Forty Years +1

"The Earth is the cradle of mankind, but one cannot remain in the cradle forever" - Konstantin Tsiolkovsky


.........Yesterday was the fortieth anniversary of the Moon landing, the first of the only six times in history that humans have actually walked on another planetary body. I was a little less than two when this happened, and by the time my youngest brother was born we had left the Moon, and we haven't been back since.

.........There have been a number of responses that I have seen to this fact. One of the drives for reaching the Moon was to "win" the space race against the Soviet Union. Once this was done, this part of the impulse was gone. We had already run this race, why stand around at the finish line instead of going out for pizza and beer? (That would be "root beer" if you're under twenty-one.)

..........Ratings for even the second Moon landing were well below that of the first, and it seemed as if there was no enthusiasm among the general population for more Moon shots. The Lunar program was also seen as a Democratic program (the landing was just six months after Nixon's inauguration), and it might have suffered from this view under Nixon and Ford. After Apollo 17, the space program turned to the shuttle, seen as preparation for a next step, but which seemed to become its own destination. Even the space station has been its own end. What next? Are we as far as we can go? Are we as far as have the will to go?

..........Another question that is asked concerns our use of resources, and this is certainly not an idle or non-compelling question, especially now. What could we do with the money that space exploration or NASA in general uses with people in poverty, desperate need of health care, and the job market dropping like the morale of a football team once Terrell Owens signs up?

..........Also, we must consider the question of priorities, even if we can assume that amount of money going into space science. Is it good to fund manned missions, or should we use the same money to fund a number of smaller efforts, in which a greater number of people can take part?

..........All of these questions demand a good answer, and I will even go so far as to say that in order to support more manned missions, an argument must be made that justifies a program against all of these points. Can a space program do more than just beat "the enemy" somewhere, and produce more in the public imagination beyond Tang (TM)? To make this argument, I want to make a wider claim about what the Moon landing provided.

..........Consider the object shown to the left. What is the value of this? Is this simply a waste of good marble that could have been ground up and used as the basis for houses, sewers, roads, etc? Is the value of this equal to the value of the material that makes it up, or the use to which the material could be put? I will venture to say that most people would say "no" to the last few questions, to acknowledge that art as a human creation has a value in the act of cultural, human expression. That beyond the day to day needs of basic human existence, we have a need that is higher, to make a higher purpose, a reason why we are here, a calling to others to acknowledge something even higher to which human beings can aspire. Even art taken as entirely secular still speaks to the fundamental human desire to define meaning for ourselves, to create ourselves as some thing above day-to-day existence. The Moon landing also made the argument that human beings can create a meaning for themselves in an even wider fashion. The statue I picked was the work of one man's genius, but the Moon landing required scientists to plot the way there, engineers to create the materials we needed to get there and back, and what we needed to keep people alive on the trip, people brave enough to risk everything on the say-so of people who had never done this before and the skills to handle what could come up, and taxpayers.
..........Lots of taxpayers. On the other hand, this enabled everyone in the country to take pride in and ownership of the Moon landing, and justifiably so, in my opinion. This, I would say, is something that we need again now.

..........When John F. Kennedy called for human exploration of the Moon, the United States was in an excellent position to commit ourselves to a great leap, a tremendous effort that we could do because the US was at the zenith of its power. The recovery of the rest of the world, directly affected in World War II, was still at the point where they were a tremendous market for the rest of the world, and had not yet returned to the production capacity that the rest of the world had before. Today is drastically different, but a space program with a clear human goal of a sustained presence on the Moon or a trip to Mars could restore not military leadership, not technological (though it would help) leadership, but leadership of vision. I can most honestly speak of this in terms of what the space program meant to me.

