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In the House of Hyades: Sigma (σ), Theta (θ), and Delta (δ) Tauri

And now for something entirely different — binocular binaries.

Grab yourself a cup of something warm and have a seat beside me in a comfortable chair.  We’re going to tilt back into Taurus and enter the well lighted House of Hyades.  And in case you’re mystified by the reference to the Hyades, it’s the open cluster of stars between Aldebaran and the point where the “V” of Taurus come together just to the southwest of it.  But more on that later.

Now I have to tell you, binoculars and I have never hit it off.  My eyes just don’t want to be forced into looking through two large lenses at once.  And in addition to the fighting eyeball feedback, I frequently find I’m struggling to get a precise focus.  I don’t know about you, but I seem to prefer my photons finely focused — as in well done — and most binoculars I’ve used insist on serving up half-cooked views — as in medium rare.  Hope I’m not making you hungry.

But I do have a handy pair of 7×35’s that get used occasionally for quick glances.  For instance, if I’m trying to find an elusive star, or if I see a rare mysterious light in the sky — no contact with E.T. yet, though.   But somewhere deep in the recesses of my double star cluttered memory, I remembered Greg mentioning he was having great luck with his 15×70 Celestrons.  So when I saw a pair come up for sale, I decided to grab them to see how much better they would be than the small pair I ignore.  Tonight we’re going to use both pairs.

Because of their size, I have the 15×70’s on a parallelogram mount.   I tried using them without it and my arms began to feel like jelly within a couple of minutes.  So I’ll set them up beside your chair, and I’ll use the 7×35’s to guide us through this maze of stars.   And better throw this blanket over your legs — the dampness out here is a bit chilling tonight in this forty degree air.

One thing that will strike you immediately if you compare views in these is how much brighter the field is in the 15×70’s. I mean the stars really leap out at you.  I’ve caught myself ducking couple of times!

The Hyades Cluster, home of Sigma (σ), Theta (θ), and Delta (δ) Tauri. Click on this image, and those that follow, for a larger view. (Stellarium screen shot with labels added)

Now, this area not only features two multiple stars visible to the unaided eye — Delta and Theta — but it’s rich in visual pairs of stars that form some rather eye-catching patterns.

We’re going to start this tour with the beautiful reddish-orange Aldebaran, a first magnitude star located a relatively close 65 light years away from where we’re sitting tonight — just a hop, skip, and a jump out into the near reaches of our galaxy.  In the binoculars, though, I’ve noticed the color seems to be a bit pale — more like white with a reddish-orange tinge.  Take a look and let me know if you see the same thing.  Aldebaran has an 11.3 magnitude companion located a wide 133″ from it, which I think we should be able to pick out with at least the 15×70’s you’re using, except that the transparency is rather poor tonight.  So we’ll have to come back to it on a better night.

Splitting Tools: Obviously, since this is a post describing binocular friendly pairs, all of three of the pairs described below are ideally suited for binoculars, even small ones — hand held 7×35’s work well, but if you use anything larger, mounted would be better.  But they’re also great candidates for 50mm and 60mm scopes, provided you use low magnifications of about 20x or so.  Too much magnification will produce very wide pairs, giving the appearance of regular field stars.

Sigma-1 and Sigma-2  (σ-1, σ-2)  (Σ I 11)  (STFA 11)
HIP: 21683    SAO: 94054
RA: 04h 39.3m   Dec: +15° 55′
Magnitudes: 4.7, 5.1
Separation: 444.1″ (7.4′)
Position Angle: 194°  (WDS 2011)
Distances: 152 and 159 Light Years
Spectral Classifications: A4 and A5

OK — with Aldebaran in the center of your binoculars, if you let your eyes travel just a bit to the east you’ll come to the Sigma (σ) twins, σ-1 and σ-2.  They’re a visual pair, and they form a right angle triangle with sixth magnitude 89 Tauri just to their west.  Now  Sigma-2 (σ-2) looks white to me, and Sigma-1 (σ-1) is just a slightly different shade of white — it looks like maybe it has a slight tinge of yellow.  In Double Stars for Small Telescopes, Haas describes them both as brilliant yellow, but that was with a 125mm telescope which would provide a richer color than we can see in the binoculars.

