Astronomically, the moon is tremendously significant to our understanding of so much of how stars and planetary systems develop. Geologically, it has already taught us much about the history of the Earth and the Solar System. Romantically, it has lit the fires of love in the hearts of untold billions of people. But to me, it has come to mean so much more than any of these.

The moon is certainly worthy of nearly endless discussion of craters and plains, phases and tides, and all the minutiae of what we’re looking at when we look at its surface. But this time, I’d like to set aside the typical technical explanation of the calendar’s picture of the month.

A little more than a year ago, we were privileged to host two wonderful high school students for the 2018-2019 school year. One is from Barcelona, Spain, and the other is from Taiwan. Over the course of the year, we came to love these girls as our own daughters. They became a part of our household so completely that we couldn’t imagine our lives without them. It was as if they had been in our home since their birth. This was a completely unexpected thing. We really thought the experience would be like having guests for an extended stay. Suffice it to say that was not the case.

Our Taiwan daughter’s name is Luna. She loves the moon, and she loves this picture. She loves her USA mom and dad. She loves that her dad takes pictures of the moon. A blanket with this image printed on it was our going away gift to her, one of the most wrenching occasions of our lives. October is her birthday, and so when I made up the calendar for this year, I chose her image for this month.

Life is like this. The best things come to us out of the blue, unplanned, unexpected. The moon knows this as well. Its very existence was the result of a cataclysmic accident billions of years ago. Yet without the moon, our planet would be dead. In 2018 a girl from Taiwan got on an airplane and showed up at our house. Our world came alive. We will never be the same.

I don’t believe in astrology. The moon has no effect on our affairs other than the effects of its physical presence. That said, there IS a moon that affected and still affects our lives, in precious, wonderful ways. Her name is Luna. Happy birthday, Luna. 我爱你

Much of the time, we know something is out in the universe because it is glowing, emitting its own light or reflecting the light of something else. But glowing matter isn’t all there is in the universe. Sometimes we know something is there only by the shadow it casts. These are the Dark Nebulae.

Imagine that instead of just looking at this image, you’re actually looking through a very, very long pipe and seeing this image. You see thousands of beautiful points of light, but you have no idea how far down the pipe they are. You try to reach into the pipe to see if you can grab one of those points, and you can’t, so you know they’re farther away than your arm. You try a broomstick, but come up empty. Everything you try only tells you that those points of light are farther away than that.

This is the situation with the universe. We have developed methods of determining distances to some things in the universe, but in most instances, the distance to a particular star is still a mystery. We only know it is vastly distant. Where dark nebulae are present, though, we have a new clue. Here, with the Cocoon Nebula, we see a sinuous streak of darkness primarily because there seem to be fewer stars in that location than in its surroundings. In fact, that’s not the case. The star field is quite uniform in this area of the sky. The dark nebula is in front of most of the stars.

Here we have a hint at the three-dimensional nature of what we’re looking at. The dark nebula is associated with the beautiful emission and reflection nebula at its end (thus the moniker) and we have techniques for determining how far away the bright part of the nebula is. In fact, it is about fifteen light years across and some 2,500 light years distant. Since the dark nebula is associated with it, we know that most of the stars in this are are farther than 2,500 light years distant.

Try to imagine this image in three dimensions. Some of the stars are just a few hundred light years distant, maybe even less than that. Others are thousands of light years away. There are stars at every distance in between. Somewhere in there, a river of obscuring matter disrupts the view. The stars behind it can’t shine through it, and we are standing in the shadow it casts.

Of the events that occur in the universe, few rival the spectacle of a star “going supernova.” If a star is sufficiently massive, when it can no longer sustain its nuclear furnace, the star will collapse upon itself. Its interior will reach temperatures of hundreds of millions of degrees, and it literally blows itself apart. For a few weeks, that single event produces more light than the rest of its host galaxy combined. The explosion produces an expanding shock wave that takes tens of thousands of years to dissipate. We know these shock waves as Supernova Remnants. The Cygnus Loop is one of these.

Spanning a section of sky at least five full moons across, the Cygnus Loop is the most spectacular supernova remnant in the northern sky. It’s a few thousand years old, and still expanding at a five hundred thousand miles per hour. As it expands, it collides with the undisturbed gas and dust in the area, heating those gasses until they glow. The hotter they are, the brighter they glow, and their color tells us their composition. Red is hydrogen and blue-green is oxygen.

The arc that forms the lower boundary of the nebula in the image is called “The Veil Nebula.” It’s a personal favorite of mine. As a young boy, an image of this nebula ignited in me a curiosity about the universe that still drives me. The Veil actually trails the leading edge of the shock front, the wispy red line that can be traced around the entire complex.

