• Choose a post by category or constellation

  • Learn the Night Sky

  • Search strategies

    Use the Search box below to find doubles by popular name, RA, or telescope size. For example, a search on "15h" will find all doubles we've reported on that have an RA of 15 hours. A search for "60mm" will find all doubles where we used that size telescope.
  • Advertisements

Of Donkeys and Hyenas: Kappa (κ) and Iota (ι) Boötis

Click on the image for a larger view, and a second time to enlarge it again. A map of Boötes can be found below. (Stellarium screen image with labels added)

Located at the very northern tip of the constellation of Boötes is a small triangle of stars which represents the shepherd’s club.  It’s up so high and so close to the end of the Big Dipper’s handle that it almost seems as if Boötes is about to give Alkaid, the star at the tip of that handle, a good whack (take a look at the map of Boötes at the bottom of this post to see what I’m referring to). These three stars (Lambda (λ), Theta (θ), and Kappa (κ)), along with Iota (ι), form an asterism which the ancient Arabs designated as Al Aulad al Dhibah, the “Young of the Hyena.”  Which is appropriate, because during my efforts to pry the 12.6 magnitude companion out of the glare of Iota “A,” I thought I heard laughter coming from up there.

But I’m getting ahead of myself.  Let’s tackle Kappa (κ) first.

Kappa (κ) Bootis (Asellus Tertius)  (Σ 1821)  (H III 11)    HIP: 69481    SAO: 29046
RA: 14h 13.5m  Dec: +51° 47′
Magnitudes: 4.5, 6.6
Separation:  13.6″
Position Angle: 236° (WDS 2011)
Distance: 196 Light Years
Spectral Types: A7, F1

West and east are reversed in this sketch to match the refractor view. Click for a larger image.

At low magnification you’ll find that Kappa (κ) shares the field with Iota (ι).  This pair of stars is an arresting sight in the eyepiece because they’re almost a mirror image of each other, as the dimmer companions are located on roughly the opposite sides of the primary.  In a 60mm scope they’re a pleasant sight at 40x.

The primary, frequently referred to on star maps as Kappa-1, is a bright blue, and the secondary, Kappa-2, is white, and based on spectroscopic analysis, also seems to have a companion.  Admiral William Smyth’s nineteenth century observation matches mine, but Haas describes them as white and silver.  At any rate, we agree on the rest of her description of them as a “showcase pair.”

The Arabic name, Asellus Tertius, translates as the “third donkey.”  Iota (ι) is the second donkey, and since I know you’re dying for the rest of this, Theta (Θ) is the first donkey.

At 13.3″ apart, this is a relatively wide pair, so I found it to be easy enough split in a 152mm scope, and it wasn’t much of a challenge in a 63mm refractor, although the view was more pleasing because the stars were closer together.

And on to Iota (ι), donkey number two ………

Iota (ι) Bootis  (Asellus Secundus)   (Σ I 26)   (H V 9)      HIP: 69713     SAO: 29071
RA: 14h 16.2m  Dec: +51° 22′
Magnitudes             A: 4.8    B: 7.4    C:12.6
Separation            AB: 38.8″    AC:   92.8″
Position angle      AB: 33°  (WDS 2011)     AC: 187°  (WDS 2000)
Distance:   97 Light Years
Spectral Types:  A: A7  B: K0V

First the colors.  I saw the “A” and “B” components as yellow and blue-white, Haas describes them as “gloss white and a nebulous star,” and once again, Smyth and I are close: “pale yellow, creamy white.”

But count yourself fortunate to see the very faint third component, let alone figure out what color it is.   I did my best to coax it into view with a 63mm refractor, but with no success.  I gave it another try with a 152mm refractor, and with averted vision at 76x, I was just able to detect it at times – higher magnification did nothing to improve it – so it’s hardly any wonder that I had no luck with the 63mm.  The glare of the other two stars is just enough to make detection of the 12.6 magnitude companion a real challenge, and as the inset in the sketch above shows, it’s hardly more than a faint point of light.  More aperture and less moisture in the air would help, no doubt, but the extra aperture was in the house and the moisture was a bit beyond my realm of influence.  Although the echo off the surrounding hills of that young laughing hyena made me wonder how much influence it might have.

But I also found that detection of 7.4 magnitude “B” was a bit tricky in the 63mm refractor.  And again, it was because of the glare from the 4.8 magnitude primary.  At times, it was easy to see, at others, it could only be detected with averted vision.

