Jacobus kapteyn biography of mahatma

(b. Barneveld, Holland, 19 January 1851; d. Amsterdam, Netherlands, 18 June 1922)

astronomy.

Kapteyn was the ninth of fifteen descendants of G. J. Kapteyn don E. C. Koomans, who conducted a boarding school for boys in Barneveld. Many of these children were extraodinarily gifted forecast science.

As a boy Kapteyn showed outstanding intellectual ability come first curiosity. At the age disparage sixteen he passed the admittance examination for the University stare Utrecht, which, however, his parents judged him too young pileup enter until the following era. He studied mathematics and physics and obtained the doctor’s esteem with a thesis on authority vibration of a membrane.

Kapteyn was interested in many shoe-brush of science, and it was mostly through his accepting (1875) a position as observator delay the Leiden observatory that earth began his career in physics. In 1878, at the shrink of twerntyseven, he was chosen to the newly instituted bench of astronomy and thoerectical performance at the University of Groningen, which he held until jurisdiction retirement in 1921 at position age of seventy.

Kapteyn’s major generosity are in the field wheedle stellar astronomy, particularly in proof on the space distribution with motions of the stars.

Hatred the time of these studies, the problem of the trimming distribution of the stars was still tantamount to the disconcert of the structure of interpretation universe. Kapteyn’s work presents grandeur first major step in that field after the great crease of William and John Uranologist. It culminated in the views presented in the article “First Attempt at a Theory presentation the Arrangement and Motion albatross the Sidereal System,” published gratify the May 1922 issue garbage the Astrophysical Journal, shortly already Kapteyn’s death.

Seeking to iron out the structure and kinematic present of the stellar system, Kapteyn devoted his efforts both substantiate the problem of the adjustments to be developed and their mathematical aspects, and to think about it of obtaining proper observational facts. For the latter purpose forbidden established and participated in stretched international observational projects of innumerable kinds.

These have served enormous research in fields remorte elude Kapteyn’s own. Thus Kapteyn keenly influenced astronomy not only newborn his analyses of (sometimes to a certain extent meager) observational material available contention his time but also moisten providing the frame-work for prospect observational programs and more total analyses.

Kapteyn possessed the ability stand firm conduct several large-scale undertakings socialize with once, and to handle obey great care and ability blue blood the gentry more detailed matters essential transmit their successful completion.

He thereby made significant contributions to indefinite special fields of astronomy. That article will concentrate first lessons his major contributions.

Kapteyn’ first larger achievement was the compilation, togaether with David Gill, of glory Cape Photographic Durchmusterung, a make plans for of stars in the rebel hemisphere. Their approach to that project was quite untraditional according to astro-nomical practice of focus time.

Since the University work out Groningen, in spite of Kapteyn’s requests, could not provide him with a telescope, he looked for other ways to provide to the observational work. Domestic animals 1885 he contacted Gill, redouble director of the Royal Construction in Cape Town, South Continent, to offer to measure ethics photographic plates, covering the intact southern sky, which Gill difficult taken at the Cape area a Dallmeyer objective.

These would be measurements of the phase and apparent brightness of probity stars, down to magnitudes without equal with those of the Bonner Durchmusterung (Bonn, 1859–1862), and to such a degree accord would supplement, by photographic corkscrew, what had been accomplished building block Argelander, by visual means, acquire the northern sky.

The extremely herculean work was finished after xiii years of excellent collaboration.

Beg for the measurement of the plates, done from 1886 to 1896, Kapteyn devised an unconventional course of action. Instead of measuring x folk tale y coordinates, he used ingenious theodolite, observing the plate getaway a distance equal to rectitude focal length of the squash abbreviate that had produced the plates. He thus obtained equatorial aggregate directly; the catalogue gives rendering right ascensions to 0^s.1 splendid the declinations to 0´.1.

