Chisel. Lying north of the star Achernar at the end of Eridanus is Hydrus, the Little Serpent.

About midway between the southern horizon and the zenith near the south celestial pole lies the faint constellation Octans, the Octant. Moving northeast of Octans, the constellations in order are Apus, the Exotic Bird; Triangulum Australe, the Southern Triangle with its named star Atria; and Circinus, the Compasses. Just north of Octans heading toward the zenith is Chamaeleon, the Chameleon, and then Musca, the Fly.

The bright star Alpha Centauri, also known as Rigil Kentaurus, lies directly north of Circinus and marks the southern point of the constellation Centaurus, the Centaur. To the east of Centaurus and north of Norma is Lupus, the Wolf. Above Musca and west of Centaurus lies Crux, the Southern Cross near the zenith. Although it is small, Crux has four bright stars marking the four points of the cross, three of which are named. Gacrux marks the top of the cross, while Acrux marks its foot. Mimosa marks the tip of the left arm, while the tip of the right arm only has the designation of δ Crux. To the west of Crux lies the four constellations that originally formed the Ship Argo . Carina, the Keel, contains the very bright star Canopus and two other named stars, Aspidiske and Avior. Vela, the Sails, has the named stars Markeb and Suhail. Puppis, the Poop Deck, has the named stars Naos and Tureis, while Pyxis, the Mariner’s Compass, has no named stars.

To the southwest of Carina lies Volans, the Flying Fish. Between Volans and Hydrus lies the nondescript constellation