..........What did the landing on the Moon mean to me? I didn't gain an interest in astronomy when I was one and a half, but over the next few years I do remember watching the astronauts returning to Earth, and being recovered by aircraft carriers (yes, Keith, I know those were SEALs), and I can remember my amazement at considering that people, actual people, were capable of firing a rocket (essentially a big, controlled bomb) off from the Earth, using it to send people into space, and then being able to work out where they would come back with such accuracy that there could be ships waiting right there to pick them up. As the seventies aged, I saw a rush of people for magic, whether it was transcendental meditation, astrology, weird new medical fads in which people hoped for some way of cheating of the universe, some way of the controlling it to get the result they wanted. I was not brought up to be "afraid" of math, as if math was some magical field that only special people could do, so even at seven I was confused about why people would turn away from the examples of all the best that we could do to trust in something with no results, but which felt nicer, as if you could ask the universe for something, and how much you believed, or how nice you were actually counted. People have even sidestepped what human beings can do to hope to jump past them, to imagine aliens visiting the Earth who will solve all of our problems if we just ask them nicely enough.

..........There is no evidence of that ever happening, and no evidence of any magic, or any space cavalry to come riding over the hill and save us from the problems that we made for ourselves. All we have is us. We have problems that we cannot solve simply by saying, "I'm fine; let each person solve this independently." We have problems that cannot be solved state by state, and now even nation by nation. As we need to work together (not *under* each other, but as a collection of individuals/localities/states/nations) we should have something that will give us an experience of true greatness, something that needs all of us to work together, and shows us that we can do what seems impossible, to give the renewal of will and the hope that our more tractable problems like disease, poverty, hunger, etc., ad infinitum, are within our reach themselves.

Ursa Major (part 3 of 3)

Messier Objects in Ursa Major

.........Wednesday night I was fortunate enough to have a wonderfully clear night, so I was able to double-check all of my impressions of the appearances, the methods of finding Messier Objects, and the maps that I have made for this purpose. Each of the Messier objects will appear with a star map showing you how to get from a bright (well, fairly bright ... well, identifiable) star to the object. Each map will be on a different scale -- some objects are close to bright stars, and some require more of a trip. On each map will be indicators matched to the field of view of common telescopes. If you can fit the entire full moon in the field of view of your telescope, then you can use my circles as good guides as to the sizes of the steps that you are going to have to make to get where you need to go.

..........Because of the name of the blog, my first pass through the sky (the first year of the blog) will cover the Messier objects, constellation by constellation. (For most constellations, I’ll be able to do this in the same entry; the Big Dipper is unusual.) There are seven (eight) Messier objects in the area of the Big Dipper, and I’ll cover them in numerical order. This is a bit unfortunate, because the first Messier object on the list, the first Messier object I’ll cover here, is …

M 40: The Lamest Messier Object of Them All …
Difficulty Level: 2 (Close to a bright star, only one jump.)

.........Because M40 is the lowest-numbered Messier object in the first constellation I’m talking about then this is the first one I’m covering, which is a bit unfortunate, all things considered. Responding to the report of Johann Hevelius, who claimed to see a nebulous patch in this area, Charles Messier attempted to find the object at the location the other astronomer gave, only to discover nothing at all. It’s quite possible that the original observer actually did see a comet but didn’t recognize it as such, and recorded it essentially as "gunk that gets in the way of identifying comets".

..........For some reason, Messier felt the need to identify something in the area with Hevelius’s observation, so a double star was identified as “M40”. (As it turns out, this even isn’t a double star, but simply two stars along the same line of sight.) If you would like to find this “object”, the path is easy enough. Start with d Ursa Majoris (Megrez), the star connecting the handle to the bowl. Just above Megrez is a triangle of stars that should all appear easily enough in your finder scope or binoculars, which leads me into a bit of an aside, since this is the first example of star-hopping that I'm using.

........When mapping a way from a bright star to a fainter object of interest, I’ll use patterns of stars (asterisms) to help fix the image in memory, but in this case I was a bit put off because it is a little hard to make anything besides a triangle from three nonlinear stars, but inspiration has struck, and I will name this asterism “the Snark”! (I'll explain this in just a second.)

.........To find M40, which I will therefore name “Boojum”, find the lowest star in the triangle (the one closest to Megrez) in the eyepiece, and the optical double which has inherited the name M40 will enter your field from the north if the star (which has the name 70 Ursae Majoris, unless you have a better name for it) is moved to the southern edge of your field. The Boojum is one of the easiest Messier Objects to find, and (sadly) one of the least interesting. Okay, it is the least interesting Messier Object.

