Open for Business

An AFSIG article by: Paul Trittenbach

Grains of salt lie on a mat

In contrast to the velvet’s black    

Suspended in their cosmos

They are orphans even as brothers…

I penned the opening stanza to that poem in 1982. Although I had interest in astronomy at the time, the poem was a philosophical treatment on how each of us assigns meaning to his life and not an ode to astronomy. I was reminded of this poem one afternoon while I was eating lunch. As I reached across the table for a platter of food, I accidentally spilled the saltshaker.

Throughout my life I have never been able to see shapes in the clouds. I never spotted a rabbit, a choo-choo train, an elephant— nothing other than a big puffy collection of condensed water vapor floating in blue sky.  Up until the moment that I spilled that saltshaker, if someone had given me a Rorschach test, I would’ve seen nothing more than a huge splotch of ink on a piece of paper that couldn’t have been recycled.  People who knew me found that ironic because I had exhibited artistic talents — photography, creative writing, painting and drawing — all of my life! Nevertheless, I always saw clouds and most other worldly shapes for what they literally were, not as abstracts.

In the second when the salt spilled out onto the table in front of me I became a student—albeit for a brief moment—in psychology. As the salt scattered across the table a very personal apparition appeared to me and without deliberation or hesitation I recognized it. For there, in front of me, wasn’t a rabbit, a choo-choo train or an elephant, but Messier 37. The ghost of Rorschach had reared up from the grave and taken his revenge upon me!

It is an interesting human trait — almost instinctual — that our brains habitually search for objects that are common to us. Recognizing human faces is one of our greatest idiosyncrasies and we seem to find them almost everywhere we look: the grills of cars, the man on the moon (or the woman on the moon, if you prefer), in landscape formations (some people even found a face on Mars created by the lighting on a mountain range), and even some foods. It seems that human faces — especially smiley faces — seem to abound. I have no doubt that many of us stargazers have seen smiley-faced asterisms in the stars.

So this month, in tribute to Dr. Herman Rorschach and completion of my lunch, it seems only fitting to offer a topic that will broaden your understanding of another cosmological object and hopefully bring a smile to your face. Open star clusters were one of the first types of cosmological objects to seize my attention as a beginning stargazer. They were so beautiful to my eyes, that to this day I liken them to diamonds, sparkling against the black velvet background of space. While some stargazers may succumb to adopting a “they all look alike to me” policy, when one delves into the physics and chemistry — the magic of the universe, if you will — they suddenly become intriguing.

Star clusters are associations of stars that are gravitationally bound to each other and moving independently of the rest of our galaxy. They fall into two categories — open and globular. Open star clusters are loose associations wherein the distance between the stars is so apparent that it is easy to resolve them in a pair of binoculars or a telescope.  Open clusters generally contain hundreds to thousands of members formed from the same nebula with members of the same type and age.  Globular clusters can possess tens of thousands or even hundreds of thousands of members. Globular clusters, on the other hand are densely packed associations wherein the nucleus is difficult to resolve into individual stars.  They are also much old, nearly as old as the universe itself. Both types have separate histories and origins.

Located in the constellation of Canis Major is the open star cluster Messier 41. Also designated as NGC 2287, Messier 41 (M 41) is a congregation of 100 young, blue-white stars generously spread over a diameter of 25 light years. At 2300 light years distance the cluster is relatively close to earth. M41 is speeding away from us at 52,120 mph.

At 250 million years of age, the stars of M41 are young in comparison to stars like our sun, which is 5 billion years old and can burn for 10 billion years. These stars burn hot and bright and will expire within only hundreds of millions of years. Although the members are born out of the same stellar nebula, as they wonder through the galaxy they tend to pick up stragglers. Messier 41 is known to contain several red giant stars and at least two white dwarfs.

At star parties I compare Messier 41 to a single member of the Perseus Double Cluster — albeit with one-third the number of stars. These diamonds spread across the background of space offer a delightful view as they sparkle in our binoculars or telescope. In our brief lifetimes we will never be able to perceive M41s migration through the Milky Way. To us it will always be a permanent fixture in Canis Major.

