David Levy's Skyward, October 2023

Pons-Brooks:  A comet for the centuries.

When David Rossetter and I began our observing session at the Tucson Amateur Astronomy Association’s  Chiricuaha Astronomy Complex on the evening of August 5, 2023,  we did not expect that  we would be treated to an evening of cosmic history.  That was the night we glimpsed Comet Pons-Brooks, a comet with an orbit that, like Halley’s comet, takes almost a human lifetime to orbit the Sun  .I might have spotted it the night before, but on this night David and I saw the same thing, a spot of haze in the darkness.  It was a faint misty cloud that bears the names of two of the most famous comet discoverers in all history, a spot of haze with quite a story to tell.

Comet Pons-Brooks was first identified by Jean-Louis Pons, the great French comet hunter, during the summer of 1812. In the late summer of  1883, on its subsequent pass around the Sun, it was rediscovered by another famous comet hunter, William Robert Brooks. I first encountered Brooks in a Sky & Telescope article I read in the second issue I received, at age 14, in April 1963.  As I digested the story, I learned how Brooks might have politely entertained a visitor to his observatory, and how that visitor eventually learned that Brooks was one of the world's most famous comet discoverers. As I relished these words, I foresaw myself, some day, also as a hunter of comets.  Not a discoverer, because that would be hard.  But as a hunter, that's easy. Those ideas stayed with me until December 17, 1965, when I began my program of searching for comets. Since then, my own life has been punctuated by several sparks of cometary light, as each new comet added brightness to the field of my telescope. I joined a group of people linked not by nation, nor either by continent, but by being citizens of the world united by a love of comets.

Emboldened by the offer by Hulbert Harrington Warner of an award of $200 for each comet discovered, Brooks managed to find three comets within five weeks of each other, on April 17,  April 30, and May 22 , 1886.   He must have known how his colleague Edward Emerson Barnard built his “comet house” partly out of funds also earned from Warner’s award.  (The Warner prize has survived through history.  The Astronomical Society of the Pacific offered its “Donohoe Comet Medal”  for a time, and later Roger Tuthill gave a plaque, and now there exists the Edgar Wilson Award, which is sponsored by the Central Bureau for Astronomical Telegrams [CBAT] of the International Astronomical Union.)

Like all serious comet hunters, Brooks was far more interested in discovering comets than in the money he could earn from these finds.  In later years his success as a a comet hunter earned him a professorship in astronomy at Hobart College in Geneva, New York.  With Brian Marsden’s 1979 Catalogue of Comet Orbits as a guide, we can surmise that Brooks discovered a minimum of 22 comets in his lifetime.

Despite this remarkable accomplishment, Brooks is only the second most prolific comet finder in world history,  The winning ticket goes to Jean-Louis Pons himself, who was “the first “discoverer” of Comet Pons-Brooks.  Truly, Pons was also not the first.  This comet might have been observed by Chinese astronomers in the late summer of 245 CE, then definitely by the Chinese in 1385, and in 1457 by Paolo del Pozzo Toscanelli.   Pons today is considered to have discovered about thirty comets.    Over the decades I observed a second Pons periodic comet, Pons-Gambart, in January 2013.   By the way, Pons had a most humble and trusting nature, and in his younger years he was ridiculed by astronomers who should have known better.

These days,  it is almost impossible for an individual to discover more than half a dozen comets.  My total is 23, but as CBAT director Dan Green (possibly correctly) stated, “he discovered 9 comets and lucked out on 11 more,” before graciously adding Comet Shoemaker-Levy 9 to my total.

Pons and Brooks shared a passion for telescopes and the fleeting comets they could detect parading about the sky.  I like to imagine that finding new comets was secondary to their pure enjoyment of the night sky, its treasures, and the secrets that it infrequently shared with those people who truly lived, and live, for its precious hours of darkness.

Image credit: H.C. Wilson, E.E. Barnard

David Levy's Skyward for April 2022

Skyward, April 2022


        Over the last few months you must have read dozens of articles, online or in print, about the Omicron variant of COVID-19.  Fortunately, this is not one of them. This article is about Omicron² Eridani. It is a faint star in the constellation of Eridanus, the River.

        Actually, there are two Omicron stars in that constellation.  The first is brighter, and is a variable star.  The second one is one of the closest stars to the Sun. Omicron², also known as 40 Eridani, happens to be not a disease but one of the most interesting star systems in the entire sky.