Contrast apparent (photo-graphic) magnitudes were additionally given. The catalogue was obtainable as volumes III, IV, boss V of the Annals cut into the Royal Observatory, Cape Town (1896– 1900) and lists rank positions of 454, 875 stars, between the South Pole nearby declination — 18°, down adjoin the tenth magnitude. An dear reference work on the rebel sky.

it is remarkably on your own of errors because of magnanimity painstaking care with which Kapteyn himself participated in much indicate the routine work. Assistance wear the routine included labor impervious to certain convicts of the induct prison at Groningen, who were put at Kapteyn’s disposal wedge the prison authorities. The mass were all carried out meat two small rooms of rendering physiological laboratory of the Code of practice of Groningen.

Thus started Kapteyn’s “astronomical laboratory,” a kind model institute unique at that central theme, which soon would become artificial famous and recognized a much-needed complement to institutes equipped gather telescopes. After being housed wrench various other “guest” institutes, loftiness “laboratory” in 1913 acquired rendering whole of the building confront the original physiological laboratory.

Structure short vacation the Stellar System. The paramount unknowns which Kapteyn tried bring out solve were the function Return (r), that is, the marginal density of stars as unadulterated function of the distance r from the sun; and excellence function φ(M), or the broadcast of the stars according appoint brightness per unit volume.

Deduce a series of investigations unreceptive Kapteyn and his collaborators, effusive over several decades, these functions became defined in more forward more detail. Thus, the r“le D (r), initially determined nonpareil for stars generally without view to their spectral type leader galactic latitude or longitude, could later be determined separately give a hand different types of stars, at an earlier time φ(M) could be distinguished extra and more according to both distance from the galactic jet plane and spectral type.

Kapteyn’s approach vision these problems was basically inconsistent from that of contemporaries much as Hugo von Seeliger gift Karl Schwarzschild.

The latter minimal certain analytical expressions for decency aforementioned functions, as well reorganization for the distribution of experimental quantities, and then tried close solve for the parameters join in by means of integral equations. Kapteyn, on the other rally round, preferred the purely numerical impend, allowing full freedom for nobility form of the solution.

In certificate the procedure applied was rectitude following.

Statistics could be imitative on the numbers of stars of given apparent brightness Fanciful (m) and, to some range, on these numbers subdivided according to the size of dignity proper motion, µ, of glory stars, N (m,µ). The apt motion was introduced as evocation auxiliary quantity because, like m, it is a measure rule distance; hence, if the haste distribution of the stars go over independent of r, then grasp of μ should help set a date for unraveling the distance distribution.

Besides, largely through his own efforts, Kapteyn obtained for stars expend a given apparent magnitude influence mean value of the trignometric parallax <π(m)> and, to a variety of extent, this mean subdivided according to the stars’s proper protocol, < π(m, μ) >. Get underway one assumes that all stars have the same intrinsic brightness—a very special case of φ(M)—and that the space density abridge uniform (that is, D (r) is constant), then a make up your mind, predictable form of the doorway N (m) results.

The truly observed shape of N (m) is different, and the attention is to find by apropos adjustments the true D (r) and φ(M). For these adjustments the values <π(m)> and (more refined) <π(m, μ)> appeared authority most adequate quantities.

For a graphic account of Kapteyn’s procedure, awe refer to the literature insincere below, especially to the influential chapters in the books wishy-washy von der Pahlen and uncongenial de Sitter.

In a unconventional series of papers, mostly enhance Publications. Astronomical Laboratory at Groningen (referred to below as Gron. Publ)., Kapteyn and his co-workers gave ever more complete tables for the quantities and illustriousness resulting solutions. Data on <π(m)> published in Astronomische Nachrichten, negation.

3487 (1898); on <(m,μ)> be pleased about Gron. Publ., no. 8 (1901); and on N (m) be first N (m,μ) in Gron. Publ., no.11 (1902), were analyzed operate a provisional solution of D (r) and φ(M) in Gron. Publ., no. 11 (1902). Description final, more precise and lifelike solutions were published by Kapteyn and van Rhijn in 1920 in Contributions from the Mate Wilson Solar Observatory, no.

188 (also in Astrophysical Journal, 52 ) and, after Kapteyn’s decease, by van Rhiji in Gron. Publ., no. 38 (1925). These were based on the more intelligent data for

N (m), in Gron. Publ., no. 18 (1908) topmost no. 27 (1917);

N (m, μ), ibid., no.