.........Why does the substitute for a disappearing Messier object get named “the Boojum”? I took this from Lewis Carroll’s poem, “The Hunting of the Snark”.

" 'But oh, beamish nephew, beware of the day,

If your Snark be a Boojum! For then

You will softly and suddenly vanish away,

And never be met with again!'

.........To help you get an idea of the brightnesses of starts seen through the telescope, the two stars that are The Boojum are ninth magnitude (9.0), about the limit of stars in the smallest telescopes. It will be good to use this to get an idea of how easy it will be to find other Messier objects, ones that are a lot more interesting.



M 81 and M 82: "I'm not touching you, am I bugging you?" Galaxies
Difficulty Class: 3 (Some jumps through asterisms)

.........To my mind, the jewels of the Big Dipper are the two nearby galaxies (near to each other, and relatively close to the Milky Way) M 81 and M82. From my point of view, these are some of the easiest galaxies to find, although you may find differently. These were some of the first deep-sky objects that I learned to find, so the asterisms that I use to find them might not appear to be as obvious to you.
Start at the end of the Dipper bowl (the star Dubhe), look north of Dubhe, and a bit to the west. In less of a shift than it would take to go from Dubhe to Merak, you will find some stars that appear to me to be a mirror-reversed Greek letter tau. Since I’m printing this on a map instead of just trying to remember a path at the telescope, I am naming this the asterism "The Chickadee". Once you’ve found this, center the Chickadee in the center of your binoculars/finder scope. If you now go due north, you’ll find what I call the broken arrow (this one needs a better name – any ideas?) : a triangle of stars that appears to me to be the back end of the arrow, which can be traced east to a star with another star of about the same brightness off the line, giving to me the appearance of a broken arrow. Visible in binoculars or a telescope’s finder scope as two faint fuzzy patches about two-thirds of the way closer to the break in the arrow than the fletching are the two galaxies we are looking for. (If you can’t see the galaxies in a finder scope, just aim for a point along the line of the arrow and hope for the best. (As always, if you don’t see the galaxies in the telescope then unlock the telescope and search in increasing circles from your starting point. Never underestimate the importance of patience in astronomy.)

..........M81 and M82 are reasonably close (as galaxies go) at a mere twelve million light years away. These galaxies appear close together in the sky because, in this case, they actual are close to each other – and they used to be closer, which affected in ways even visible now.




M81: Bode’s Galaxy

.........M81 was first discovered by Johann Elert Bode in 1774, and is often called "Bode's Galaxy". The total brightness of this galaxy is magnitude 6.9, implying that the object should be fairly bright, but this can be misleading. By luck, I started this so that the final constellations that I talk about will be constellations with a lot of galaxies. This is lucky because galaxies can be some of the hardest objects to observe. In stars, including clusters of stars, we’re looking at a lot of point sources of light – even with streetlights, moonlight, etc., clusters can still be seen. In galaxies and nebulae, the light is smeared over an area; any increase in the background light can drown out the image entirely.

..........Bode’s Galaxy is a fairly reliable target, a face-on spiral galaxy will two bright arms. It will appear as a bright smeared dot of light, and on the very clearest and darkest of nights, the two spiral arms of M81 will be visible as well.

.........I have an anecdote about Bode's Galaxy that I now feel compelled to share (otherwise, you ould just skip to the next paragraph.) In 1993, a supernova was observed in M81 and, as these things do, for a few weeks that one dying star gave out as much light as the rest of that galaxy. This made a lot of news, as there is lot of physics and astronomy that we can learn from supernovae, plus it was cool to watch. At that time, I was living close to Cape Canaveral, and had the opportunity to watch a night launch of the space shuttle. I had brought my telescope to the launch site to get a close view of the shuttle, but after a while of counting heat tiles, I began to get distracted. On a whim, and not expecting very much because we were surrounded on all sides by brilliant streetlights, I aimed the telescope at Dubhe, and moved the scope about as far as I remembered it being to the west, and then north, to get to M81, and looked in the telescope. By some astounding quirk of luck (although I tried to pretend that it was skill), I could see the field with M81 in the telescope! The galaxy was invisible due to all of the background light, but the star field plus the supernova was recognizable. There, my secret is now out.

