Saturday, June 16, 2018

At the Birth of Creation - HD 150283

Most amateur astronomers love to boast about the furthest thing they've either seen or imaged in the sky, so how about spending a glance or two taking in the oldest object up there you're likely to ever see? I'm talking about the blue-white subgiant star HD140283 in the constellation Libra. HD140283 is an extremely metal-poor visitor to our neighborhood from the galactic halo (its inclined orbit about the Milky Way's core causes it to pass through the spiral arms twice per revolution), and is currently a mere 190 light years away.



HD140283 has been baffling astronomers for more almost 2 decades now, ever since its age was calculated back in the year 2000 to be approximately 16 billion years - in other words, older than the universe itself! Well... thanks to Hubble, we have now refined those earlier estimates downward, and the star is currently thought to be 14.5 billion years old, plus or minus 0.8 billion years. This is one case where that "plus or minus" turns out to be extremely important! Subtracting the full uncertainty factor from the estimate gives us an age of 13.7 billion years, i.e., about as old as the universe itself. HD140283 must therefore be one of the very first stars ever to have formed.

Indeed, HD140283, now affectionately nicknamed "Methuselah" by those studying it and officially the oldest known star in the universe, fits the expectations of what such a star would look like. Its metallicity (the percentage of a star's mass made up of elements heavier than hydrogen or helium) is only about 1/250th of the sun's. Recall that the younger a star, the higher its heavy element content, due to "seeding" from preceding generations of stars gone supernova. (It is believed that the early universe contained no heavy elements whatsoever.)

Astronomers believe that HD140283 did not form in the Milky Way, but is instead a survivor of a long-lost dwarf galaxy that was sucked into and absorbed by our own galaxy about 12 billion years ago. Its highly elliptical orbit within the halo is testimony to this long-ago cataclysm. At the moment, HD140283 is passing through our sun's spiral arm at a speed of more than 800,000 miles per hour - so fast that it can actually be seen to change position against the background stars in Hubble images taken only a few hours apart!

At magnitude 7.2, HD140283 should be an easy binocular object, but is best seen through your telescope. WARNING! Starhop instructions follow! Start by locating the constellation Libra, and identify the two brightest stars, Zubeneschamali (mag 2.6) and Zubenelgenubi (mag 2.7) (Don't you just love those names?), a.k.a., Beta and Alpha Librae. Making a rough equilateral triangle with these two stars is the magnitude 3.9 Gamma Librae, over to the left. Using a line between Gamma and Beta Librae as the hypotenuse of a yet smaller right triangle, you can then locate the magnitude 4.6 star 37 Librae, which would mark the point where our imaginary 90 degree angle would be. (This second triangle would be hanging off to the left of the first one.) From here it is an easy star hop of approximately three full moons leftward and slightly down to our target, HD140283. There is no other star in the immediate vicinity even approaching this one in brightness, so there should be little difficulty in making a positive identification.

Just remember when observing this "dot" that you are looking back to the very beginnings of our universe. Quite a thought.

Wednesday, June 13, 2018

BOOK REVIEW: Objects in the Heavens, by Peter Birren

Amongst the most impossible questions to answer at a star party is "What is the best telescope? Which one should I buy?" Of course the best answer to that imponderable is "The best telescope is the one that you'll use." Well.. the same thing goes for handbooks, manuals, and star charts. The right question to ask is "Am I going to use this?" And as regards Peter Birren's Objects in the Heavens, the answer is an unqualified YES.

I saw this book advertised on Page 5 of the June 2018 issue of Reflector Magazine, and was sufficiently intrigued to check out the website (www.birrendesign.com). What I saw there convinced me it was worth a try, so I ordered a copy. I have to say it arrived in near record time.

