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 122mm 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

Friday, July 20, 2018

The Music of the Spheres

Seven poets sing of the stars:


Look thou no further, but affix thine eye 
On that bright, shiny, round, still moving mass, 
The house of blessed gods, which men call sky, 
All sow'd with glist'ring stars more thick than grass, 
Whereof each other doth in brightness pass.
(Edmund Spenser)

The infinite shining heavens Rose 
and I saw in the night
Uncountable angel stars
Showering sorrow and light.
(Robert Louis Stevenson)

Look how the floor of heaven
Is thick inlaid with patens of bright gold.
There’s not the smallest orb which thou behold’st
But in his motion like an angel sings.
(Shakespeare)

The heavens declare the glory of God
And the firmament sheweth his handywork.
(King David (the Psalms), KJV Translation)

BEND low again, night of summerstars.
So near you are, sky of summer stars,
So near, a long arm man can pick off stars,
Pick off what he wants in the sky bowl,
So near you are, summer stars.
(Carl Sandburg)


Look at the stars! look, look up at the skies! 
O look at all the fire-folk sitting in the air! 
The bright boroughs, the circle-citadels there! 
Down in dim woods the diamond delves! the elves'-eyes! 
(Gerard Manley Hopkins)

As I watch the bright stars shining, 
I think a thought of the clef of the universes and of the future. 
A vast similitude interlocks all,
All spheres, grown, ungrown, small, large, suns, moons, planets,
All distances of place however wide,
All distances of time, all inanimate forms,
All souls, all living bodies though they be ever so different, or in
different worlds,
All gaseous, watery, vegetable, mineral processes, The fishes, the brutes,
All nations, colors, barbarisms, civilizations, languages,
All identities that have existed or may exist on this globe, or any globe,
All lives and deaths, all of the past, present, future,
This vast similitude spans them, and always has spann’d,
And shall forever span them and compactly hold and enclose them.
(Walt Whitman)




Friday, July 6, 2018

Magnus Frater

I'll be on the road for the next two weeks and away from my computer, so I thought I'd sign off (for now) with one more posting, this one about our own Sun's probable sibling, born out of the very same cloud of gas.


From left to right
90 Herculis, HD 162989, and HD 162826

I am speaking, of course, of HD 162826 in Hercules. This star is currently 110 light years from our Solar System, and has an apparent magnitude of 6.7. Its chance alignment with two slightly brighter stars, HD 162989 (magnitude 6.04),  and 90 Herculis (magnitude 5.16) is a huge aid in finding it. The 3-star asterism lies approximately halfway between super-bright Vega and the globular cluster M92 and just three degrees north of Theta Herculis (magnitude 3.85). It is ridiculously easy to find through binoculars. Theta Herculis is a naked eye star, to the left of the northwest corner of Hercules' "Keystone" (which contains the mighty M13 globular). Find that, and place it at the lower edge of your binocular field of view. The 3 stars shown in the above image will be near the top of that same field of view. [see footnote] The star on the far right is the one you're looking for. It's that easy!


Red arrow points to HD 162826

So why do we believe that HD 162826 was born in the same stellar litter as our own star? Three reasons:

1. It is the same age as our Sun (4.6 billion years).

2. Its chemical composition is a close match to the Sun, especially in elements that typically vary wildly between different stars, such as barium and yttrium. There are only 30 stars known in the entire Milky Way galaxy that are as close a match to our Sun as HD 162826.

3. It has been calculated (by computationally "winding back the clock" of the orbits about the galactic center of HD 162826 and the Sun) that 4.6 billion years ago (that is, when the two stars were born), they pretty much occupied the same space.

HD 162826 may indeed be the Sun's litter mate, but it is no twin. It is 15% more massive than our star and shines at an absolute magnitude of 3.92 (as compared to 4.83 for the Sun). If our Earth were circling round HD 162826, it would have be orbiting at a distance of Mars to be the same temperature.

Hmm... HD 162826 is a rather awkward moniker for so close a relative. It was a pain typing it nine times for this posting. Considering its mass, perhaps we ought to just call it "Big Brother" (or, more formally, we could use the Latin Magnus Frater).

Footnote: This assumes the top of your field of view is to the north. At the time of this posting (early July), HD 162826 will be very close to the zenith, so your own orientation may be quite different. So with that caution, let us say that the 3-star asterism will be to the north of Theta Herculis in your binocular field of view, and leave it at that.