A Short Commentary on David H.Levy’s, “The Quest for Comets.”

 

 

 

 

 

 

 

 

 

 

 

 

 

 

For as long as I can remember, I’ve been a fan of David H. Levy. Over the years, I’ve bought and read arguably all of his books and magazine articles. The enthusiasm he portrays in his writings is positively infectious. As soon as you read a few lines of his work, he reels you in with first rate story telling. His modesty too shines through, in the equipment he used through much of his life, and in the way he maintained this humility in the aftermath of fame and notoriety.

A native of Montreal, Quebec, Canada, David’s early love of the night sky, and in particular, comet hunting, has landed him the enviable position of being one the most prolific comet discoverers in all of human history, with a tally of no less than 22 to his name. Night after night, when others grew tired, bored or preoccupied with worldly pursuits, David took the covers off his telescopes and pointed them skywards in search of new treasure. Today he and his wife Wendee live in Vail, Arizona, where he continues the love of his life; hunting for comets. In later life, David took degrees in English literature and was awarded a PhD. in early 2010 from the Hebrew University of Jerusalem, for a thesis entitled; The Sky in Early Modern English Literature: A Study of Allusions to Celestial Events in Elizabethan and Jacobean Writing, 1572–1620.

HST image of the dark impact sites in the southern hemisphere of Jupiter which occurred in July 1994. Image credit: Wiki Commons.

Although he has written no less than 34 books, it is arguably his title, The Quest for Comets, that brought Levy so much attention, both in North America and around the world, for in it, he describes amongst many other things, the discovery of Comet Shoemaker Levy 9, the fragments of which collided with the Giant Planet, Jupiter, in July 16 through 24 1994. I remember the event vividly, as I was then a final year graduate student presenting a paper at an international science symposium in Toronto, Ontario. With no telescopic equipment available to me, the best I could do was to sit and watch the live television feeds in sheer amazement, as one by one, the fragments of the comet, sundered into 21 pieces by the enormous tidal forces generated by the planet, smashed into its southern hemisphere, upwelling dark material from deep within its interior. This catastrophic event, marking the demise of one measly interloper from the Oort Cloud, represented the culmination of a 16 month monitoring program from the faithful night on March 24 1993, when it was first picked up on a photographic plate of the 40cm Schmidt telescope atop Mount Palomar, California. The Quest for Comets first appeared on the bookshelves 1995, less than a year after the famous collision event and, as usual, I devoured its every word from cover to cover!

Preface: While only a few pages in length, Dr. Levy provides the essence of his calling in life:

Setting up the telescope for comet hunting is pretty easy. All I really have to do is to make sure the cover is off. With the telescope’s slow, deliberate motion across a portion of the sky, comet hunting is not like a star party, where people line up to look at an object. When that happens, the sky is asked to be a servant, showing off Saturn, the moon, or some galaxy on cue. It’s the opposite with comet hunting. When I start a session, I have only a vague idea of what I may find in the next hour or so as I move the telescope forward for a few minutes across a region of sky, then backward through the next sector. Whether I find a star cluster or a galaxy, a red star or a bright double star, is really up to the sky, not me. The sky is master, my telescope the receiver, and I am the watchman.

viii

He later describes the momentous night he discovered his very first comet in Aquila, prosaically coined 1984t, the twentieth such object to be found during that year, and all done from his back yard in Arizona!

For Levy, hunting comets is;

…the slowest of all sports. It demands time; not time set by the hunter but by the sky itself. The moon acts as a referee brightening the sky and limiting the period available for searching. The game is especially competitive just after full moon, when a sky that has been too bright for hunting is suddenly thrust for 1 or 2 hours into darkness, and comet hunters all over the world rummage through it in a scramble for new comets.

ix to x.

Chapter 1: The Terrible Swift Sword: The Pleasures and Perils of a Comet

Covering pages 1 through 13.

In this opening chapter, Levy describes some of his earliest days of skygazing at Quebec’s Jarnac Pond, with his parents and grandparents. He tells of the excitement of witnessing a brilliant meteor shower from the August Perseids. He was just 14 years old during this memorable event and already in possession of a small telescope; most probably, ‘Echo’, a small, 9cm aperture, long focus Newtonian reflector. He acquired the instrument in 1960 and in another one of his books, The Sky: a User’s Guide (1991), Levy recounts the very first time he looked through a telescope, this telescope; the target, Saturn:

My first experience with a telescope back in 1960 was an awesome surprise. Two bright objects, Jupiter and Saturn, were well placed for this first look through Echo, my 9cm ‘Skyscope.’ I remember not being too impressed with the first night’s look., seeing only a doughnut shaped light where a planet should be. I learned the most important thing about telescope’s that night, that they need to be focused. The next night also was clear, and with the telescope my parents and I were able to adjust the size of the doughnut by pushing the eyepiece in and out. As the doughnut got smaller the image settled into an oval ball, not unlike what Galileo had seen. Then we saw what had always eluded the great seventeenth century observer; the image settled on a ball surrounded by an exquisite set of rings.

I was stunned……

pp 107

Small can be good, a valid point Levy picks up on when he discusses the comet first ‘discovered’ by Lewis Swift on July 15 1862, the body we now know as Comet Swift Tuttle. Truth be told, it was seen by several others, both near home and abroad, and at about the same time. Swift used a 4 inch refractor to pull it out of the sky. Surprising? Not really! Though there are arguably better choices available today, back then a 4 inch refractor would have made a formidable light bucket; drinking up many photons from those darker 19th century skies. Levy then unveils the scientific and historical interconnections that wove the conceptual fabric we understand as Comet Swift Tuttle in the modern era: a dirty snowball of rubble,mixed with a cocktail of ices, particularly water.

Chapter 2: When Beggars Die

Covering pages 15 through 22.