Because the members of open clusters are of similar chemical composition and age, they generally possess the same properties and provide excellent laboratories for studying stellar formation. Some open clusters are so large — spread over many light years of distance — that they are visible to the unaided eye. Some examples of these include the Pleiades, the Hyades and M41. Many open clusters will easily resolve in a pair of binoculars. Some large clusters, such as M7 and IC 2391, have been described as far back as ancient times.

NGC 752 (Caldwell 28) is a gorgeous star cluster hidden in the constellation Andromeda. It is generally overshadowed by the Perseus Double Cluster, and the Andromeda and Triangulum galaxies, but I don’t think it is a cluster that should be overlooked. Although this cluster will resolve in a pair of binoculars it is best viewed through a telescope. The cluster contains 70 stars.

NGC 752 is a contradiction among open clusters. While most open clusters contain young stars — in the millions to hundreds of millions of years in age — the stars of this cluster are nearly 2 billion years old.  Many of the most massive blue-white stars of this cluster have already moved off the main sequence and become red giants.  Some of the most massive have already reached the end stages of their lives and become white dwarfs and neutron stars.

NGC 752 has a magnitude of 5.7 and is located 1300 light years away. It is a very large cluster, spread out over a large swath of space, approximately 75 x 75 arc minutes. It is the distance between the stars that gives away the cluster’s age. Over time, all open cluster disintegrate as their gravitational grip weakens. Use a wide-field eyepiece, sit back and enjoy viewing this sparkling cluster.

While some clusters, such as the Pleiades, have been described since ancient times, they are best viewed through binoculars or a telescope, which is able to resolve more of their individual components. Galileo was the first astronomer to describe 50 members among the Pleiades. Previous descriptions by ancient astronomers counted as few as 6 to 7 members.  Nine of the brightest stars were named after the Seven Sisters of Greek mythology.  Today, the Pleiades is known to contain 1000 members. Clusters of both types were classified by early astronomers as nebulae because early telescopes and the unaided eye were unable to resolve those patches of light into stars.

577 light years away, in the constellation Cancer is the open star cluster Messier 44 (M44). Also known as the Beehive Cluster, Praespe, Cr 189 or NGC 2632, it is one of the nearest open clusters to Earth and can be seen as a blurry patch with the unaided eye. M44 is known to contain 1,000 members, residing in a radius of 39 light years. The young stars of this cluster are between 600 to 700 million years old.

The Hyades (M44) in Cancer is one of the closest open cluster to Earth at 151 light years distance. NASA Image, Bob Franke
The Hyades (M44) in Cancer is one of the closest open cluster to Earth at 151 light years distance.
NASA Image, Bob Franke

As mentioned before, most stars within a cluster are of similar age and type. But M44 is somewhat of an enigma, with its population consisting of various stars that simply don’t fit the model.  The population of M44 is divided between M-class red dwarfs, which constitute 68% of its members; F, G and K spectral classes constitute 30% of the cluster’s population; and 2% are spectral class A stars. The cluster is also known to possess 11 white dwarfs and five giants of KOIII and GOIII have also been discovered.

The heaviest members have migrated toward the center of the cluster in a process known as Mass Segregation. While less faint members of the cluster now occupy the halo, or outer region of the cluster, the brighter more massive stars occupy the interior. The brightest members of the cluster possess a magnitude of 6.0 and are spectral class BO.

In 2012 astronomers discovered two planets orbiting two sun-like stars within the cluster — the first discovery of its kind. These planets are hot super Jupiters and orbit very close to their parent stars. Astronomy has come a long way since Galileo first turned his telescope on this cluster in 1609. At that time, he reported observing 40 members in the cluster. The ancients knew of this cluster and documentation of it reaches as far back as the Greek astronomer Claudius Ptolemy (AD 90-168), who described it as a nebulous mass within Cancer.

