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Ice cubes in the water jar – Zeta (ζ) Aquarii and friends

Zeta (ζ) Aquarii   (H II 7) (Σ 2909)       HIP: 110960   SAO: 146107
RA: 22h 28.8m Dec: -00° 01′
Mag: 4.34, 4.49  Sep: 2.3″ PA: 166° (WDS 2013)
Distance: 103 ly
Spectral type: F3 IV-V

(WDS data updated 9/13/2014)

It’s almost Neptune’s birthday, otherwise I would not be prowling around this particular section of sky – it tends to look empty  and the constellations that do fill it use a lot of fourth and fifth magnitude stars and when you connect the dots they seldom  look like their names imply –  but oh what a beauty I have been missing – Zeta (ζ) Aquarii. It’s easy to find, can be split with a 60mm, and yields a closely matched pair with the slightest tint of colors.

But I’m jumping ahead of the game – this year Neptune is in Aquarius and completing it’s first Neptunian “year” – almost 165 years since it’s discovery. You can read all about it here, including star-hopping charts and instructions. But when I went to that section of sky the other night and found  Neptune peeking barely above my tree line – I got thinking about what else might be here and that “water jar,” or “Y” really caught my eye. It is practically dead on the celestial equator and so should be visible to much of the world.

Here’s the general vicinity I’m talking about.

Click image for much larger – readable – version. Looking south on a Summer morning you’ll see the general region that includes our target double. There are only two, bright “guidepost stars” in this region, Altair and Fomalhaut, and except for the  familiar “teapot” the asterisms tend to be made of fourth and fifth magnitude stars and are best seen in binoculars. What I’ve labelled the “Arrowhead” is a good deal of the constellation Capricornus. The pair of stars at the northeastern tip, which includes Deneb Algiedi, are easy to find and a good guide.  The “Circlet” and the “Water Jar” itself can be seen with the naked eye if your skies are reasonably free of light pollution, but are easier targets for binoculars. (Prepared from Starry Nights Pro screen shot.)

It was about 2 am and though the water jar was faint, it was well above my tree line. The whole asterism just fit in my 15X70 binoculars – lower power ones with a wider-field would do better.  Checking the charts I found the central star of this 4-star asterism is a double – not only a double, but one Sissy Haas rates as a “showcase double” and with good reason. Here’s a closer view.

Click chart for a much larger version. I included the insert from the Johann Bayer. Uranometria atlas of 1603 to help you understand why it’s called the “water jar” because there’s no way this asterism look like any water jar I’ve ever seen. (Prepared from Starry Nights Pro screen shot.).

There’s a hint of color here. The brighter one seemed  to hold a slight tint of lemon in the 85mm refractor. The other a hint of grey.  Sissy Haas says they have a pretty color “whitish citrus orange.” In the 60mm I had to crank up the power, got a hairline split, and saw no color.

But here’s what really delights me about Zeta Aquarii.  I see it as part of a wonderful sequence of similar doubles that if viewed in succession would give one a practical lesson in the meaning of “separation.”  The others are Nu Draconis, Gamma Arietis, and Porrima. Along with Zeta Aquarii these four are each made of a pair of stars that are nearly equal in brightness and the pairs each orient in a roughly north/south direction. But they differ signifcantly in separation.

At 63.4 seconds, the 5th magnitude pair in the dragon’s head can be split with binoculars if you can hold them steady enough.  The “Ram’s Eyes,” Gamma Arietis, are a beautiful sight in just about any small telescope being at the breaking point between 4th and 5th magnitude and separated by 7.5 seconds. The Zeta Aquarii pair is just a bit brighter, but more of a challenge. Haas list the spearation as 2.0 seconds. To me they seemed a bit wider than that because I found them so much easier to split than Porrima. Porrima, in the spring of 2011, has given us more of a challenge with a separation of  1.7 seconds and a brightness that puts them right on the borderline between third and fourth magnitude.

Of course, all of these aren’t well placed for observing at the same time, but all could fit into the same July night.  Porrima would be first on the agenda, low in the southwest after sunset and still a challenge object.

