Thursday, October 18, 2018

Averted Imagination

One of the oldest jokes in amateur astronomy is to (laughingly) accuse someone of using "averted imagination" while observing some really difficult object, such as a super faint galaxy or an impossible to split double star. Heck, I've on occasion accused myself of doing so. But truth to tell, it's often hard to delineate the line between desperately trying to see something and just plain imaging that you are successful at doing so.


Sirius and Sirius B (off to the lower left)

Case in point: last winter I was convinced I had finally, after numerous attempts, seen Sirius B (the white dwarf companion to Sirius) through the eyepiece. It didn't stay in view, dang it, but kind of "popped" in and out - the tiniest imaginable point of light nestled right up against the overpowering glare of Sirius. I even stepped away from the telescope and returned to see whether it was still there. And it was... But alas, when I did some calculations at home later that evening (science ruins everything!), I had to admit that whatever I was seeing could not possibly have been Sirius B - it was on the wrong side! (And yes, I did take into account my telescope's mirror imaged view.) So I sadly had to conclude that I was not only using averted vision to see my mystery object, but averted imagination as well.

So yes, an overactive imagination can be a real problem. It is likely a major component of why Percival Lowell and his contemporaries kept seeing all those canals on Mars. (I myself have seen them twice, despite knowing full well that they do not exist!)

But there may be an equal and opposite error possible.


A City on Mars, as imagined by artist Leslie Carr (1951)

Take a good look at the illustration right above this paragraph. I found this in a most remarkable book by science popularist and science fiction writer Arthur C. Clarke, The Exploration of Space (published in 1951, the year before I was born). It supposedly depicts a future settlement on Mars, but when you think about it, what it actually depicts is a quite unremarkable 1950s midwestern American city. Just look at that architecture! In fact, why is there architecture at all? You're under a dome - what need for buildings? And the cars! The dome looks to be all of 400 yard across. Just where are you going to drive? Plus, it would be sheer insanity to waste so much valuable (and limited) real estate on something as useless as roads. Finally, I wish I could see the pedestrians up close. I am sure they would fit in unnoticed in any random crowd of shoppers in downtown Indianapolis.

Now I am not pointing these things out to make fun of the illustrator - far from it! But what I am saying is there was a Failure of Imagination when designing the image. The implications of colonizing Mars were not thought through, and there was a (likely) unconscious assumption that the styles and norms of 1950 would not be out of place in 2150 (or whenever this future city was supposed to be built).

Another and far more glaring example of such a failure of imagination is when the news media inevitably announce every new discovery of an Earth-sized exoplanet as a "Second Earth", neglecting the too numerous to count differences (or possible differences) between said exoplanet and our home body. It seems that all that counts in such reporting is the mass of the planet and the distance from its sun. But there are a myriad of other qualifiers that must be met before we can even begin to speak of an "Earth 2", among them being age, atmosphere and water content, plate tectonics, possession of a moon, a rotating iron core (to create a magnetic field), prevalence of asteroids and comets in the system, distance from gas giants (if any), axial tilt and rotation rate... failure to match in even one of these traits  means we might as easily be looking at a second Venus as a second Earth.

Do we do the same thing when seeing some Deep Sky Object for the first time? Do we assume without thinking about it that "You've seen one globular cluster, you've seen 'em all!" and fail to see that M13 doesn't look at all like neighboring M92?

So we really ought to approach each new object with a mental clean slate - no preconceptions, no assumptions. These are the bad habits that prevent us from seeing subtle differences that ultimately make the difference between one genus and species and another.

Monday, August 20, 2018

Don't Hate the Moon!



Some years back, a fellow HAL member (who shall remain nameless - he knows who he is) quite calmly stated at a Carrs Mill impromptu star party, "You know, if I could shoot down the Moon, I would." It brought to mind the old Looney Tune character, Marvin the Martian, who was always saying, "I'm going to blow up the Earth! It obstructs my view of Venus."

And yes, truth be told, the Moon does "obstruct" our view of deep sky objects - especially the fainter ones. In some ways, it's the ultimate in light pollution. All those moonlight sonatas and syrupy old love songs about walking in the moonlight... "Bah, humbug!" is the reaction of all too many amateur astronomers. I especially hear this reaction when one of our all-too-rare clear nights coincides with a full or near-full Moon. (There almost seems to be an inverse correlation between how much Moon is up there and the percentage of cloud cover.)

But, please. Let's not throw out the baby with the bathwater. In and of itself, the Moon is one of the most rewarding objects up there to observe (see my postings on this subject from Nov. 30th and Dec. 2nd, 1017, entitled "Explorers!").