We find the “Witches Broom” nebula at the top of the image. Honestly, I don’t see a broom or a witch, but that’s what it’s come to be called. It bisected by a bright naked-eye star, unassumingly named 52 Cygni, so named because it was determined to be the 52nd brightest star in the constellation Cygnus. Between the Veil and the Witches Broom, we see a sinuous nebulosity that terminates in a triangular shaped region called “Pickering’s Triangle.” It was discovered by Williamina Flemming, one of E.C. Pickering’s famous “Computers,” a group of talented women who worked for him at the Harvard College Observatory in the early 1900’s.

The irregular shape of this shock front is the result of variations in the density of the gasses and dust in the region. When the shock wave encounters denser medium, it slows down, releasing some of its kinetic energy as heat and light. This lets us understand the nature of the matter throughout the area, because where the brightness of the nebulosity attests to the density of the otherwise unobserveable matter.

Supernovae are one of the primary mechanisms for spreading elements heavier than hydrogen into the environment. Manufactured in the final seconds of the doomed star’s life, elements throughout the periodic table are created in incredible amounts and blasted into the same stuff the resulting shock wave will compress to trigger star formation activity. So the end of a star’s life is the beginning of the lives of many stars. Those stars will incorporate the heavy elements created by the supernova. The forming stars also create disks of matter, orbiting the gravitational center of the system. Those disks are chock full of everything it takes to make planets. Our planet formed in exactly the same way. Every atom in our planet and its atmosphere heavier than Hydrogen was transported from an ancient supernova site to the place where our solar system formed. You and I are made from the same stuff.

The Cygnus Loop, and innumerable other examples long since faded, are where the matter that makes up everything came from. This image does not show the death of a star. It shows the beginning of everything.

Virtually everyone on Earth has seen the moon. It is far-and-away the most common way people everywhere experience the night sky. For millennia, songs have been written about the moon and its influence on humanity. “Claire de Lune” and “Moon River” are a couple of my personal favorites. There are legends involving the moon’s effect on people, particularly the full moon. It appears in ancient petroglyphs. Many cultures consider it a goddess and worship it. Yet, for all that attention, we have learned about its surface, its composition, and its history only within the last few hundred years. Today, even with relatively modest equipment, we can see the lunar surface in breathtaking detail. This month we celebrate the 50th anniversary of the Apollo 11 landing, with four images of the moon.

Let’s start with Clavius. This crater is one of the largest on the moon, and is situated near the moon’s south pole. The result of waves of asteroid bombardment over the last couple of billion years, this region is exceptionally rugged. While much of the near side of the moon is covered by relatively smooth “seas” of lava flows, no such geologic activity occurred in this area. This left the shattered and churned upper crust intact here. Even in this image, we can see thousands of craters large and small, young and old, crowding and overlapping each other, evidence of the intensity of the bombardment so long ago.

Mare (mar-ay) Imbrium is a gigantic lava flow, easily visible to the naked eye when the moon is full. This image shows about a third of it. To early astronomers, it looked like a sea, thus the name “Mare,” latin for “sea.” If it is a sea of anything, it’s a sea of lava, now hardened, the result of the impact of a very large asteroid. This asteroid was almost large enough to shatter the moon itself. Fortunately for us, that didn’t happen. Ranges of mountains surround Imbrium. They are essentially the walls of the crater formed by the impact. We can tell this feature is relatively young because has relatively few craters in it. Astronomers piece together the timeline of the moon’s surface by “crater count” studies. Fewer craters means that region is younger than another region with more craters.

Like Earth, the moon has poles. They are defined by the moon’s rotational axis, which is fairly well aligned with our own. This is one of the remarkable coincidences that leads us to believe the moon was once part of the earth. Because of this alignment, it is impossible to study the poles from earth. We can see where they are, but their features are hidden. With the arrival of the Lunar Reconnaissance Orbiter in 2009, we finally got our first glimpses of the polar terrain. That doesn’t keep me from taking pictures of the area though. We can see high crater rims silhouetted against space, and brilliant rays emanating from the region, evidence of large impacts there. Scenes like this make me feel like I’m orbiting the moon myself.

Last, but not least, we come to my absolute favorite region: The Straight Wall and its surroundings. Visible just right of lower center, this feature is only visible for a few days each month, as the sun is just rising or setting there. In images and telescopes, it looks like a sheer cliff, almost as straight as an arrow, bisecting the remains of a ruined and flooded crater. In fact, it is a relatively gentle slope of perhaps ten degrees, that is still shadowed until the sun is at least that high in the sky. It owes its straightness to the geology underneath it. It lies on the edge of a lunar sea, Mare Nubium. The impact that created this mare fractured the crust giving the molten lava beneath a path to the surface. As it filled in the basin created by the impact, it cooled and hardened. As it cooled, it contracted, which pulled the surface downward in places. The Straight Wall is one of those places.

