As is well known, S.W. Burnham started his serious observing of double stars with a 6-inch refractor he purchased from Alvin Clark. A project I thought to pursue with my 6-inch f/15 refractor was to re-observe all of Burnham’s 6-inch discoveries. I was interested to see if I could replicate the observations, to see what he saw. Unfortunately, Stelle Doppie and other resources do not list discovery apertures, so I turned to an online copy of his A General catalogue of 1290 double stars discovered from 1871 to 1899, in which Burnham specifies the telescope he used for each pair. The introduction is a very good summary of Burnham’s career.
Since Burnham used progressively larger instruments, one would assume that, knowing the publication dates and the apertures he used with each set of stars discovered, one could deduce the aperture from the designation number, the earlier designations being with the 6-inch, the middle with the 18.5-inch, and the later with 36- and 40-inch telescopes. This generally works well but it is not always the case: for example some discoveries at Lick with 12-inch were published along with many discoveries made with the 36-inch, and a few are out of sequence because Burnham inadvertently left them out of prior publications. Besides, in the Catalog the pairs are ordered by right ascension, so they are all mixed up and can’t easily be sorted into groups by discovery aperture.
I had used Burnham’s Catalog as a reference many times, looking up individual stars I happened to observe. But now I wanted to read the whole work start to finish. With a spreadsheet of the WDS data, I read through the book and made a note of the discovery aperture, along with any interesting comment Burnham would make about the pair. I started to notice some interesting things about Burnham and his discoveries.
In the Catalog Burnham provides his and other observers’ measurement data, but he never describes a pair the way an amateur might today—it’s a scientific publication, after all. He doesn’t describe the degree of split or the delta mag, and only very rarely does he write in any kind of excited way about the act of observation. Whenever the data hints at it, he provides a prediction of whether a pair might be a physical binary. Not being strong in math myself, I was impressed at his ability to visualize the motion of stars while reading a table of measures & the stars’ proper motion, and determine whether they might be physical -- in his head -- so familiar he must have become with star motion.
There are only a few pairs which he knew to be binary with certainty. He needed more time to pass, with more data to be collected, to know for sure. Reading these notes, I often wished I could tell him “how things turned out.” I have the benefit of both 120 years of time and an electronic database at my fingertips to pull up the answer. Very often his predictions were correct. Not only this, but he also frequently correctly predicted whether the binary would have a short period, and even at which point it was in its orbit. When studying binaries, the passage of time becomes the theme. I realized while reading that Burnham was as far away in time from William Herschel’s most active period as I am to Burnham.
He did a good job following up on observations of suspected pairs, diligently following up even many years after the original observation. He was very attentive to what was in the field, discovering pairs while measuring already discovered pairs (those of others and even of his own), either part of the system or within the field of view. Burnham speaks with respect for Aitken, and likely saw him as a worthy successor and custodian of the Great Refractor. I imagine Aitken regarded Burnham as his master. It seems they routinely used 1000-2000x on the 36-inch.
It is commonly accepted that Burnham had an “eagle eye,” especially for closely separated pairs and those with a significant delta magnitude. To test this, I made note of pairs which have contemporary orbits calculated. Using SkyTools’ Interactive Atlas feature, I plotted the orbits for Burnham’s discovery date but also those of earlier observers to see whether or not they could have discovered it during their time—assuming they pointed their telescopes at the star—since the orbital position of the companion could have been different. I compared Burnham’s 6- & 9.4-inch discoveries with the orbit as of 1826, when Friedrich Georg Wilhelm von Struve (STF) had the famous 9-inch refractor in operation. I compared Burnham’s 12-, 15.5-, and 18.5-inch discoveries with the orbit as of 1845, when Otto Wilhelm von Struve (STT) was active with the 15-inch Pulkoko refractor. I could have used John Herschel’s 18-inch to compare, but it seems to me most of Herschel’s pairs are wider than Otto Struve’s. Burnham writes in the introduction of the Catalog of his particular interest in detecting binarity, and that close pairs were the most likely to be revealed as binary in his lifetime, so he spends most of his observing time on closely separated pairs. This is at least one reason Burnham has so many discoveries of close pairs—one finds what one seeks. When Burnham had the 36-inch Lick refractor, he was in a league of his own (even beyond much of the grasp of the UNSO’s 26-inch) – so I didn’t make a point to compare orbits with others. However, it would be an interesting project to review Aitkens’ and Hussey’s discoveries on the 36-inch during the early 1900s with the orbits during Burnham’s tenure from 1889-91.