Now this very upcoming weekend is a case in point. It appears that we're going to be presented by the weather gods with at least 5 clear nights in a row (Wednesday through Sunday), with a Full Moon on Saturday. So you have a choice. You can either stay indoors and mope, crossing your fingers that the skies will be clear for the next New Moon, or you can use this opportunity to take a look at some sadly overlooked lunar features over on the seldom observed "left side" of the Moon's Earth-facing hemisphere. They are far too many to list outside of a textbook, but allow me to highlight 1 or 2 per evening.


The crater Aristarchus and surrounding terrain, as seen by Apollo 15 astronauts

Wednesday: The brilliant crater Aristarchus (brightest spot on the nearside hemisphere) will just be coming into view, around about 10 o'clock (2 o'clock in a mirror-imaged view). If you're patient enough, you can actually watch the endlessly fascinating surrounding terrain emerge into the sunlight, as dawn sweeps over it over the course of the evening.


Schiller

Meanwhile, down in the southern hemisphere, the dramatically misshapen crater Schiller is close to the terminator. This bizarre feature was created by a object striking the Moon at an extreme angle - almost missing it altogether.

Thursday: Go back once more to Aristarchus. The entire region will be in sunlight by this time, and the crater itself will be almost too bright to look at.


The Marius Hills, as imaged by the Lunar Reconnaissance Orbiter
(Click on image to see full resolution.)

Further south at approximately 9 o'clock (3 o'clock in a mirror-imaged view) and not far from the terminator, you'll come upon one of my personal favorite areas of the Moon to observe - the Marius Hills. This is a region of literally hundreds of volcanic domes and related features such as collapsed lava tubes. I remember well the first time I laid eyes on this feature, not knowing what I was looking at. Through the 80mm scope I was then using, it appeared that the Moon had either a bad case of acne or else goosebumps! The low elevation domes naturally show up best when they're smack on the terminator. They rapidly fade into invisibility as the shadows disappear just hours after dawn. So take a look while you have the chance!


Reiner Gamma, as imaged by Lunar Orbiter 4

Friday: For lovers of mystery and enigma, the Moon on Friday presents Reiner Gamma, one of the strangest features anywhere on its surface. Astronomers still do not completely understand how this feature originated, but they have some pretty good guesses. First of all, it is not a topographic feature. If you were standing right on top of it, you'd never know it was there. There is not an inch of elevation difference between its light and dark swirls, it being entirely an albedo feature. But orbiting lunar probes have detected a powerful, localized magnetic field directly under Reiner Gamma. It is believed that this field has charged fine dust particles in the regolith with static electricity, which has caused them to line up like iron filings around a magnet, like we used to do in high school science classes. (Do they still do that?) Reiner Gamma is found to the southwest of the Marius Hills.

No one knows why the magnetic field is there, making Reiner Gamma all the more intriguing.


Mare Orientale, as imaged by Lunar Orbiter 4

Saturday: To top things off, if you look over at the lunar horizon at about 8 o'clock (4 o'clock if your scope gives you a mirror-imaged view) you can catch a glimpse of the edge of what is possibly the most spectacular feature on the entire surface of the Moon, both near and far sides - the Mare Orientale. This is a truly gigantic impact basin (nearly 600 miles in diameter) although from the Earth we can only see its extreme eastern parts. Sometimes, you just have to take what you can get!

Sunday, August 12, 2018

Recharging my Batteries


This year's Stellafane was a landmark for me, in that this was the first year when I truly could not remember for certain how many of these I've attended. I have to admit that I'm an addict. I started going up to Stellafane several years ago when I was fully intending to move to New England, and thought it would be the perfect way to get acquainted with the local astronomy clubs. Well, here I am still in Maryland, and seemingly here to stay. But every summer, I feel the draw of the Vermont mountains, with their dark skies and quaint little towns filled with wonderful restaurants and totally unique art galleries and local crafts shops. I'm always done for the year with my Christmas shopping after a week in Vermont - and this year was no exception. I think I contributed about 700 dollars to the state's economy.

As for Stellafane itself, it's an opportunity to hobnob with hundreds and hundreds (there were as many as 1000 in attendance this year) of like-minded astronomy fanatics. Some of my favorite moments at various Stellafanes have occurred not on the observing field, but in the food tent or up at the Clubhouse, meeting perfect strangers and talking literally for hours about viewing conditions back home, our local clubs, our own and others' equipment, our observing triumphs (and failures), our children and/or grandchildren, the Drake Equation, plate tectonics, hot Jupiters, red dwarfs, meteorite hunting in New Hampshire, World War II, global warming, how amateur astronomy is going to hell in a handbasket, and ten million other topics.