In this chapter Levy brings much of the ideas about comets entertained by ancient, pre scientific cultures including the Chinese, Chaldean, and Greco Roman writers. As part of the ‘heavenly host,’ comets, like the fixed and ‘wandering’ stars, were part of the divine realm. Many ancient cultures considered divine beings to live in remote places where human habitation wasn’t possible. Because they moved, this was an unmistakable sign to the ancient mindset that they were alive and that their light was the shining glory of life itself. But because cometary bodies appeared only occasionally, it was easy to associate their appearance in the night sky with portents of good or evil. Levy gives mention to a passage in the First Book of Chronicles from the Bible in which David might have been describing a comet in the sky;

David looked up and saw the angel of the Lord standing between heaven and earth, with a drawn sword in his hand extended over Jerusalem. Then David and the elders, clothed in sackcloth, fell facedown.

1 Chronicles 21:16

Intriguingly, there was a comet in 971 BC which fits well with the reign of David, according to the best Biblical scholarship. Levy claims this allusion to a ‘comet’ was a portent of an ‘ill advised census’. The first line of chapter 21 provides the reason;

Satan rose up against Israel and incited David to take a census of Israel.

1 Chronicles 21:1

Chapter 3: Taming the Shrew

Covering pages 23 through 36

In this chapter, Levy lays the historical foundations of how comets were gradually accepted as bona fide members of our solar system. Johannes Kepler, of planetary orbit fame, was probably the first person to observe a comet telescopically in the autumn of 1618, but throughout much of the seventeenth century, scientists were still very unsure about the nature of comets. Indeed, levy recounts much of the heated dispute between Galileo Galilei and the Jesuit astronomer, Horatio Grassi, who insisted that comets move in circular orbits following the system developed by Tycho Brahe. But it was obvious to Galileo that comets couldn’t possibly move in circular orbits because they would return with clockwork precision.

The breakthrough came at the end of seventeenth century when Sir Edmond Halley, using the best positional data provided by John Flamsteed, who was lucky enough to observe the motions of three bright comets in 1680, 1682 and 1683, to compute their orbits using the new physics of his good friend, Isaac Newton. Indeed, as Levy points out, Halley was the first to show that the comets that appeared in 1531, 1607 and 1682 were one and the same and that the same body would return to grace the skies at the end of 1758. Sadly, Halley did not live long enough to see it but it was picked up in December of 1758, to the delight of mathematical astronomers around the world.

Since this time, more and more comets have been shown to be periodic; some long and some, like comet Encke, with very short periods (of the order of a few years). Levy pays tribute to the great ‘celestial mechanicians’ of the 20th century, including Andrew C.D. Crommelin and the late Brian Marsden (whom this author had the pleasure of having dinner with at European Astrofest, in Kensington, London).

Chapter 4: Comet or Planet?

Covering pages 37 through 45

Levy spends this chapter summarising the monumental contributions of the Herschels to astronomy in general, and comets in particular. Sir William’s most famous discovery; the planet Uranus; began life as ‘probable comet’ before the mathematician, Anders Lexell, showed in August 1781 that its orbit was far too circular to be such a body. It was only after these calculations were made could Herschel safely conclude that his discovery on the faithful evening of March 13 of the same year was actually a new world orbiting beyond Saturn. Arguably the most proficient of comet hunters in the Herschel family was Sir William’s remarkable younger sister, Caroline (discussed more fully in a previous chapter of the book), who, with a neat little 6 inch aperture speculum reflector discovered her own tally of eight comets over the entirety of her long and extraordinary life.

The great younger sister of Sir William Herschel, Caroline Herschel (1750 –1848). Image credit: Wiki Commons.

Chapter 5: The Sport Begins

Covering pages 47 through 62.

No comet hunter worth his/her salt, could ever underestimate the groundbreaking work of the Frenchman, Charles Messier, who took the time to paintstakingly catalogue a large list of so called comet masqueraders; nebulae, bright and faint, open and globular clusters, supernova remnants and the most prominent planetary nebulae that were likely to fool many a tyro into thinking they had discovered a new comet. Indeed, as Levy explains, some 98 per cent of all false comet discoveries are attributed to mis–identifying a Messier Object!

Messier’s famous list of deep sky objects is arguably the first list of celestial real estate every dedicated amateur astronomer observes, especially if you’re a would–be comet hunter. Levy informs us that he learned to recognise these objects beginning in 1962 with his 9cm ‘Echo’ reflector, but finished his Messier list in 1967 with the help of a larger instrument;

In 1962 I began my own Messier hunt with a single observation of the Pleiades, M45. (Why Messier included this big, bright, cluster, which does not look at all like a comet, is a bit of a mystery.) In spring 1967, using a larger telescope that I had in 1962, I finished my list while observing from my grandfather’s cottage at Jarnac Pond, Quebec.

pp 52

The ‘larger telescope’ Levy is referring to is most probably a 8” Cave Newtonian reflector (affectionately named ‘Pegasus’), which he mentioned in an online article for Sky & Telescope entitled, Why Name a Telescope?

In the late summer of 1964, fellow amateur David Zackon lent me his 8-inch Cave Newtonian while he was away at school. Eventually my parents agreed to buy the telescope from him for $400, and it is now named Pegasus. It has some of the finest optics of any telescope I own.

As anyone who knows about telescopes will tell you; the move from a 9cm to a 20cm aperture telescope is an enormous one, so Levy would have been greatly impressed at the increase in light grasp and resolution. Indeed, with the exception of a few catadioptric telescopes much later in his career, Levy made use of Newtonian reflectors almost exclusively in his solitary comet searches. He held these telescopes in very high esteem as evidenced by a remark he makes in his other book, The Sky: A User’s Guide:

It is true that such reflectors are considerably less expensive than are refractors of the same size. This does not mean that they are not as good; in fact, Newtonian reflectors are more widely used by experienced observers than any other type. Since all wavelengths of light reflect to the same focus, and since light simply bounces off a mirror rather than passes through it, special glass is not necessary.

pp 57

In this regard, this author wholeheartedly agrees. For purely visual use, and in apertures over 4 or 5 inches, refractors are a monumental waste of resources. Levy clearly knew this all too well. Indeed it could be argued that the obsession with refractors, as exhibited on contemporary telescope forums, has more in common with pornography than with amateur astronomy!