These are generally short period pairs since they are mostly the ones both confirmed to be physical and with an orbit I can compare. I have no way of knowing whether a prior observer made attempts at any of these stars, but for the sake of the comparison I assumed if they did, and thought of what could have prevented them from making the discovery. For the 6- and 9.4-inch discoveries, often the pair was out of STF’s reach because it was too close to periastron during his time, but Burnham was fortunate to observe it at apastron, the difference in separation over the intervening years overcoming STF’s advantage in aperture. For the 12-, 15.5- and 18.5-inch discoveries, I find STT mostly could have discovered the pair, as frequently they were close to the same separation as in Burnham’s time. I don’t know if Otto Struve did not have enough time to observe as broadly as Burnham, didn’t have the same interest to seek and discover new pairs, or simply was not as good an observer.
Burnham observed at a time when there was still a lot of unpicked fruit on the tree, as it were, and there was much to discover by looking diligently. Sadly, this is not the case for us today, where the edge of discovery requires satellites and interferometry. Besides his progressively dominant advantage in aperture, having a mountaintop site to observe from, and luck in the orbital position of his pairs, I think what set Burnham apart from other observers was his decided interest and love of close binary pairs. I call it “love,” though Burnham doesn’t bring himself to call it that in the introduction, only that “My attention for some reason or other, which I am unable to explain, had been almost exclusively directed to double stars previous to this [before receiving his 6-inch]…. This preference was not in any sense a matter of judgement as to the most desirable or profitable department of astronomical work, or the result of any special deliberation upon the subject. I came about naturally, without any effort or direction on my part.”
Following are my comparisons of pairs which were later confirmed physical and which have orbits calculated. The SkyTools graphics are a bit crude, and sometimes their data is out of date, in which case I used the orbital solution from Stelle Doppie and show roughly where the pair would have been in prior times. I have more comments to make about the Catalog, especially regarding some possibly undiscovered pairs, but it requires more time and research.
BU 80 AB: 1.0” at 1872 discovery with the 6-inch. "One of the most interesting binaries from the rapid relative motion, and the large movement of the system in space…. The distance is decreasing, with a corresponding increase in the angular motion. It will probably soon become a difficult object to measure."
Physical, 97-year period, 104.55 light years distant. Interestingly the companion is now in nearly
the same position now as it was in 1826, so it would make a good test for 8- or
9-inch aperture to simulate whether Struve could have caught it. Burnham was correct that the pair would
tighten “soon,” when he wrote his comment in 1899 the companion was rapidly
moving to periastron. It is now coming
off the rapid periastron and will gradually make a quarter turn and widen by
2040.
23H 18M 54.45S +05° 24' 19.8" P.A. 251.8 SEP 0.81 MAG 8.18,9.39 SP K0 DIST. 32.05 PC (104.55 L.Y.)
Figure 1a: BU 80 in 1826 (Struve)
 Figure 1b: BU 80 in 1872 (discovery)  Figure 1c : BU 80 in 2020  BU 101 AB: 9 Pup. 0.58" at discovery with the 6-inch. "One of the most interesting of the rapid binaries from its short period, and the proper motion of the system." WDS confirms physical with 23.33-year period. Burnham provides an orbital solution, and comments: "It was evident at the beginning, before it was measured at all, that this was a binary, as otherwise the proper motion of one star in two or three years would make it a very easy pair, and one which could not have been overlooked by prior observers." |
A challenge but certainly detectable by a 6-inch in 1873. Prior observers like Struve likely missed it since it was closer to periastron – during Struve’s active time ~1826 the star was ~0.25”, out of reach of his 9-inch. Currently it’s coming off apastron and will close rapidly over the next ten years, becoming unobservable to most. I observed this in February 2020, 20-inch, 1067x: “Elongated to notched, orientation correct, light orange. Very tough.”
07H 51M 46.31S -13° 53' 52.8" P.A. 303.7 SEP 0.44
MAG 5.61,6.49 SP G1V DIST. 16.5 PC (53.82 L.Y.)
Figure 3:
BU 101 in 1873 (discovery)
Figure 4:
BU 101 in 2020
BU 151 AB: Beta Del. With the 6-inch at 0.7” in
August 1873. "It was evident at
this time that it would prove to be a binary system, as otherwise it could not
have escaped detection by prior observers.
It has now (1899) completed substantially one revolution since it was
discovered."
Physical with a 26.68-year period. Struve didn’t stand a chance in 1826, the companion was at periastron. This is a very difficult object in 2020; I attempted it in September with my 20-inch at all powers up to 1067x, and the best resolution I could get was a “slight snowman.” By 2026 it should be more easily seen.
20H 37M 32.87S +14° 35' 42.7" P.A. 220 SEP 0.22 MAG
4.11,5.02 SP F5IV+F2V DIST. 30.93 PC (100.89 L.Y.)
BU 178 AB: 0.6” at discovery in 1873. "The change, if any, is slow, but it can hardly fail to prove a binary."