But the meat and potatoes of any star party, whether it be a Carrs Mill Impromptu or a major regional like Stellafane, is what did you see. We had one superb night this year (Thursday), one so-so (Friday), and one cloud out (Saturday). So Thursday was the "Make or Break" evening, as far as observation went. And in my books, it all by itself was worth the 8 and 1/2 hour car ride north.

On Thursday night, I observed:

Venus
Jupiter
Saturn (saw 5 moons)
Mars (could make out the polar cap and Syrtis Major)
The Lagoon Nebula
The Trifid Nebula
The Small Sagittarius Star Cloud (M24) - came back to this again and again!
The Swan Nebula
The Eagle Nebula
The Wild Duck Cluster (M11)
The Dumbbell Nebula
M71 (globular cluster in Sagitta)
The Coathanger
61 Cygni (double star in Cygnus)
Albireo (double star in Cygnus)
Omicron Cygni (triple star in Cygnus)
Barnard's Star
B111 (dark nebula in Scutum)
M22 (globular cluster in Sagittarius)
M4 (with binoculars)
HD 162826 (with binoculars)
Several Perseid meteors (2 of them spectacular!)
The star fields of Cygnus (it spoils it if you look for anything in particular - just look!)
M6 (open cluster in Scorpius) - the last thing I looked at, just before tearing down
The Milky Way (just looked away from the eyepiece and drank it all in)
6 or 7 satellites
The International Space Station

The scope I used that night was my 102mm Stellarvue refractor with a variety of eyepieces.

The conditions were far less promising on Friday evening, so all I set up was my 60mm refractor, because I wanted to be able to tear down at lightning speed if I decided it wasn't worth hanging around. Besides, I could always look through other folks' monster Dobs if I felt like it! That night I had my best eyepiece view this opposition of Mars. Absolutely amazing how big it appeared. I know it wasn't, but damn if it didn't seem bigger than Jupiter. But Mars looked best of all naked eye, like a baleful red eye rising over the tree line. I couldn't get enough of it.

On Saturday, I woke up to wall-to-wall cloud cover and off-and-on rain. But it didn't bother me. I hiked up to the Stellafane Clubhouse and had some great conversations with the people who had entered their scopes into competition. Met one gentleman who had attended every Stellafane since the year I was born (1952)! He talked to me for half an hour about how one tested a newly ground mirror for accuracy, and showed off some equipment used in the process which he had designed and built himself. I admired the work of Sara Schechner who makes astonishingly beautiful astronomically themed quilts (her day job is the David P. Wheatland Curator of the Harvard University Collection of Historical Scientific Instruments). I ran across two young women from Roland Park in Baltimore, attending their very first Stellafane, and discussed the pros and cons of urban astronomy. I spent a good hour with a 77 year old man (whose name I never did get - he wasn't wearing his name tag) who told me his life story, occasionally with tears in his eyes. He was so interesting, I wish I could have taken notes, but that would probably have been rude. I saw (but did not speak to) Al Nagler as he walked by my telescope on the observing field. I hope he noticed my 9mm Nagler eyepiece!

(True Story: A couple of years ago, I was sitting right next to Al for a good 30 minutes during lunch at the food tent, and had no idea who he was. In my defense, I hadn't the slightest idea at the time what Al Nagler looked like. It wasn't until I was getting up to leave that two other people walked over and said hello to him, thus enlightening me to my now totally wasted opportunity to speak with one of my heroes.)

All in all, a great star party, and definitely not my last Stellafane. I look forward to the day when I can bring my now 5 year old granddaughter along with me. (Of everyone in my extended family, she is the most interested in (dare I say obsessed with?) astronomy.)

So here I am, back in light-polluted suburban Maryland, batteries recharged and ready for another year of stargazing!

Thursday, August 2, 2018

Things To Come

I know 2019 might seem like a long time away still, but it's not too early to plan for two major astronomical events which will be visible in their entirety from Maryland.


Total Lunar Eclipse
All the world's sunsets seen at once,
as reflected by the Moon

First: A Total Lunar Eclipse beginning at 9:36 PM on Sunday, January 20th, and ending at 2:48 AM on Monday morning. For once, we'll be able to see the entire thing - from the moment the Moon enters the Earth's penumbral shadow (9:36 PM) to when totality begins (11:41 PM) to when totality ends (12:43 AM) to the last hurrah (2:48 AM).