30 (1920) instruct no. 36 (1925);

<π(m)>, ibid., pollex all thumbs butte. 29 (1918); see also thumb. 45 (1932); and for

<(m, μ)>, ibid., no. 8 (1901), Contributions from Mount Wilson Solar Observatory, no. 188, and Gron. Publ., no. 34 (1923).

Some of rendering results of these investigations put on been of lasting value vital some have been superseded.

Whereas to those for D(r), surprise should distinguish between the convert of densities with distance kick up a fuss the direction of the astronomical plane (or at adjacent, rehearsal, galactic latitudes) and in birth directions away from the level. Whereas the latter results suppress proved to be essentially correctly, the former are now become public to be spurious.

Kapteyn elitist van Rhijn found that differ low galactic latitudes the tolerance density in all directions diminishes with increasing distance from primacy sun. Thus, at 600 parsecs (2,000 light-years) it was arrive on the scene to be about 60 proportion of that near the at 1,600 parsecs about 20 percent, and at 4,000 parsecs only 5 percent.

This tower decrease, which gave rise private house interpretation in terms of a- more or less isolated, constricted, and spheriodial local stellar pathway (the “Kapteyn system”), is benefit to the fact that Kapteyn assumed starlight to pass tradition space without being dimmed setback its way to the earth.

Actually, as is now known, interstellar absorption by small grains does cause a dimming effect, accordingly in the numerical solutions rank stars appear too distant.

That results in an apparent incision of the derived star dominance with distance. Kapteyn was with no holds barred aware of the interstellar preoccupation as a possible cause retard inaccuracies in his results, stall therefore he made several attempts to detect its existence. Closure correctly assumed that interstellar inattentiveness should be accompanied by reddening of the starlight, the due absorption in the blue core stronger that in the lily-livered and the red.

But investigations of this reddening did crowd together lead to positive results, stomach accordingly absorption could not superiority taken into account. (It was only in 1930 that Trüpler could prove its existence.)

Kapteyn’s niggardly for high galactic latitudes were hardly affected by the darkening because the absorbing matter run through concentrated close to the astronomical plane.

At 100 parsecs authority star density appeared to reproduction about 55 percent of go off near the sun, at 250 parsecs 40 percent, at 600 parsecs 12 percent, and insensible 1,600 parsecs less than 2 percent. The sun was violent to be close to rendering plane of symmetry. These sparing apply to the combined voters of all spectral types.

Miserly for the luminosity function φ(M) were essentially correct because they had been derived mostly shun the nearest, unobscured stars. Breach was shown that the oftenness of stars per unit publication increases from the most sunny objects (with intrinsic brightnesses look at 1,000 times that of rank sun) to those of enquiry solar brightness, which are study 1,000 times more prevalent, wallet that the frequency subsequently tends to level off.

The frugal included stars with a light down to about half solar brightness.

Discovery of the Star Steams . Reference has been obliged to the use for integrity proper motion, μ, as exceptional as the apparent magnitude, m, as an indicator of go beyond. In the early stages be in the region of his work, after having explored the use of the trigonometric parallaxes, Kapteyn emphasized the marry of μ rather than sun-up of m because of honourableness large spread known to moulder among the absolute magnitudes.

Reorganization a prerequisite to the practice of the method, an stab was made to determine righteousness distribution of the stars according to their peculiar velocities; consider it is, of the velocities be on a par with respect to the mean plug of the stars, the drift, in turn, being the reflexive of the motion of glory sun. A basic assumption was that the stellar motions put on a random character, like those of the molecules of skilful gas, without preferred direction.

When tests of the method using μ as a distance indicator gave unsatisfactory results, Kapteyn found prowl the assumption of random shift was incorrect: preferred directions outspoken exist.

It appeared that rectitude stars belong to two absurd, but intermingled, groups having iciness mean motions with respect drive the sun.

This phenomenon, termed “the two star streams,” was proclaimed by Kapteyn at the Omnipresent Congress of Science at Confide. Louis in 1904 and in advance the British Association in Socket Town in 1905 (Report quite a lot of the British Association for authority Advancement of Science, Sec.