The prolific French comet hunter Jean Louis Pons (1761 – 1831). Image credit: Wiki Commons.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

On pages 52 through 55, Levy recounts some aspects of the life of one of his comet hunting heroes from yesteryear; Jean Louis Pons (1761–1831). Emerging from a peasant family, Pons was given a job as caretaker at Marseilles Observatory, France, but soon he was making his own observations. Using a rich field telescope of his own design; the so called Grand Chercheur“(Great Seeker); Pons went on to discover at least 26 comets (indeed he may have discovered a total of 37 comets according to some sources) making him, after Carolyn Shoemaker, the greatest comet discoverer of all time. Levy  spins an amusing yarn concerning Pons and the then Director of Seeberg Observatory, a one Baron von Zach. Experiencing a prolonged hiatus in his comet discoveries, Pons asked von Zach if there were anything he could do to improve his lot. Von Zach obliged him:

Search when there are lots of sunspots on the sun, the German astronomer suggested as a practical joke. Half expecting that Pons would make a fool of himself and redesign his program to search the night sky when the sun sported large spots, von Zach was very surprised to get a letter from Pons with profuse thanks. Large spots indeed formed on the sun, and soon afterward he dutifully found a new comet. To this day no correlation between comets and sunspots has been found.

pp 53

The late 19th century, so Levy reliably informs us, presented a golden age in comet hunting, doubtless stoked by the emerging culture of awarding medals of achievement (often accompanied by a cash prize). Indeed, it is arguably true that such a culture led directly to the careers of other celebrated comet hunters, including Edward Emerson Barnard(1857–1923) and the Scots born, William R. Brooks (1844–1921).The decade beginning 1880 witnssed a veritable parade of bright comets entering the shallows of the solar system. Indeed, we have yet to witness a period like this in our own time, but with comets, everything can change in a matter of days or weeks.

Chapter 6: A Different Drummer

Covering pages 63 through 76.

No great observer exists in a vacuum. Rather, they stand on the shoulders of other observers who came before them. In this capacity, Levy continues to pay homage to the great comet observers of the late 19th and early twentieth centuries. Coming from all walks of life, and doing all manner of jobs by day, by night they were united in their love of the night sky and their diligence to carry out long hours of searching in order to find the next icy comet to grace our skies. Here you will find excerpts from the lives of the Australian comet hunter, John Tebbutt (1834-1916), who used a variety of small equatorially mounted refractors in a simple wooden observatory of his own fashioning to scan the dark skies of Windsor, New South Wales. Retiring in 1904, Tebbutt stepped down from active searching  but found two comets (amongst many other things); one in 1861, the other in 1881.

From there, Levy pays his respects to the great British observer, William F Denning (1848 –1931), whom we have met elsewhere in the book, who searched the skies for comets from his home in Bristol, England, using a 10 inch f/7 With Browning reflector. In particular, Levy retells the amusing story of how Denning lost out on the discovery Comet 1881 IV on the night of July 11 of the same year, because he felt inclined to go for a nap! The honour of this comet find went to John Schaeberle of Ann Arbor, Michigan, who swept it up three days later on the evening of July 14. Still, Denning bagged several comets of his own over his long telescopic career.

Continuing on, Levy mentions the contributions of the Americans, John Mellish and Leslie Copus Peltier, as well as the Japanese comet hunters, Minoru Honda (1913–1990), discoverer of a dozen comets between 1940 and 1968, Kauro Ikeya (born 1943) and Tsutomu Seki (born 1930), who will always be remembered for their diligent searches for comets. Arguably one of the most endearing of all comet hunters which Levy gives mentions to is the Englishman, William Reid, who moved to South Africa in search of better skies. Discovering a total of eight comets, Reid’s modesty and generosity to his fellow amateurs was exemplary:

At the turn of the century, William Reid, another British amateur astronomer, moved to South Africa, where he discovered Comet Reid 1918 II in June 1918. Within the next 8 years, he found an additional seven comets. Not only did Reid dislike calling attention to himself, but he was also notably generous to his fellow comet hunters. As the story goes, he once found a comet (probably 1926 III), but before he reported it, he heard that G.E. Ensor, an acquaintance, had independently picked it up as well. Realizing that his competitor had never discovered a comet and feeling that he had enough comets to his credit already, Reid declined to report it himself. Thus the comet Reid is known as Comet Ensor 1926 III.

pp 67.

Fred Lawrence Whipple (1906–2004), seen here as a graduate student in 1927, who went on to become one of the founding fathers of modern comet science. Image credit: Wiki Commons.

 

 

 

 

 

 

 

 

 

 

 

 

In this chapter also, Levy also pays his respects to the great professional astronomer, Fred Lawrence Whipple (1906–2004), of Red Oak, Iowa, who spent most of his career at Harvard College Observatory, and was arguably the first to understand the physical nature of comets in essentially modern terms. Comets, Whipple claimed, are ‘Dirty Snowballs.’

Chapter 7: The Comet Cop

Covering pages 77 through 87.

Dr. Brian Marsden (1937–2010) , as I remember him.