So there's a good reason to brave the cold of a mid-winter's night!


A Transit of Mercury

Second: A Transit of Mercury. Maybe not as rare or dramatic as 2012's Transit of Venus, but since I won't be around for the next one of those (on December 10th, 2117), I'll take what I can get! Mercury will make first contact with the Sun at 7:36 AM (exactly 50 minutes after sunrise) on November 11th, 2019 and be fully between us and the Sun approximately one minute later. The elusive planet will have left the Sun's disk completely by 1:04 PM, after a transit time of 5 hours 25 minutes. So once again, weather permitting, we'll be able to see the entire event - and this time in daylight!

Now just about everyone in HAL knows that I am a huge fan of Mercury, and that we're lucky to get just a passing glimpse of him in the evening twilight before the planet slips below the horizon. But here we'll get to observe him for a full five and one half hours! How cool is that?

Thursday, July 26, 2018

Triangulation

Every stargazer knows the Summer Triangle. Heck, it's like the Big Dipper or Orion. Just one of those things up there that we all take for granted, not really thinking about them. "Oh, there's the Triangle. Must be summer." And on we go.



But let's take a moment to really explore the obvious. What exactly are those stars which make up the Summer Triangle? First off, what are their names? From north to south, they are Deneb (Arabic for "tail"), Vega (Arabic for "falling") and Altair (Arabic for "flying eagle"). They are, respectively, the 19th, the 5th, and the 12th brightest stars in the entire sky. That is, at least as seen from the Earth. In and of themselves, their order in descending brightness would be Deneb, Vega, and Altair. In fact, although Deneb appears to from our vantage point to be the dimmest of the three, it is one of the brightest stars in the entire Milky Way Galaxy, shining with a luminosity of 200,000 Suns (yes, you read that correctly). Only its enormous distance from us makes it appear less bright than otherwise. Vega, which boasts a luminosity of 40 Suns, is but 25 light years distant, making it appear to be the most brilliant member of the triangle. And bringing up the rear, Altair shines out with a radiance of a mere 10 Suns, but at 16.75 light years, it is the nearest of the three.


So let's start with Deneb. "Tail" is certainly an apt name for this star, as it marks the tail feathers of the celestial swan Cygnus (Albireo being the beak). In addition to its fantastic brilliance, this star is HUGE. Were it our own star, our poor Earth would be just grazing its surface in its present orbit. Ouch! Deneb weighs in at a little less than 20 solar masses, but is spewing out into interstellar space roughly the equivalent of one Earth mass every 500 years. Currently a blue-white supergiant, astronomers believe that Deneb with ultimately expand even further, evolving into a red supergiant before collapsing in on itself and going supernova. But that's a few million years into the future, so there's no immediate threat to our lovely summertime asterism.

Next on our list is Vega, the brightest (to us) of the three. Vega has quite a history to it. It used to be the Earth's North Star (14,000 years ago), and will be again in about another 13,000 years. (It will be so much easier then to do polar alignment, with such a bright North Star.) It was the first star (other than the Sun) to be photographed, and the very first to have its spectrograph taken. At about 500 million years old, Vega is quite the youngster. But due to its mass (about twice that of the Sun), it is racing through its time on the Main Sequence. In another half billion years, it will begin to swell into a red giant before losing much of its mass in the form of a lovely planetary nebula. (So stick around!)


Vega and the Sun to scale. Note the enormous equatorial bulge on Vega.

Vega rotates so quickly (once every 12.5 hours) that it is very near the point where it would tear itself apart from centrifugal force. This was hidden from astronomers until recently, since we are looking down directly onto one of Vega's poles, and cannot observe its squashed shape directly.

Vega is surrounded by what appear to be multiple discrete disks of dust and small bodies, possibly in the process of coalescing into planets. So we may actually be observing a solar system in the very act of creation!

Last but not least on our list is Altair. Those of you who are my age, or are fans of 1950s B-grade science fiction movies, will recall that Altair was the parent sun of the "Forbidden Planet" in the movie of that name - home to the mad scientist Morbius and his beautiful daughter Alta, Robby the Robot, and the Monsters from the Id.


A Monster from the Id

In our far more boring reality, Altair is a fairly typical main sequence star. It is somewhat less than twice the mass of our Sun and shines at 11 times its brightness. Like Vega, it has an extreme rotation rate, spinning on its axis once every 9 hours. This results in an equatorial diameter a full 20% greater than its polar measurement.

Only 17 stars other than our own Sun have ever been imaged as anything other than a point source of light. Below is a 2007 image of Altair taken in the infrared. Note the oblateness. And unlike Vega, we are not looking down on one of the poles.


