Tuesday, 10 April 2012

Johann Bode's three lost objects

The German astronomer Johann Elert Bode (1747 - 1826) published a list of 75 deep sky objects in 1777 in the "Astronomisches Jahrbuch" for 1779. Five years later, Bode published an updated (but sadly not corrected) list of 110 objects. Simply too many errors remained to make Bode's catalogs a hit like that of Charles Messier's. Luckily, even today some objects, namely M81 & M82 and M92, are still marked as being discovered by Bode. [4]

As with nearly all the deep sky catalogs, certain entries in Bode's catalog are shrouded in mystery, deception and romance. Well, maybe not romance but at least some good old fashioned mystery. Some objects are simply considered lost. The two asterisms in Bode's list are no longer even associated with Bode himself, even though he was the probably the first person to note these at least a hundred years prior to others.

To simplify things, the three objects presented here are marked as Bode 1 – 3.

Bode 1 (published in 1777) = IC 1434?

Original coordinates: 03 23 +57 30 (Ecliptic B1780.0)
Precessed coordinates: 22 09 08 +52 54 40 (Equatorial J2000.0)

Bode's first object is most commonly associated with the faint open cluster IC 1434 found at least by reverend Thomas Espin (1858 – 1934) in 1893 and added to the first Index catalog (1895) by J.L.E. Dreyer [1]. According to SEDS.org internet site by Hartmut Frommert and Christine Kronberg the cluster was "independently found by Espin in 1793" [2]. This is obviously a typo as Espin lived in the 19th not the 18th century. Still, no matter how you put it, IC 1434 just does not fit the bill.

Bode's coordinates do match IC 1434 very well. The only problem is how can an observer look for something in this region of the sky, namely Lacerta, observe IC 1434 and completely miss two other brighter and more obvious clusters: NGC 7209 and NGC 7243. Without knowing the specifics of Bode's telescope, apart from the focal length of 7 feet, it is a big guessing game but the aperture might have been around 2.7 inches (7cm). Telescopes during that time commonly had magnifications of over 100 and very poor optics. With the high magnification in mind, one might understand why Bode might have not seen the two NGC clusters. Still, just to loose the few remaining hairs from my head, he rediscovered IC 4665 which basically is as sparse and big as a cluster can get. So anything more we know about his telescope? We can at least compare his notes to those of Messier's:

Charles Messier saw "A cluster of 7 or 8 very small stars"
Johann Bode saw "A nebulous star cluster"

Messier: "Cluster of small stars"
Bode: "A vivid nebulous patch, in which no stars were recognizable" but later on "Around the new nebula there appeared many small stars in the 7-foot telescope"

Messier: "Cluster of small stars in Auriga"
Bode: "A star cluster"

Bode, just like Charles Messier, failed to see individual stars from any of the globular clusters. At the same time, we can see from Bode's sketches he did manage resolved M67 (stars magnitude 9.6 and fainter) and M38 (stars magnitude 8.4 and fainter) [3]. This means his telescope much have reached at least 10th magnitude stars.

So how is it even possible he saw IC 1434? He mentions it as a "star cluster" so it seems he managed to resolve the object, whatever it was he was observing. With the statistics of IC 1434 being 9.0 magnitude and the brightest stars close to 12th magnitude it is fairly easy to say he did not observe IC 1434. Did Johann Bode use a different, larger aperture telescope in his discovery of the first object? Bode was appointed to the Berlin observatory in 1772 and became the director in 1786, so he must have had access to the observatory's telescope(s) if there every was a bigger one. Still, I think it is very, very far fetched to say Bode saw IC 1434 based simply on the fact that his coordinates are close to it. Even if he might have seen it, he probably would have described it as a "a nebula" or "a nebula without stars" rather than a cluster.

So what did Bode see? The only thing in the "tail of Cygnus" is of course M39 but this is already listed in Bode's catalog as number 75 and the location is correctly listed: "West near Pi at the tail of Cyg". With a bit of a reach, one could associate Bode's object as NGC 7243. This is east of Pi Cygni but no where near the tail or even in the constellation Cygnus. It would have probably been listed as "west of Alpha Lacertae" or something similar. Then again, Bode's original coordinates actually are in Lacerta, instead of Cygnus. Bode's own maps show the borders of both constellations nearly in modern form. Best bet in this puzzling case is that Bode independently found M39, poorly marked the position and then later added Messier's M39 in his list as well. Far fetched? Yes. Then it could be that he actually saw NGC 7243 but the coordinates are well off. So this issue will remain unresolved.

Bode 2 (published in 1777) = HD 1825 group

Original coordinates: 29 37 +45 55 (Ecliptic B1780.0)
Precessed coordinates: 00 22 51 +53 57 19 (Equatorial J2000.0)

In Johann Bode's description of Charles Messier's object number 29 on the night of December 5th 1774 he also mentions an object "in Cassiopeia a similar cluster with the stars Zeta and Lambda at the head west of it in an obtuse-angled triangle."

Little north of Bode's coordinates is a bright asterism of 7 stars brighter than magnitude 11. The brightest star is 8th magnitude HD 1825. This is obviously the grouping Bode was talking about and observed. The very same group is currently logged as Alessi J0022.7+5417 in the Deep Sky Hunters database for asterisms.

Draco 102 = Bode 3 (published in 1782), Bode's cluster, Kemble 2

Original coordinates: 279 30 +72 10 (Ecliptic B1780.0 and Equatorial J2000.0 for Dec)
Precessed coordinates: 18 19 26 +72 16 47 (Equatorial J2000.0)

Directly east of Bode's coordinates is an asterism some might know as "Mini Cassiopeia" or "Kemble 2". The nickname "Kemble 2" comes from Canadian Lucian J. Kemble (1922–1999) and he is well known by some from Kemble 1 / Kemble's Cascade in Camelopardalis. It is not known to me how this little group got the nickname "Kemble 2" but to be precise, there is no reason to do so. This is an original discovery of Johann Bode circa 1782, two centuries prior to Lucian Kemble. Of course asterisms don't have official names so anyone can call it whatever they want.


[1] NGC/IC observers. Dr. Wolfgang Steinicke. 2010.
[2] http://seds.org/messier/xtra/ngc/i1434.html
[3] http://www.lsw.uni-heidelberg.de/foerderkreis/bode/images/atlas/tab30.jpg
[4] http://seds.org/messier/xtra/similar/bode1782.html