The Hyades ( Collinder 50, Melotte 25, Caldwell 41), in the constellation Taurus, is one of the closest open clusters to Earth at a distance of 151 light years. This spherical group of stars covers a diameter of 15 light years and shines at a magnitude of 0.5. The cluster consists of stars of the same age, chemical composition, origin and motion through space, providing a valuable laboratory for the study of open clusters. The stars of the Hyades are approximately 800 million years in age.

The cluster is located in the head of the bull, and visually appears to be associated with the red giant Aldebaran.  Aldebaran, however, is not a member of the cluster. The cluster forms a V-shaped asterism consisting of five stars: Gamma, Delta 1, Theta Tauri, Zeta 1 and Epsilon Tauri. Of those stars, Epsilon Tauri is the first to be identified as having a planet — a super Jupiter.

The Hyades cluster is believed to have formed from the same stellar nebula as M44, the Beehive cluster. Both clusters appear to contain stars of the same age, composition and traveling in the same direction, from a similar point of origin. The Hyades is one of the few clusters of which the distance has been accurately measured, allowing astronomers to more accurately measure distances and scales in the universe. Anyone who enjoys viewing the Perseus Double Cluster should enjoy viewing the gorgeous blue-white gems of this cluster.

Open clusters may no longer reside within the molecular clouds of the nebulas that created them. One such example is M45, the Pleiades. The molecular cloud associated with M45 is not the progenitor of the cluster, but instead is one through which the cluster is currently moving. Because they are loosely bound together, most open clusters will disintegrate over a period of a few hundred million years. At times, the most massive open clusters survive longer.

Probably the most famous open cluster is Messier 45 (Melotte 22), the Pleiades in the constellation Taurus. I knew of it as a child, before I possessed an interest in astronomy. From the small town I grew up in, people would point to the cluster and tell me “it’s the Seven Sisters.” I remember their claims that seven stars were the most anyone with good eyesight could see, and they believed that was how the nickname came about. Until I developed an interest in astronomy, I carried that explanation with me. In reality, from a good dark location, people have seen up to 14 stars in this cluster of 500 members.

The Pleiades is a cluster of hot, young B-type stars of approximately 100 million years in age. The cluster seems to be immersed inside a reflection nebula, that was originally believed to be a remnant of the progenitor to this cluster and is known as the Maia nebula, named after the star Maia. However, this nebulosity is not the nebula from which Messier 45 formed, but a separate structure M45 is traveling through.

At a distance of 444 light years, M45 is one of the closest clusters to Earth. The cluster occupies a radius of 43 light years and possesses a mass of approximately 800 suns. Surrounding the star Merope is a bright reflection nebula known as Merope’s Nebula or Temple’s Nebula (named after its discoverer, astronomer Wilhelm Temple). Additional reflection nebulas have been discovered around the stars Electra, Taygeta, Celaeno and Alcyone. These nebulas are illuminated by the bright, hot blue stars of M45, which emit ultraviolet radiation to ionize the gases of the nebula. The Merope Nebula can be seen through a 4-inch aperture telescope under dark skies. M45 is currently breaking up, as the gravitational attraction between the member stars weakens. The cluster is expected to survive for only another 250 million years.

The nebulosity associated with M45 is not the progenitor of the cluster. Instead, it is a nebula through which M45 is passing. NASA Image, Robert Gendler
The nebulosity associated with M45 is not the progenitor of the cluster. Instead, it is a nebula through which M45 is passing.
NASA Image, Robert Gendler

Estimates show that 25% of the objects in the Pleiades are brown dwarfs. Brown dwarfs are gas giants that range in mass from 15 × to 75 × the mass of Jupiter. These planets do not contain enough mass to create the core temperatures necessary to initiate thermal nuclear fusion. In essence, they are failed stars. The entire combined mass of these brown dwarfs is only about 2% of the total mass of M45.

Spitzer Space Telescope analysis of one of the stars, HD 23514, has resulted in the discovery of a large planetary disk orbiting that star. HD 23514 is a main sequence star that is less than 1 million years old. The Pleiades are also known to contain some white dwarfs. This creates a conundrum because astronomers cannot understand how a cluster so young can contain stars that have begun with enough mass to have reached the end of their life cycle in such a short period (100 million years).  Astronomers believe that the stars are not stragglers, picked up by M45 on its trek through our galaxy. Stars with such low mass as the B-type members of M45 would usually take billions of years to evolve to the white dwarf stage. The only conclusion astronomers can form is that the stars started out so massive that they rapidly evolved to the white dwarf phase. ( Perhaps one day astronomers will confirm the discovery  of a luminous A-class star with seven brown dwarfs orbiting it.)

The B-type stars of M45 do not possess enough mass to result in supernovas at the end of their life cycles. Instead, they will shed their outer shells to create planetary nebulas (PN). With its close proximity to Earth these planetary nebulas should be a spectacular sight for professional and amateur astronomers like.

The radiant gems of the open star cluster Messier 37 — my saltshaker cluster —  in the constellation Auriga has often been referred to as one of the most brilliant and beautiful open clusters in the winter sky. Of the three clusters of the constellation — M36, M37 and M38 —      M37 is the brightest. The cluster possesses 150 members at a visual magnitude of 12.5 or less. Collectively, this cluster shines at a magnitude of 6.2. Of the three clusters in Auriga, M37 and M36 are visible to the unaided eye from a dark location.

Often referred to as one of the most brilliant and beautiful winter open clusters, M37--my saltshaker cluster--is the brightest of the Auriga clusters (M36, M37,M38) NASA Image
Often referred to as one of the most brilliant and beautiful winter open clusters, M37–my saltshaker cluster–is the brightest of the Auriga clusters (M36, M37,M38)
NASA Image

The members of this cluster are relatively young, at around 300 million years. But scattered among the blue-white stars that dominate this cluster there are at least a dozen red giants and some white dwarfs. These are likely stragglers picked up by M37 on its trek through the Milky Way. CCD observations of the cluster down to magnitude 22.0 have revealed that it has a population of more than 14,000 members.

Messier 37 (M37, NGC 2099) is located 3,600 light years from Earth and spans a diameter of approximately 25 light years. When viewed through a pair of binoculars or a small telescope the core of the cluster reveals about a dozen stars down to magnitude 10.0.  By employing averted vision, dozens of stars surrounding the center of the cluster come into view. The center of the cluster is dominated by a bright red giant.


There are worlds of salt and sand

scattered throughout the universe

where upon them someone may stand

questioning his place and worth

Throughout history, salt has played a significant role in society. Salt has been used to purify, season and as a form of currency—every bit as important as gold. In the Bible, salt is referenced 30 times and Jesus is quoted as telling his disciples “Ye are the salt of the earth,” a reference to a good and worthy person. But some historians believe that Jesus’ reference to “salt of the earth” was not about the goodness and worthiness of the person, but as a reference to the fact that some types of salts — including magnesium salts —  have been used as fertilizers since ancient times.

Ancient Greeks traded salt for slaves and when a salve was not worth his price it was said that he “was not worth his “salt.”  It was a scarce commodity in ancient times, having to be extracted either from surface outcrops, such as dried-up inland seas, or boiled from brine. Some historic references claim that the ancient Romans paid their soldiers partially in salt — and our modern word for salary is derived from solarium argentum, a soldier’s pay. This claim is  refuted by historians who claim that by the time of ancient Rome, processes for extracting salt from boiling brine had been perfected. But, today, in Ethiopia, many people are paid in pressed bars of salt.

Some historians have traced the use of salt back to prehistoric times. Ancient trade routes were established by the Romans, the Phoenicians and the empires of the Mediterranean along salt trails. The Romans are said to have salted their leafy greens and vegetables, leading to the modern-day word of salad. The word salvation is supposedly derived from Catholic religious rituals in which covenants were often sealed in salt.