Omicron² is a triple star system that is only about 16 light years away.  Its brightest component is a Sun-like star faintly visible to the unaided eye on a good night. It lies in northern Eridanus, the River, just a few degrees west of Rigel at the foot of Orion.  The secondary is a white dwarf star.  Unlike the companion of Sirius,  this star is 9th magnitude and not near the brighter star so it is easy to see in a small telescope.   The third star is not far from the secondary, but at 11th magnitude it is also not difficult to spot.  This third star is a red dwarf.

       Although red dwarf stars are the most plentiful, by far, in our region of the Milky Way galaxy, they are almost impossible to see because they are so small.  The closest one to us is Proxima Centauri, or Alpha Centauri C, which at 4.24 light years is the closest star to the Sun.    Also because they are so small and intrinsically faint, only a few of them are easy to find.  40 Eridani C is one of the easiest to find.

       This interesting star has something else going for it.  In 2018 astronomers discovered a planet orbiting the primary star.  With a rapid orbit around Omicron², such a planet would receive much more radiation from the primary star than Earth gets from the Sun.  But in 2021 new observations cast doubt on whether this planet exists at all.

        Whether Omicron² Eridani really hosts a planet is subject to debate.  But in the universe of Star Trek, it surely does.  It is the home of Vulcan, Mr. Spock’s home world. In the episode “Operation Annihilate”, which appears near the end of the first season, Spock is blinded by the intense light used to immobilize the invading parasites on the planet Deneva.  However his blindness is temporary because of the existence of an inner eyelid.    Vulcan is said to orbit Omicron² Eridani’s primary star, and since it is so much  brighter than our Sun,  even though Vulcan is at the same distance that Earth is from our Sun, they need the inner eyelid to protect their eyes.

       I rather enjoy the idea that the fictitious Vulcan happens to orbit one of my favorite real stars.  And unlike the Omicron variant, which one hopes will be eradicated soon, we admire Omicron² Eridani, the real star, and wish it to ”Live long and prosper.”

Observers' Challenge – February 2022

by Glenn Chaple

M42– Emission Nebula in Orion (Magnitude 3.6, Size 70’x60’)
M43 – Emission Nebula in Orion (Magnitude 9.0, Size 20’x15’)

This month’s Observer’s Challenge is (drum roll) M42/M43, the Orion Nebula! You might ask why a deep-sky object that’s easy to find (it’s in the Sword of Orion) and see (it’s bright enough to be viewed with binoculars) would be considered a challenge.

Let’s begin with M42, the brighter of the two. It was discovered in 1610 by the French astronomer Nicolas-Claude Fabri de Peiresc and cataloged by Charles Messier on March 4, 1769. Binoculars and small-aperture telescopes will reveal the bright northeast part of M42, which resembles the outspread wings of a celestial eagle. One challenge is to visually capture the nebula’s faint southerly region. Because M42 spans 85’ by 60’, you’ll want to work with a low-power, wide-field eyepiece. A second visual challenge is to detect M42’s greenish hue. I’ve seen it with a 13.1-inch f/4.5 scope, but not with a 4.5-inch. What is the smallest aperture that will reveal this subtle hue? Find out, and forward your result to Challenge coordinator Roger Ivester.

Fainter and thus overshadowed by M42, M43 eluded detection until reported by Jean-Jacques Dortous de Mairan in 1731. Messier entered it in his catalog on the same date as M42. It is separated from M42 by a dark, dusty lane and surrounds the irregular variable star NU Orionis (magnitude range 6.5 to 7.6). The nebula’s published magnitude of 9.0 might be on the low side, as I’ve seen M43 with a 60mm refractor. Admittedly, it was small and faint, and only visible when I ramped up the magnification to 140X to remove M42 from the field of view. What I saw was a roundish haze surrounding NU Orionis. In larger instruments, M43 will take on a comma shape.

Looking for another challenge? At the heart of M42 is theta-1 (θ1) Orionis, a stunningly beautiful multiple star birthed from the surrounding nebulosity. The four brightest members, all hot and massive O- and B-type stars, form a lop-sided diamond known as the Trapezium.