Physical, 106-year period. Burnham (very luckily) discovered it right at apastron; it would have been impossible for Struve and likely unobservable with the 36-inch when at periastron. It is now coming off apastron and closing rapidly, ~0.2" by 2040 -- catch it while you can!
22H 55M 10.96S -04° 59' 16.4" P.A. 323.6 SEP 0.57
MAG 6.03,7.75 SP G4:III DIST. 83.4 PC (272.05 L.Y.)
Figure 6: BU 178 in 1826 (Struve) / in 1873 (discovery / in 2020
BU 208 AB: 1.4” at discovery in 1874. "It appears to be a most interesting system from the rapid relative change and from the large proper motion…. Rapid motion in angle may be expected with the close approach of the two components." Appendix, with updated measures to 1899: "This binary appears to be rapidly closing." Discovered just at apastron, it certainly would rapidly close during the late 1890s.
WDS lists as physical with 123-year period. Amazingly in Struve’s time the companion was on the exact opposite side of the orbit, and on the wider side too—he would have a clear shot at it. Currently the companion is near the SE side of the orbit’s periastron, and a difficult object at 0.4”, though will widen after 2029.
08H 39M 07.90S -22° 39' 42.8" P.A. 62.6 SEP 0.45 MAG
5.37,6.81 SP G6IV DIST. 19.4 PC (63.28 L.Y.)
Figure 7: BU 208 in 1826 (Struve) / in 1874 (discovery)
Figure 8: BU 208 in 2020
BU 382 AB: 1.0” at discovery in 1874. "This is a binary in direct angular motion…The distant companion discovered by Herschel [H 1828] is evidently fixed. It is called blue by Dembowski."
WDS physical with a 104.85-year period. Burnham got lucky with this one to find at 1" at discovery, it was at periastron during Struve’s time. It is now closing fast and will make a quarter turn by 2040 at ~0.3".
22H 53M 40.16S +44° 44' 57.1" P.A. 247.3 SEP 0.64
MAG 5.97,7.79 SP A3M+F6V DIST. 56.92 PC (185.67 L.Y.)
Figure 9: BU 382 in 1826 (Struve) / in 1874 (discovery) / in 2020
BU 271 AB: Discovered at 1.8” with the 9.4-inch refractor at Dartmouth College in 1874. "It is a most interesting binary from the large common proper motion of the components…. The relative motion is slow, so that the period must be a long one."
WDS confirms physical with a 157.5-year period. Struve should have been able to get this one. Now it is a very difficult object, coming off a very close periastron at 0.162" (2021). It will widen very rapidly, reaching 1.667" by 2030. (The orbital solution in SkyTools is incorrect so I am mocking up a simulation from Stelle Doppie’s).
21H 19M 45.62S -26° 21' 10.3" P.A. 19.3 SEP 0.4 MAG
6.73,9.76 SP G5V DIST. 17.97 PC (58.62 L.Y.)
BU 1007 AB: 126 Tau. Burnham writes:
"Discovered with the 12-inch on Mt. Hamilton in 1881. It was single or too close for the 36-inch
1890-92. The measures since then show
but little change in the angle, but a while revolution may be covered by the
observations. The components are nearly
equal, and therefore some of the measures may require a correction 180
degrees. In my measure with the 40-inch
in 1897 it was noted: 'The distance is less than 0.3"; the smaller star is
p.' In the first set of measures
in 1881 with the 12-inch it was stated: 'The measured distances are decidedly
too large.' The distance is probably
always less than 0.25". There is
little double of its being a binary of short period."
In WDS it is confirmed binary with period of 111.02 years, with last apastron at ~0.281" in 2000. At discovery in 1881, it was coming off apastron and slightly wider (0.3”) than it is in 2020. STT should have had it with the 15-inch in 1845, as the companion was near apastron. I’m a little surprised Burnham said it was too close for the 36-inch in 1890-92, as it would be only slightly closer (~0.25”?) and should have been in range.
05H 41M 17.72S +16° 32' 03.1" P.A. 253.5 SEP 0.15
MAG 5.04,6.56 SP B8V+B7V DIST. 194.93 PC (635.86 L.Y.)
|
Figure 11:
BU 1007 in 1845 (STT) / in 1881 (discovery) |
Figure 13: BU 1007 in 2020
BU 1026 AB: Discovered with the 12-inch in 1888 at
0.5”. "There appears to be a very
decided change in the angle since my measures in 1888."
WDS confirms physical with a 66.84-year period. Fortunately, it’s at apastron now, otherwise by 2050 the separation is extremely close. For Struve the Father the companion was at apastron, but his 9-inch may not have been up to the task considering a 1.5 delta magnitude. For Struve the Younger, the separation was too close. Burnham and us today have B at apastron!
00H 12M 08.05S +53° 37' 26.1" P.A. 324 SEP 0.35 MAG 7.25,8.46 SP A7VN+F2V DIST. 119.9 PC (391.11 L.Y.)