M82: The Starburst Galaxy / Cigar Galaxy

.........With M81 in the center of the field of view, one can move the telescope so that M81 moves to out of the southern edge of the field of view, and then move the telescope gently along the other axis, and M82 will appear, a thin jagged line of light. The Starburst Galaxy is an irregular galaxy that can almost fit in the same field of view with M81. Galaxies are divided into four major groups: spiral galaxies, barred spiral galaxies (a spiral galaxy with a bar structure in the core), elliptical galaxies, and “irregular” galaxies, galaxies in which something has happened to distort the shape of the galaxy. In the case of M82, this was a close pass, in which M81 caused a lot of the gas clouds in M82 to collapse into new stars. More recent studies show that M82 is probably a barred spiral galaxy seen edge on, with the burst of new star formation somewhat hiding the shape.

M 97: The Owl Nebula m = 11.20
Difficulty Level: 5 (close to a bright star, but individually quite faint.)

.........I’ve found the Owl Nebula one of the hardest Messier objects to find in the sky. At a total visual magnitude of 11.20, and that is considering all of the light concentrated at one point, which it most certainly does not. I wouldn’t advise looking for the Owl Nebula on anything but clear, moonless nights.

.........The Owl Nebula is a planetary nebula, made up of a rough bubble of gas ejected from a star as it goes into "retirement", casting off its outer layers and becoming a white dwarf. A planetary nebula is an expanding cloud of gas, so it has a limited lifespan, until the cloud gets to diffuse to see, or too far from the central remant of the star to shine in absorbed and reemitted light. this puts a clock on it of about one hundred thousand years. A long time as far as library fines go, but nothing on the time scale of stellar existences. There are therefore relatively few planetary nebulae (only four in Messier's list), and this is the hardest to see.

M101: Didymus

m = 7.70
Difficulty Level: 4 (Easy star hop, individually faint)

.........This galaxy is a large, face-on spiral, quite an impressive sight that will even allow you to see the spiral arms, but the night has to be pretty much perfect. On my excellent viewing night this week, I was able to star-hop to the correct field, and see all of the stars that I was supposed to see, but there was no sign of the galaxy. Stuff like this gave rise to my third law of living, "You can do nothing wrong, and still lose."

.........Messier 101 was named "Didymus" (by me) because it is its own twin, of a sort. Charles Messier recorded this galaxy as M101 and later recorded the same galaxy as M102. In the case of M40, Messier found something nearby and get it a number. In the case of the galaxy M91, in Virgo, Messier recorded a non-comet at a position where nothing was later found, and the number was simply assigned to another galaxy nearby that was bright enough to have been seen by Messier, but was otherwise unrecorded.

M108: Galaxy
m = 10.10

.......... Both M108 and M109 are faint spiral galaxies that are difficult to observe when the night is not completely dark, and the sky is not completely clear. M108 can be found on the same star map as M97.

M109: Galaxy
m = 9.80

..........Both M108 and M109 are faint spiral galaxies that are difficult to observe when the night is not completely dark, and the sky is not completely clear.

Difficulty Level: 4 (Easy star hop, individually faint)

Ursa Major, Part 2 of 3 (Blog #4)

“Thou art as opposite to every good
As the Antipodes are unto us,
Or as South to the Septentrion”

Henry VI, part III Act I, scene iv, lines 134-136

.........The first and last stop on our year-long tour of the constellations (at least the ones that can be comfortably viewed from mid-northern latitudes) will be Ursa Major. To be more familiar, I should be referring to Ursa Major as the Big Dipper, an asterism of the seven brightest stars in the constellation. (An asterism is a recognized pattern of stars that is not itself a constellation. In some cases as we will see later this summer, an asterism can include stars from more than one constellation.) I am following tradition in this as all of the early catalogs began with Ursa Major and Ursa Minor (again, more commonly recognized by the Big Dipper and Little Dipper).

