When last we left the Great Bear, we were still stuck within the constraining angles of its Bear-muda Triangle. But it’s time now to wriggle free from the clutching corners of its three-sided grasp and sail into the open expanses of Ursa Majorian space in search of a four-starred rendezvous. Two of those four rendezvousing stars will genuinely put your star-hopping skills to the test, requiring some intense navigation through relatively dim and unpopulated regions of the sky. But never fear – with a little patience and a strong dose of – ahem — four-bear-ance, we’ll round ‘em up.
And just to add some allure to this journey, three of our targets happen to triple stars.
So turn off those GOTO controls, strap yourself in, and lean back – waaaaay back, in fact. This is the time of the year when the Great Bear plods slowly and deliberately across the very top of the celestial vault — make sure your neck and knees are limbered up and loose or they’ll be lotsa pain to pay later.
We’ll begin with 36 Ursae Majoris . . .36 Ursae Majoris (AB is LDS 2863, also HJL 127) (AC is ARN 4)
HIP:51459 SAO: 27670
RA: 10h 30.6m Dec: +55° 59’
Magnitudes AB: 4.88, 8.86 AC: 4.88, 11.62
Separation AB: 122.50” AC: 240.60”
Position Angles AB: 303° (WDS 2012) AC: 292° (WDS 2003)
Distance: 42 Light Years
Spectral Classification: “A” is F8, “B” is M0
NOTE: All three components share common proper motion and radial velocity per WDS Notes file.
I think we’ve been deja-vu’d again. The three members of 36 UMa look suspiciously like the three members of the last triple star in our previous adventure, 23 UMa, which looked suspiciously like another triple star in that adventure, H V 73, albeit with a ninety degree twist to the west — seems to be a whole lot of cloning going on up here. Whatever the case, real clones or random circumstances, I find myself rather fond of the gentle arcing curves of all three of these star arrangements.
Over at the north edge of the eyepiece you’ll see the eleventh magnitude flicker of HJ 1178, a dim double with magnitudes of 11.71 and 12.24 separated by 5.2″ at a position angle of 119 degrees (WDS 2004). There’s no spectral information at that link, but judging by the photograph, they both seem to have a weak orange tint.
36 UMa has more than a few three-letter abbreviations attached to it, which should indicate an interesting history, but much of it is tantalizingly vague. The first abbreviation, LDS, refers to the Luyten Proper Motion Catalog, named for Willem Jacob Luyten, a Dutch-American astronomer. The Washington Double Star Catalog (WDS) shows the first date of observation for the AB pair as 1905, but since Willem was born in 1899, unless he was an astronomical prodigy at the age of six, it was someone else who made the first observation. However, that observation was apparently recorded in a 1927 Catalog, The Munich Sternwarte. Although I tracked down the catalog, I couldn’t find anything that resembled a double star measurement.
The second set of initials, HJL, are no help either in unearthing that first observer, since they refer to J. L. Halbwachs, who published a proper motion study in 1986 which included the AB pair. And the last set of initials, ARN, refer to Dave Arnold, an active contributor to the Journal of Double Star Observers (JDSO) and are associated with the AC pair. His observations were first recorded in 1991 in The Double Star Observer (Vol 8, No. 5, 2002), a publication which I’ve had no luck in finding. If anyone can supply a link to that publication, I would be thrilled right to the tips of my focus fingers.
Meanwhile, let’s move on to star number two:
Σ 1495 (H V 111) HIP: 53750 SAO: 27861
RA: 10h 59.8m Dec: +58° 54’
Magnitudes: 7.25, 8.84
Position Angle: 36° (WDS 2009)
Distance: 626 Light Years
Spectral Classifications: K2, K0
Let’s go back to Merak (Beta UMa) again (here’s that chart) and extend a line north to Dubhe (Alpha UMa). These two stars are the pointers to Polaris, so this should be familiar territory. Stop halfway along that line and look into your finder, where you’ll find two faint stars pointing west to fifth magnitude 42 UMa. The closest to our line is 6.60 magnitude HIP 53951, a K2 class star (orange) — the one beyond it in the direction of 42 UMa is our target, 7.10 magnitude Σ 1495, both components of which are also class K stars. In fact, there are quite a few class K stars in the area we’re going to cover, so I’ll point them out as we bump into them.
And here’s what you’ll find in the eyepiece of a five inch refractor at 73x:
This is a comparatively dim pair of stars, but their colors help them stand out from the rest of the faint background. Adding more magnification will bring out the orange hue, but the color is subtle enough that you really need a dark night to see it well – too much moonlight or light pollution will overwhelm the orange tint.
Based on the information in Lewis’s compilation of Struve’s stars, this pair seem to be moving toward each other very slowly:
Sir William Herschel’s first observation of this pair of stars, which is shown below, includes a description of his target as being at the center of three stars forming an arch. . .
. . . and if you look at the chart again, you can clearly see what he was referring to — rather striking to think we’re actually looking at the same three star configuration Sir William was looking at 231 years ago.
On to star number three, now, and a chance to put your star hopping skills to the test!
Σ 1462 HIP: 52413 SAO: 27744
RA: 10h 42.9m Dec: +50° 48’
Magnitudes AB: 7.41, 10.10 AC: 7.41, 9.60
Separations AB: 8.00” AC: 193.30”
Position Angles AB: 175° (WDS 2002) AC: 59° (WDS 2002)
Distance: 344 Light Years
Spectral Classifications: “A” & “B” are A3
Here’s our chart again, and we’ll start by going to back to what should be a familiar place by now, Merak. Pay careful attention or you’ll find yourself looking for this star in all the wrong places.