Labeled A to D in order of increasing right ascension, they shine at magnitudes 6.7, 7.9, 5.1, and 6.7, respectively. A and B are eclipsing binaries- the former, bearing the variable star designation V1016 Orionis, fading to magnitude 7.5 every 65.4 days, the latter (BM Orionis) dipping to 8.5 every 6.5 days. Galileo discovered the three brightest members (A, C, and D) in 1617. The fourth (B), was discovered by the French astronomer Jean Picard in 1673. It can be difficult in a small-aperture scope, especially at the low magnification needed to view the entire Orion Nebula. If seeing conditions allow for a magnification of 200X or more, a 6-inch telescope will reveal two more stars – E (magnitude 10.3) and F (magnitude 10.2). Four other members, G, the tight double H1 and H2, and I, are extremely faint at magnitudes 14.5 to 15.5 and require large scopes and optimum seeing conditions. These are a true challenge!

Oh yeah- here’s a final challenge. See if you can view the Orion Nebula, its gaseous wreaths embracing a diamond-like clutch of newborn stars, and not feel a sense of awe and wonder. The Orion Nebula lies some 1350 light-years away. Cosmically young, it is just 2 or 3 million years old. The stars in the Trapezium are even younger, perhaps no older than 300,000 years. M42 and M43 have linear diameters 23 and 7.5 light-years, respectively, while the brightest stars in the Trapezium span a distance of about 1.5 light-years. 

The purpose of the Observer’s Challenge is to encourage the pursuit of visual observing. It is open to anyone who is interested. If you’d like to contribute notes, drawings, or photographs, we’d be happy to include them in our monthly summary. Submit your observing notes, sketches, and/or images to Roger Ivester (rogerivester@me.com). To find out more about the Observer’s Challenge, log on to http://rogerivester.com/category/observers-challenge-reports-complete.

[Photographs by Mario Motta]


David Levy's Skyward for January 2022

Imagination and the Astronomical League.

“A Dragon Lives forever, but not so girls and boys.”

Three quarters of a century ago, during the Second World War, the famous Harvard astronomer Harlow Shapley, along with Charles Federer, founding editor of Sky and Telescope Magazine, launched an association of astronomy clubs across the United States.  It is called the Astronomical League, and it thrives to this day with more than 100 astronomy clubs.  Unlike the national Royal Astronomical Society of Canada, the League is designed to be a more loosely structured organization.  According to Carroll Lorg, its current president, one of its most critical and central goals is to inspire the next generation to enjoy the night sky. If that goal should fail, the possibility exists that there may be no Astronomy for future generations.

As part of this vital goal, the Junior Astronomical League, a new subset of the Astronomical League, is now meeting every second Sunday over zoom.  But there is something more.  My next book will be devoted to those young stargazers.  It actually began as a typewritten saga I wrote in 1958 when I was ten years old, and of all the 40 plus books I have written, this is Wendee’s favorite.   I am now completing a second edition of this book, in which a small group of children go on a stargazing adventure with Clipper, a magic beagle, and with Eureka, an enchanted reflector telescope.  They go past the Moon and planets, the stars, the distant superclusters of galaxies, and even the great voids in distant empty space.

In its final chapter, this book explores the theme articulated in the last verse of Peter, Paul, and Mary’s eminent song “Puff.”   ”A dragon lives forever, but not so girls and boys.”  The children, now grown, go to university.  When they complete their college education, the young woman, adept at math and physics, becomes an astronomer, but the young man goes on to become a lawyer.  He marries, has children who are now grown themselves, and unhappily gets a divorce.  To recover he decides to take a vacation trip to Arizona. Driving his rented car one evening, he pulls off the road, gets out of his car, and looks at the stars. As childhood memories flood back, a second car pulls off.  The young woman astronomer gets out of her car.  The two cannot believe they are reuniting, and they catch up for hours.  Then there is a break in their conversation.  As the couple looks up silently at the stars, the magic beagle, and the telescope, appear and take shape.  In that one ultimate celestial adventure, the  magic of the night has returned.


Observers' Challenge – January 2022

by Glenn Chaple

NGC 1501 – Planetary Nebula in Camelopardalis  (Magnitude 11.5, Size 52”)

            There are two major reasons why this month’s Observer’s Challenge, the planetary nebula NGC 1501, is largely unobserved. First of all, it’s located in the extremely faint circumpolar constellation Camelopardalis. Star-hoppers will have a rough time navigating around a constellation that lacks stars brighter than 4th magnitude. A second reason has to do with its published magnitude- 13.0 in a number of web sources and observing handbooks. That’s faint enough to scare away anyone observing with a small-aperture scope! But 13.0 is its photographic magnitude. Its visual magnitude is a more accomodating 11.5.