It’s remarkable to me that we can see the moon’s surface this well. It’s about 250,000 miles away at any given time, and when you think about it, that’s a long way. But it’s even more remarkable to me that we’ve actually been there. I could go on for a long time about my own experiences and how the Apollo program affected me, but suffice it to say here I am, 50 years later, still in love with the heavens!

With the advent of the 1950s, two new telescopes had come online, the famous 200″ Hale Telescope, and it’s important partner, the Samuel Oschin 48″ Schmidt Camera. That telescope had a very wide field of view, and was used to create the first ever complete photographic survey of the northern hemisphere sky. A twin was used to complete the survey for the southern hemisphere, and for the first time, astronomers had a view of the whole sky. The revolution had started.

In 1953, and again in 1959, an astronomer named Stewart Sharpless went through every single image from what was then called the Palomar Observatory Sky Survey, looking for glowing clouds of Hydrogen that had been missed by earlier astronomers. He found 312 of them, and his catalog of these objects is used by astrophotographers to this day to find beautiful and less-often photographed objects..

SH2-29 is typical of these Hydrogen clouds. Stars are forming here, and as their nuclear fusion processes begin, they bathe the area in their light. The ultraviolet light they shed causes the Hydrogen to fluoresce, and their visible light illuminates the dust around them, creating reflection nebulae. Dark, sinuous lanes of dense dust cross the area, which is framed by enormous amounts of obscuring dust.

This dust contains the basic building blocks of life: compounds of Carbon, Hydrogen, and Oxygen. Many such molecules have been detected in clouds like this, everything from simple water and methane to sugar complexes. There’s a relatively exhaustive list of the compounds discovered to date on Wikipedia. In one way or another, all of these molecules are part of our daily existence. Their existence in places like this offer yet another testament to the fact that “We are made of star stuff.”

So, while this picture is perhaps not eye-poppingly spectacular, in it we see ourselves, as things were maybe four billion years ago. People ask me all the time if I think there is life elsewhere in the universe. To them I answer “It seems likely.”

A famous song from the early 20th century starts with the line “Though April showers may come your way, they bring the flowers that bloom in May.” April is typically not a great month for deep sky astrophotography, .so when May comes around and some of us astrophotographers can’t wait to get back to photographing the stars, we sometimes photograph another star: our own.

It turns out that our star is extremely photogenic, and there are some who make images of little else in the sky. It’s tricky to get a good image of the sun and this one, while adequate, is nowhere near the fabulous images I’ve seen from seasoned practitioners of solar photography. Even so, there’s plenty to see here.

The sun is, of course, literally blindingly brilliant. To look directly at it for any length of time risks permanent damage to your retina. The same holds true of cameras. To photograph the sun, its brightness must be reduced by a factor of a million or more. Even then, it can be a relatively featureless disk, with a few sunspots interrupting its seemingly smooth “surface.” When all but the light of Hydrogen is eliminated, though, we can see the true textures and features of the light-emitting surface of the sun.

In this image, most notably, we see a bright region to the lower right. This is called an “Active Region,” primarily because there’s a LOT going on in things like this. The brightest parts are extremely hot, much hotter than the normal temperature of the surface, made so by the intense twisting of the magnetic field in the area. This magnetic field seems to emanate from the dark sunspot and its associated bright region, organizing the otherwise random texture of the sun’s gasses. The magnetic field lines are easily traceable here. This region is a good candidate for a solar flare. If the magnetic field gets twisted enough, it could produce a major flare, disrupting radio and satellite communications, power grids, and producing displays of northern lights.

Solar prominences are usually considerably more benign. These clouds of glowing gasses occur in all kinds of shapes and sizes. Most are rather small, but some gigantic ones have been photographed over the years. A quick google will turn up some spectacular examples. There are a couple of them at the right edge of this image. These are easy to see against the dark background of space, but they’re not the only ones present in the image. The many dark ribbons crisscrossing the surface are all prominences; they’re just not as plain as the ones at the edge. Their dark appearance tells us they’re cooler than the surface.

One great thing about photographing the sun is that you can do it during the day. Long sleepless nights are not needed, and in fact, are not even useful since you obviously can’t photograph the sun at night. (You’d be surprised at how often I’m asked why when I say that.) The next time you glance up at the sun, keep in mind that there’s a lot going on there you can’t see!