First of all, the externals. The book measures 8.75X5.5 inches, so it is a very convenient size (unlike the mammoth 2 volume Night Sky Observer's Handbook published by Willman-Bell, my
go-to reference guide). I like the spiral binding - allows the pages to lay flat with nothing lost in the fold. I haven't taken it out in the field yet, but the paper does not appear to be dew resistant, so you might want to take precautions against it getting damp. The author uses his own idiosyncratic symbols for various objects, but I quickly got the hang of it, and found some of his innovations rather useful (such as making the distinction between binocular and telescopic objects). The star charts are for illustrative purposes only. The book might be best used in conjunction with Sky and Telescope's Pocket Sky Atlas.

Objects in the Heavens is divided into 3 major sections. The first is a very fine reference/introduction aimed at a novice audience. It's amazing how much is covered in such a small space (40 pages). It would be exhausting just to list the topics covered. Everything from explaining how various types of telescopes work to what is meant by right ascension and declination to a quick tutorial on how we got the constellations as they now exist, and literally dozens of other subjects as well.

Seven pages of the introduction are dedicated to the Moon. This is probably the weakest section in the book, but it's hard to see how it could have been otherwise. The Moon really requires a book to itself to do justice to the challenges of observing it. But I do give Mr. Birren credit for dividing his treatment of the subject by days after new moon. So he has a list of the major features sitting atop the terminator for each day. Unfortunately, the accompanying illustrations are just too small to be useful on their own. For the most part, I have no quarrel with the features he chose to highlight.

The introduction ends with 4 very attractive charts, one for each season.

The meat of the book is Section Two, a constellation-by-constellation listing of Deep Sky Objects (magnitude 10 or brighter) with brief, often amusing, descriptions of what you're looking at, accompanied by a chart of the constellation itself. The introduction says there are 830 objects identified in this book - enough to keep most stargazers busy for several years, if not a lifetime. I like the balanced nature of Birren's listing. It's not top heavy with galaxies or overly dominated by open and globular clusters. There are nebulae galore and enough double stars and even singleton stars to satisfy even a fanatic like myself. (Almost! I checked for some of my favorites, and was sad to find many of them them missing. But come on, there are countless thousands of the things up there viewable through the average telescope. So if Struve 2398 (one of my favorites) was omitted, I can't really complain now, can I?

I was pleased to find Barnard's Star listed, but disappointed to not see Lalande 21185 in Ursa Major. What gives, Peter? How did you miss that one?

But on the flip side, there are more than enough listings that I had never heard of, which just goes to show that any list compiled by a single individual will never match another's. And that's a good thing.

The constellations are listed alphabetically and not in the order they appear in the seasons, just as they are in the Night Sky Observer's Handbook.

The final section is enough space to record 15 sketches of your own observations. You can order separately a second volume entirely devoted to sketching. (I did not, so I cannot comment on it.) I heartily endorse the author's maxim: "Trust nothing to memory!" Good advice.

Bottom line? Objects in the Heavens is value for money ($24.95), and I will definitely be consulting it when planning future nights out under the stars.

Monday, April 30, 2018

The Daytime Sky

This is a reprint of something I wrote for the now defunct HAL Forum way back in September 2013. I thought it worth revisiting in these beautiful spring days.



This morning was just too beautiful to let pass without taking advantage of it, so I decided to walk the 3 mile round trip to the grocery store to get the handful of items I needed for tonight's dinner. Along the way, I couldn't help but notice the horizon-to-horizon cloud-free sky overhead. My first thought was, "Why couldn't it be like this in the middle of the night, dammit?"... But my second thought was, "Wow, look at all that blue up there - it almost hurts the eyes!" And boy, was it ever blue. As it can only get on one of those late-summer, low humidity, hint of fall in the air, mornings like today. I found I couldn't take my eyes away, and had to stop for a while before I ran into something.