At any rate, this pair of doubles – or one double and an elusive triple – is really an attractive sight.  And with three donkeys and a young hyena close by to provide a good laugh or two, you won’t feel like you’re out there in the dark all by yourself.

Credit goes to Jim Kaler’s web site for information on the names of these two stars.  My observations were made on June 5th, 2010, and the sketch was done just over a year later, on June  25, 2011.

Stellarium screen image with labels added.


2 Responses

  1. I got another look at this pair of doubles this morning at about 6AM after spending some time on Algieba and Saturn. I had revised this post the day before, so these two stars were fresh in my mind – and I hadn’t looked at them since April.

    I pointed a 60mm refractor equipped with a Carton 800mm focal length lens up in the direction of Bootes’ club, got down on my knees in the cold gravel of my driveway to peer through the finder, found them, got lined up, and took a look in the 20mm TV Plossl (40x).

    Fantastic! Both pairs of doubles were in the field and easy to identify. As I mentioned in the above post, they’re almost mirror images of each other, so it’s easy to be able to tell you’ve got them. I especially liked the view of Kappa, which is the closer spaced of the two – the pair that Haas describes as “hair-split.”

    I switched to a 15mm TV Plossl (53x) and decided to see if I could find that faint third companion that had given me so much trouble in April, but I wasn’t sure which one of the two stars it belonged to. It seemed to me it was Kappa, so I looked and looked, but no luck.

    By now my fingers were about the temperature of solid icicles, and I still wanted to get a look at Izar, so I gave up and moved over to it. Later, when I went back in the house to check my notes, I found that the 12.6 magnitude companion I was looking for belonged to Iota instead. Which gives me a good reason to go back and try again!

    But on to Izar for a quick view, and then over in the southeast, where an amazingly bright Venus just about twenty degrees from the crescent moon was whispering to me.

    And what a view that was! Because the image in a diagonal equipped refractor flips east and west, the crescent of Venus was almost an exact mirror image of the lunar crescent.

    Now THAT was a view that I will not forget for quite some time! A telescopic crescent echoed twenty degrees away by a much larger naked eye version!


  2. 1AM, June 26th, 2011

    If someone had told me in December of last year, when I added the comment prior to this one, that the temperature six months later would be a cool forty-seven degrees, I never would have believed them — but here I am, wearing the same winter coat I had on that night.

    I made the sketch shown in the post above last night, using my six inch Celestron f8 refractor under rather murky conditions — too murky at least to ferret the elusive 12.6 magnitude “C” component of Iota out of the darkness. You might say there wasn’t an iota of a chance.

    So twenty-four hours later I’m back again, and this time I have the beast, my six inch f10 refractor equipped with a Jaeger’s lens, pointed at Iota. The transparency tonight is noticeably improved, so I have my focus fingers crossed for this attempt.

    Even though I just looked at them last night, when I see Kappa and Iota sitting in the eyepiece again tonight, I’m still stunned by their beauty. You just don’t see two double stars of similar magnitudes in the same field of view all that often — it’s a sight that can’t fail to force a few involuntary Star Splitter sighs even when you know what to expect.

    But when I cast a focused eye over at Iota, I see that 12.6 magnitude “C” is missing again. So I remove what I half-seriously describe as my low power wide field eyepiece, an 18mm Radian (84x), and replace it with a 14mm Radian. After about a minute of intense staring through its magnified 109x view, I catch a glimpse of what looks to be “C” with some careful averted vision.

    Now that I think I may have it, I don’t want to overdo the magnification because I’ve seen too many faint points of light get magnified out of existence in the glare. So it seems that a newly re-acquired 12mm Radian and its 127x should be about right. In it goes, followed by some more careful scrutiny, and after about thirty seconds, I see it pop into view right where its position angle and separation say it should be.

    And then it pops out of view.

    A few seconds later it’s back — and a few seconds later its gone.

    Here again and gone again ….. more times than I can count.

    I think this must be what a virtual particle looks like.

    Pop in to view and poof out of sight.

    But you know, you just can’t be that picky when you’re trying to dig a 12.6 magnitude dot of light out of the glare of two stars, one of which is right at 100 times brighter, and the other a mere 1575 times brighter.

    In other words, call it a success and know when to stop.

    So I did both, added it to the sketch, put the 18mm Radian back in the diagonal, and grinned as I soaked up more than my quota of Kappa and Iota photons. 😉

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: