Why "What Is Up" Has Been Down ...

.....I have not had a post go up since September for a couple of reasons that I wanted to share with you (though this is an aberration - the whole point of this blog is the sky, not me).  At the end of September, I had a bicycle accident that resulted in a hairline fracture of the S4 vertebra, which led to a couple of weeks of intense pain, which was much worse at night.  At the same time, my work situation became extremely negative, a full-fledged cautionary tale about the total lack of protection the worker has without a union.

.....In any event, the continuing evolution of a look for the monthly star map is coming very soon, and I will also begin looking toward the transit of Venus across the face of the Sun on June 5th, 2012.  It will be possible to actually watch the disk of the planet Venus cross the Sun.  This is definitely something to try to see, since we won't be able to see this happen again until December of 2117!

The September Sky

.....This blog has not been updated in an uncharacteristically long stretch because of personal pressures with the beginning of a new school year, and my move to a new house, with an actual backyard - a backyard that has a line-of-sight to zero streetlights, instead of the eight at the apartment!  I hope that I don't become what I criticized (in backyard astronomers who assume everyone has good skies) now that my situation has improved!  (I am am in the city proper, though not a bright part of not a big city.)

.....Halfway through the month, here are the stars for September.  As is usual for this first pass, the constellation covered are in blue, tending to the west, while up-and-coming constellations have the eastern sky in red.

.....The limiting magnitude for this map is fourth magnitude, which could still be fairly optimistic for a lot of suburban and urban viewing.  When I did this, I also had to redraw a number of constellation patterns, as there are some constellations arranged in ways to make the figure hopefully look weakly, vaguely, as their namesakes, but squeezing this in often used faint stars that are hard to see under bright skies.

 

....Ursa Minor, the Little Dipper, is high on this list.  Only three of the seven stars can reliably be seen, so many, many people looking for the North Star by using the Little Dipper identify something else.  Pisces, wrapped around Pegasus, is another faint constellation with only a few bright stars.  If we overlay this map onto stars down to the limit of visibility, we find the patterns our backyard astronomy books promise us, but buried in an embarrassment of riches.

.....Locating constellations in September should start with the Summer Triangle.  The Triangle is at its zenith, the highest point in the sky,connecting the brightest stars in Aquila, Lyra, and Cygnus.  Rising in the East is the Great Square of Pegasus, a dimmer figure in a dimmer part of the sky.  You will be well rewarding for wandering out into the summer sky: the nights are cool enough to keep down the humidity (and hopefully the mosquitoes), and the last views of the summer Milky Way are visible in the southwest, the Milky Way itself passes directly above us.  Good Luck!

Eagles

.....The second constellation joined by the Summer Triangle is Aquila, the Eagle.  (We move east in our examination of the constellations, and we have covered enough now to see blue constellations to the south and west, and red, or "not yet covered" mostly to the west.)  Altair, the bright star bracketed by fainter stars to the northwest and southeast, is the bottom star of the Summer Triangle, and the brightest star in Aquila.  Altair is also fairly close to Earth.  The light that you see tonight left on November 15th, 1994 (plus or minus a month).

.....Here is the "Binocular View" of most of Aquila, with the names of the named stars included.  This includes some very long names for very faint stars.  I refer to Deneb el Okab Borealis/Australis, or "The tail of the eagle north/south".  (The Arabs clearly visualized this image differently than I have drawn it here.)  Deneb el Okab Borealis has a visual magnitude of 4.00, making this one of the faintest named stars we have covered.

.....The next step, on the next go 'round, would be to have more detailed maps of the cool clusters, nebulae, galaxies, etc., to be found in Aquila especially since the summer Milky Way passes through the constellation ... but there are none to be easily found.  There are no Messier Objects, no Caldwell Objects (a list constructed by Sir Patrick Caldwell-Moore to include material Messier didn't), and the Sky Atlas 2000.0 Companion (to one of the most prominent star atlases extant) has numerous objects, with notations like "extremely faint", "not well detached", "appears stellar".  All of the cool thing in Aquila seemed to have slipped to bordering constellations.  (Sagitta, the faint constellation above Aquila, has three cool deep-sky objects.)

.....So let's digress into eagles in general.  There are a lot of stars named "Something, something eagle", because, well, eagles are cool.  Eurasia has about fifty types of eagles, while North America has two.  This was unfortunate, as the first country to become independent in North America (the United States of America) took the bald eagle as its symbol, Mexico put the golden eagle on its flag, and Canada got ... the loon.

.....Countries all over the world have used an eagle as a symbol.  This makes sense.  When you see an eagle on a flag, seal, official souvenir baseball cap, you think, "I wonder which aspect they are going for: freedom, vision, heck, even apex predator?"

.....As opposed to the alarmingly common two-headed eagle, which only brings to mind the question, "How many hit points does it have?"  (And yes, out of all my choices, I am choosing to pick on Austria-Hungary, a nation that has been defunct for coming up on a century.  You never know what people are going to get peeved over.

.....Let's sum up.  Using the symbol of an eagle (one head, left), you get this.  Use the two-headed eagle (right), you get, "Ahhhh!  AAAHHHH!  Someone protect the CHILDREN!"

Sagittarius, or the Effort A Culture Must Exert If It Does Not Have Tea

.....One of the best summer constellations is Sagittarius the archer.  Its central figure made of fairly bright stars, and it is filled with deep sky objects, open clusters, globular clusters, and nebulosity.  The only downside to Sagittarius is that it is low in the sky (in the Northern Hemisphere), so Sagittarius is only visible from late July to late September, but when it is visible, Sagittarius is a visual feast.  If you have a dark sky, the summer Milky Way appears to split between Sagittarius and Scorpius (due to a tremendous amount of non-luminous gas and dust between us and the center of the Milky Way).  If you do not have dark skies, this is still a very rich constellation for binoculars, especially in the central figure of the constellation.