All that brilliant blue got me to thinking about how we visualize our place in the universe. All too often, we thoughtlessly dismiss how the Ancients viewed the cosmos - Earth at the center, everything else revolving about us in concentric spheres, like a gigantic version of one of those Russian nested dolls. But when we pay attention to how artists and writers living before Copernicus actually depicted the Cosmos and forget what we have projected back onto them, we discover that wasn't really the case at all. A far more accurate statement would be that they considered the Earth to be the bottom of the universe, and only incidentally its center. Near the end of The Divine Comedy, Dante imagines himself has having traveled to the Sphere of the Fixed Stars, looking back on the Earth:

My eyes went back through the seven spheres below,
And I saw this globe, so small, so lost in space,
I had to smile at such a sorry show.
Who thinks it the least pebble in the skies
I most approve.
(Paradiso, Canto XXII, lines 133-37)

And there are many, many other examples as well. But this should suffice to put to rest the misguided idea that the Ancients somehow believed that we occupied some sort of privileged spot in Creation.

But what does all that have to do with that blue, blue sky up there this morning? Just this - up to only a few centuries ago, Mankind thought that the whole universe looked like our daytime sky. They were well aware since at least 200 BC that the Sun was far larger than the Earth, so it was easy for an educated person to deduce that the Earth's shadow would be a cone (as it in fact is). And being unaware as yet of the refractive properties of light, they may be excused for imagining that the darkness of the nighttime sky was restricted to that part of the Heavens which happened to be within the Earth's shadow. The rest of "everything up there" was assumed to be as brilliantly lit as the noontime sky on a cloudless day. What a glorious vision! No wonder Milton could write such lines as:

Those happy climes that lie
Where day never shuts his eye
Up in the broad fields of the sky.


But we know better now, right? Hah! Speaking for myself, despite all I know about the structure of the universe, the Milky Way, the Solar System and our place in it, I still picture the sky as being somehow "overhead", with myself "down here" looking up at it. I still refer to Sunrise and Moonset, and to Polaris not moving in the sky. And it's damn hard to not think in that way.

It was only a week or so ago, when for a brief moment at a Carrs Mill Star Party, I caught a glimpse of what it would be like to visualize things as they actually are. There were only two of us there that evening, Dwane and myself. I was looking straight overhead at Vega, when without warning I (quite literally, and not figuratively) practically lost my balance, I got so dizzy. I suddenly saw Vega as not being above my head, but rather straight in front of me. The Earth was no longer beneath me, but instead I felt like it was a wall to my back, with me somehow pinned to its side - looking not up, but out, at the stars around me. I had to sit down.



I was almost relieved when things got back to normal - Earth down here, stars up there. (It was rather fun to take a peek at Reality - but just not for long.)

Do get out there on the next clear, sunny day and try to look through all that blue up there. It can be exhilarating (as long as you can get back down).


Thursday, April 5, 2018

In Defense of Starhopping


"Lonely Scope" 
Image by Mike Krauss, taken the night I first saw Barnard's Star
80mm Stellarvue Refractor on Manfrotto tripod

I'm occasionally kidded at star parties for my lack of "technological" accessories in my gear. I'm out there with tripod, mount, refractor, and 3 or 4 eyepieces, and of course my chair. But that's it. No go-to software, no computer even, no tracking... heck, I don't even have a finder scope. For my part, I enjoy being able to set up within 5 minutes tops and then sitting back to watch others struggle with a million pieces of equipment while I take in the deepening twilight, waiting to catch the first stars coming out for the night.

And then, after we're all set up and everyone is polar-aligned, I start out on my list of "must sees" for the evening - sometimes finding what I'm looking for in a matter of seconds, and at other times struggling for half an hour or more to nail down that uber-faint 10th magnitude star that (let's be honest) looks like every other star in my field of view.

Meanwhile, everyone around me is selecting their targets from the database on their go-to mounts, and I can hear the whir of the scopes as they slew round to the exact spot in the sky desired. No hunt, no search, and any frustration is levied at either the equipment or the alignment.

Now I can appreciate the utility of such a procedure, if your primary purpose for being out there that night is imaging. You're not going to be looking at anything anyway, and the less time searching the more exposure time you have. I get that.

But I must be perfectly honest here. When the purpose is observation, I fail utterly to understand the desire to forego the hunt and head straight to the target. Would somebody please tell me where's the satisfaction in allowing our machinery to have all the fun? Would a fisherman enjoy a day out on the lake if he brought along a robot that located all the fish and reeled them in? Would you admire a diving catch by a right fielder at Oriole Park, if you knew that his glove was guided to just the right spot by embedded software within a prosthetic arm? (Hm... I wonder. Will that be a real world problem in the near future?)