What’s that?  So you see the yellow, too!  Great, I thought maybe my eyes were being tricked by the two little 35mm barrels on this pair I’m using.

Now you can take your choice of two eye-pleasing asterisms here — either the right angle triangle formed by the Sigma twins and 89 Tauri, or the parallelogram formed if you include the 6.6 magnitude HIP 21474 to the southwest of 89 Tauri.  Regardless of which you prefer, you’re guaranteed a stellar configuration either way.  I kind of lean toward that uniquely shaped parallelogram.

Oh, and to answer your question about the numbers attached to the Sigma pair: the -1 and -2 are assigned to them based on location.  The one farthest to the west gets the one, the next one to the east gets the two.  And if you look at the chart above, you’ll see that holds true for the Theta (Θ) twins and the Delta (δ) triplets.  Pay careful attention to this astronomical trivia — there might be a quiz when we get situated in the House of Hyades soon.

Theta-1 and Theta-2  (θ-1, θ-2)  (Σ I 10)  (SFTA 10)
HIP: 20894    SAO: 93957
RA: 04h 28.7m   Dec: +15° 52′
Magnitudes: 3.4, 3.9
Separation: 341.20″  (5.7′)
Position Angle: 348°  (WDS 2011)
Distances: 157.9 and 149.0 Light Years
Spectral Classifications: G7 and A7

I remember very clearly the first time I split these two stars.  It was without a scope on a night that was very clear and transparent.   I was looking up at Taurus because Aldebaran had caught my eye, and as I was enjoying the view of it and the Hyades, I suddenly realized I was seeing two very close, but distinct stars, just southwest of Aldebaran.  Now that really caught me off guard since I had never noticed them before, so I grabbed an atlas and identified them right away.  Since then, I’ve used these two stars frequently to gauge the transparency.  On a scale of one to five, five being the best, you need a four — above average — to pull off this trick.  And dark skies help a lot, too.

If you ask Jim Kaler, he’ll tell you the jury is still debating as to whether Theta-1 (θ-1) and Theta (θ-2) are gravitationally linked.  But Theta-2 (θ-2) has a companion located a mere couple of a hundredths of an arc second away — a little on the close side, and more than a bit beyond binocular range — which whirls around its parent once every 140.7 earth days.

We’re focusing now on the area within the circle! (Stellarium image with labels added)

Now if you position Aldebaran on the northeast side of your binocular field, Theta-1 and -2 will come into view over on the southwest side.  Both of these stars are white, but Theta-1 (θ-1) seems to have a slight tinge of red to me.  What?  You don’t see it?  Here, you better have some more hot tea.  You’ll be able to see the warmer colors better that way.  🙂

OK, if you start at  Theta-1 (θ-1) and let your eyes travel a bit to the northwest, you’ll come to fifth magnitude 75 Tauri, which looks to me to be white with a slight bit of yellow mixed in there somewhere.   Now, from Theta-2 (θ-2), look over to the east and you’ll find a pair of fifth magnitude stars, 80 and 81 Tauri,  with sixth magnitude 85 Tauri extending on a line beyond them to the northeast.  And just northeast of the Theta (θ) pair is another pair of stars, fifth magnitude HIP 21029 and 6.5 magnitude HIP 21053.

Now if you look into those binoculars closely — or at the chart above — that last pair, along with the Theta twins, and the 80/81 Tauri pair, form a very unusual triangle of three pairs of stars.  And, if you’re keeping track of all this for the quiz, you can add these notes: Both 80 and 81  are telescopic doubles — 80 Tauri has an 8.1 magnitude companion 1.6″ from the primary, and 81 Tauri has a 9.4 magnitude companion at a more distant 162″.

Like I said, this area is just full of eye-catching patterns.

But wait just a second.  Before you put those binoculars down to ask another question, look a bit closer at that triangle of double pairs and you’ll see …….

(Stellarium screen image with labels added, click to enlarge the House).

And you were wondering if we would ever get there.

Kind of leaves you breathless, though, doesn’t it.  Yeah, I know — star stuff does that sometimes. I wouldn’t take off that coat, though.  There’s no heat in that house, at least not from where we sit at about 150 light years away.

