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Theta Aurigae: “And the light of its passage is night on the face of the world.”

Where does the time go?  If I didn’t know better, I would swear it sometimes moves as fast as light.

To be less vague and more specific at the same time:  it seems like it was just a short while ago when I made plans to spend some extended time on Theta (θ) Aurigae, but in reality it’s been five months — and now it’s rapidly slipping out of sight in the western sky, curving out of my reach beyond earth’s northwestern horizon.  I can only silently curse the weather gods, the rain makers, and the purveyors of poor seeing – very silently at that, because if they hear me, it’s likely to get worse.  😉

I did get a peek at Theta (θ) some time back in November or December, and what I saw lit an ember that has smoldered and moldered in my mind ever since.  I really should have sketched it then, but wrapped as I was in a cloud of naive expectation that the clear skies would continue, I confidently intended to get back to it in the next night or two.  That never happened of course, but the image I retained in my mind of a bright primary with a very, very small dot of light, almost snuffed out under the glare of primarial glow, remained a vision that only grew more enticing in the following months.

Of course it had competition from other worthy lights in the sky, which only extended my planned return trip.  And even though I got back to it several times, poor seeing repeatedly obscured any hope of a second sighting of the 7.2 magnitude secondary.  But persistence pays dividends sooner or later, and later finally materialized on a very clear full moon night – always a sure bet – so I grabbed it before Auriga slipped out of my grasp for several months.

Theta (θ) Aurigae     (OΣ 545)   (AC is H V 89)   (AD is H VI 34)   
HIP: 28380   SAO: 58636
RA: 5h 59.7m   Dec: +37° 13’
Magnitudes   AB: 2.6, 7.2      AC: 2.6, 10.7      AD: 2.6, 10.1
Separation    AB: 4.0”             AC: 55.2”            AD: 135.3”
Position Angle  AB: 304° (WDS 2009)    AC: 300° (WDS 2007)    AD: 351° (WDS 2002)
Distance:  173 Light Years
Spectral Classification: All A0

Theta (θ) is certainly not difficult to find, even on a full moon night.  It holds down the east corner of the pentagonal shaped figure that outlines the lower two-thirds of Auriga.  Admiral Smyth takes a contextual approach on p. 143 of The Bedford Catalog, locating it like this:

“A neat double star, in the Waggoner’s left wrist; where a line from Procyon through Epsilon (ε) in Castor’s knee, and 14° beyond, will find it, in the direction of the brilliant Capella.” (Stellarium screen image with labels added, click to enlarge).

My approach is simply to go due east from first magnitude Capella to Beta (β) Aurigae, make a ninety degree turn to the south, and go the same distance to Theta (θ).  I suspect the Admiral’s sea-going years inclined him toward a wide angle perspective, whereas my land-based field of view has been narrowed and winnowed down to tighter diameters as a result of being happily glued to an eyepiece for hours on end.

The D&G f/15 as it prepares to feast on starlight.  (Click on the image for a larger view).

BUT —  if you’re going to reach into that eyepiece with your eye(s) and pry Theta (θ) apart, you gotta restrict your vision to arc second precision.   After all, four arc seconds between primary and secondary requires some hard gazing, especially when the secondary shines with about seventy-five times less intensity than the primary.

So I pulled out the big gun this time, the five inch f/15 D&G refractor that I rescued from the light polluted suburbs of Seattle.   I could swear the first time I pointed it into the dark skies over the north Pacific, it quivered and trembled from one end of its long white tube to the other with an astronomical amount of appreciation for all the additional starlight.  And, considering the fantastically fickle seeing conditions of the past few months,  I needed it’s long focal length talent to give me an extra edge for the prying apart part of the observation.

And what did I see in it?

The “C” component is seen just below and to the left of the primary and secondary, and “D” is above and to the left, the whole complicated complex forming an extended isosceles triangle.  And in case you missed it, “B” is tucked in tightly against the primary.  (East and west reversed to match the refractor view, click to lose this caption).