Now I just got out of Howard County General Hospital, where I spent the better part of last week trying to not lose my right leg to a virulent infection. (I am on the mend!) While there, I had nothing else to do but read, read, and read some more. One of the things I took in was a short story by the English writer G.K. Chesterton, which went something like this. Two brothers meet up with a wizard who offers to grant one wish to each of them. The first brother, who always wanted to "see the world", wishes that he would become a giant, so he could walk with ease from wonder to wonder and take it all in. The second brother's wish is that he would become just inches tall. Both wishes were granted, and the first brother immediately set off on a whirlwind tour of the globe. But it wasn't long before he tired of the whole affair. It took no effort to go from the Great Wall of China to the Parthenon to Machu Picchu, and before you knew it, everything simply bored him. He returned home miserable and unsatisfied, despite having "seen it all".

Meanwhile, his brother (now only 2 inches tall) went from flower to flower, from stone to stone, from raindrop to raindrop, drinking in the wonder and beauty of it all. The strenuous effort it took to climb atop a mere stone in the back garden only made the view from the summit all the more appreciated.

This story immediately made me think about starhopping. It's rather like being 2 inches tall in a garden of spectacular beauty. It takes time to go from star to star, from Messier object to Messier object, and sometimes you never do get to where you wanted to go. But you don't care! In fact, the hunt is often (but not always) more satisfying than the finding. And there are unsuspected discoveries to be made along the way. I've long ago lost count of the lesser-known globulars, the NGC-cataloged open clusters, the unnamed sparkling asterisms, and even the odd unlooked-for Messier objects that I chanced upon while looking for something else - sights I otherwise might never have laid eyes on. (That is how I first saw the Sunflower Galaxy.)

What follows is something I wrote several years ago and posted to my (now inactive) earlier blog, Celestial Pilgrimage:

One of the wisest books I know, The Little Prince by Antoine de Saint-Exupery, contains the following passage (which I have here slightly altered): "People no longer take the time to learn anything. They'd rather buy things ready-made in stores. But since there are no stores where you can buy what is truly important, people no longer have anything of importance ... It's the time you spend on something that makes it so important."

Take the time. You will thank yourself afterwards.


Monday, March 19, 2018

M67 - An Unusually Ancient Open Cluster


Open clusters are not generally long-lived objects. They are (in cosmic timescales) relatively quickly torn apart by gravitational influences as they wander through the galaxy. So after a few scant hundreds of millions of years, their individual stellar components live out the remainder of their lives as solitary stars (just like our own sun, and nearly every other star in the Milky Way Galaxy), and their parent cluster is only a memory.

But every now and again, an open cluster will manage to hold itself together, even after multiple passes through the galactic plane (the zone of maximum disruption). Messier 67 is a prime example of this rara avis. Estimated to be somewhere between 3.2 and 5 billion years old, M67 is quite the oldster. Composed of approximately 500 stars, of which about 100 closely resemble our own Sun, the cluster contains the mass of more than 1000 Suns. The consensus amongst astronomers is that M67's initial mass, some 4 billion years ago, was more than 10 times what it has managed to retain. What a sight that would have been!

But however glorious it may have looked in the distant past, M67 remains quite the eye pleaser. At apparent magnitude 6.1, it verges on being a dark sky naked eye object. Through my 8X56 binos, it is a distinct fuzzy patch just to the right of Alpha Cancri. In my 90mm Stellarvue refractor, I can make out dozens of stars enmeshed in a faux nebulosity, which in reality is the remainder of the cluster's stars which lie beyond my scope's capability to resolve. To my eye, M67 looks like nothing so much as a giant comma lying on its side. Either that, or a cat seen from behind, with its tail prominently displayed.

M67 lies somewhere between 2600 and 2900 light years from the Earth. Practically every type of star can by found within the cluster, from white dwarfs to blue stragglers, from Sun-like main sequence stars, to red giants.