Although NGC 1501 can be viewed with small-aperture scopes under dark-sky conditions, its mottled appearance requires larger instruments. The 14.5-magnitude central star will challenge an 8-inch telescope. Embedded in the surrounding nebulosity like a pearl in a shell, it gives NGC 1501 its nick-name, the Oyster Nebula.

If you own a GoTo scope, you can get to the Oyster by punching in its 2000.0 celestial coordinates: RA 04h 06m 59.4s, DEC +60° 55’ 14.4”. Star-hoppers can begin at nearby Kemble’s Cascade- a remarkable asterism consisting of a 2½ degree-long near-straight chain of some 20 magnitude 7 to 10 stars punctuated near the middle by a 5th magnitude star.

To find the Cascade, make a low-power (25-30X) search of the area marked by a line drawn from beta (β) to epsilon (ε) Cassiopeiae and extended an equal distance beyond (refer to finder Chart A). Once you’ve found it, keep the low power eyepiece in place and take a moment to admire this stunning stellar arrangement. At its southernmost end, you’ll spot a tiny sprinkling of stars. This is the open cluster NGC 1502. A switch to a higher magnification (60-75X will reveal several dozen stars of 9th magnitude and fainter surrounding a pretty double star (Struve 485, magnitudes 6.9 and 6.9, separation 18 arc-seconds).

If you had gone directly to NGC 1502 via GoTo technology, you would have missed an amazing asterism, a neat little star cluster, and an attractive double star. Your final leg of the star-hop takes you 1.4 degrees south of NGC 1502 (refer to Chart B). Once the Oyster comes into view, you’ll want to switch to the highest magnification your telescope and the seeing conditions will allow.

My first encounter with NGC 1501 was via a 3-inch f/10 reflector (Edmund Scientific’s Space Conqueror) on the evening of February 2, 1986. According to the notes I wrote in my logbook it was “very faint, but definitely seen. Visible at 60X.” A sketch made with 120X shows the roundish form I saw. I was surprised to see this planetary at all, as my source gave a magnitude of 13.3, and I estimated it to be more like 11.0.

NGC 1501 was discovered by William Herschel on August 27, 1787. Its estimated distance is around 5000 light years, which translates to an actual dimension of 1.3 light years.         

The purpose of the Observer’s Challenge is to encourage the pursuit of visual observing. It is open to anyone who is interested. If you’d like to contribute notes, drawings, or photographs, we’d be happy to include them in our monthly summary. Submit your observing notes, sketches, and/or images to Roger Ivester (rogerivester@me.com). To find out more about the Observer’s Challenge, log on to rogerivester.com/category/observers-challenge-reports-complete,

David Levy's Skyward for December 2021

David H. Levy

Daffy Duck

Agreed, this seems like an awfully daffy title for an astronomy article. But there is method to the madness, and there is a story.  During the late summer of 2019 there was a star party in southeast Arizona that featured a dark sky and five perfect back-to-back nights  As I spent hour after hour hunting for comets, I came across the sprawling North America Nebula in the northern sky constellation of Cygnus the swan. But this time something different appeared. It was a strange structure, the outline of a dark nebula bordered by a slightly brighter cloud.  The whole feature was rather subtle, so that sometimes it was there, and then it faded so that sometimes it wasn’t. I spent some time trying to determine a name for it. It looked like the head of a duck.  I couldn’t call it the wild duck nebula, as there is a cluster with that name.  And Donald Duck is a bit confusing. So how about calling it the Daffy Duck nebula?  

Thus, the structure is named after Daffy Duck. It is No. 403 in my catalog of interesting things found during my more than 56 years of comet hunting. I believe it is a small dark construction at the northern tip of the North America Nebula, about where Hudson Bay is not accurately located.  It could have been where the Gulf of Mexico is, but that area is virtually impossible to spot visually, even under a dark sky.  Like the Horsehead Nebula in Orion, it is very difficult to spot and it is best viewed only in a photograph.  The accompanying picture shows it at its top, a little to the left of center.  The accompanying photograph was taken using the Hubble Space Telescope.

There are more than four hundred other celestial objects that have come my way over the years.  Beginning with NGC 1931 which I spotted in January 1966, many of these are already well-known deep sky objects in the night.  But a few are interesting groupings of stars, called asterisms, that no one has pointed out before.  One of my favorites is a structure of faint stars I call “Wendee’s Ring.”