.....Let's take a look at that now.  The stick figure above is supposed to represent a centaur holding a bow, prepared to take out Scorpius execution-style.  This obviously didn't work, because Scorpius is still there, and Sagitta (the constellation of the arrow, as opposed to the constellation of the archer) is north of both constellations, having apparently bounced off of the natural armor of Scorpius.

.....Far easier to visualize is a more modern asterism , the Teapot.  Drawn below, the bright stars of Sagittarius' center form an excellent teapot, with stars like Nunki and Ascella as part of the handle, Kaus Borealis as the top of the dome, and Kaus Media, Alnasl, and Kaus Australis as the spout.  This may still involve some scorpion hate, but it strikes me as far more effective to go after a scorpion with boiling liquid than an arrow much smaller than the scorpion.  Plus, really, scorpions?  %#@& those guys.

.....This brings up a couple of additional points.  Sagittarius seems to have a number of named stars, but scores low points for originality.  What's up with that?  As it turns out, "Kaus" is Arabic for "bow", so three of these stars represent the bow.  (In that case, if someone could give me the Arabic word for "teapot", then I could rename seven stars in one fell swoop.)  "Arkab" is Arabic for "hamstring". 

.....As an aside, the US Navy commissioned a cargo vessel named "Arkab", named after the star(s) that conveyed cargo to Pacific bases during World War II, traveling more than 60,000 miles.  Despite Arkab being Beta Sagittarii (implying that at least one of the Arkabs should be the second-brightest star in Sagittarius), the Navy ship is the coolest fact about Arkab.  Arkab, and Rukbat (Alpha Sagittarii) are actually quite dim, nowhere near being the brightest stars.  In many other constellations, the star "Alpha The-What-The-Heck-Ever-i" isn't the brightest, but it is usually close, or part of a clear pattern (as in the Big Dipper). This time it just makes no freaking sense.

.....One the "Binocular View" close-up of the Teapot, a number of Messier Objects are listed.  Even in a pair of binoculars, the globular cluster M22, and the Lagoon Nebula (M8) are obvious, and wonderful targets.

The New Standard In Charts!

.....I have worked at this for some time, and I have now settled on a system of chart scales.  (I had intended to let each chart be at what seemed like an appropriate size scale for that individual constellation, but the advantages of using a standard set of scaled views are pretty appealing.  Some constellations, such as Draco or the combined Ophiuchus and Serpens, naturally fill a field of view thirty degrees in radius.  (At arms length, both hands held together - or, as I now notice, your right hand and a friend's right hand - span thirty degrees in the sky.)  For smaller constellations such as Lyra (shown below), the "Constellation View" shows the constellation in context with other constellations around them, which serves (I hope) to make them easier to find.  On the "Constellation View" charts, the faintest stars are sixth magnitude, the theoretical lower limit of visibility for the average person with a dark, moonless, sky.

.....Smaller constellations should still get a view of the whole constellation, and larger constellations could be served by higher resolution views of interesting areas.  These maps are "Binocular View" maps, making the implicit assumption that this closer view serves to let use find interesting areas, and search through them.  For this reason, the faintest magnitude plotted on the chart is eighth magnitude - too faint for the unaided eye (although perhaps I shouldn't be trying to avoid getting Google hits for the word "naked" - a hit is a hit, after all), but visible in binoculars.

.....The final goal for this blog is to help the reader (especially the reader relatively new to observing, or observing through light pollution) find interesting telescopic objects.  This brings us to "Finder View", with a radius of five degrees, and showing the amount of sky typically visible through a "standard" small telescope.  These will usually be used to help the gentle reader find cool things to look at, and the faintest star going down to tenth magnitude, bright enough to be fairly easily seen through a small telescope.

.....The map above zooms in on one of the easiest to find deep-sky objects, the Ring Nebula (M57), a planetary nebula (the swelling former outer part of a star, dissolving into space).  In a small telescope, this appears as a fuzzy bright doughnut of light.

Sagittarius, or the Effort A Culture Must Exert If It Does Not Have Tea

.....One of the best summer constellations is Sagittarius the archer.  Its central figure made of fairly bright stars, and it is filled with deep sky objects, open clusters, globular clusters, and nebulosity.  The only downside to Sagittarius is that it is low in the sky (in the Northern Hemisphere), so Sagittarius is only visible from late July to late September, but when it is visible, Sagittarius is a visual feast.  If you have a dark sky, the summer Milky Way appears to split between Sagittarius and Scorpius (due to a tremendous amount of non-luminous gas and dust between us and the center of the Milky Way).  If you do not have dark skies, this is still a very rich constellation for binoculars, especially in the central figure of the constellation.

.....Let's take a look at that now.  The stick figure above is supposed to represent a centaur holding a bow, prepared to take out Scorpius execution-style.  This obviously didn't work, because Scorpius is still there, and Sagitta (the constellation of the arrow, as opposed to the constellation of the archer) is north of both constellations, having apparently bounced off of the natural armor of Scorpius.

.....Far easier to visualize is a more modern asterism , the Teapot.  Drawn below, the bright stars of Sagittarius' center form an excellent teapot, with stars like Nunki and Ascella as part of the handle, Kaus Borealis as the top of the dome, and Kaus Media, Alnasl, and Kaus Australis as the spout.  This may still involve some scorpion hate, but it strikes me as far more effective to go after a scorpion with boiling liquid than an arrow much smaller than the scorpion.  Plus, really, scorpions?  %#@& those guys.