.........The stars of the Big Dipper have been recognized as a constellation from the earliest times. Homer seems to have recognized the Big Dipper (as a bear) as the only circumpolar constellation as “Arctos, sole star (here taken as constellation) that never bathes in the ocean wave” The Big Dipper appears in the Bible, in the book of Job “He [God] made the Bear and Orion, the Pleiades and the constellations of the South (9:9)”, and “Can you bring forth the Mazzaroth in their season, or guide the Bear with its train (38:32)?” Note that the Dipper is not represented as a bear with an incongruously large tail, but as a bear with three followers (cubs? hunters?). (It is unknown what Mazzaroth represents. It could refer to a southern constellation using the pattern of parallelism in Hebrew poetry, or it could represent the zodiacal constellations as a set. It could also represent a handy gardening tool with a built-in mulching attachment; we just don’t know.)

.........In addition to being such an easy asterism to find in the sky, and in addition to leading the viewer to a number of other bright stars (hey, you have to learn the sky starting somewhere), the Big Dipper is one of the oldest constellations. I feel that I’m being fair in saying “the Big Dipper” here, as opposed to “Ursa Major”, because “Ursa Major” itself is an expansion of the Big Dipper. Sure, it was an expansion that took place several hundred years BCE while the other circumpolar constellations were created at this time, but the Big Dipper was old even at this time. It is impossible to know just how old, but the idea of the Big Dipper as a bear is surprisingly widespread, in bold defiance of the fact that it looks nothing like a bear. (The idea that Ursa Major is old enough to go back to a time in which bears looked a lot more like dippers has, unfortunately, little evidentiary support.) The writer Thomas Hood took a different tack:

“Imagine that Jupiter, fearing to come too nigh upon her teeth, layde hold on her tayle, and thereby drewe her up into the heaven; so that shee of herself being very weightie, and the distance from the Earth to the heavens very great, there was great likelihood that her taile must stretch. Other reason know I none.”

.........Our constellations are (largely) the Latin names of Greek constellations, many of which were taken from Babylon and India, so overlap here is highly unsurprising. Admittedly, the Germanic nation did not consider this a bear, but a wagon (which makes sense, seeing the bowl as the wagon and the handle as the bar that the animals would be attached to); what is surprising that a number of North American cultures also saw a bear here. (To their credit, they only saw the bowl of the dipper as a bear; the three stars of the handles were hunters chasing the bear, catching it in the fall when the bear, low in the evening sky, would drip blood onto the trees, changing their colors.

.........There has been some conjecture that the Big Dipper is the remnant of some Paleolithic bear cult, but this might be reading too much into this. Beyond the elephant, the bear is the largest land creature, so the most important group of stars is probably predisposed to be called “the bear”. If there is anything to the idea that the Dipper was considered a bear even before the migrations to America, it might be as William Whitney (American philologist of the nineteenth century) supposed, looking at how the Sanskrit word Riksha can mean either “star” or “bear”, depending on the gender of the word. The seven most important stars in the sky could then have been the "seven bears", or just eventually lumped together as "the bear". Or, maybe a North America culture just picked "bear", and the constellation name spread. There is currently no way to know.

.........I was considering also discussing the number of times that different constellations appear in literature, but starting with the Big Dipper made this prohibitive, since references to it are so common. Perhaps my third pass through the constellations can cover its literary lights (see you in 2011). I'll tell you what: I'll cover the Bible, Shakespeare, Dante Aligheri, and Homer, and ask the gentle reader to take the rest. If you run across a literary reference to a constellation, please let me know. (I'll cite you -- you're name will be in a blog ... wow!) I did find three appearances of the Big Dipper in Shakespeare as well. In addition to the quote that begins this entry (the Septentrion, or “seven stars” is the Dipper), the Big Dipper is also referenced in Henry IV, Part I, where it is used as a timepiece (I'll discuss this more when we talk about the Little Dipper, and using the stars to the north as a clock) and a reference in King Lear where Shakespeare has one of the villains of the piece speak in what we would now consider to be enlightened skepticism about astrology. I'll go into more detail on this when I talk about the first zodiacal constellation on our tour -- Ophiuchus! (Don't recognize this as apart of the Weekly World News zodiac? I'll explain soon ...)

.........In this post, I'll speak about viewing Ursa Major with the eye, and add in binoculars and telescopes in the next blog. I have discussed in a previous blog entry how the two stars at the end of the bowl, Dubhe (which comes from its title as the back of the bear) and Merak (which comes from its title as the loin of the bear) can be used to find the North Star, Polaris. There are several other bright stars that can be found using the stars of the Dipper as well.

.........Confining ourselves to the stars of the constellation itself, take a look at the center star of the handle, the bright star Mizar. Mizar has a magnitude of 2.23, a fairly bright star. Close to Mizar in the sky, close enough to be seen with the eye, if your eyes are good, and easily with a pair of binoculars, is a fainter star, Alcor. Alcor has a visual magnitude of 3.99, which means that we are receiving about five times as much light from Mizar as we are from Alcor; we don't see Mizar as five times as bright, because our eyes don't work such that twice the light equals twice the brightness. If that were true, then your head would all but explode as you went inside and turned the lights on after being out looking at the stars!

.........Mizar and Alcor are separated by a distance in the sky that is about 1/3 the apparent size of the Moon in the sky. Many cultures have used this star as a test of vision, requiring a reasonably sharp eye to see this as two stars and not one. There has been a question as to whether Mizar and Alcor are actually part of a double star system, or if the are simply close to the same line of sight in the sky. This is somewhat similar to seeing two people sitting together on a bus and assuming that they are married. It does seem that these two stars are indeed orbiting each other, but widely separated. The closer star, Mizar is about 78 light years away, which means that the light you see tonight left the star's surface in early June in 1931, and has spent all that time traveling through space. Alcor is about three light years away from Mizar, or about 190,000 times the distance between the Earth and the Sun. If these stars are orbiting each other, it will take about 43 million years for each orbit. Mizar is itself a double star, but you will need a telescope to see that. Both stars are about the same brightness, and much closer. They orbit each other in only about 104 days, a much smaller separation.

........The next post will take us through Ursa Major with binoculars and telescope, and we will see if we can then move on to another constellation.

SPECIAL ADDITION: Check out this link!

Ursa Major, Part 1 of 3 (Blog #3)

Before we get started …
..........This entry is much later than I had hoped it would be, and it has grown into quite a monster in the meantime – I promise, this is larger than the standard entry will be, and much more space than the average constellation will get. Heck, I had to break Ursa Major in three parts! This is part I, "Ursa Major As a Guide to the Sky". The next two will be "Ursa Major, the Constellation" and "Ursa Major, Telescope Stuff". Posting frequency will drop to (probably) once per week in the fall, but I want to post more frequently in the summer. For example, I hope to finish Ursa Major this week.

Downloading
.........Much of the writing time between posting was directed to working out a way to make star maps that were done entirely by myself, so that I could replicate them as I would. However, once I post these as images, much of the detail gets lost; to correct this, I have uploaded the image files to a Google discussion group. (If you choose, you are free to ask questions about the blog, certain topics, or things that you would like to see there, but I would appreciate if you would comment about individual blogs in the space after the blog entry.) There, you may download the images to get maps that I hope you might find useful.

My Starting Point
.........There is method luck to my madness, as I begin at Ursa Major. Let us start with the Big Dipper, the most recognizable part of Ursa Major. The Big Dipper makes a good starting point because for most of America, it is a circumpolar constellation; that is to say, the star is close enough to the pole that it never sets below the horizon, and so it can be seen all year long. I will continue on into summer constellations, in which most of the things that binoculars or telescopes will lead you to are clusters of stars, which (as collections of points) can still be seen on moonlit or suburban nights. This will lead us through the year, ending with the constellations of spring, which have many galaxies, some of the most difficult deep-sky objects to observe. So, if you want to get into astronomy (or deeper into astronomy) summer is a good time to start (if you can stay up late enough to chase twilight). I’m starting with the Big Dipper because it is one of the most recognizable patterns in the sky, and one of the easiest to find. In June skies, the Big Dipper will start the night near the zenith (directly overhead) , and in July the Dipper is still high in the northwest by 11 PM.