Spring ushers in a sky almost completely devoid of anything other than galaxies. In this season, as we look upward from our northern hemisphere perch, we are looking out of our galaxy, perpendicular to its plane, through the few stars that stand between us and billions upon billions of galaxies. There’s little dust and gas to obscure our vision, and the blackness of the sky is because we can see all the way to the edge of the universe.

While we are familiar with the grand parade of nearby spiral galaxies like M31, the Andromeda Galaxy, and M51, the Whirlpool Galaxy, the majority of galaxies in the universe are much smaller and less organized affairs. Dimly let with relatively few stars, we can only see these galaxies well enough to study them if they’re close by. IC 1613 is such a galaxy. Classified as a Dwarf Irregular, it has almost no organization and at 11,000 light years across, is remarkably small. By comparison, our own galaxy is estimated to be in the vicinity of 53,000 light years across, and the Andromeda Galaxy is a whopping 110,000 light years in diameter.

Dwarf galaxies such as this one are relics from an earlier epoch in the evolution of the universe. Most of the stars in IC 1613 appear to be about seven billion years old, about half the age of the universe. These galaxies are the building blocks of the large galaxies we can see, being gravitationally incorporated over time. IC 1613 has avoided this fate, at least thus far, and because it’s situated nearby on a very clear line of sight, we can study it very carefully. Those studies have gauged its distance quite accurately at 2.38 million light years. This is about the distance of the Andromeda Galaxy.

IC 1613 is somewhat unique in that it does have an active starbirth region, visible as the red knot on the upper right edge of the galaxy. How any hydrogen gas has lasted this long in this galaxy is a matter of considerable curiosity. We can only conclude that even the most mundane of galaxies is capable of surprising us.

This image came about at the request of a friend of mine, who was doing a visual observing program that included this galaxy. She concluded it was not visible in any telescope she had access to, and questioned why on earth it would have been included in such a list! She asked me to take a picture of it, and when I did, I concluded the same thing. I don’t think there’s any way an amateur sized telescope could see this galaxy.

In spite of my friend’s lack of success with this galaxy, you can enjoy it in this calendar image. Imagine this is the most common type of galaxy in the universe, but beyond a few tens of millions of light years they’re just too small and faint to observe. Imagine that our sun possibly formed in a galaxy just like this, and was subsequently swept up into a growing mass of stars that eventually became the Milky Way. It’s entirely possible that we came from a galaxy much like this one!

Riding high in the late winter sky, in the constellation Auriga The Charioteer, a vast cloud of hydrogen glows as it produces copious numbers of stars. Among these clusters, M38 reigns supreme. There are few clusters in our sky to rival the sight this one presents to both the visual astronomer and the astrophotographer.

Surrounded by an extensive envelope of hydrogen, in which plenty of new stars are still forming, M38 is a cluster in the middle span between its fast and furious beginnings and sedentary old age. The hot blue stars are nowhere to be found, with their life ended as supernovae or having been gravitationally ejected. What’s left is stars that will live for billions of years.

These stars will eventually completely disperse and are doubtless in the process of doing so even now. This happens because of gravity. Stars exert a gravitational pull, and when one star ventures too close to another, the less massive star picks up speed as it moves by. This is the same effect we see with space probes as we use planets to give them a “gravity boost.” This isn’t the only condition for a star’s expulsion from the cluster. The cluster itself, as the sum of all its constituent stars, has a gravitational field. When stars are gravitationally accelerated to a speed greater than the cluster’s escape velocity, that star will exit, never to return. As more and more stars exit, the gravitational pull of the cluster diminishes, which makes expulsion even easier and more likely. Once the process starts, it’s irreversible, and it happens for almost all clusters.

Just below M38 is the less massive cluster NGC 1907. Though it appears to be smaller, we can’t say for certain that it is simply by looking at a visual light photograph of it. It may just be much farther away, and so appear to be smaller much like a distant building appears smaller than your outstretched hand. Without studying the cluster with specific photographic and spectrographic techniques designed to estimate the distances to star clusters, we can only say that it is probably less massive M38, owing to the smaller number of stars it contains. Interpreting scenes in this way gives us a sense of the three-dimensional nature of what we’re actually looking at.

In fact, those studies have been done for M38 and NGC 1907. M38 is about 3,500 light years distant, while NGC 1907 is about 4,500 light years away from us. This distance difference is not enough to account for the difference in apparent diameter, so with that information, we can conclude that NGC 1907 is indeed smaller than M38, and in fact may not have even been born of the same cloud of hydrogen. These clouds typically are not 1,000 light years across.