Figure 14: BU 1026 in 1826 (STF) / 1845 (STT) / 1888 (discovery) / in 2020
BU 1147 AB: Discovered with the 12-inch in 1889 at
0.3”. "This star was suspected to
be a close pair with the 12-inch, and verified with the 36-inch. It is difficult with the large aperture…. [Proper
motion belongs to both stars]. It is a physical system, and should be in rapid
motion."
WDS confirms physical, 73.997-year period, currently at periastron of 0.071", widening quickly to 0.256" at 2030, apastron in ~2050. Skytools charts off so using Stelle Doppie here. Certainly difficult with a 12-inch, and STT would happen to need a superb night to have suspected it.
23H 02M 36.34S +42° 45' 28.1" P.A. 201.4 SEP 0.05
MAG 5.19,7.70 SP A3VN DIST. 129.2 PC (421.45 L.Y.)
11H 53M 43.07S +73° 45' 21.6" P.A. 69.8 SEP 0.52 MAG
7.23,8.32 SP F8V DIST. 58.17 PC (189.75 L.Y.)
Figure 15: BU 794 in 1845 (STT) / in 1881 (discovery) / in 2020
18.5-inch vs. 15-inch
BU 696 AB: Discovered in 1877 with the 18.5-inch at 0.5”. "Obviously the movement of both stars is the same."
WDS confirms physical with 160.3-year period. Burnham discovered it near apastron; STT didn’t stand a chance as it was near periastron. It is now just coming off periastron where it takes only 10 years of being <0.1" to whip around the primary star, then widen back to its discovery separation, which will be around 2030. Interesting orbit. Sky tools charts not working.
22H 04M 30.12S +15° 51' 28.6" P.A. 353.7 SEP 0.3 MAG
7.95,9.63 SP G0V DIST. 93.37 PC (304.57 L.Y.)
BU 513 AB: Discovered in 1878 with the 18.5-inch at a whopping 1.0”. "This most interesting binary was discovered with the 18.5-inch, but at that time it was easily seen with the 6-inch. It is now (1898) a very difficult object, and only measurable with a large aperture under the best conditions."
Physical with a 61.14-year period. Burnham discovered at apastron, while STT could not have seen it during his time. We are now unfortunately heading to the period when it will become a “very difficult object” again. I tried and failed to see it in my 12.5-inch in 2018.
02H 01M 57.55S +70° 54' 25.4" P.A. 355 SEP 0.48 MAG 4.65,6.74 SP A3V DIST. 35.26 PC (115.02 L.Y.)
Figure 17: BU 513 in 1845 (STT) / in 1878 (discovery) / in 2020
BU 603 AB: Discovered in 1878 with the 18.5-inch
at 1.5”. "Certainly binary in slow
retrograde motion. A more rapid change
in the angle may be expected."
WDS confirms physical with 129.74-year period. Indeed, Burnham was correct to predict the companion was heading into periastron. It’s rather a surprise that neither STF nor STT discovered it as it was growing toward apastron during their times. For us it will close a little in the next 20 years.
11H 48M 38.71S +14° 17' 03.2" P.A. 328.4 SEP 1.01 MAG
5.97,8.53 SP A8III DIST. 59.74 PC (194.87 L.Y.)
Figure 19:
BU 603 in 1826 (STF) / in 1845 (STT) / in 1878 (discovery) / in 2020
BU 612 AB: Discovered in 1878 with the 18.5-inch
at 0.3”. "It was very soon apparent
from the measures that this was a binary system in rapid motion. In the twenty years covered by the measures,
the companion has passed over an arc of 175-degrees. Glasenapp…has computed an orbit from which he
finds a period of 30.00 years....This represents the observations as well as
could be desired, but evidently the arc was too short for any very accurate
determination, and even now widely differing apparent orbits will satisfy the
observed positions equally. It is
probably that the measures of the next ten years will furnish sufficient data
for an orbit which shall substantially correct."
WDS provides an orbit of 22.46-years, currently (2020) 0.09" periastron, it will be at apastron in 2030. It was a bit wider in STT’s time, and even reached apastron in 1851, but perhaps not observed.
13H 39M 34.68S +10° 44' 46.7" P.A. 1.4 SEP 0.09 MAG
6.35,6.47 SP F1V DIST. 59.99 PC (195.69 L.Y.)
Figure 21: BU 612 in 1845 (STT) / in 1878 (discovery) / in 2020
BU 614 AB: Discovered in 1878 with the 18.5-inch at 0.6”. "This very difficult pair was discovered with the 18.5-inch. The principal star [A] is identical with that of STT 271, which was marked 'oblonga?' in the Poulkowa Catalogue of 1843, but rejected as single in the revised edition of 1850. It is not certain that the very minute star now measured [11.7m] has any connection with the suspected elongation previously noticed. At the time of making the measures given [here], the principal star was perfectly round, with the 18.5-inch and 36-inch refractors. It is the southern star of three in the field."