Actually, I have to thank Greg for pointing out this asterism.  It really is unique, and once your eyes recognize the pattern, it jumps right out at you.

And now that we have a home, the next thing we’re going to do is jump off the roof.  So let’s climb up to the peak, where 75 Tauri is located, and we’ll make a short leap straight up from it to the northwest and come down very gently right in the middle of the Delta (δ) threesome.

A leap to the northwest from the roof of the House of Hyades lands us right in the middle of the delectable Delta (δ) trio. (Stellarium screen image with labels added, click on the chart for a larger view)

And once more, another pattern emerges before our binocular fortified eyes.

Delta-1 (δ-1)                   Delta-2 (δ-2)               Delta-3 (δ-3)
Σ 1746                                      BUP 56                       H VI 101
HIP: 52913                                20542                           20648
SAO: 137808                            93907                           93923
RA:  4h 22.9m                     4h 24.1m                         4h 25.5
Dec:   +17° 49′                      +17° 27′                        +17° 56′
Mag:         3.75                              4.80                               4.30
Sep:                                 13.8′ from -1                43.2′ from -2
Dist: 153.2 LY                       145.9 LY                        147.9 LY
Spec:          K0                                  A7                                  A2

The Delta (δ) trio of stars forms a very recognizable triangle of just slightly more than ninety degrees.  As I look at them, Delta-2 and -3 appear to be the same shade of white, and Delta-1 seems to me to have a slight tinge of yellow to it.   You can see that, too?  Wow, our eyes must be on the same wavelength!

OK, now look closely at this area and you’ll see four pairs of stars to the southeast of Delta-2 (δ2) that form an interesting pattern.  They caught my eye because the first two pairs (1 and 2 on the chart above) are arranged parallel to each other, as are the last two pairs (3 and 4) which point a bit more toward the south.  If you spend enough time here, your eye will no doubt detect other patterns.  I’ll leave that to you while I pour us some more tea.

Now the Delta (δ) trio are not gravitationally linked, which you can see if you look at their distances as shown above.  But each of them have companions, although those of Delta-1 and -2 are detectable only with spectroscopes or very large instruments.  The two companions of Delta-3, however, can be seen in a small to medium telescope.  The brightest is a 7.5 magnitude star at a tough distance of 1.5″, and the other is an 8.7 magnitude star located at a much more detectable distance of 77″.  I haven’t looked at these with a scope yet, but I’m filing a mental note right now to come back to them.

The Hyades

As we sat down at the beginning of this evening, I mentioned the Hyades cluster and described it as consisting of most of the stars between Aldebaran and the point where the “V” comes together at Gamma (γ) Tauri.  As you look at this area in the binoculars, or on the first chart above, it’s kind of difficult to form an image of a single cluster in your mind.  Instead, as we’ve just seen, what stands out is several groupings of stars.

So to make the “clusterness” of this cluster more visible, I listed the distances of all the labeled stars in the first chart.  I started with the Sigma (σ) pair and then worked my way to the southwest until I came to Gamma (γ) and then back up to the north.  Now Jim Kaler says the average distance of the Hyades cluster is fixed at about 152 light years, and that number begins to make a lot of sense if you look at the numbers on the chart below.

Just a quick glance at the distances you see on it shows that all but a few of these stars lie within a narrow range of 142 to 159 light years from us.  Out of the twenty-three stars in that list, only the four in red clearly stand out as non-members because their distances are nowhere close to that range.  The only one there is really any doubt about is HIP 21053.

And for a view of the Hyades in three dimensions — including a movie (!) — take a look at this site.

OK, what do you say we drop back in through the roof of the House of Hyades and see if the Hyadeans have any thing to eat.  Of course, I’ve never eaten there, so we might be better off to just get off this cold, damp deck, and go see what we can find in my kitchen.  At least it will look like something you’ve seen before.

And since you tolerated that maze of numbers on the chart rather well, we’ll just forget the quiz.  The images of all those star patterns in our memory will keep us mentally occupied for a while, anyway.

Cup of tea and a slice of cake?