Salt is literally a sustainer of human and animal life. Sodium chloride, the chemical that we identify as table salt, provides ions in solution that are essential for nerve and muscle function as well as regulation of body fluids. It plays a significant role in blood volume and blood pressure. But when it is taken in excess amounts it can lead to serious health conditions that can damage the heart, kidneys and lead to strokes. All terrestrial life evolved from the ocean and in a normal concentration the salt content in our bodies is the same as that of seawater.

Salt and sand play both metaphorical and literal roles in my poem. In previous paragraphs I outlined the role that salt has played in human history — both literally and figuratively. Oxygen is the most abundant element in the earth and it is no surprise that combined with silicon it forms the most abundant mineral basis for rocks. Silicon dioxide also plays an important role of trace element — albeit in very minute amounts — within the human body.  It has often been said that there are more stars in the universe than gains of sand on all the beaches of the world. Like salt, silicon dioxide, and more specifically, silica, plays a significant role in our materials and technology.

I don’t believe that the jury is in on whether or not intelligent life can exist on planets in star clusters. Open star clusters contain stars too young, and with a limited lifespan, to be capable of developing the planets necessary to promote the evolution of intelligent life. However, astronomers are still debating whether or not intelligent life may exist on planets in globular clusters. Although my poem was not astronomy themed, it contains stanzas that could easily fit a discussion about intelligent life on other worlds. Certainly we stand upon a grain of sand, one of possibly billions in the universe, gazing in awe into the cosmos and pondering our existence.

Ever since I received my first telescope at the age of eight I have looked up into the night sky and wondered if there was intelligent life on other worlds. No, it wasn’t because I was concerned that we might be alone in the universe. I wondered if intelligent life elsewhere endured similar problems to mankind. Did they suffer from the pettiness, the greed, the desire to overpower and the lust to conquer that we do? Do they have pollution in their air and water? Do they suffer from poverty and disease? Do they have wars that threaten them with extinction, or have they solved the complex problem of cooperation?

Astronomers, philosophers and men of the cloth have all stared skyward asking the same questions of existence and hoping to arrive at slightly different answers. I imagine that the Jesuit priests of the Vatican Observatory are hoping to look into the face of God for the answers to our existence, while astronomers are hoping to reveal the ultimate equation for everything, and philosophers simply want the answer to the meaning of life. Astronomy is definitely a humbling experience, wherein we deal with such enormous distances, sizes and power that it is mind-boggling! No matter how you dice or slice the numbers, the universe is huge and we are definitely small. Perhaps it is this revelation of scale that drives us to seek an answer to the meaning of our existence.

I don’t pretend to have an answer to the meaning of existence. In all my years in amateur astronomy I have never stood at my telescope and pondered it. I am a fan of the universe. I marvel at its elegance and how everything in existence can be constructed out of the evolution of the hydrogen atom into all the atoms, chemical compounds and structures found in nature. While each structure may appear to be different, it is simply an optical illusion caused by a rearrangement of the building blocks of the cosmos. Perhaps Rorschach is rolling in his grave with laughter now that I realize how much my poems’ analysis of the way each of us assigns a meaning to our lives is similar to the very questions that our species has asked ever since the very first human gazed upon the night sky.

Ironically, I have never referred to the stars as grains of salt in any my conversations. Today, I liken them to diamonds against the velvet background of space. At one time, however, salt was every bit as valuable as diamonds are today. But for the time being, I will stand at my telescope and gaze upon those grains of salt on velvet black. All of the stars of the universe, created from the same Big Bang, are living out their lives in this universe as galaxies, star clusters and solar systems — they are orphans, even as brothers.

On a good winter night, take it upon yourself to get outdoors under a black velvet sky and look at the glittering grains of salt in the open clusters of the Milky Way. Perhaps you will just simply marvel at the radiant beauty of these cosmic gems. Perhaps you will visualize the elegance of chemistry and physics. Perhaps you will find some familiar personal shapes or even smiling faces. Whatever you see when you gaze upon them, I guarantee that you are not crazy.