At the bottom of the image, cropped in the calendar version, we see two bright areas known as “The Spider” and “The Fly.” The Spider seems to have long legs, perfect for sneaking up on the smaller fly to devour it. I’ve always said astronomers have too much time… personally I don’t see a spider OR a fly!

Like most such clouds of hydrogen, there is considerable structure in this one. It is shaped by the forces of nature, gravity, stellar winds, radiation pressure, and shock waves from supernovae and new stars. Long festoons of glowing gasses drape the area, with dusty silhouettes creating large dark voids where, in fact, there is more matter than where the gasses are more clearly seen.

Other clouds of hydrogen are almost featureless, blank slates which have yet to collapse into stars which will create the chaos we see in scenes like these. This phase of a hydrogen cloud’s life is actually rather brief. It exists, dark and hidden, until something happens to trigger star birth. That event creates a chain reaction, which will ultimately disperse both the cloud and the stars it created into the vastness of the galaxy.

In the winter sky, toward midnight, you can look in the southern sky and see the brightest star in our sky: Sirius. Often giving off brilliant flashes of blue, green, and red, this bright white star is unmistakable. About a hand width straight east of it is where we find these two star clusters: M46 and M47.

M47 is the cluster on the right. It sparkles with bright blue stars, set against a crowd of stars of various brightnesses. These stars are massive and young. We know this because to be that blue and bright, they must be fusing hydrogen into helium at an astonishing rate. This means they won’t live long, ending their lives in a few million years as stupendous supernova explosions. Thus, M47 is a young (astronomically speaking) cluster of stars.

In contrast, M46, the cluster visible on the left of the image, is an older cluster. Gone are its blue supergiants, along with any star that lived its life fast and died hard. These stars are all mainstream, run-of-the-mill stars, most of which will last billions of years. In fact, it’s old enough that one of its stars has entered the final phase of life: a planetary nebula. These are so named because they’re generally round, and mimic the appearance of planets through the eyepiece of a telescope. This one does seem to be associated with M46, and adds a beautiful jewel to an already lovely scene.

That M46 is still discernible as a cluster at this age is remarkable. Most clusters would have long ago dispersed into the general stellar population of the galaxy. Only the most massive star clusters have the gravitational power to prevent this. M46 is obviously massive enough to avoid that “fate.”

There are two other clusters clearly visible in this image, though they are much closer to complete dispersion. One is above M47 at about 11 o’clock, and the other is to the lower left, about 7 o’clock. Another cluster is present, but is not discernible against the starry background. We only know a cluster remnant is present because there is a statistically unlikely group of stars of similar age in its location. This cluster is to the lower right, but you can’t find it!

Every star in this image began life in a cloud of dust and gas like last month’s image of M78. The stars formed in clouds like that created clusters similar to these, with hundreds or even thousands of stars in each. As time progressed, the hot blue stars exploded and the rest were left to join the hundreds of billions already orbiting the galactic center. Last month we saw stellar nurseries. This month we see adolescent, adult, and old age stars. In March we’ll see toddler stars!

In the evening, Orion’s Belt, a row of three brilliant stars, can be seen rising in the southeast, at least for us mid-latitude northern hemisphere dwellers. It’s an iconic sight, written about by civilizations as ancient civilization itself. What those civilizations couldn’t know, is that there’s much more to Orion than meets the eye. This image includes two perfect examples, situated just north of the eastern star of the belt: Alnitak.

M78 consists of two regions of brightly glowing “reflection nebulae,” seen here at right-center. These objects are very dusty, and the brilliant light from the newborn stars embedded within the clouds of dust illuminate their surroundings with their blue light. Just like dust on your dresser, though, it is thinner and thicker in places. Where it is thicker, even the light of these brilliant stars cannot penetrate, and we see those areas in silhouette against the brightly glowing background.

M78 is crowded with young stars, most of them too dim for their light to get through even the thinner dusty regions. The light from the brighter stars will resolve that problem. Since light actually exerts pressure on atoms, molecules, and tiny grains of dust, the light from the bright stars is in fact literally blowing the dusty shroud away. Soon, relatively speaking, there will be “naked” star clusters in the place of M78. An unrelated example of one of these can be seen near the left edge of the image.

The lovely red arc that dominates the left side of the image is thought to be a supernova remnant, the almost-spent shock wave from the explosion of an ancient massive star. It is very large, basically wrapping the entire east side of Orion. E. E. Barnard, the famous mapper of the Milky Way, discovered this glowing loop, and this it’s named after him. Perhaps it’s no coincidence that there are so many starbirth regions in Orion. There is a lot of hydrogen and dust in this part of the sky. The compression of this passing shock wave may have been enough to trigger regions of gravitational collapse in this massive cloud, the first step to forming a new star.