(WDS data updated 9/9/2014)


2 Responses

  1. Yep, Aldebaran is three, maybe four stars – I know, i just saw all of them at once – and they’re all bright ornange. Of course the winds were gusting up around 30-40 mph, the observatory door was banging, and low clouds were scudding across the waxing Moon and threatening to shut down the House of the Hyades – more like the House of Hades tonight.

    But it was clear and we’ve had so much dismal weather, I had to give it a try. I thought I’d see if the 25X100s could drag out that 11.3 magnitude companion to Aldebaran John mentioned – thought I might beat him to it. But it’s probably dark on the West Coast now and he is supposed to have clear skies and I’m sure I can’t see it under these conditions. Good luck John!

    Funny – I made a discovery, tonight, of a fairly new astronomy weather service out of Australia called Skippy Sky. You can find it at:


    Like the Clear Sky Clock I usually use, it colorcodes and for it blue is good, and red is bad. It showed the seeing in my area tonight as a bright red. Maybe I should have heeded the instructions on the Web site which went like this:

    “Red on the Seeing scale means stay inside and have a red wine – Seeing will most likely be atrocious. Blue means get out there and
    turn blue in the cold, ‘cos the Seeing is likely to be worth it.”

    Well, i got the worst of both worlds. The seeing was atrocious and I went outside despite the temperature being 25° F and I don’t even want to think of what that means in terms of wind chill. I wore boots because the snow was soft and aqishy this afternoon, but by evening it undergone a quick freeze and I could walk on top of it.

    Fortunately I was in the Observatory most of the time.

    I did get to put the ETX 90 on the same parallelogram mount that the binoculars had been on and that worked wonderfully. So I feel I have the scopes in the Observatory the way I want them – or will when a couple of new ones arrive later this week – man these things do breed, as John has warned! 😉

    And yes, I tried the ETX90 on Aldebaran with a 13mm Nagler – it has expensive taste in eyepieces – and again I saw three or four version of Aldebaran bouncing around and no companion.

  2. Ah, Theta and Theta, you sure looked wonderful tonight!

    I mentioned in the post above that the first time I had split Theta-1 and -2 was with these star-starved naked eyes of mine. And I still remember that night as clearly as if I was standing there right now.

    But it’s been a while since the Sky Gods served up a sky that would allow that again, so it had pretty well slipped from my stellar thoughts.

    And then a couple of nights ago, at 4AM, I spied that pair of dazzling devils once again — on a very unlikely night, too.

    It had rained off and on until about 11 PM, but then, just as the Clear Sky Clock promised it would, some invisible hand peeled back the clouds and the stars re-appeared in the sky like magic.

    It took an hour or so for the seeing to settle down, and after a couple of more hours, the transparency became stunning. I spent all that time wedged in my chair looking at several different objects, trying to prevent the penetrating dampness from putting a damper on an excellent session.

    Finally, I had to call it quits. I could tolerate the numbness in my fingers and toes, but that dampness was not only penetrating through my clothes, it was all over my clothes. And my scope. And my dripping Star Splitter hat was beginning to imitate a sponge.

    So it was time.

    After getting everything off the deck and back into the house where I could dry it off, I took my usual post-observing walk to limber up and restore circulation. Actually, the main reason for the walk is my four-legged observing companion, who drags me back out with the leash in his teeth wrapped around my legs.

    At any rate — after the walk, I stood in the drive staring up at the sky, which was just too darn good to leave outside the house. I must have stood there a good fifteen minutes, soaking up the views overhead which were etched in the sky in that unusual transparency —-

    —– and then I spied them!

    Theta-1 and Theta-2.

    Distinct — separate —– white ——- awe-inspiring.

    In a telescope, you would describe them as just a bit more than a hair’s width apart.

    Those two stars lurk up there on many a night, inseparable to the naked eye, due to lack of atmospheric cooperation. But as Taurus ascends the eastern sky at this time of the year, I always remind myself to take a look. Probably 98% of the time they’re un-splittable without optical aid.

    But not tonight!!!!!!

    I stared a while longer, and then remembered the Delta Triplets. Got Delta-1 and Delta-3, and even had a glimpse of Delta-2, too.

    And the Pleiades? Got all seven of ’em!

    Put those optical instruments away — we don’t need ’em tonight!

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