AB is physical with an 830.72-year period, but B’s magnitude is 9.95 in WDS. I wonder at the large magnitude discrepancy – 2 delta magnitudes is tough but not “very difficult” at 0.6” for an 18.5-inch, or even STT’s 15-inch. Perhaps Burnham misjudged it because delta magnitudes often appear to be larger for very close pairs than they actually are, when measured by photometry? As for the suspected elongation of STT 271, neither the Simbad nor Gaia DR2 layers in Aladin give a second star next to A which would elongate it. Skytools charts are incorrect for this pair; likely the elongation was due to conditions or an astigmatism in the telescope.
13H 53M 56.79S +10° 08' 19.9" P.A. 98.3 SEP 0.45 MAG
8.02,9.95 SP F0 DIST. 141.84 PC (462.68 L.Y.)
BU 631 AB: Discovered 1878 with the 18.5-inch at 0.4”. "A binary in slow retrograde motion."
WDS gives a 147.5-year period, now 0.4" as at discovery and heading out to apastron -- periastron is ~0.04"! Burnham would have missed this one if observed 20 years earlier.
17H 39M 57.70S -00° 38' 21.2" P.A. 77.1 SEP 0.32 MAG
7.23,7.40 SP B9IV DIST. 245.7 PC (801.47 L.Y.)
Figure 23: BU 631 in 1845 (STT) / in 1878 (discovery) / in 2020
BU 648 AB: Discovered in 1878 with the 18.5-inch at 0.6”. "At [the time of discovery] it was a very difficult object, but in recent years the distance is considerably increased, and it has been measurable with moderate apertures. It was certain at the beginning that this was a binary system…The maximum distance of the companion appears to have been reached, and the change in angle is now slow. It will be impossible to form any idea of the apparent orbit for some time to come, but there can be no doubt that this will be a most interesting physical system for investigation in the future."
Physical with 61.41-year period. By 2033 it will be at periastron ~0.35". Seems to be too close for STT to find it. Burnham was correct about the timing of periastron being ~1899. I observed this in in September 2017 with my 12.5-inch in poor transparency: “at 277x an orange not quite round disk, suspected a close pair. At 553x it splits with seeing, 0.8", 3 delta mag, in diffraction.” Also in September 2019 with my 8-inch at 333x, “3 delta mag, at first diffraction, needed critical focus and seeing.” Finally July 2020 with my 6-inch f/15 refractor: “Orange A and a just split, very small, very faint B, seen only with 285x --175x suspected, 456x image quality not good.”
18H 57M 01.61S +32° 54' 04.6" P.A. 234.5 SEP 1.31 MAG 5.34,7.96 SP G0V DIST. 14.87 PC (48.51 L.Y.)
Figure 25: BU 648 in 1845 (STT) / in 1878 (discovery) / in 2020
BU 696 AB: Discovered in 1877 with the 18.5-inch at 0.5”. "Obviously the movement of both stars is the same."
WDS shows physical with 160.3-year period. Just coming off periastron – which is where it was during STT’s time – where it takes only 10 years at <0.1" to swing from behind the primary star. It widens back to its discovery separation by 2030. Interesting orbit. SkyTools charts incorrect.
22H 04M 30.12S +15° 51' 28.6" P.A. 353.7 SEP 0.3 MAG
7.95,9.63 SP G0V DIST. 93.37 PC (304.57 L.Y.)
BU 883 AB: Discovered in 1879 with the 18.5-inch at 0.4”. Burnham describes is as a "very remarkable and interesting binary system." Appendix 1899: "A recent examination of all the measures of this star leads to the conclusion that the most probable period is about seventeen years."
WDS confirms it as physical, and recent orbital solutions puts the period at 16.28-years, now at periastron. The motion is so rapid that in the 34 years elapsed between 1845 (Otto Struve) to 1879 (Burnham’s discovery) the companion had made two full revolutions, and was in virtually the same position in its orbit. STT should have seen it if he tried for it. Today it is very tough, but we only need wait 4-5 years until it is an easier target.
04H 51M 12.48S +11° 04' 05.0" P.A. 309.4 SEP 0.15
MAG 7.75,7.50 SP F7V+F7V DIST. 46.88 PC (152.92 L.Y.)