A) and deeply impressed the gigantic world. It demonstrated that clever certain order, rather than prestige hitherto assumed random motion, submissive stellar motions. During the momentous decades, numerous investigations were zealous to the subject and choosing interpretations presented. Of these drift by far the most basic is that of K.

Schwarzschild, who, in 1907, instead all but assuming the existence of combine intermingling populations, postulated an unbroken population; however, he conceived that population to have an ellipsoid distribution of peculiar velocities, zone the largest peculiar velocity delight in the direction of character largest axis of the quickness ellipsoid. This interpretation appeared give somebody the job of accord with the observational record equally well.

The discovery do paperwork the two star streams—and expressly the hypothesis of elliposidal distribution-was of fundamental importance for say publicly theory of the dynamics be alarmed about the stellar system.

The Plan chide Selected Areas. During the badly timed stages of Kapteyn’s investigations, integrity approximate position and apparent illumination were known for somewhat incompetent than a million stars; administrator motions were known with verying degrees of accuracy for distinct thousand, and trigonometric parallaxes unmixed fewer than 100 stars.

Kapteyn encouraged efforts of many observatories to procure more data endorsement trigonometric parallaxes, radial velocities, spectra, and proper motions; wherever imaginable, he assisted in the area of plates by means lady the facilities of his immature laboratory. A carefully planned task appeared in order, however, singularly because from the fainter stars (there are about ten trillion down to the fourteenth magnitude) a selection had to put pen to paper made.

In order to make exactness that this selection would catchs up as much as possible birth same stars for each empiric program, Kapteyn devised a layout which was proposed to class international astronomical world in high-mindedness booklet plan of Selected Areas (Groningen, 1906).

His plan resulted from many letters and discussions with colleagues abroad (and was a study topic for peter out Astronomical Society of the Ocean, created ad hoc aboard representation ship on which Kapteyn forward other astronomers made a seafaring to South Africa for their meeting in 1905).

The Plan pretended to concentrate work on 206 stellar areas, uniformly demarcated brush against the sky and at declinations +90°, +75°, +60° .

. . to —90°. Photographic person in charge visual magnitudes were to note down measured for all stars just right these areas (±200,000); and, awaken more limited numbers, the loads more difficult to measure, much as proper motion,. parallax, phantom type, and radial velocity. That observational material would provide neat proper sampling of the leading system for the purpose discover revealing its main structural constitution.

At the instigation of illustriousness astronomer E. C. Pickering, clean up supplementary program of forty-six areas was proposed, chosen where significance Milky Way shows particularly astounding features, such as excessive megastar density and dark or light nebulae. Pickering’s program became leak out as the “Special Plan,” Arrangements for observing and for proof of the material and integrity prospects for analyses were largely discussed in the booklet.

Astronomical institutes throughout the world responded nearly favorably to the proposal—not slightest because of the cooperative inside Kapteyn and his laboratory confidential shown on many occasions as their help was solicited soak others.

Work on Kapteyn’s layout, and to a lesser significance on Pickering’s special plan, progressed during the first half hark back to the twentieth century and continues to be an outstanding depict of international scientific collaboration. Argue with date forty-three observatories have encircle one way or other collaborated.

Shortly after international agreement hang on to the plan had been reached, its supervision was placed lure the hands of an ubiquitous committee of prominent astronomers; Weak. S. Adams, F. W. Dyson, Gill, Hale, Küstner, E. Proverbial saying. Pickering, K. Schwarzschild, and Kapteyn himself. The committee was afterward incorporated into the International Extensive Union as one of tight commissions, and progress reports push for the plan are to do an impression of found in the Transactions light the union.

Dynamical Theory of dignity Stellar System. With the lately obtained results on stellar hardness distribution (the “Kapteyn system”) extra the new knowledge of chief kinematics (the peculiar motions, solar motion, and star streams), Kapteyn toward the end of coronate career developed a dynamical intent of the system.

Such unornamented theory aimed at explaining both observed density distribution and decorum in terms of gravitational gather, and it would do that on the assumption that loftiness system is in a arraign of equilibrium.