.....This brings up a couple of additional points.  Sagittarius seems to have a number of named stars, but scores low points for originality.  What's up with that?  As it turns out, "Kaus" is Arabic for "bow", so three of these stars represent the bow.  (In that case, if someone could give me the Arabic word for "teapot", then I could rename seven stars in one fell swoop.)  "Arkab" is Arabic for "hamstring". 

.....As an aside, the US Navy commissioned a cargo vessel named "Arkab", named after the star(s) that conveyed cargo to Pacific bases during World War II, traveling more than 60,000 miles.  Despite Arkab being Beta Sagittarii (implying that at least one of the Arkabs should be the second-brightest star in Sagittarius), the Navy ship is the coolest fact about Arkab.  Arkab, and Rukbat (Alpha Sagittarii) are actually quite dim, nowhere near being the brightest stars.  In many other constellations, the star "Alpha The-What-The-Heck-Ever-i" isn't the brightest, but it is usually close, or part of a clear pattern (as in the Big Dipper). This time it just makes no freaking sense.

.....One the "Binocular View" close-up of the Teapot, a number of Messier Objects are listed.  Even in a pair of binoculars, the globular cluster M22, and the Lagoon Nebula (M8) are obvious, and wonderful targets.

Names Out the Wazoo

.....The name of this constellation is more widely recognizable through Harry Potter than through astronomy awareness, but that might not be unfair.

,,,,,The constellation Draco the dragon is a northern circumpolar constellation.  For much of the northern hemisphere, Draco is above the horizon  for all of the year.  North of the Mason-Dixon line, Draco is always in the sky, winding part of its length between the DIppers.  Well, if this is the case, why is Draco so much less familiar?  The short answer is that Draco, while large, has no bright stars.  The brightest star in Draco has a visual magnitude of 2.23, or the 69th brightest star in the sky.  Draco's primary claim to fame is that Thuban, one of its stars, is periodically the North Star.  Thuban's last pass at glory came during the construction of the pyramids (giving us about twenty-two thousand years until its next turn at the pole)

.....Draco is quite a large constellation, filling our starting placement map.  No zooming will be necessary.  One might note that while Draco has no truly bright stars, its has a number of named stars.  This seems strange at first blush, so let's conjecture why this might be...

.....First, when many of our constellations were being named (or at least getting the names that would stick), Draco contained the North Celestial Pole, with the entire sky appearing to rotate around Thuban the way that the sky now appears to rotate around Polaris.  This naturally made  Draco an important constellation, so its stars were more likely to receive names.  But ask yourself this question: Why did stars receive individual names in the first place?  Imagine yourself standing outside, looking up at the stars with at least one friend (unless you are actually doing this, in which case I salute you, and hope that your presumably mobile device has a dimming feature).  Pick a star.  Now, how would describe which star you had picked to your friend?  If your star was the brightest in a given area, you might describe it that way, and if it was not, there is an excellent chance that you used that bright star as part of your directions.  If we start with a set of named stars, then we can cut out a lot of the uncertainty right from the get-go: "It's that star right below Vega," you might say (if it happened to be that star).  Now, if you were looking a Draco, Draco is (a) very large, and (b) low on bright stars.  that could lead to a number of stars in Draco getting names, just to have a starting point telling one not terribly bright star from another.

.....Speaking of names, the name Draco is probably more recognizable as Harry Potter's classmate and frequent antagonist from the eponymous series.  Readers (as opposed to movie viewers) may have recognized a number of star and constellation names, mostly in the Black and Malfoy families.  (What, did an astronomer cut J. K. Rowling off on her way to the coffee shop one day?)  Here are the names used, and where in the sky they can be found: 

Andromeda Tonks, nee Black, the mother of Nymphadora Tonks:  Andromeda is a fall constellation, now visible on the eastern horizon once night has fully fallen.

Alphard Black :The son of Pollux Black and the uncle of Sirius Black

Arcturus Black, patron of Sirius Black:  Arcturus is the brightest star in the constellation of

Boötes. 

Bellatrix Lestrange, nee Black, major villain: Bellatrix is one of the bright stars that form the winter constellation of Orion.  Bellatrix (Latin for "female warrior") is the western shoulder of Orion.

Cassiopeia Black:  Cassiopeia is a circumpolar constellation for much of the northern hemisphere, most prominent in the fall sky, appearing as an "M" or a "W", depending on what side of the Mississippi River you're on .  (At least around here. :) )

Cygnus Black: Cygnus (aka the northern cross, containing the star Deneb) is a major summer constellation.

Pollux Black:  Pollux is a bright star in the winter constellation of Gemini.

Regulus Arcturus Black:  Regulus is the brightest star in the constellation of Leo.

Sirius Black:  Sirius is the brightest star as seen from Earth (fine, barring the Sun, for the pedants out there), and is located in the winter constellation of Canis Major.

Callidora, Cedrella, Charis, Dorea, Elladora, Hesper, Isla, Lucretia, Marius, Phineas:  These are not star names.  Ms. Rowling apparently had other ideas, or ran out of star names that she liked.  (Oh come on!  What about "Microscopium Black", or "Aldhibain Black"?  That's a missed opportunity right there!)

.....Draco also takes part in a giant summer man-versus-reptile showdown.  As intimated here, and more visible on the August star map, Hercules is stomping in Draco's head, back-to-back with Ophiuchus while Ophiuchus is wrestling with Serpens.  Thankfully, the constellations were derived thousands of years before the advent of Freudian analysis.