Figure 27: BU 883 in 1845 (STT) / in 1879 (discovery) / 2020
BU 895 AB: Suspected even with the 6-inch but
confirmed in 1879 at 0.3” with the 18.5-inch; it is a component of STF 888
AB-C. It has an interesting discovery
pattern: "1873.9: Elongation
suspected in 250-degrees with 6-inch; 1875.9: Appeared round with 18.5-inch;
1879.00: Elongated in 120-degrees 18.5-inch." "Rapid motion would be
expected in a pair of this class, and it may prove to be a binary of short
period. The measures since 1888 do not
show very rapid change in the angle, but the distance at this time is probably
about maximum, and one half or a whole revolution may have been described
between 1879 and 1887. only the largest
apertures will show any difference of magnitude in the components. In 1828 Herschel noted, 'the large star
suspected to be a close double.' This
remark seems to have attracted no attention; at all events, the close pair was
missed by Struve and other observers who measured AC.”
WDS has it as physical with 103.69-year period. Approaching apastron in 1826, and coming off it in 1845, so the Struves should have seen it. Now at periastron, we need another decade or two to see it easily.
06H 19M 58.96S +28° 25' 36.6" P.A. 245.1 SEP 0.1 MAG
8.16,8.35 SP A6V DIST. 132.98 PC (433.78 L.Y.)
Figure 29: BU 895 in 1845 (STT) / in 1879 (discovery) / in 2020
BU 949 AB: Discovered in 1880 with the 18.5-inch at 0.6”. "Motion is probable" is all Burnham says.
WDS confirmed physical, 56.33-year period, Burnham happened to discover it at apastron. About two and a half revolutions have been made since discovery, it will widen appreciably by 2025.
16H 08M 27.25S -10° 06' 08.4" P.A. 21.7 SEP 0.07 MAG 7.08,8.19 SP F7V DIST. 64.68 PC (210.99 L.Y.)
Figure 31: BU 949 in 1845 (STT) / in 1880 (discovery) / in 2020
BU 953 AB: Discovered in 1879 with the 18.5-inch at 0.3”. "It was a very difficult pair with that aperture at the time of discovery, and is still more difficult since. It is a binary in rapid motion…This is the sp of two 8m stars." Appendix: "The rapid angular motion continues. It is probably a short-period binary."
WDS confirms physical with 220.78-year period. It was at periastron, 0.3", at discovery, 0.23" now. It was roughly the same separation in 1845 as 1879.
16H 36M 39.05S +69° 47' 34.7" P.A. 53.3 SEP 0.23 MAG 8.56,9.27 SP F2V DIST. 106.95 PC (348.87 L.Y.)
Figure 32: BU 953 in 1845 (STT) / in 1879 (discovery) / in 2020
BU 957 AB: Discovered in 1880 with the 18.5-inch
at 0.6”. "Apparently without
change"
WDS has this as physical with only a 90.33-year period. Burnham discovered as it approached apastron, at the slowest part of its orbit; he needed about 20 more years to see the data reveal a binary system. Unfortunately for us it is heading toward periastron and will be impossible to see visually until the 2040s.
17H 15M 34.66S -10° 17' 50.9" P.A. 54 SEP 0.07 MAG 7.51,9.69 SP F5V DIST. 108.11 PC (352.65 L.Y.)
BU 962 AB: Discovered in 1879 with the 18.5-inch at 1.4”. "…it was therefore certain at the time of my second set of measures in 1881, that this was a binary system from the common proper motion of the components. The distance has been steadily decreasing, and it is now (1898) an extremely difficult pair. This is principally due to the great difference in the magnitudes of the stars. It will probably be a very difficult pair to measure for some years.... Of course it is impossible at this time to say anything about the probable period." Appendix: "The angular motion is now rapid, and it has become a very difficult pair to measure."
WDS 76.1-year period. It is a wonder how STT or other observers from 1830-1860 could have missed it before Burnham – 3 delta magnitude, perhaps, making it too difficult? Burnham was correct it was a very difficult object in 1900, ~0.2”. It is now coming off periastron at 0.36” but will rapidly separate by 2024.
17H 34M 59.58S +61° 52' 28.4" P.A. 207.9 SEP 0.36 MAG 5.28,8.54 SP F9V+K3V DIST. 14.19 PC (46.29 L.Y.)
Figure 34: BU 962 in 1845 (STT) / in 1879 (discovery) / in 2020
BU 989 AB: Discovered in 1880 with the 18.5-inch at 0.3”. Component of STF 2824. “It is not only a most important physical system, but has a 'period' shorter than any other known binary in the heavens. It has been followed with the micrometer through more than one and a half revolutions. It is at all times a close pair, the maximum distance being but little more than 0.2"; but as the components are of nearly the same magnitude, the elongation can be seen with a moderate aperture....Future investigations probably will not materially change the period, but may improve some of the other elements of the orbit." The original pair was discovered by Herschel but not measured until Struve; cannot tell yet whether this pair is physical.