In this chapter Levy mainly discusses the work of the late Brian Marsden (1937–2010), who after graduating from Cambridge University, took his doctorate at Yale and resided in the United States for the rest of his life. His area of expertise was celestial mechanics and served as the Director of the Central Bureau for Astronomical Telegrams (CBAT) from 1968 until 1999. Like every other avenue of human interest, there are plenty of crackpots in amateur astronomy and Levy recounts some of the ‘colourful’ characters Marsden had to deal with in his day to day job. Indeed, Marsden admitted that the vast majority of the cases dealt with at CBAT alleging a new comet find were either genuinely mistaken or pure hoaxes.  Levy writes:

In his quarter century at the helm of the CBAT, Marsden has received few phone calls in the middle of the night, “and never a useful one,” he added. About 90 per cent of reports of new comets turn out to be false; mostly ghost images of bright stars or planets just outside the telescope field, photographic flaws, or two different galaxies thought to be a moving comet. Occasionally there are outright hoaxes. Once when someone from Columbus, Ohio, reported a comet, Marsden replied that he would wait for confirmation before issuing a circular. Some days later, a telegram arrived under the guise of the Tokyo Observatory with the required confirmation. However the telegram’s return address was not Tokyo but Columbus, Ohio! Another time an observer tried to claim credit for a comet that had already been announced; he alleged to have observed it the previous night. This time Marsden noted that the would be discoverer could not have observed the comet, since it had been raining all that night at the site

pp 83.

Levy goes on to describe another unscrupulous individual who, once confronted about his prevarications, turned nasty and despatched threatening hate mail to the CBAT staff, before committing suicide!

And they’ve not gone away! This author is well aware of a few deluded souls who would go to almost any length to perpetuate a lie within the hobby!

Chapter 8: Comet Tales

Covering pages 89 through 109.

In this, arguably one of my favourite chapters of the book, Levy describes the kind of dedication one needs to find comets. As you can imagine, it’s not for the faint hearted. It typically requires hundreds or thousands of hours searching the sky at dusk or just before dawn. Here, Levy discloses that, through no fault of his own, his comet searching programs decreased in intensity as he entered college in the late 1970s and by the early 80s, having clocked up a very respectable, 900 hours at the eyepiece, he still hadn’t found a new comet. But he took solace from the efforts of his fellow comet hunters, most especially the Californian amateur, Don Macholz, who had amassed 1700 hours of telescope time before he bagged his first comet and another 1700 hours of searching finally landed his second find. Levy wisely figured that the best way to increase his chances of finding a comet of his very own was to move to a location where more clear skies were available to him. So in 1979, Levy set up home in Tucson, Arizona;

Certain times of the month are crucial for comet hunting; right after a full moon and around the new moon. If I wanted a better statistical chance of discovering comets, I needed a site with a greater likelihood of recurrent clear nights during these periods. Therefore in 1979 I decided to move to Tucson, Arizona, where some 300 nights a year are clear enough to stalk comets. I chose the community of Corona de Tucson, some 20 miles east of twon, where the sky is pretty dark. I built a small observatory out of a 9 x 10 foot garden shed, designing the structure such that the roof slid off to reveal the open sky. Within a year I had a 16 inch diameter reflecting telescope, and then I resumed comet hunting in a big way.

pp 91

By this time, Levy had also acquired his beloved travel telescope, ‘Minerva,’ a 6 inch f/4 Newtonian reflector. What an excellent choice for travelling optics! After extensive testing and the slight modification of 5.1 inch (130mm) f/5 reflector, which outperformed much more expensive 90mm and 100mm refractors, this author settled on a similar sized telescope for serious astronomy away from home. You can read all about that telescope, known affectionately as ‘Plotina’ here.

Levy named his 16 inch f/5 Dobsonian, ‘Miranda.’

In an amusing addition to this chapter, Levy ‘discovered’ a comet while conducting an interview with Clyde W. Tombaugh, discoverer of the minor planet, Pluto. Examining the old photographic plates from the 13 inch astrograph at Lowell Observatory, he came across a plate which recorded an unknown comet. Tombaugh (discussed elsewhere in the book) himself had found another one in his own plate searches but despite trying to follow them up, there was no way that either of these objects could be characterised enough to delineate an orbit; there was simply not enough data. Still, finding comets from digital images, either from large observatory class telescopes, or space based satellite data, has become very popular in recent years.

1987 was a bumper year for Levy, when his diligent searches turned up not one, but two comets, the first on January 5, 1987 and the other, on October 11, both of which were swept up with Miranda. The January 5 find was especially auspicious, since David had made two New Year’s resolutions; the first to finish a book he had been writing and the second, to find a new comet, and both had been fulfilled in the first week of the new year!

The move to Arizona clearly paid off for Levy, for in the next three years, he discovered as many new comets! To provide a sense of what it is like to discover a comet, best to listen to the master himself. This is an excerpt from the book regarding the discovery of a periodic comet, which he found while hunting in the constellation of Aries in June 1991;

The telescope’s field of view was about 1 degree across, or two moon diameters, and full of faint stars, I found nothing fuzzy or unusual in that field, so after a few seconds, I moved the telescope eastward and checked the adjacent field of view. After a minute of slow sweeping in this way, I moved the telescope again. Now a bright fuzzy patch of light entered the field of view, and for a second, a now familiar “red alert” went off in my brain. But this fuzzy patch didn’t fool me for long: By its elongated shape and its position, I knew that this was a distant galaxy called Messier 74. This galaxy is a highwayman, guilty of stopping comet hunters dead in their tracks. More than 200 years ago, it duped Messier, who sketched its position and then checked back later to see if it had moved, as all comets do. When the object remained frozen in the sky, he added it to his catalog as he went on in search of slowly moving cometary prey.

I’ve encountered M74 so many times that I know it as an old friend. But the sky was brightening so there was no dawdling over M74 now. I nudged the telescope down the field and another and another, slowly moving toward the horizon. When it got low to see distant treetops, I turned the telescope southward and then started sweeping back upward along an adjacent track.  Another minute passed by, and then the mental alert went off again: There was another fuzzy spot.

For an instant I thought it was M74 again, since the galaxy was so close by. But wait a minute: This object was quite a bit brighter. With mounting tension I put in a higher power eyepiece and looked more closely. While M74 had relatively sharp edges all around, this thing had a brighter center, then faded off so slowly that I could hardly tell where it ended and the sky began. Sharp edges are characteristic of a galaxy filled with stars; the gradual fading is a comet’s typical signature. This, I decided was a comet.

pp 102/3

This was the seventh comet discovered by David H. Levy from the comfort of his back yard! Cool or what! After the CBAT confirmed the new object, it was named Period Comet Levy 1991q.