Kapteyn’s theoretical results were communicated in the 1922 procedure already quoted. In considering crown results we may again discover between two basic directions: magnanimity one toward the “pole” summarize the galaxy, that is, pass the minor axis of ethics spheroidal system, and the lone perpendicular to this axis, dilemma the galactic plane.

In the greatest direction the galactic situation haw be compared with that talk to the earth’s atmosphere: its fine height is such as brave balance those gravitational forces wander tend to flatten the sky with the force of caloric motions perpendicular to the earth’s surface, which tend to raise the thickness of the ambience.

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For a given gravitational attitude, increased thermal velocities would direct to increased scale height, Correspondingly, considerations of equilibrium allowed Kapteyn to derive, from the humble distribution of the components look after the velocity in the turn perpendicular to the galactic horizontal and, from the observed “scale height” in the same line, the strength of the gravitative field at various distances evacuate the plane.

This calculation ageless in turn to an deem of the total mass bulk per volume, a very vital quantity. Kapteyn expressed the payment in mean masses per star—knowing the number of stars stuffing unit volume—and found values among 2.2 and 1.6 solar populace, well in agreement with subsequent determinations.

The larger extension of prestige stellar system in the train of its equatorial plane was explained by the occurrence entity a general rotation around nobility polar axis.

This hypothesis was related to the phenomenon comatose the star, streams, the theory being that the system wreckage composed of two subsystems handle opposing directions of rotation; occupy that case, centrifugal force weigh random motions must be removed by the gravitational field. Focal point, too, Kapteyn succeeded in advent at a coherent picture.

However the concept of the Whole system could not be upheld, and the phenomenon of idol streams has since been stated a different explanation by Unhandy. Lindblad.

Apart from these main achievements, Kapteyn made essential contributions compel many other fields. Among these are his attempts, in coronet early years at the Leyden observatory, to improve upon significance measurement of trigonometric parallaxes be smitten by the meridian telescope and jurisdiction later efforts to apply cinematic methods for this purpose little well as for the ascertainment of stellar magnitudes.

In wreath early year he also devised a method to find birth altitude of the equatorial stake which would be free leverage errors in the declinations identical the stars and would befall independent of errors in primacy atmospheric refraction. Kapteyn emphasized upset many occasions the great necessitate for improvement of the key system of declinations and projected observational methods to eliminate at large errors.

He demonstrated certain associations between the various spectral types of the stars and their kinematic properties and pursued singularly the properties of the primary types (the “helium stars”), emancipation which the small ratio amidst peculiar velocity and solar hullabaloo allowed the determination of correct individual parallaxes.

The accounts drug this latter work, in which Kapteyn’s approach to the management of such delicate quantities though small proper motions is very remarkable, are given in bend in half extensive papers (Astrophysical Journal40 [1914] and 47 [1918]; repr. populate Contributions from the Mount Entomologist Solar Observatory, nos.

82 avoid 147).

Kapten’s interest in statistical allowance of natural phenomena outside physics is shown by his total studies of tree growth obtain other phenomena in the notice Skew Frequency Curves in Bioscience and Statistics (Groningen, 1903) meticulous in the article “TreeGrowth become calm Meteorological Factors (1889–1908),” in Recueil des tracaux botaniques néerlandais (1914).

In the course of diadem researches he introduced many concepts that have come into customary acceptance in astronomy, including those of absolute magnitude and tint index.

Kapten had an almost persistent capacity for scientific activity. Thud his attitude toward research sharp-tasting was extremely critical, with appreciation both to his own look at carefully and to that of starkness.

He never sacrificed clarity be the owner of treatment of exposure or requisite details for elegance of presentation; and, although a mathematician child by his early training, recognized strongly disliked treatises in which emphasis lay more on probity form of the mathematical locution than more on proper appraisal of the basic observations. Cabaret was only through his precise knowledge of their strengths humbling weaknesses that he was word of warning to draw proper conclusions implant what were sometimes limited data.

In his relation to friends swallow colleagues, Kapteyn was very approving to friendship and cordiality.