Naming Stars
.........The Big Dipper can also serve to introduce how stars are tracked individually as well. Of all the stars that can be seen with the naked eye (there are slightly more than 5,000 as the HIPPARCOS satellites saw it), there are about two hundred that have individual names. These are typically the brightest stars in a constellation, and show the limits of the usefulness of designating stars individually in such a unique manner; after all, could you reliably remember five thousand names? (Heck, have you ever had to correct a grandparent or other family member? Odds are, there aren’t five thousand in the family.) Here is a star map of Ursa Major with all of the named stars shown: (at least, before people start claiming stars to name themselves.)


.........Another method was derived by Johann Hevelius in a star atlas published in 1603. He tried to name the brightest star in a constellation “alpha of that constellation”, so the brightest star in Ursa Major should be a Ursae Majoris (then b, g, d, and so on). Ursa Major is an unfortunate starting point for introducing this system, because in this case, as you can see, Hevelius simply started by making a pattern of the Big Dipper. Here is a map of the Big Dipper with stars named in this system:
.........The stars of the Big Dipper can also be used to provide a sense of scale across the sky. Judging scale is one of the biggest problems in getting used to moving around the sky, because in the sky there are no points of reference that we see on the ground. Fortunately, we have fairly reliable measurement tools at the end of our arms – we can use our hands. (Yes, your hands are almost certainly not the same size as mine, but your arms are also differently sized than mine as well. This balances out.)

.........Consider the “distance” between the stars Dubhe and Merak. I put the word “distance” in quotes, because we have to define what we mean by distance. If I describe the physical distance as 45 light years, how does that help you? We’ll use “distance” to refer to the angular distance between two things in the sky, so that an object on the horizon due north will be 180⁰ away from an object just above the horizon due south. In this way, the distance between these two stars is just a little bit more than five degrees. As shown in the diagram below, this distance against the sky is about the same as the angular size of three fingers held at arm’s length. This can also be used as an order to your bartender if the viewing isn’t good. (PARENTS: If you little one comes in, sighs, and says, “Gimme three fingers of Redpop”, then s/he has been reading this blog.)

.........The stars Dubhe and Phad are ten degrees apart. This is about the distance between your fingertips is you extend your hand as shown below, a form that is either reminiscent of a certain arachnid-based superhero from a company with “marvelous” lawyers, or – if you were a young person in the 70’s or 80’s – the “secret devil sign” beloved by metal bands and freaked out middle-aged PTA moms. Of course, if a freaked-out PTA grandma sees you making a devil sign to the night sky, then you might need to refer back to the “three fingers” – once the police leave.

.........The stars Dubhe and Alioth are fifteen degrees apart, which can be measured by the hand sign below, which I have christened the “dude”. (Pronounced “duuuuuuuuude”.)

.........The Big Dipper can also be used as a guide around the sky as well. A line that passes through Merak and Dubhe will pass very close to the North Celestial Pole, and hence, the North Star. (This is helpful, because while the North Star Polaris is a reasonably bright star, it is nowhere near the brightest star in the sky, though this is a common misconception.)

.........A line passing through the other end of the bowl will come very close to the bright star Regulus, in Leo. This star is setting very close to sunset now, carrying Saturn with it into daylight anonymity.

.........If you follow the curve of the Big Dipper's handle, the curve will arc towards the bright star Arcturus, in Bootes (coming soon), and if you go past Arcturus, you will speed on to Spica, in Virgo (next to last of this series, next spring).

........Get familiar with the Dipper and the stars around it, and I'll be back to write about the stars of the Dipper itself, and a famous test of vision across the ancient world.