From Merak, angle south and slightly west two degrees to 5.1 magnitude 44 Ursae Majoris, which is a class K3 star. Now make another two degree leap in the dark, this time due south, and you’ll spot a line of three faint stars – 6.75 magnitude HIP 53155 and 6.40 magnitude HIP 53157 (a class K2 star) form a tight pair in your finder, both of which point south to 7.0 magnitude HIP 53173. All three of those stars point south another two degrees to 6.60 magnitude HIP 53134 (another K2 star), which forms a faint triangle with 7.0 magnitude HIP 52495 (class K1) and – at last – our goal, Σ 1462. If you got this far, you’ve succeeded in negotiating through six degrees of sparsely populated interstellar space, which qualifies you for a position as a junior pilot on the Starship Enterprise. 😉
And here’s the 95x view in a five inch refractor:
We’ve lost the prevailing orange so common in this sector of the sky, and are now looking at a white primary shadowed closely by a mere puff of secondarial light, with a pale shimmer of grayish light just over three arc minutes to their southeast. And we’ve also lost the arcing triple curve that was a characteristic of 36 UMa and the other two stars mentioned earlier.
In looking at the data in Thomas Lewis’s book mentioned above, you can see quite clearly that the secondary was moving closer to the primary at least through the last observation shown in 1901:
Based on the 2002 WDS data, it appears the distance between the two stars is increasing once again, which would seem to indicate an orbital situation, but the WDS Sixth Orbital Catalog doesn’t include a listing for Σ 1462.
And as for that distant “C” companion, the first observation of it was made in 1880 by R.S. Ball from the Dunsink Observatory in Dublin, Ireland.
Meanwhile, let’s make another long leap in the dark to our final star.
Σ 1402 (AC is GIR 2) HIP: 49382 SAO: 27506
RA: 10h 04.9m Dec: +55° 29’
Magnitudes AB: 7.91, 8.92 AC: 7.91, 9.60
Separations AB: 32.70” AC: 132.30”
Position Angles AB: 106° (WDS 2010) AC: 175° (WDS 2007)
Distance: 6523 Light Years
Spectral Classifications: “A” & “B” are K5; “C” is G0
Since we’ve been using it as a launching point for this tour, let’s go back to Merak and that line we extended earlier to Upsilon (υ) Ursae Majoris, and this time we’ll go all the way to Upsilon (υ) and stop for a look around. Here’s that chart once more to keep you on track – pay close attention to it or you’ll end up lost in Lynx.
Extending a line four degrees to the southwest of Upsilon (υ) will take you to 5.25 magnitude Phi (φ) UMa, but we’re not going that far. Instead, look just a bit shy of two degrees along that line and you’ll see a distinctive triangle of stars formed by 5.05 magnitude HIP 47965 (class M3, and west of the line), 5.95 magnitude HIP 48802, and 5.50 magnitude HIP 49005 (class K5), both of which are on the east side of the line. That last star forms a triangle with two fainter stars, 7.20 magnitude HIP 48981 (class K1) and 7.65 magnitude HIP 49262. A one degree leap further south through a barren void will bring you to another faint triangle of stars, with its apex on the opposite side. 7.90 magnitude HIP 49130 anchors the west side of the triangle, 7.20 magnitude HIP 49506 (class K1) occupies the east corner, and sitting innocently in the south corner is our goal, 7.80 magnitude Σ 1402, which just happens to contain two more class K stars!
Even though both the primary and secondary are classed as K5, the only color I could detect in the secondary was yellow. But considering the orange I saw in the primary was rather weak, that really isn’t too surprising.
The AB pair is gradually widening since its discovery in 1830 by Sir John Herschel, and a gradual change in PA is also obvious in the data below from Lewis’s book:
The AC pair was added in 1991 by P.M. Girard – his observation is shown below, taken from the Webb Society’s Double Star Circular of 1996:
And one thing stands out immediately if you take a comparative look at the data for AC — Girard shows a separation of 80.89”, which clashes with the 132.30” separation measured in 2007 in the WDS. Brian Mason of the U.S. Naval Observatory (home for the WDS) was kind enough to supply me with the observational data for Σ 1402, which shows a Hipparcos-Tycho measurement taken at about the same time as Girard’s – it shows a separation of 132.345” with a PA of 174.5 degrees. That PA matches Girard’s and the separation matches the 2007 WDS observation (which by the way was made by Dave Arnold, who we came across in 36 UMa). At any rate, it would appear the 80.89” separation credited to Girard in 1991 is in error.
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So much for stellar sleuthing through this bear-en interstellar sector south of the Dipper’s bowl.
Special thanks to Brian Mason for supplying me with observational and historical references to 36 UMa, Σ 1462, and Σ 1402, all of which are greatly appreciated.
Next stop? Who knows – I’ve got my eyes on Phi (φ) UMa, just a few degrees south of where we ended this tour. It sports a separation of 0.41”, well below my resolving radar no doubt, but there’s promise in the fact that its two stars are virtually the same magnitude – 5.3 and 5.4. If I can detect an elongation in my six inch f/10, you’ll hear the rousing rattle of my Plössls all over the world!
Clear Skies! 😎