But it wasn’t this comet that would bring world wide fame to Levy, so much as a comet he discovered back in March 19 1988 (Comet Levy 1988e). It was around this time that Levy first made the acquaintance of Carolyn and Eugene (Gene) Shoemaker (1928-1997), who had been using the 18 inch Schmidt camera atop Mount Palomar, California, to look for new asteroids and comets. The Shoemaker’s more ‘high tech’ approach to comet hunting had bagged them quite a few finds, but it was one in particular, Comet Shoemaker Holt 1988g, that intrigued everyone, Marsden included. Once the orbit computed for Levy 1988e was compared to that of 1988g, it turned out they were identical save for one significant difference; Comet Shoemaker Holt 1988g arrived at perihelion about three months after that of Comet Levy 1988e. Pondering these facts, Marsden advanced this explanation; 12,000 years ago, he suggested, these bodies were part of one greater comet that spliced into two pieces as it orbited the Sun. Slowly, over the ensuing millennia, the bodies drifted apart, one behind the other, as it were. To Levy, this was the stuff of dynamite!

Chapter 9: An Asteroid Hits the Earth

Covering pages 111 through 122

Meteor Crater, Arizona. Image credit: Wiki Commons.

In this chapter, Dr. Levy discusses his long time partners in comet hunting; Carolyn and Gene Shoemaker. With a Ph.D in geology from Caltech, Gene made his name in scientific circles by providing definitive scientific evidence that Meteor Crater, Arizona, was excavated as a result of a 50 metre nickel–iron rich asteroid colliding with the Earth some 50,000 years ago, during the Pleistocene epoch. Prior to Shoemaker’s work, some geologists had entertained the idea that the 1.2 kilometre–wide and 120–metre–deep impact crater might have been caused by vulcanism. By 1960 Shoemaker had uncovered sediments that had been turned upside down, as well as minerals like coesite and stishovite (rare forms of silica formed by high pressure shock waves) which could only have been formed by shock heating to temperatures far in excess of those generated by extant volcanoes. Carolyn (born 1929), married Gene in August 1951, and after a brief spell as an schoolteacher, quit her post in order to raise a family. Later she was to join her husband on Mount Palomar in the search for asteroids and comets.

Eugene Merle Shoemaker(1928-1997). Image credit: Wiki Commons.

 

 

 

 

 

 

 

 

 

 

 

 

What is particularly interesting about this chapter is the unusual curriculum followed by graduate students in the physical sciences (at least at Caltech). Gene was instructed to acquire proficiency in written and spoken French and German languages, so as to be able to competently assimilate the findings of European science. Such thoroughness is unheard of today!

Chapter 10: A Turn on the Road to the Moon

Covering pages 123 through 128

In this short chapter, Dr. Levy continues to chronicle Gene Shoemaker’s progression from geology to planetary science and his joining of the astrogeology department of the US Geological Survey, which based itself at Flagstaff, Arizona. From the late 1950s until the end of the 1960s, the United States was hurled into a Space Race. Shoemaker’s work establishing the origin of Meteor Crater as an impact event with an extraterrestrial body, naturally lent itself to a study of the extensive cratering record of the lunar surface. That the Moon’s craters are to a very large extent caused by impacts and not vulcanism is certainly not a new idea. Recall, for example, how this author discussed the experimental work of Sir Robert Hooke back in the 17th century, where he experimented with firing projectiles into soft clay to see how well they resembled lunar crater formations?  The 1960s witnessed new ways of studying crater ejecta as a means of establishing their relative age and Shoemaker was instrumental in developing this fledgling new field (and which remains a fundamental part of undergraduate training in planetary science today). What Dr. Shoemaker really wished for though, naturally enough, was to get his hands on bona fide lunar rocks, or at least get much higher resolution images of lunar crater fields. Alas, he would never have the physical fitness levels to make the astronaut grade but at least he could explore the lunar regolith vicariously through the adventures of the Ranger and Apollo missions.

Chapter 11: Exploring Craters; From Ranger to Apollo

Covering pages 129 through 145

Levy develops the themes he introduces in chapter 10, by discussing the interesting question of whether the Moon has suffered impact events in historical times. The chapter opens with a brief overview of the so called Canterbury Chronicle, where five monks recorded what appeared to be a impact with the lunar surface over 800 years ago. The event was recorded by the abbey’s chronicler, Gervase.In 1976 the geologist, Jack B. Hartung, proposed that this described the formation of the crater, Giordano Bruno.

Lunar crater Giordano Bruno. Image credit; NASA.

The collision of an asteroid or comet with the Moon would cause a plume of molten matter rising up from the surface, which is consistent with Gervase’s account. In addition, the location recorded jives well with the crater’s location, just beyond the lunar northeastern limb. The relative youth of the crater is also evidenced by its spectacular ray system: caused by a ‘rain’ of micrometeorites, which kicked up enough dust to  erode a ray system relatively quickly (in geological terms). So it is reasonable to hypothesise that Giordano Bruno was formed during the span of human history, perhaps in June 1178, when the Canterbury monks made their observation. However, there are problems with the formation of such a large crater in relatively recent times. For one thing, the impact creating the 22-kilometre-wide crater would have ejected enough debris to trigger a vigorous meteor storm on Earth lasting at least a week, and yet there are no accounts of such an event from the historical records of the extant European, Moorish or Chinese civilizations. Their absence from the astronomical records presents a major objection to the theory that Giordano Bruno was formed within the last millennium.

Though Dr. Levy never mentions it, another explanation is that the monks may have witnessed an exploding meteor moving directly along their line of sight and aligned with the Moon. Because meteors appear about 50 and 80 miles up in the atmosphere, the laws of geometric perspective suggest that only a relatively small region of Britain (in this case Canterbury) would have the perfect geometry to make it look like as though the Moon suffered an impact.

The rest of the chapter discusses the Ranger, Sureveyor and early Apollo space missions to the Moon. In particular, their findings showed that the Moon does indeed suffer impacts of many kilogram sized and smaller objects pretty much all the time.

Chapter 12: A Pretty Good Moon for you, Shoemaker!

Covering pages 147 to 154

In this chapter Levy describes the venerable 18 inch Schmidt telescope and the work it carried out to discover earth crossing asteroids and comets at Mount Palomar. He writes:

As Palomar’s first telescope, the 18ninch has a noble history. Astronomer Fritz Zwicky used it to photograph fields of distant galaxies, and in these galaxies he discovered many exploding stars called supernovae. The 18 inch telescope is a photographic telescope capable of taking pictures of large areas of sky at once; each film covers 8.75 degrees of sky, the equivalent of more than 17 full moons lined up. On a single film, the searcher could record a large nugget of sky. Here was an ideal telescope for searching for comets and asteroids.

pp 147

To photograph with the Schmidt camera, the operator would first punch 6 ¼-inch (15.5-cm) circles of unexposed film with a film cutter (the “cookie cutter”) in the telescope’s darkroom. Then, the film was carefully mounted inside a film holder that applied the appropriate spherical curvature to it in order to ensure that objects photographed would all be sharply focused all across the film. The tightly-closed holder would then be positioned inside the telescope tube through a small door on its side. After removal of the holder’s cap, the film was ready for exposure in an adjacent darkroom. Levy mentions that in the 1970s, the telescope used IIa D film but in 1983 the staff switched to socalled ‘hypersensitised’ Kodak 4415 technical pan (which film astrophotographers my well remember), which was a little slower than the latter, but was far less grainy, so reducing the number of potential false positives picked up.

Beginning in the early 1970s, Shoemaker hired another Caltech scientist, Eleanor Helin (1932–2009), to initiate a new program dedicated to finding as many Near Earth Objects (NEOs) as possible; mostly consisting of either Apollo or Amor asteroids having diameters between 1 and 2 kilometres. To find them, the telescope took two exposures in succession; the first lasting 20 minutes and the second, for  just10 minutes (the telescope operating at f/2). This would allow any NEO to betray itself as a trail of light. Later, the 48 inch Schmidt camera was occasionally used to search for objects beyond the sensitivity of the 18 inch instrument.

With the arrival of Voyager 1 at Jupiter in 1979, Gene Shoemaker would get involved with the imaging team to study the thousands of photographs of the giant planet and its retinue of large satellites it was sending back to Earth. Levy vividly recalls the excitement as more of more of the Jovian system was being televised live across the United States but even this didn’t totally deter Levy from doing what he did best; hunt for comets. Just as Voyager arrived at Neptune Levy writes:

 

Voyager’s encounter with Neptune took place a few days before one of the Shoemakers’ monthly observing runs at Palomar. Since her husband would be tied up at the JPL. Carolyn asked me to observe with her at the 18 inch telescope. It would be my first observing run at Palomar. As I prepared to leave for California, I wanted to see Voyager’s views of Neptune and its big moon Triton. Tuscon’s public broadcasting station was carrying Voyager’s images live, and it seemed like my TV set was connected directly to the spacecraft then speeding by Triton. What a night to remember, I thought. But it was also a clear night. In between vies of Triton’s crater scarred surface, I went outside to the backyard to do my thing; that is hunting for new comets. At 9 P.M. I opened my backyard observatory and aimed Miranda my 16 inch telescope on a patch of sky in the west. For half an hour I’d scan, then I would go inside to catch a few minutes of Voyager as it sped by Triton. Back out in the observatory, back in again.

It would have been simpler to just spend the evening in front  of the tube watching the most riveting broadcast since Armstrong’s 1969 walk on the Moon, but I was glad I didn’t. Just past 11:00 P.M. I nabbed my fifth comet, Okazaki-Levy-Rudenko, 1989r.

pp 154

Chapter 13: Eage Eyed Carolyn 30 Comets and Counting.

Covering pages 155 through 165

There is nothing glamorous about searching for comets. There’s the simple, low tech procedure of observer, alone with his/her telescope, sweeping the skies slowly for signs of a faint, icy interloper. And in more recent times, a telescope is mated to a photographic plate and a guided exposure is made with the hope that the developed plate will reveal something new. Both require patience, preparation and long hours at the telescope. Nights can be cold and long, especially in winter. Of course, both of these ways have now been superseded by fully automated surveys using highly sensitive CCD detectors, but it does not in any way diminish the great sense of achievement one feels in being the first person to see one of these wonders of creation.

In this chapter, Dr. Levy provides a very palpable sense of what it is like to do the routine work of searching for comets using the wonderful 18 inch Schmidt telescope. Throughout the 1980s, he joined Gene and Carolyn on Mount Palomar very month to carry on this routine but very important work. The photographic plates had to be carefully loaded, the great telescope pointed at the right part of the sky. The mount, though state of the art when it was built in the mid 1930s, had to be manually guided and the process repeated many times in the course of a night.

Carolyn Shoemaker at the 18 inch Schmidt telescope, Mount Palomar. Image credit: Wiki Commons.

For the first two decades of Shoemaker’s marriage, Carolyn was busy raising her family but as they grew and fled the proverbial nest, she found herself with more time on her hands, and after spending a few years as a florist, Carolyn joined her husband in his ongoing search for comets and asteroids and though she felt a little clumsy at first, she soon became adept at operating the telescope and carrying on the stereomicroscopic examination of new plates. But what she longed for most was to discover comets of her very own.  And her wish came true in September 1983, when she was the first to stumble on Comet Shoemaker 1983p. Levy writes:

Comet Shoemaker 1983p was the first of a procession of comets. By 1987 Carolyn had found eight, surpassing Caroline Herschel as the woman who found the most comets. “Passing Herschel’s record was a special goal for me, not because there was anything personal at all there, but because it was a landmark and special in a way to find more than any other woman had found so far,” she told me. With her fifteenth comet find just 2 years later, Carolyn surpassed William Bradfield’s 14 comets, her second goal.

pp 163

But Carolyn also deeply respected the old ways of looking;

“Visual comet hunting, she said, “ takes an awful lot of patience that I’m not sure I would have. It involves a lot of cold hours and a lot of looking before you find anything. What I do involves a different sort of persistence. But the stereomicroscope is a better tool than many amateur comet hunters have.”

pp 163.

Levy explains that Carolyn Shoemaker went on to discover a total of 30 comets as of 1995, but she found a couple more by 2002.

Chapter 14: Are We the Progeny of Comets?

Covering pages 167 through 180

Ever since comets have been shown to harbour substantial quantities of simple organic matter, some planetary scientists have been rather zealous in trying to establish that such matter might have led to the origin of life through purely naturalistic means. What Levy presents in this chapter is pretty much consonant with the world view promulgated by celebrated planetary scientists such as the late Dr. Carl Sagan, who in his popular writings dating from the late 1960s to the early 1990s, portrayed life as a “cosmic phenomenon,” no more unique to the Earth than planets are unique to our solar system. Demonstrating a rather poor understanding of just how weak the evolutionary paradigm is, Sagan was absolutely convinced that life was an inevitability given the right conditions. In the quarter century or so since the ‘Sagan era’, scientists have gained a much greater understanding of just how complex even the simplest lifeforms are and the sheer impossibility of such life emerging from a blind, stochastic process envisioned by the various chemical evolutionary models presented to date. In order to grapple with the details of Sagan’s fallacy, I would highly recommend that Dr. Levy carefully read two books which very effectively address these issues;

Rana, F. & Ross, H. Origins of Life: Biblical and Evolutionary Models Face Off, RTB Press (2014).*

Rana, F. Creating Life in the Lab, Baker Books, (2011).

The emerging scientific consensus as of 2017 is that;

  • There was no primordial soup at any time in the last 4.2 billion years.
  • There is no plausible mechanism for generating homochiral molecules on the primordial Earth
  • The earliest lifeforms were already complex and could not possibly have evolved.

 

Indeed, as Ross and Rana point out*;

Carl Sagan once compared Earth’s early oceans to a thin French consommé. In retrospect, his statement(unintentionally) insulted the French soup. Even the purest water on Earth today has a higher concentration of amino acids; by a factor of a hundred million, than could possibly have been deposited from outer space into earth’s oceans before life originated. In short, while extraterrestrial production of some prebiotic compounds does occur, the contribution of these materials to a prebiotic soup on Earth appears negligible. So does atmospheric synthesis of prebiotics.

pp 101

 

In short, the notion that we are just a ‘bag of chemicals’ is a gross simplification of what really goes on inside the cell. And since Dr. Levy is fond of quoting the odd verse from Holy Scripture, this author would like to issue a ‘Scriptural’ retort, as it were, to Sagan’s dated and naive view of living systems;

For thus says the Lord:

“You have sold yourselves for nothing,

And you shall be redeemed without money.”

                                                                                      Isaiah 52:3

 

Chapter 16: Could a Comet have Slain the Dinosaurs?

Covering pages 181 through 197

The fossil record, as incomplete as it is, testifies to a long and complicated history of life on Earth stretching back nearly four billion years. What this record attests to is that for long periods of time, life goes on with little or no change in either form or function but every now and then, an environment collapses causing whole ecosystems to go extinct. This catastrophism is then followed by the ‘sudden’ (at least in geological terms) appearance of new organisms eking out a living in new ecosystems. Thus, the story of life on Earth is one of long periods of stasis followed by sudden innovation and change.

In this chapter, Dr. Levy discusses the question of whether an asteroid or comet could have precipitated the extinction of arguably the most successful large animals (after humans) ever to have walked the face of the Earth. Accordingly, Levy mentions the famous KT boundary strata, where a global layer of iridium rich clay some 6mm thick corresponds to a time about 64 million years ago, when the dinosaurs were extirpated. He also discusses the likely smoking gun for this event as evidenced from the large (60 kilometre diameter) crater found under the waters of the Gulf of Mexico; the so called Chixulub Crater situated off the northern coast of Mexico’s Yucatan Peninsula. Following the traditions of his scientific contemporaries, Levy asks the question of whether impacts of comets and asteroids with the Earth can also drive the evolution of organisms?

As a long time sceptic of the evolutionary paradigm, this author would suggest to Dr. Levy that there is no mechanism yet identified that can transform one kind of animal into another, exactly as stated in the first Chapter 1 of the Book of Genesis. That is, macroevolution has not been demonstrated. Many individuals look at the history of life on Earth and observe that it appeared to have started out in simple, unicellular forms and progressed to more complex creatures with the march of time.  Accordingly, they attribute this ‘progression’ to a kind of evolutionary unfolding. But I would suggest that this is the wrong way to look at the data.

Certainly, the first lifeforms on Earth were microscopic, unicellular organisms. But what many people fail to recognise is that such organisms are also the hardiest. For example, bacterial species have been found to eke out a living in concentrated sulphuric acid and crude oil, or are observed to thrive in places where they are subjected to lethal doses of radiation. Still others can survive in boiling hot water or inside frozen ice deposits. Thus, the Creator of all living things placed these organisms on the primitive Earth to help clean up the hostile (read toxic) environment in which they found themselves in. Only after these chemical poisons were removed from the planet’s surface in large enough quantities, could more complex forms of life be introduced, which would not have survived in earlier epochs. Indeed, it is easily shown that the more complex the plant or animal, the more vulnerable it is to physiochemical change. In short, God created whole ecosystems that would work to create an environment in which human beings would eventually flourish, whilst also working to produce the deposits of fossil fuels and a rich array of minerals that would assist humanity in launching a global technical civilization. Once ecosystems could not efficiently maintain a stable physical environment, they were promptly replaced by new ecosystems which could better cope with the changing circumstances (for example, a steadily brightening Sun or changing concentrations of greenhouse gases etc). Thus, what the fossil record attests to is not evolution per se, but an elaborate sequence of events that removes and replaces lifeforms, so as to maintain the best possible conditions for people like the wonderful Dr. Levy to eventually live and work in!