.....Also, wow, this sould have been much more timely if I had posted it a month ago...

Lyre Solo (or Solo Lyre)

.....The constellation of Lyra is small, but it holds one corner of the Summer Triangle, and the fifth brightest star in the sky - the second brightest star in the northern sky.  Lyra contains the star Vega noteworthy because this constellation, unlike some others like Scorpius, is quite high in the sky in the northern hemisphere, passing directly overhead of the southern United States.  (Spookily, Vega passes almost directly overhead of Washington D.C..) 

.....While this is something that I have done for the last few constellations, I have a more well-defined standard format for how constellations are presented.  The first map shows the sky, centered on the constellation in question, with a radius of thirty degrees.  For all but the largest constellations (and Lyra is kind of small), this will show a number of bordering constellations.  This gives us a standard starting point, and helps us find the constellation in the sky.  (In the case of Lyra, this helps us find other constellations as Vega is pretty hard to miss.)

.....Zooming in on Lyra (this map has a radius of eight degrees, we see Lyra as it is usually portrayed, a triangle of stars sharing a corner with a parallelogram.

.....Looking up on a summer night, Lyra seems quite and serene.  Less than a dozen stars, one bright, but otherwise quite.  Actually, Lyra has some notable weirdness to its stars.  Vega is larger and more luminous than the Sun, but its brightness in the sky is due to its closeness.  Vega is only a little more than 25 light years away, so the light that you can see from Vega tonight left in late April of 1986.  Being close, Vega is relatively easy to study, and astronomers have fond a massive disk of gas and dust around Vega, with irregularities that might indicate the presence of planets.  Weirder than this is the other star only in the "triangle" of Lyra, designated Epsilon Lyrae.  Through binoculars (and on the second map), this star is revealed as a pair of stars close together in the sky.  This is no coincidence; those are actually orbiting a common center of mass - but it get stranger.  Looking through a telescope with high magnification on a clear, steady night, each of these stars is revealed as a double star in their own right, so this is also called the Double-Double, four stars orbiting in pairs that orbit each other.

.....Even weirder is Sheliak, or Beta Lyrae.  Sheliak is 882 light years away, so for the light reaching us (from 1129, the year of the Council of Troyes franchising the Knights Templar - let's see what Dan Brown does with that) to still make Sheliak the second brightest star in constellation must be something outstanding indeed!  Sheliak is also a double star; nothing strange in this, most stars orbit in pairs (or more).  In Beta Lyrae's case, the two stars are so close together that the gravity of each star distorts the other, and material is pulled off of one towards the other.  These stars are orbiting so quickly that as the stream of gas moves toward the hotter star, it misses the star, building up into a disk.  Even this disk overflows, with material escaping into space from the poles, and leaking out from the opposite side of the accretion disk

.....Because Lyra is a fairly tiny constellation, I have included two telescope objects on this map as well.  This kind of skips ahead in my plans, since I intend to discuss these objects on my next tour of the constellations, but if you have even the smallest of telescopes, the object M57, aka the Ring Nebula, is straightforward to find between Sulafat and Sheliak.  (When I was in seventh and eighth grade, my backyard telescope had a lens actually slightly smaller than the human eye, and a tripod with legs six inches long that I would need to balance on the posts of a chain-link fence.  I could find Jupiter, Saturn, the Orion Nebula, the Andromeda Galaxy ... and the Ring.  The other deep-sky object is M56, a globular cluster that is one of literally dozens of globular clusters that can be seen in the summer sky.

.....As a last point, I have previously discussed how the north star can be hard to find because the constellation it is in is so faint.  Also, there are a number of people who (if pressed) will claim that the North Star is the brightest star in the sky.  (There is at least one who simply tongue-in-cheek defines the North Star this way be fiat.  Her car has GPS, so navigating by the stars is not a daily requirement.)  The North Star is not the brightest, but due to the Earth's long, slow 26,000 year wobble on its axis, if you wait about twelve thousand years, you (or your head in a jar) can see Vega as the star closest to the pole.

The August Sky

.....August is one of the best observing months of the year.  The nights are starting to get a bit longer (still cursed by Daylight Savings Time), and the Summer Milky Way, including the center of the galaxy, moves across the center of the sky from Perseus in the northeast, through Cassiopeia, Cepheus, Cygnus, Aquila, Sagittarius and Scorpius.  While I have not yet discussed many of the constellations with the Milky Way, just wandering through this section of the Milky Way with binoculars is wonderfully rewarding.

.....As before, constellations that have been covered in the blog are shown in blue (Ursa Major, Ursa Minor, Boötes, Libra, Corona Borealis, Hercules, Ophiuchus and Serpens, and Scorpius), with other constellations in red.  Saturn is being lost in the west, so if you want to observe Saturn, you'll have to do it in evening twilight, though if you look east starting at about 1 AM, you can see Jupiter rising.  As always, constellations we have yet to cover are in red.

.....August is most notable for the Perseid meteor shower (on which more later).  In short, during the first part of the month, meteors will be more common, many of them seeming to track from the northeast and the constellation Perseus.  Try to squeeze out meteor observing early, though, because while the meteor shower peaks on the night of August 11th, so does the full Moon.

The Best Meteors of the Year ... Darn It!