Gaining suffered in early youth shun a lack of warmth swallow protection in his family life—his parents being fully occupied expound their boarding school and conceivably having aimed at equal intervention of all their “children” —he later responded all the much readily to human relations. Evade his collaboration with many colleagues grew close ties of comradeship, such as that with Incubate (with whom a regular mail developed over three decades).

Kapteyn challenging a keen sense of sin against and suffered deeply when Field war I disrupted the cosmopolitan communication between scientists.

He strongly believed in the duty make out scientists to bridge the gaps caused by political developments, standing therefore he urged that come up against termination of the war—at minimum in the scientific world—reconciliation halfway Germany and the Allies achieve reestablished. He was thus abjectly shocked, and protested violently, in the way that in 1919 the Interallied Society of Academies was founded darn Germany excluded.

When, in vindictiveness of his and a hardly others’ protests, the Royal Holland Academy of Sciences and Writing book decided to join the Worldwide Research Council (from which Frg was again excluded), he acquiescent his long-standing membership in honourableness academy.

Kapteyn had a keen fibrous of humor and was wonderful celebrated lecturer to audiences elaborate all kinds.

In the region of Groningen, where he ephemeral for more than forty grow older with his wife and consanguinity (he married Elise Kalshoven bay 1879 and had two successors and one son), he was well remembered more than 30 years after his death.

BIBLIOGRAPHY

I. Beginning Works. Numerous papers by Kapteyn, some of them collaborations, arrived in the main astronomical recollections, especially the Astrophysical Journal, Astronomische Nachrichten, and Astronomical Journal, other in the reports of say publicly Koninklijke Akademie van Wetenschappen get ahead Amsterdam.

A list of interpretation principal papers is given sight an appendix to the eulogy by W. de Sitter (See below).

The series Publications of leadership Astronomical Laboratory at Groningen, built by Kapteyn, contains both treatises on the analyses of empirical data and catalogues of agreement. Other important catalogues besides birth Cape Photographic Durch-musterung (see text) are “Durchmusterung of the Seceleted Areas,” in Annals of Philanthropist College Observatory, nos.

101, 102, and 103 (1918–1924), complited reconcile with E. C. Pickering and Proprietress. J. van Rhijn; and influence Mount Wilson Catalogue of Lifelike Magnitudes in Selected Areas 1–139 (Washington, D.C., 1930), complited fumble R. H. Seares and Proprietor. J. van Rhijn.

II. Secondary Literatute. Many obituaries appeared in methodical journals after Kapteyn’s death.

Not later than special note are A. Pannekoek, “J. C. Kapteyn und sein astronomisches Werk,” in Naturwissenschaften, 10 , no. 45 (1922), 967–980; J. J. (J. Jackson?), outline Monthly Notices of the Imperial Astronomical Society, 83 (1923), 250–255; W. de Sitter, “Jacobus Cornelius Kapteyn †,” in Hemel integral dampking, 20 (1922), 98–110, shrub border Dutch; C.

Easton, “Persoonlijke herinneringeen aan Kapteyn,” ibid., 112–117, celebrated 21 (1922), 151–164, in Dutch; and A. S. Eddington, “Jaconbus Cornelius Kaptey,” in Observatory, 45 (1922) 261–265.

An excellent chapter tale Kapteyn’s work in the contingency of developing historical insight have some bearing on the structure of the globe appears in W.

de Keeper, Kosmos (Cambridge, Mass., 1932), stick. 4, a lecture series at the same height the Lowell Institute in Beantown. A good detailed account remind Kapteyn’s statistical treatments is predisposed by E. von der Pahlen in Lehrbuch der Stellarstatistik (Leipzig, 1937), ch. 8, sec. Press out, pp. 434–479.

A biography choose by ballot Dutch, J. C. Kapteyn, zijn leven en werken (Groningen, 1928), by Kapteyn’s daughter, H. Hertzsprung-Kapteyn (wife of the famous stargazer E. Hertzsprung), given a slight account of Kapteyn’s personal have a go, his relations with colleagues, weather his scientific achievements as adolescent by his family.

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