The Creation accounts in Psalm 104 beautifully attest to this scheme of events.

All of life on Earth works in unison not only to make human life possible, but also to allow humanity to thrive! Our kind has been given dominion over all other lifeforms as well as the planet’s resources to use wisely and productively. Ultimately though, this sequence of events is not sustainable in the long term. Nor was it planned to be!

Chapter 17: Getting Hit Again

Covering pages 199 through 209.

Comets became the centrepiece of modern apocalyptic imagery.

In this chapter Dr. Levy discusses the perennially interesting topic of whether or not the Earth will next encounter a collision with an asteroid or comet. Using examples from historical times, such as the Tunguska Event in Siberia which occurred on June 30, 1908. It is thought that a 100 metre diameter asteroid exploded over the Tunguska River, the resulting shock wave felling trees some 40 kilometres in all directions from ground zero. He writes:

The Siberian object did its damage without even bothering to hit the ground. As it entered the atmosphere, it encountered such high pressures that at 8.5 kilometers up, it disintegrated in a tremendous explosion. Coincidentally, Siberia got hit again less than half a century later, this time by a much smaller 70 ton iron meteorite that left dozens of small craters, the largest about 27 meters across.

pp 203.

Levy very clearly explains why small objects collide with the Earth all the time, but as the object size increases so too does the frequency of such collisions decrease. Indeed, Dr. Shoemaker was able to derive an empirical relationship whereby the probability of a collision scales inversely with the square root of the size of the object. Mass extinction events are reserved for objects in the range of 1 to 10 kilometres in diameter, and are expected to occur with a frequency of between 10 and 100 million years. The chapter ends by putting such an event in perspective, tempered by an amusing consideration of the estimated risks associated with other events in life.

Chapter 17: Deflecting the Terrible Sword.

Covering pages 211 through 225.

Following on from the content covered in the last chapter, the author discusses the options available to us were we to face a collision with an asteroid or comet that would threaten human civilization. Accordingly, Levy mentions the various deflection technologies conceived of up to this time (1995), as well as the various ‘space watch’ or ‘space guard’ initiatives being conducted by astronomers around the world. Though somewhat sensationalised in recent years by Hollywood box office hits like Armageddon and Deep Impact, these surveys will help safeguard humanity against the antics of marauding asteroids and comets. We are no longer helpless, unable to divert such a disaster, as we were for most of our history. Today, when more people are living on Earth than at any other time in history, we truly have the means of safeguarding our civilisation against such a cosmic disaster. Levy concludes:

Over thousands of years, we have come full circle with comets. Feared at first and later studied and enjoyed, they are now feared again as harbingers of doom. But unlike the soothsayers of yesteryear, today, with a considerable amount of planning and a lot of care, we may be able to travel to a comet and change its path so that it sails harmlessly by.

pp 225

 

Chapter 18: Maxwell’s Silver Hammer; A String of Pearls Strikes Jupiter

Covering pages 227 through 239

By now, we have reached the climax of Levy’s wonderful adventures with comets, for it is in this chapter that he explains the sequence of events that transformed just another comet (in this case CometShoemaker Levy 1993e) into arguably the most sensational astronomical event of the twentieth century. Further observations of the same comet by a number of observers using large reflecting telescopes that dwarfed the 18 inch Schmidt telescope used by its discoverers showed that the same comet had been sundered into a veritable “string of pearls,” as a consequence of approaching Jupiter too closely (actually it came within just 50,000 kilometres of Jupiter’s cloud tops in July of 1992). What’s more, Dr. Marsden, working at the CBAT, who had been working on its orbit, discovered that a collision with Jupiter was inevitable and would occur in July of 1994. Because of the interest the comet was now generating amongst the professional community, Marsden decided to rename it Periodic Comet Shoemaker Levy 9.

Hubble Space Telescope image of the 21 fragments of Comet Shoemaker Levy 9 as they appeared on May 17 1994, just weeks before their violent collision with Jupiter. Image credit Wiki Commons.

As the weeks went by, some astronomers predicted a rather lacklustre collision event, “like throwing pebbles into an ocean,” but as more detailed calculations were made concerning the amount of energy that the crash would release, astronomer, Steve Edberg, raised the stakes by predicting that the collisions would be “more like dropping an olive into a Martini.” The truth, of course, was somewhere between these extremes, as history so clearly presented.

Ultraviolet image(@255nm) of the major impact events of the fragments of Comet Shoemaker Levy 9 with Jupiter captured about 150 minutes after the collision events on July 21, 1994.Image credit: Wiki Commons.

 

Epilogue

Covering pages 241/2

 

To be continued…….

 

De Fideli.

The Life & Work of Dr. William Doberck (1852-1941)

The Makree refractor erected in Hong Kong.

The 13.3 inch Markree refractor erected in Hong Kong.

It gives me great pleasure to present an essay written by my compatriot, Dr. Kevin MacKeown (now at the Unversity of Hong Kong) on the life and work of the Danish astronomer, Dr. William Doberck (1852-1941), who, amongst other things, dedicated his professional career to double star astrometry.

Dr. William Doberck ( 1852-1951).

Dr. William Doberck ( 1852-1941).

Most significant for me was his spell at Markree Observatory, Co. Sligo, Ireland (my homeland), where he used a magnificent 13.3 inch refractor, with a lens fashioned by Robert A. Cauchoix of Paris, which was privately owned by a wealthy British gentleman, Edward J. Cooper. There the telescope was used to catalog 60,000 stars. After leaving the west of Ireland, Doberck moved the telescope to Hong Kong Observatory, where he served as its first director between 1883 and 1907.

You can view this essay here.

 

Neil English is working on a new book – Tales from the Golden Age – honouring the life and work of the greatest telescopic observers in history.

De Fideli.