.....The most reliable meteor shower of the year is the Perseid meteor shower, usually peaking on the night between August 11th and August 12th.  In younger years, this was the one time during the year that I could get the whole family as interested in astronomy as I was, a situation that I found was pretty common.  In recent years, I have often held public observing sessions, which have turned out really well, as there is no bottleneck at the telescopes; meteor observing is laying back, getting comfortable, and trying to keep as much of the sky as possible visible to see shooting stars.  Easy to set up, and enjoyed by all.

.....I'm not doing that this year.

.....Let me explain why.  Every dark, moonless night not dominated by city lights, we can expect to see a few shooting stars per hour, flashing randomly across the sky. These typically come from one of three sources: Leftover bits of flotsam and jetsam that have been floating around the solar system for the last five and a half billion years (cool), little bits that have been boiled off of comets as they passed around the Sun (also cool), or nuts/bolts/heat shields/tool boxes that have come off of space craft and are crashing back down to Earth (less cool).

.....Each time a comet passes through the inner solar system, if it still has much of its original ice, that ice will boil off, taking some dust pebbles with it, and the ice will reflect sunlight, resulting in the bright coma and tail. What happens to this once the comet goes back to the outer reaches of the solar system? Nothing. That comet rubble stays in orbit, resulting in the comet's orbit eventually becoming a dusty tube of gunk around the Sun. If the Earth should pass through this gunk, then when the particles hit the Earth's atmosphere they will light up from the heat of friction generated from going from a temperature of less than three hundred degrees below zero (Fahrenheit) to thousands of degrees. Since all of these meteors are coming from the same general area in space, they will appear to come from the same general area of the sky, meaning that the meteors will all seem to radiate out from the same point. (Called, reasonably enough, the "radiant".)

.....Each August, the Earth passes through the remnant trail of the comet Swift-Tuttle, generating the Perseid meteor shower because the radiant of the meteors (the dotted circle in the image below) is in the constellation of Perseus.  Meteor showers do not require a telescope or binoculars; just go outside and look (in this case to the northeast, especially after midnight).

.....A lot of this is part of the standard run up to a meteor shower.  What makes this year different is that the meteor shower peaks only about a day before the full Moon.  Looking at different sources, the number of meteors per hour for the Perseid Meteor shower is usually given as a number between 60 and 120.  (Wow!)  Now let's look at that as the sky gets brighter due to the Moon.  Even if we take the most generous version, that considers that we can see all the way down to our eyes limit.  With the bright Moon, we can't.  With an interfering Moon, even if we could see down to fifth magnitude (as opposed to sixth magnitude, our limit), we would go from 120 down to about 46.  The full Moon is much more limiting than this, however.  Even if we assume a third magnitude limit, we're down to about seven.  Per hour.  With any bad or humid air, this could limit us to second magnitude (maybe three meteors an hour, if we're lucky), or first (maybe three meteors every four hours).  This is enough of a enthusiasm-killer that it's better to look to next year, when the moon will be much less troublesome.

.....Looking for Perseids can still be done in the nights leading up to Thursday night, but the Moon will drown out most of them.  Here is a map of the northeastern part of the sky on Thursday at about midnight.

The Best Meteors of the Year ... Darn It!

.....The most reliable meteor shower of the year is the Perseid meteor shower, usually peaking on the night between August 11th and August 12th.  In younger years, this was the one time during the year that I could get the whole family as interested in astronomy as I was, a situation that I found was pretty common.  In recent years, I have often held public observing sessions, which have turned out really well, as there is no bottleneck at the telescopes; meteor observing is laying back, getting comfortable, and trying to keep as much of the sky as possible visible to see shooting stars.  Easy to set up, and enjoyed by all.


.....I'm not doing that this year.

.....Let me explain why.  Every dark, moonless night not dominated by city lights, we can expect to see a few shooting stars per hour, flashing randomly across the sky. These typically come from one of three sources: Leftover bits of flotsam and jetsam that have been floating around the solar system for the last five and a half billion years (cool), little bits that have been boiled off of comets as they passed around the Sun (also cool), or nuts/bolts/heat shields/tool boxes that have come off of space craft and are crashing back down to Earth (less cool).

.....Each time a comet passes through the inner solar system, if it still has much of its original ice, that ice will boil off, taking some dust pebbles with it, and the ice will reflect sunlight, resulting in the bright coma and tail. What happens to this once the comet goes back to the outer reaches of the solar system? Nothing. That comet rubble stays in orbit, resulting in the comet's orbit eventually becoming a dusty tube of gunk around the Sun. If the Earth should pass through this gunk, then when the particles hit the Earth's atmosphere they will light up from the heat of friction generated from going from a temperature of less than three hundred degrees below zero (Fahrenheit) to thousands of degrees. Since all of these meteors are coming from the same general area in space, they will appear to come from the same general area of the sky, meaning that the meteors will all seem to radiate out from the same point. (Called, reasonably enough, the "radiant".)

.....Each August, the Earth passes through the remnant trail of the comet Swift-Tuttle, generating the Perseid meteor shower because the radiant of the meteors (the dotted circle in the image below) is in the constellation of Perseus.  Meteor showers do not require a telescope or binoculars; just go outside and look (in this case to the northeast, especially after midnight).

.....A lot of this is part of the standard run up to a meteor shower.  What makes this year different is that the meteor shower peaks only about a day before the full Moon.  Looking at different sources, the number of meteors per hour for the Perseid Meteor shower is usually given as a number between 60 and 120.  (Wow!)  Now let's look at that as the sky gets brighter due to the Moon.  Even if we take the most generous version, that considers that we can see all the way down to our eyes limit.  With the bright Moon, we can't.  With an interfering Moon, even if we could see down to fifth magnitude (as opposed to sixth magnitude, our limit), we would go from 120 down to about 46.  The full Moon is much more limiting than this, however.  Even if we assume a third magnitude limit, we're down to about seven.  Per hour.  With any bad or humid air, this could limit us to second magnitude (maybe three meteors an hour, if we're lucky), or first (maybe three meteors every four hours).  This is enough of a enthusiasm-killer that it's better to look to next year, when the moon will be much less troublesome.