Porrima  (Gamma {γ} Virginis), also designated as Σ1670 (STF 1670)
RA: 12h 42m    Dec: -01° 27′
Magnitudes:  3.48, 3.53  (WDS 2009)
Separation:   1.7″  (Spring 2011)
Position Angle:    44° (2010)
Distance:   38 Light Years
Spectral Type: F0, F0

Go here for details.

Sometime after midnight you should get a good shot at the Dragon’s Head and Nu Draconis.

Nu (ν) Draconis

RA: 17h 32m Dec: +55°11′
Mag: 4.88, 4.86 Sep: 63.4″ PA: 311°
Distance: 99 ly
Spectral type: A6, A4

Go here for details.

In the early morning hours Zeta Aquarii is best places. And the for the Ram’s eyes  (Gamma Arietis) ot’s best to wait until just before astronomical twilight begins a couple hours before sunrise. Then it should be well placed in the eastern sky.

Ram’s Eyes  – Mesarthim – (Gamma [γ] Arietis)
RA: 01h 53.5m   Dec: +19° 18′
Mag: 4.5, 4.6   Separation: 7.5″  PA: 0°
Distance: 204 LY
Spectral Classification: B9, Ap

Go here for details. 


3 Responses

  1. Thanks to Greg’s tip a few days ago, I took a look at Zeta ζ) Aquarii this morning at about 2AM. It was still in a somewhat murky section of the sky, but the seeing was better than average — I’ll call it a IV, with V being perfect — so that gave me an advantage that it turned out I needed. I remember trying to split this one last year and being completely defeated by the atrocious seeing.

    I have darker skies than Greg, so I had no problem seeing the Water Jar asterism, and Zeta (ζ) was conspicuous at the center of it. At a separation of two arcseconds, it’s tight, but the equal magnitudes give you an edge in the battle. Thinking of Greg’s description of it, I was using a TV85 also.

    My first look at it this time was in a 20mm TV Plössl (30x), which was quickly replaced with a 12.5mm UO Ortho (48x). Haas describes the color as “citrus,” which strikes me as a good description. At least it matched what I was looking at this morning — kind of a slight orange with enough white mixed in to make it a bit pale.

    I could see that 48x wasn’t going to split it, although it did contribute a hint of elongation. So the next move was to a 9mm UO Ortho (67x). That didn’t do it either, but the elongation was more distinct.

    I had declared this as “small eyepiece night,” which means anything larger than a TV Plössl was banned from the box of eyepieces, so next I reached for an old 7mm Celestron Ortho (86x), and the view in it almost looked like a split. But the best part was it was steady — I didn’t see the usual unpredictable out of control jumping and hopping I normally would expect to see in my skies, especially low in the southeast.

    I smelled victory close at hand, so I grabbed the 7mm’s sibling, a 6mm Celestron Ortho, and the 100x it gave me was the magic number. Zeta (ζ) surrendered a hair split that was absolutely delightful — two round, orangish globes with a delectable bit of black sky streaking between them.

    Now I still had two more “small” eyepieces up my sleeve of optical delights, so I continued the downward mathematical progression and grabbed a 5mm UO Ortho (120x). And it was as if someone had pried those two stars apart with a small lever — this time, not a hair split, but a SOLID split. But the jumping and hopping nemesis was back.

    However — I didn’t come this far to stop. There was still a 4mm Celestron Ortho crying out for a turn, and I couldn’t in good conscience say NO to 150x — and I didn’t.

    If you want to experience the full glory of Zeta (ζ) Aquarii, this is the way to do it. At 150x I was looking at two distinct quivering orange globes of light with almost enough room to pour a thin stream of water between them from out of the Aquarian water jar and barely get the diffraction rings wet. There was some seeing related vibration, but it really wasn’t bad at all.