WDS physical with just an 11.57-year period, it is nearing apastron now (2020 0.21") periastron in 2023 0.237", then a rapid closure to 0.053" by 2025, 0.111" by 2030. I observed this on 27 November 2020 with my 20-inch, 1067x, and saw “Overlapping disks, moderately strong notch, near equal.” I look forward to seeing this close to single then wide up again over the years.
21H 44M 38.70S +25° 38' 42.0" P.A. 325.5 SEP 0.15 MAG 4.94,5.04 SP F5IV DIST. 34.22 PC (111.63 L.Y.)
Figure 35: BU 989 in 1845 (STT) / 1880 (discovery) / in 2020
Discoveries with the 36-inch
BU 1077 AB: Dubhe. Discovered in 1889 with the 36-inch at 0.9”. "The measures at Mt. Hamilton were sufficient to show that it was a binary…and it was evident at the time it was first seen double that the companion had the same movement in space, as otherwise it would have been recorded as a double star long before…. It is not improbable that this is about the maximum distance, and that it may prove to be a short period. With a much nearer approach it will be difficult, if not impossible, to measure with the largest instruments now in use."
WDS confirms physical with a 44.448-year period. Struve the father didn’t have much chance as the nearly 3 delta magnitude pair was ~0.35”, but Struve the Younger should have been able to see it, difficult as it is. It happens to be at nearly the same place in its orbit in 1845 as in Burnham’s 1889 discovery, and in fact pretty close to where it is today.
11H 03M 43.84S +61° 45' 04.0" P.A. 337.6 SEP 0.8 MAG 2.02,4.95 SP G9III DIST. 37.68 PC (122.91 L.Y.)
Figure 38 BU 1077 in 1826 (STF) / 1845 (STT) / 1889 (discovery) / in 2020
BU 1092 AB: Discovered in 1889 with the 36-inch at 0.3”. Component of HV94 (AB-D). "The very recent measures of AB by Aitken with the 36-inch (power 1900x) show decided change in angle and distance. It is probably in rapid motion."
WDS confirms physical with a 48.93-year period. At apastron now, will close rapidly and be 0.16" by 2037. Catch it while you can!
22H 36M 08.65S +72° 52' 51.1" P.A. 221.2 SEP 0.37 MAG 8.30,8.30 SP F5 DIST. 84.46 PC (275.51 L.Y.)
Figure 40: BU 1092 in 1889 (discovery) / in 2020
BU 1111 BC: Discovered in 1889 with the 36-inch at 0.2”. Component of STF 1835. "The measures of only nine years are sufficient to show that this is a binary in rapid motion. It will probably take a place with the short period systems….It is not improbable that the distance now is about maximum, and that the mean angular motion is much more rapid."
Indeed physical, 40-year period, near periastron in 2020 -- and it has made just about three revolutions since the General Catalog was published, so Burnham was essentially correct about the position of the star in its orbit. I observed it in April 2020, 20-inch, 1067x: “!! Short period pair, it is a component of STF 1835. I get a notched near equal elongation with a clear direction in relation to the A star. Very cool.”
14H 23M 22.59S +08° 26' 41.7" P.A. 19.9 SEP 0.28 MAG 7.40,7.70 SP F0V+F2V DIST. 65.92 PC (215.03 L.Y.)
BU 1118 AB: Discovered in 1889 with the 36-inch at 0.4”. "[based on Auwers' proper motion data] it was certain at the time of discovery that it was a binary system, since the components must be moving together, or it would have been discovered before… It is probably that the distance is very nearly maximum."
Physical with an 87.58-year period, the B star is nearly occulted by A at periastron. It is conceivable that STF could have discovered it (or at least have seen elongation) in 1826, and his son in 1845, as the companion was in the 0.4-0.5” range. Burnham had a moderate chance in his 18.5-inch in 1878 though it would be a difficult ~0.25”. Currently it is coming off apastron and by 2027 will have made one half orbit -- it requires urgent observation before it closes!
17H 10M 22.66S -15° 43' 30.5" P.A. 228.6 SEP 0.51 MAG 3.05,3.27 SP A1IV+A1IV DIST. 27.09 PC (88.37 L.Y.)
Figure 41: BU 1118 in 1826 (STF) / in 1846 (STT) / in 1878 (BU 18.5-inch) / in 1889 (discovery) / in 2020
BU 1129 AB:
Discovered in 1889 with the 36-inch at 0.3”. "If [the proper motion in Ast. Gess.
Catalogue]..is substantially correct, this is a physical system."
WDS confirms physical with a 121.7-year period; periastron puts it at ~0.02"! It is now 10 years past one full revolution since discovery.
19H 21M 36.09S +52° 22' 34.9" P.A. 339.8 SEP 0.32 MAG 7.69,7.84 SP A8III DIST. 205.34 PC (669.82 L.Y.)