.....Looking for Perseids can still be done in the nights leading up to Thursday night, but the Moon will drown out most of them.  Here is a map of the northeastern part of the sky on Thursday at about midnight.

Why I hate Microsoft's Spellchecker

.....The constellation of Scorpius (the Scorpion) appears in the southern sky at this time each year, as seen from the Northern Hemisphere. There are several myth explaining this constellation; of them, one holds that this is the scorpion that killed Orion the Hunter, thus explaining why the two constellations can never be seen in the sky together. (There is more than one story concerning the death of Orion, so this may explain why Aesculapius is credited with bringing Orion back back from the dead to be killed in more interesting ways by the gods. I've had days that felt like that.) A different myth from Hawai'i explains that this constellation is Maui's fishhook, which got caught on the bottom of the ocean and dredged up the Hawaiian Islands.

.....There have some good news, and I have some bad news ... oh, what the heck, I'll start out with the good news, everybody likes good news ... Scorpius has a number of bright stars, and it's basic pattern (a scraggly line) is fairly easy to follow. Furthermore, as we will see on our next cycle through the constellations, Scorpius has a number of bright star clusters, and some of them look very attractive through binoculars. (Two bright open clusters can be found by looking just to the northeast (up and left, on the map) of Shaula and Girtab. these are labeled as M6 and M7, and they are quite nice sights in binoculars or a telescope. This is not a surprise, as the summer Milky Way goes through Scorpius and Sagittarius, and covers most of these constellations. In fact, on this map the center of our galaxy is about 30,00 light years away, in a direction just north of M6.

.....The map below shows Scorpius on our "standard" sized maps, with a radius of 30 degrees (where the angular distance across the sky from the end of a fully extended pinky to the end of a fully ectended thumb, held at arm's length, is about 15 degrees.

.....Let's zoom in a bit (the radius of this image is 20 degrees) so that the traditional star names clearly refer to their associated stars, and we get a bit of a closer view.

.....The bad news is that Scorpius is located far to the south in the sky. In the northern hemisphere, Scorpius spends less time above the horizon, rising in the southeast (instead of the east), and setting in the southwest. On the chart below, I am showing the approximate horizon for Scorpius, at its very highest, for a selection of American cities. (If you don't live in one of these cities, go by latitude.) For areas that correspond to the northern United States (Philadelphia is at about the same latitude as Beijing, and is actually south of Istanbul), Scorpius is only fully above the horizon for a brief time. Add to this that this map assumes an uncluttered southern horizon, so that any trees, hills, or Pump 'N Munches will interfere with that, and that when looking that low on the horizon you are looking through more than five times as much, wobbly, humid, dusty air as when you look straight up, observing Scorpius can feel like you are trying to do so from the bottom of a swimming pool.

.....So if you are living in the continental United States, or at comparative latitudes (in Asia, the horizon of Karachi, Pakistan would be roughly equivalent to Miami), then the existence of the stars in the highlighted area will simply have to be taken at my word.

.....Now if you have gotten your knowledge of the sky from a newspaper column across from Family Circus, or if you are a spellchecking program, you may have been subconsciously changing the name of the constellation to "Scorpio" but that's not its name. Spread the word, okay?

Snakes! Why'd It Have To Be Snakes?

.....One of the largest constellations in the summer sky is actually two constellations. In another sense, it could be thought of three constellations. Technically, the constellation of Ophiuchus is the Serpent Bearer, and the constellation of Serpens, the serpent that he his carrying/wrestling with. Here is a map of the constellation:

.....And below is the representation of this constellation as Johann Bayer drew it in the star atlas Uranometria, in case my description of the constellation didn't make sense to you ...

When illustrating a figure named "man wrestling giant serpent" it is a wise artistic move NOT to show from the front.

.....which would be reasonable, as while most constellations at least make some sort of surface level of sense (the hunter, the scorpion, the northern crown, the swan, ...) what the heck is up with "the guy holding snake"? When does that make sense?

.....Here's where the problem comes in. Suppose that it is not a good night, and the limiting magnitude is 2.00. (This would be a really bad night in the country, but if you live somewhere with a lot of streetlights, this could come into play as a bright night or if that part of the sky is over some of these lights.) In that case, you see nothing in this area.

.....With a little better sky, and a limiting magnitude of 4.00, at least the "house" shape of Ophiuchus shows up. Serpens is largely invisible yet, and since there are no real patterns in Serpens, just a "scraggly line of stars", this constellation is still invisible. (On our next pass through the constellations, next year, this does at least give us bright stars to allow us to start finding all of the bright globular clusters in these two constellations.)

.....We need to be able to see all the way down to fifth magnitude in order to make out the patterns of Ophiuchus and Serpens. On the map at the beginning, for this constellation I had to show stars down to sixth magnitude in order for the patterns to be apparent.

.....All of this can distract from the basic oddness of the constellations themselves. I'm not referring to Serpens being split in half, with Serpens Caput (the head) and Serpens Cauda (the tail), but the story of the constellation itself. The constellation group seems to be so old that there is not "a" story associated with the stars, but a "well, I guess it means..." explaining the large pattern of a guy wrestling with a snake. The most common explanation is that the star group represents Aesculapius, the son of Apollo who became so proficient at medicine that he could bring the dead back to life. (One of his subjects was Orion the Hunter, or this could be a Classical retconn to account for the two different legends of Orion's death.) This, as one might guess, is one of the fast ways to land you on the gods' &^%$ list, so he was immediately struck down and placed in the heavens. The serpent has represented the medical profession (including the intertwined serpents of the Caduceus) because the ancients saw the snake shedding its skin and got the idea that the snake could therefore regenerate its way to immortality, a feat actually reserved for Timelords. There are many, many other myths that have been attached to these stars from " Hey, maybe it's Izhdubar opposing Tiamat" to "Hey, let's change it to Saint Benedict among the thorns".

.....I was going to now try and see if I could find some other pattern among the stars that might be more recognizable than, well, something that no one has recognized, when Anne Marie walked behind me and asked, "Which constellation is the frog?"

.....Frog? What the heck are you talking ...

.....Well, blast.

.....Lastly Ophiuchus is actually the thirteenth constellation of the Zodiac, as the path of the Sun crosses that little leg sticking out of the bottom. Ophiuchus actually contains the Sun from November 30th until December 17th. Scorpius only contains the Sun from November 22nd until November 29th. (Yes, neither of these match up with what the columns in the newspapers say: those are based entirely on the Babylonian religion of 2500 years ago, and have slightly less reliability than, say, Charlie Sheen.

The July Sky

.....The was a bit of a blip posting this, so here is the correct version.

.....Below is shown an image of the night sky as it is at ten PM in early July (corresponding to nine PM in mid-July, and eight PM by late July.  We can now start to see how the sky changes over time by comparing the sky in July with the sky in June (also shown below).

 

.....As before, I have included constellations that have already been discussed (Boötes, Ursa Major, Libra, Ursa Minor, and the asterism of the Summer Triangle) as well as some constellations that will be coming soon, such as Ophuichus and Serpens, Scorpius, Sagittarius, Lyra, Aquila, and Cygnus).  Note that on the maps below, the points of the compass are shown as on the maps above.  To see these constellations, take your computer (or print out the map, totally your choice) and turn it so that the labeled north (south, east, west, whatever) is at the bottom of the map when you are looking north (south, east, west, whatever.

.....The summer sky can illustrate a couple of different points.  The map below shows all stars theoretically visible, all the way down to sixth magnitude.  There are two reasons why I don't use this map for my basic sky map; sadly, the vast majority of people don't get to see the sky like this (I did, last week, and I'll be writing about that tomorrow), and if you did see the sky like this, it might well overwhelm even a fairly experienced suburban skywatcher.  Also on the map below, you might note that there are more stars in the eastern sky than the western sky, and that there almost seems to be a band going from the south to the northeast.  This is the summer Milky Way with the center of our galaxy between Scorpius and Sagittarius (and then another 30,000 light years), so hopefully this makes sense.

.....This map assumes that the reader can see stars of fifth magnitude or brighter.  This is still wildly optimistic for most people, but as you will see, I kind of need to go to this level in order for the patterns as generally associated with the constellations to make any sense.

 .....This map shows the sky to a limiting magnitude of fourth magnitude (remember that the lower the number, the brighter the star).  Holes start to appear in the constellation patterns.

 .....If the sky is cloudy or bright enough that nothing fainter than third magnitude can be seen, then only the larger patterns (such as the Summer Triangle) can be seen.

 .....Now that only second magnitude stars or brighter are shown, then only the brightest stars appear, but it is still enough to allow you to orient yourself.

.....If first magnitude stars are visible, one might wish to go back inside and expand your mind or hang out with loved ones, or, at this point, just watch some TV.

.....Finally, it could be completely cloudy:

Libra (Reprsie)

.....Libra is the first of the constellations along the Zodiac that I have written about here. What is the Zodiac? The ecliptic is the path that the Sun takes through the sky, and the planets all stay within 7° of this line (If we skip Mercury, all the planets are within half this distance of the ecliptic). The ecliptic passes through twelve constellations (traditionally; as the constellations were given boundaries by the International Astronomical Union in 1930 the ecliptic passes through thirteen constellations), and these constellations are the Zodiac. Besides being the only zodiacal constellation with no bright deep sky objects, Libra is also the only zodiacal constellation named after an inanimate object.

.....Our constellations can be traced back to the forty-eight the Greeks had (there are eighty-eight constellations now), but the constellations of the Zodiac are much older. This makes sense because while many of the constellations can be thought of as “sky-decorations” the Zodiac allowed the ancients to track the seasons. Of the zodiacal constellations, Libra might one of the youngest.

.....Libra as the balance represents that the Sun would be in this sign at the Autumnal Equinox, when the day and night would be equal lengths, or at least it was. According to the boundaries as they are now, the Sun would be in Libra at the equinox from about 2200 BC until about 700 BC. Close to this time, if Libra did not exist as a constellation of its own, then it could have been created, to allow for twelve (one per month) constellations around the zodiac. I imagine (spoken in some Indo-Aryan root), "Okay, we need a new constellation for this point where the day and night are the same length. Remember, everything else on this list is a living thing, hence the 'zoo' in 'zodiac'." Six hours of debate follows, in which Chester (or the Indo-Aryan root for "Chester") rejects a bunch of things because they're "stupid, ten more things are dropped because Bert is allergic to shellfish, the "Claws of the Scorpion" is out because Bob of the High-Pitched Voice sat on one once, and then, "&#@% it, we'll call it the "scales", happy hour is almost over. (The bartender gave the lizard an extra squeeze, or something. Heck, I don't know what ancient beer was like.) Geez, this could have been the first "designed by committee" in history.

.....Even when not using the strict modern boundaries, the wobble of the Earth around its axis (which I discussed in a post on Ursa Minor) would have carried the equinox into Virgo, where it is now (and where it will be until AD 2450). This seems to indicate that Libra as a scales must have existed when the equinox was well inside Libra, but there are many references to these stars as Chelae, the claws of the scorpion. First, as seen below, the stars of Libra work well as the claws of the scorpion, whereas with Libra as a scales, the scorpion’s claws seem a little pathetic. The (seriously cool) names of the stars could refer to this, with Zubeleschamale translating as “the northern claw” and Zubelelgenubi as “the southern claw”. This is contested in some sources (alright, I admit it – in an unsourced article on Wikipedia) in that the Arabic (zubānā) and Akkadian (zibanitu) words for “scorpion” and “scale” are the same. Life becomes more complicated with the constellation having either four claws or four scales, but Richard Allen’s Star Names: Their Lore and Meaning considers Zubelalgubi as a degenerate version of the name “Zubelelgenubi”, and Zubenelhakrabi (the scorpion’s claw) as belonging to g Scorpii, which was apparently due to a need to invent two new claws when the other ones became Libra.

.....Why were the scorpion’s claws made into the balance of Libra (assuming, of course, that this is what happened)? Sure, there would be pressure to have twelve constellations on the Zodiac, one per month, and the reason of having a balance at the point where day and night are balanced make sense, but I have another idea why an inanimate object was added to the Zodiac where it was …

Five minutes before the first sexual harassment lawsuit

.....Zubenelgenubi is a fairly easy double star to split, with the companion star being dimmer, but not tremendously dimmer (magnitudes of 2.8 and 5.2), and about 4 minutes of arc apart, or about one-eighth the size of the Moon in the sky. I could split this double star with a pair of binoculars, so this represents an excellent opportunity to do the same, and take the first step towards learning how to observe and split double stars.

The Summer Solstice

.....(First, I hope that this is not causing anyone to skip my post on viewing Mercury, posted yesterday.) Here's what set me off.  I was directed to a story on the solstice.  First I'll give you a post on why this is the summer solstice for the northern hemisphere, and try and keep from going off on the problems I saw in the "news" story.  If you are at a cookout, the closer you are to the fire, the warmer you are.  If you are getting an English muffin out of the toaster, the closer you are to the toaster, the warmer your hand is.  In that case, it seems intuitive that the Earth is warmer when we are closer to the Sun.  It seems intuitive, but it is completely, totally, and utterly wrong.

.....The Sun does not move around the Earth (something that is only moderately difficult to get students to accept), but it looks like it does, in the same way that the sky can be treated as a big imaginary sphere.  As the Earth rotates, the North Celestial Pole (NCP) is the point in the sky that appears directly above the Earth's north pole, and the South Celestial Pole and Celestial Equator are ... I hope that you get the idea.  Since the NCP is directly overhead at the north pole, or 90° above the horizon, and the NCP is on the horizon, or at an angle of 0° above the horizon, we can see that the angular height of the NCP is the same as our latitude.  We can then track the apparent path of the Sun across the sky as the ecliptic.  Why we have seasons comes from the fact (a fact that does not depend on whether USA Today says that it is true or not) that the Earth does not rotate with its equator in the same plane in which it is orbiting, but is tilted by 23.5°.  This means that the ecliptic is tilted by 23.5° to the celestial equator (the Earth's equator projected into space) as shown.  The Earth keeps this tilt constant as it orbits, the star Polaris always above the Earth's North Pole, as shown below.  (Not to scale.)

.....The effect of this is that during part of the year, the northern hemisphere is "leaning into" the Sun, and during part of the year, the northern hemisphere is "leaning away" from the Sun.  Imagine that we pick a point on the Earth, and then trace the path that it takes over one day, a circle inscribed across the Earth at your latitude.  The effect that this has on the day comes from two things.  First, notice that the point, at the northern hemisphere summer solstice, spend the majority of its time on the sunlit side of the Earth.  It is hotter in the summer partly because the Sun is above the horizon for a longer period of time.  The northern hemisphere has its longest time of daylight on the summer solstice because the tilt of the Earth points the northern hemisphere most directly towards the Sun on this day. 

 .....The second reason why summer is hotter has to do with the height of the Sun in the sky.  In summer, a quick glance at the diagrams above should show that the Sun is much higher in the sky in the summer, as opposed to the winter.  The Sun provides the same amount of energy to the Earth at all times, but if the Sun is low in the sky that same energy is spread over a greater area, having a lesser effect.  To take Winona, Minnesota, (with a latitude of 44°) as an example, the North Star is 44° above the northern horizon, which means that the celestial equator is (90°-44°=) 46° above the southern horizon.  On the summer solstice, the Sun is  above the celestial equator, or a maximum value of 69.5° above the horizon, as opposed to the winter solstice, when the Sun is only 22.5° above the horizon, at best.  These two effects combine to make summer hotter, and, as the observant may have noticed, at all times (not just on the summer solstice), the seasons in the northern hemisphere are the exact opposite as seasons in the southern hemisphere.

.....The Earth is actually closest to the Sun in January.  This might seem strange, but really, the Earth's orbit is so close to being a perfect circle that this difference is not detectable.  One might expect the Southern Hemisphere's summer to be slightly hotter than the Northern Hemisphere's Summer, but the Southern Hemisphere is mostly water, and water has a strong moderating influence on temperature changes.