I saw a bright primary tinted with a light yellow hue, which was carefully creeping towards white at the relatively low magnification provided by a 20mm TV Plössl (95x).  But approaching ninety-five times closer to Theta (θ) only gave me the slightest hair of a hint of the secondary, so I shifted into warp speed by merging the 20mm eyepiece with a 2.4x Barlow, and warped my way 229 times closer to my goal – and then I noticed the primary had lost its yellow glow and slipped all the way over to white.

Ah, but who cares about color now!  There shone that secondarial light in all it’s diminutive dancing glory!  This  was what I came for!  Throbbing just beyond the edge of its more brilliant parent, it vibrated and quivered and shivered as enthusiastically as a young robin about to be released from the parental nest for the first time!  Get me closer, Scotty!

I could hear the star ship creak and groan as we lurched and warped to 305x using dilithium crystals that looked remarkably like a 15mm TV Plössl in a 2.4x Barlow — but we were streaking so fast all I could see was a magnified blur.  Better back ‘er back down, mate, the ship is shakin’ and this is playin’ havoc with me poor ole eyes!

Now no doubt that other expert of celestial navigation, our dear Admiral Wm. H. Smyth, was moving at a much slower relativistic speed when he recorded his colors.  Through the port hole of his six inch refractor, he saw the primary as “brilliant lilac” and the secondary as “pale yellow.”

Sir William Herschel and I are closer on the color of the primary – he reported it as “fine w.[hite]” and described another star as “reddish.”  That was probably the 10.1 magnitude star now identified as “D”, since he apparently didn’t see the much closer “B”.

In fact, Sir William owns the deed to discovery of  this small sector of the galaxy, having spied Theta’s multiple starlight on two different occasions.  He uncovered that 10.1 magnitude component on September 26th of 1780, and named it H VI 34 — and returned to unearth its 10.7 magnitude sibling from the sky two years later, on September 5th, 1782.  That one he baptized with H V 89, but it’s now known as the “C” member of the family.

So who claims credit for that dancing secondary that dazzles me so?  Apparently not Sirs James South and John Herschel, who recorded an observation of Theta (θ) on November 13th, 1823, (their catalog number is SHJ 68) but reported only the fainter stars.  It seems as though Otto Struve spied it in 1871 as near as I can tell, and hence the designation OΣ 545, also known as STT 545 in non-Greek nomenclature.   S.W. Burnham also came across it in 1888, apparently independently, with the thirty-six inch Clark refractor of the Lick Observatory.

At any rate, in the early part of this 21st century, we all know the secondary is there now, and we can even see it in a four inch refractor if we look closely!  But I wouldn’t turn down an offer of a peek into that thirty-six inch Clark, if S.W. were to offer it.

The Waggoner is seen here looking for his missing chariot.  (Stellarium screen image with labels added, click to enlarge).

While mining my sources for various gems of material for this post, I came across a four line stanza offered up to Auriga by Swinburne.   You may have noticed that the Admiral’s directions above referred to Auriga as the “Waggoner,” which is because the constellation has been portrayed since Greek and Babylonian times as a Charioteer without a chariot.  The portrayal at the right is typical – you can see the young waggoner/chariot driver holding a goat and two kids, which are the chariot’s detached motive power.  What might be best described as a more roughly hewn version can be seen here in Flamsteed’s  Atlas Coelestis (scroll the contents in the window at the left about two-thirds of the way down to see the map of “Camelopardal and Auriga”).

These four lines have something of the sensation of star ship speed hovering about them   . . . . . . .   and the final line sort of  leaves you covered with dust and standing in the dark as the glow of the chariot recedes into the dim distance:


Thou hast loosened the necks of thine horses, and goaded their flanks with affright,
To the race of a course that we know not on ways that are hid from our sight.
As a wind through the darkness the wheels of their chariot are whirled,
And the light of its passage is night on the face of the world.

Algernon Charles Swinburne’s Erechtheus
(From Allen, p. 83)


Clear skies on the face of your world!   😎

And a quick P. S. here:  If you care to take a ride north to Beta in that chariot with William Herschel and I, hop aboard right here.


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