M67 is not hard to find. Start by locating the dim constellation of Cancer, between bright Gemini and dramatic Leo. The Main Attraction in Cancer is of course the Beehive, or M44. The Beehive (also known as the Manger) is to the upper right of Delta Cancri, which lies smack on the ecliptic. (Fun Fact: Delta Cancri's proper name is my favorite of all the stars in the sky, the Babylonian word  Arkushanangarushashhutu - and no, I am not going to try to pronounce that!) Below and to the left of Delta Cancri is (despite its "Alpha" designation, the somewhat fainter star) Alpha Cancri. M67 is located not far to the right of Alpha Cancri.


Not so long ago, astronomers seriously wondered whether M67 was our own Sun's parent star cluster, principally due to the large number of Sun-like stars within it. But recent computer simulations of the non-intersecting paths taken by M67 and Sol have ruled such a thing to be extremely improbable.


Friday, March 16, 2018

Why is the winter sky so beautiful?

Well. Mainly, because there are so many bright stars visible in wintertime - far more than in the summer. And this, despite the fact that we enjoy the glorious star clouds of Cygnus, Sagittarius, and Scorpius during the hotter months. But let's face it, the individual stars making up those constellations are not, pound for pound, the equal of those composing Orion, Gemini, or Auriga... not to mention glorious Sirius, Procyon, or Aldebaran.

So why are there so many more brilliant stars up there in the winter? To understand why, we need to know a bit about the geography (so to speak) of our galaxy, and our place in it.


Take a look at the above illustration. Although the matter is not "settled science"just yet, there is broad consensus that the Milky way is composed of a nucleus, four spiral arms, and an uncertain number of "spurs" (broken off pieces of spiral arms). Our sun happens to be located on the inner (that is, closer to the galactic center) edge of the Orion Spur. Between us and the galactic core are no less than three spiral arms, the closest being the Carina-Sagittarius Arm. But when we look in that direction (in the summertime), our gaze has to first traverse many thousands of light years just to get to even the closest, or Sagittarius, Arm. So no matter how intrinsically bright any stars are in that direction, they're going to look dimmer just from sheer distance.

Not so in wintertime! We are smack up against the Orion Spur, and the blue-white or red supergiants in that direction are therefore that much closer. So it's mainly a cosmic optical illusion. The winter sky does not boast a greater number of bright stars - it's just that those that happen to be in that direction are significantly closer to us.

But who cares? Get out there and enjoy the spectacle of the glorious winter sky!

Thursday, March 1, 2018

After you've looked at M42...

... what is there to see in the winter sky? Actually, tons! For those of us unfortunate enough to live in the Northern Hemisphere, the winter sky contains more objects of interest than any other season - and that includes the summer Milky Way. Now I'm not going to attempt to list them here, but rather direct your attention to one undeservedly overlooked open cluster in Canis Major, NGC 2362.


This image captures what NDC 2362 looks like through my 90mm refractor.

The first time I chanced upon this Jewel of the Sky, I wasn't looking for anything in particular. I was simply letting the turning Earth beneath my feet bring new wonders into my field of view, while I allowed my scope to drift unguided. Then a most marvelous sight riveted my attention, and my aimless drifting was definitely over for the night. I simply couldn't get enough of this spectacular cluster, with its giant central star Tau Canis Majoris (which is actually part of the cluster, and not just a chance line of sight association).

To my eye, this cluster has a distinctly triangular shape, and is full of color. NGC 2362 is a baby amongst its fellow open clusters, being only about 4 million years old. Its central (and brightest) star is Tau Canis Majoris, a class O supergiant which turns out to be a fantastic multiple star system composed of at least 6 stars (and probably more). At magnitude 4.4, Tau Canis Majoris ought to be visible naked eye when observed under dark skies.

This cluster rewards the patient viewer, as many subtle details emerge as your eye becomes accustomed to the sight, and fainter members make their presence known.



NGC 2362 is approximately 5000 light years from our solar system.