So now summer's most prominent asterism ought to be more than just a triangle. Its component stars are fascinating individuals, which are worth getting acquainted with.

Tuesday, July 24, 2018

Pure Magic

We all have as observers different reasons why we track down different objects. Sometimes it's because this or that star is intrinsically interesting, or because it possesses one or more superlative (the biggest, the closest, the oldest, the furthest, etc.). Sometimes it's because the object is bright and splashy, and fills one's field of view with all sorts of complexities.


30 Cygni off to the upper left - 31 Cygni A and B off to the lower right

But every now and then we check out this or that deep sky object because.. well, darn it, because it's beautiful! Such is the case for Omicron Cygni. It's not just that their arrangement is aesthetically pleasing - their brilliant colors (bright gold and electric blue) rival those of the more famous (and nearby) Albereo.


Another view of 30/31 Cygni, showing off their colors

Now Omicron Cygni isone of the more confusing appellations up there, because several stars in Cygnus all go by that  label. Much better to use the Flamsteed designations 30, 31, and 32 Cygni, all of which make up "Omicron Cygni". Confused? So am I.

But there's more to Omicron Cygni than a pretty picture (although that's quite enough). The stars are interesting in their own right. 30 Cygni is a blue-white giant star, 610 light years distant, shining with the radiance of 324 Suns, making it a magnitude 4.83 star to our view. Nearby (visually, at least) 31 Cygni is an easily splittable binary. Despite its apparent nearness to 30 Cygni, the 31 Cygni system is 880 light years from our Solar System, so the 2 are actually separated by 270 light years. 31 Cygni's A component is an orange supergiant, 4,300 times brighter and 200 times the size of our Sun. Its dimmer B companion appears to different observers as either bright blue or "dirty" white. The three stars, although in actuality quite distant from each other, make up an attractive apparent triple star due to a chance line of sight alignment.


32 Cygni at upper left, 30 and 31 at bottom right

Meanwhile, 32 Cygni sits off about 1 degree to the north, completing the view through any eyepiece with a moderately wide field of view. At 1,100 light years away, it is the most distant of the "Omicron" stars in Cygnus. 32 Cygni is a spectrographic binary. (Its components cannot be separated visually.) The A component of this system shines with a luminosity of 6,600 Suns and is bright orange. Meanwhile, its poor B companion star has to make do with only 300 times the Sun's luminosity, and by itself would be a blue-white main sequence star. The 2 components make up an eclipsing binary, similar to Algol over in Perseus. Because the plane of the stars' orbits is precisely aligned with our line of sight, we can spectrographically study the solar wind of the primary star during each eclipse. From these observations, astronomers have concluded that 32 Cygni A is losing an incredible full stellar mass every 77 million years. Wow.

By the way, the colors in the above image do not do justice to the glorious view one gets through the eyepiece. I never fail to spend a minute or three just drinking in the view whenever Cygnus is high in the sky. Don't miss it this summer!

Monday, July 23, 2018

Mirror, Mirror...

Ever wonder what our Sun would look like, if you were observing it from outside the Solar System? Well, take a gander at HIP 569498, over in Draco.



This magnitude 8.7 star, at 208 light years away, is the closest analog to the Sun that we know of in the entire sky. Its mass is practically identical to the Sun, the difference being basically a rounding error (1.02  ± .02 solar masses). Its surface temperature is only 17° Centigrade higher that the Sun's (5521° vs 5504°). Its radius is a mere 9,000 km less than the Sun's (687,000 vs 696,000). Most importantly, its lithium content is identical to that of the Sun to within observational parameters. Lithium content is one of the markers that varies most widely from star to star, so an identical measurement is amongst the rarest of the rare. The two stars share many other close similarities as well.

But it is no solar birthmate. HIP 569498 is approximately one billion years younger than the Sun and shares no common orbital parameters (about the galactic center) with the Solar System.

HIP 569498 also apparently possesses no "hot Jupiters", so it is entirely possible that one or more Earthlike worlds exist within the star's habitable zone.

So take a few moments to contemplate this "dot" in the northern skies, and imagine some stargazer on a world 208 light years away looking in our direction. He would be seeing exactly what you are.


By the way, HIP 56948 has two very unofficial names other than its catalog listing. They are Intipa Awachan ("Sun's Twin" in Quechua), and Zilia ("Jealous" in ancient Greek). How unofficial are these monikers? They are the winners of a New York Times readers' poll conducted in 2007, so give them all the respect (that is, very little) that they're due.


HIP 56948