    There certainly is a resemblance here to Porrima. As I looked at these two glowing orange globes with their faint diffraction rings shimmering in silhouette against the black sky, I thought back to the first time I split Porrima. The similarity is uncanny — apart from the difference in color, you would never be able to tell these stars apart if you were playing a celestial game of “Guess the Double in the Eyepiece.” (Don’t look for that one — the pilot episode was canceled because of poor seeing).

    This one is highly recommended, especially to thirsty, parched-throated Star Splitters with visions of pungent slices of orange dancing in their heads.

  2. Pungent slices of orange – OK, that adds flavor to Hass’ rather dry description 😉 I did not see that much color, however, even with the 6-inch scope.

    That’s what I was using this morning when I got a glance – but only a glance – with the Celestron 6″ F8 refractor. Very nice. This is a great warm-up star for tackling Porrima, actually, but by next year I suspect they’ll be the same or Porrima will actually prove easier – won’t that be fun!

    I had a star-hopper student out last night, so my observing was mostly instructional. Got to bed at midnight and was up at 3:30, but by the time I got to the observing deck with tea in hand I was pushing my luck. Boy does astronomical twilight start early! I still could pick up the Water Jar – fits nicely inthe finder as I swung the 6-inch to it, and easily split the pair with a 7mm Nagler I believe – but I was getting nervous and not paying close attention because my goal was to try to see the disc of nearby Neptune.

    As I looked with binoculars panning to the southwest of the water jar I picked up the now familiar pattern of the current Neptune field, but the leaves of a huge hickory tree were about to eat it. Darn. Just as I got the scope on it, that’s what happened. i could see the fifth magnitude star just north of Neptune, but not Neptune – we’re talking about a miss by less than 15 minutes of arc! And that hungry tree moved inexorably eastward and ate it right up. Neptune, I knew, would emerge on the other side of the tree in about half an hour, but by then the pre-dawn sky would be way to bright for me to find it, so I switched to the King and his court, now fairly high in the East.

    What a pleasure to see Jupiter with two distinct equatorial bands – and a huge change from last year at this time. Three moons were strung out to one side – I paused, got my tea and an 11mm eyepiece , and bingo – there were four! Had I just missed one emerge from an eclipse? Apparently not according to the Jupiter script at Sky and Telescope.

    Ah well – will be plenty more nights this summer to see Neptune and to experience another refreshing bite of that nearby orange.

  3. Well I gave it another try this morning, but the skies were afflicted with atrocious seeing. It was so hopeless it wasn’t even on the chart. I may have to add a negative side to it to accompany the numbers on the plus side. Even Polaris periodically swelled up to the size of Jupiter every few seconds, engulfing that poor diminutive dot of light next to it.

    That was at 11PM. At 2AM, it really hadn’t gotten any better. And by 2:30, the northeastern sky was starting to brighten up so much it looked like a light dome from a large city.

    But I gave Zeta (ζ) a try in the C102 since both it and the telescope were handy. No luck, though — it was bloated and hopping around even at 55x.

    Neptune was next since it was nearby, and other than a beautiful blue dot, there wasn’t much I could do with it. At times it swelled up to Jupiter’s size, too.

    And then I remembered. Neptune’s birthday!

    So, very quietly, I started humming “Happy Birthday dear Neptune!” to myself. Klaus was sitting on the deck near me, and he picked up the tune, and before long he was humming and I was singing — and in three part harmony, too. I stayed in the middle register and he alternated between the low notes and a few high-pitched yips for emphasis. OK, I admit it might have gotten a bit loud when he started to tap out a beat with his two front paws, but I really caught the spirit of the whole thing at that point.

    Now the neighbors thought otherwise. When I saw the light come on, I figured we better cease and desist. But I could hear the voices behind me and a few words like “weird” and “unbelievable” and “nuts” floated through the early dawn dusk to me.

    Heck — It was only two nights ago when they sat attentively and watched a huge fireworks display that shook the surrounding hills and rattled our houses — so I really wasn’t too concerned about a couple of forlorn voices in the dawn darkness singing to Neptune.

    I mean, geez, it won’t happen for another hundred and sixty-five years.

    Hope they’re asleep tonight when I light the candles — all 165 of them. 😎

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