Figure 43: BU 1129 in 1889 (discovery) / in 2020
BU 1163 AB: Discovered in 1890 with the 36-inch at 0.2”. [appendix, regarding 1899 measures]: "A very decided change since my measures in 1890. In nine years the angle has increased more than 20-degrees."
WDS shows physical with an astonishingly short 16.11-year period -- 2021 periastron is 0.01", and it will widen to apastron 0.376" by 2030.
01H 24M 20.48S -06° 54' 52.8" P.A. 206 SEP 0.23 MAG 6.59,6.98 SP F3V DIST. 46.64 PC (152.14 L.Y.)
Figure 44: BU 1163 in 1890 (discovery) / in 2020
BU 1173 AB: Discovered with the 36-inch in 1890 at 0.1”. With understatement, Burnham writes: "The close pair is very difficult." In the Appendix, regarding the 1899 measures: "some change in the close pair is probable"
WDS physical, 296.96-year period, coming off periastron in Burnham's time. It will make a quarter turn by 2040.
02H 58M 35.99S +24° 08' 01.7" P.A. 109.1 SEP 0.17 MAG 8.30,8.35 SP K0 DIST. 277.01 PC (903.61 L.Y.)
BU 1185 AB: Discovered in 1890 with the 36-inch at 0.2”. Appendix: "Very decided change in angle."
WDS physical, 27.4-year period, it is now at apastron, so a bit easier for us compared to Burnham’s discovery. It will make one half turn by 2033! One to watch.
04H 25M 51.66S +18° 51' 50.9" P.A. 203.8 SEP 0.25 MAG 8.09,8.89 SP G3V DIST. 44.29 PC (144.47 L.Y.)
Figure 45: BU 1185 in 1890 (discovery) / in 2020
BU 1212 AB:
Discovered with the 36-inch in 1890 at 0.5”. "It was evident at the time of discovery
that the close pair [AB] was a binary from the common proper motion of the
components, as otherwise the duplicity would been seen long ago… The motion of
AB is slow so far, but it is probable that the components have about the
maximum separation at this time [in 1899], and hereafter the angular motion
will be more rapid."
WDS physical with a 48.65-year period. Now coming off periastron of just 0.038", it will widen to 0.333" by 2030, and back to 0.5” in 2046. Burnham was correct about the timing of apastron in ~1899.
21H 39M 31.39S -00° 03' 04.1" P.A. 320.3 SEP 0.16 MAG 6.94,8.44 SP F6V DIST. 43.98 PC (143.46 L.Y.)
BU 1220 BC:
Discovered with the 36-inch in 1889 at 0.1”. Component of STFB 12. "It is a difficult pair and beyond the
reach of ordinary apertures. [Due to
proper motions] "…it is certain that ABC constitute a vast physical
system. The two small stars, D and E, on
the contrary, are strangers to the system, and are fixed in space, the change
shown by the measures being due to the proper motion of the other
stars."
WDS STFB 12 A-BC is physical. BC is physical with an 83.61-year period. It was exceptionally difficult in 1889, though near equal 10th magnitude stars would be in the “sweet spot” for a 36-inch, being not too bright to cause a lot of diffraction, and not too faint to clearly resolve. It is now at 0.403" and closing fast to 0.019" in 2030, not getting splitable again until 2060. Catch it while you can.
23H 15M 51.01S -09° 04' 42.8" P.A. 105.6 SEP 0.43 MAG 10.50,10.70 SP K3 DIST. 45.93 PC (149.82 L.Y.)
BU 1266 AB:
Discovered in 1891 with the 36-inch at 0.2”. Component of STF 3018. "It is a binary, and probably of short
period…. There is no change in C since the observations of Struve."
WDS physical with 48.4-year period. Burnham discovered at apastron. In 2020 at 0.19", will widen to 0.258" by 2030. I observed this in November 2020, 20-inch, 533x: “Very subtle elongation, seen as merely a bump on one side. Very tough. Light orange stars. My estimated PA is 90-degrees off.”
23H 30M 26.29S +30° 49' 54.6" P.A. 134.3 SEP 0.18 MAG 8.35,8.14 SP F7V DIST. 68.07 PC (222.04 L.Y.)
BU 1295 AB: 2 Cam. Discovered with the 40-inch in 1901 at 0.2”. Component of STF 1295. "The principal star of the Struve pair is a close and somewhat unequal double, and is certainly a binary system, and probably in rapid motion. The Struve companion was measured by me in 1888 with the 36-inch, and the close pair would have been detected with the present distance." Burnham says C does not belong to the system.
Physical with 26.65 period. Burnham discovered near apastron. 0.22" now and will widen slightly over the next few years.
04H 39M 58.03S +53° 28' 23.7" P.A. 182.1 SEP 0.18 MAG 7.35,5.86 SP A8V DIST. 44.46 PC (145.03 L.Y.)
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