These always welcome objects in the sky are fun to observe and they enhance my enjoyment of my hours under the stars.  When I can see Daffy Duck, it reminds me of the happy hours I spent as a child at Beaver Lake, an artificial pond near the top of Mt. Royal in Montreal, that hosts dozens of mallard ducks. On clear, moonless nights now, I offer a cosmic hello to Daffy Duck and the many objects in the night sky I have come to treasure as good friends.

David Levy's Skyward for November 2021

David H. Levy

Galaxies, just for the sake of argument

A few weeks ago, I received a message from Cameron Gillis, an amateur astronomer who wrote that he liked galaxies.  Just for fun, I decided to take the opposite approach, a philosophical reversal.  If he likes galaxies, then I hate them.  As we prepared for our meeting I began to explain the various reasons why I hate them.  When, for example, I am observing with a telescope and the Andromeda galaxy enters my field of view, I quickly leave the telescope and ride my bicycle to the end of our driveway and back.    The more I stretch the story the greater the laughter becomes.  I especially get annoyed by the dark Hydrogen-II regions that stretch across  its hideous girth.  The cluster of galaxies in the Virgo cluster, particularly Messiers 84 and 86, are so bland that I sometimes have to leave the telescope altogether!    

The worst galaxy is our own. When I look up at the evening sky, the Milky Way obstructs my view as it straddles the night from Cassiopeia all the way down to Sagittarius. The stars are so thick that I can hardly see black sky between them.  Except of course, when I come across Baade’s window.  This area of sky  rattles me because there,  some darkness appears.  Discovered by Walter Baade, this window allows us to see almost to the center of our galaxy.  It is an awful sight. The majesty of the night is nowhere more apparent than when I am viewing the center of our galaxy, in Scorpius and in Sagittarius, through my telescope.  It is wondrous. So wondrous that I still hate it. Because it wastes my time when I am mesmerized by it, the emotion of viewing the galaxy from my backyard is so strong that it strengthens my heart and pierces my soul.

The worst part of seeing our own galaxy on a clear autumn night is that the dark lanes of hydrogen dust straddle its length. Dark areas are called giant molecular clouds. They are not lit by nearby stars; they just are there.  In the far distant future, they will generate new systems of stars and planets like our Earth.  They are called giant molecular clouds or Hydrogen  (H II) regions.

In distant external galaxies, dark clouds like these can straddle their whole length. The Andromeda galaxy has several of these H II regions that one can observe through a small telescope if one looks carefully enough.

Deep in the southern sky, but still visible from most of North America, lies Caroline Herschel’s galaxy.  It is No. 253 in the NGC, the New General Catalogue.  Under a bright sky it is hardly anything, but from a dark site it resembles a long resting caterpillar. It has a most prominent dark hydrogen lane running across its length.

Along with  globular star clusters, those round conglomerations of hundreds of thousands of stars that orbit the outskirts of galaxies, including our own, galaxies are the oldest structures in  the Universe. The oldest ones started to build within half a million years of the Big Bang, when the Universe was in its infancy.

So much for hating galaxies. When I say that I hate them, I write merely for the sake of argument and humor.  Galaxies are almost like people, each one different, each one with its special characteristics. One way of looking at them is to compare their gigantic sizes with our puny selves. But there is another way.  Small as we may be, each of us is unique. Galaxies are huge, but aside from their differing shapes, they are still much alike. But in all this Universe, among all these galaxies, there is just one, only one, of each of us.  Our ideas, our personalities, are precious.


August 13 GAAC Meeting Program Note

Observing the universe relies to a great degree on our ability to model starlight, and thereby predict underlying stellar properties, such as mass and chemical composition.

At our 8:00 pm, Friday August 13 GAAC meeting, Center for Astrophysics Dr. Seth Gossage will continue the thread begun by our July speaker, Dr. Ioana Zelko, asking how we can know what we are looking at. What can the light we detect tell us about the object, so very far away, that produced it?

Light can reveal more about a star than just stellar mass and chemistry. Dr. Gossage will also, and in particular, review next generation stellar models built to explore the effects of stellar rotation. Stars spin, and this is also a fundamental stellar property (alongside mass and chemical composition), which helps determine the evolutionary course of a star, and its light output for the entirety of its lifetime.

Our August 13 meeting will be held again at our old home, the Lanesville Community Center at 8 Vulcan Street in Lanesville. We hope you can be there in person. For those who can not make it, the meeting will also be streamed on the GAAC Facebook page.