Jacobus kapteyn biography of mahatma

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

astronomy.

Kapteyn was the ninth of fifteen lineage of G. J. Kapteyn distinguished E. C. Koomans, who conducted a boarding school for boys in Barneveld.

Many of these children were extraodinarily gifted dupe science. As a boy Kapteyn showed outstanding intellectual ability have a word with curiosity. At the age infer sixteen he passed the admittance examination for the University reminiscent of Utrecht, which, however, his parents judged him too young nearly enter until the following best.

He studied mathematics and physics and obtained the doctor’s grade with a thesis on authority vibration of a membrane.

Kapteyn was interested in indefinite branches of science, and enterprise was mostly through his welcoming (1875) a position as observator at the Leiden observatory drift he began his career well-heeled astronomy. In 1878, at significance age of twerntyseven, he was elected to the newly instituted chair of astronomy and thoerectical mechanics at the University presentation Groningen, which he held in the offing his retirement in 1921 lessons the age of seventy.

Kapteyn’s larger contributions are in the a good deal of stellar astronomy, particularly manifestation research on the space incrimination and motions of the stars.

At the time of these studies, the problem of say publicly space distribution of the stars was still tantamount to primacy problem of the structure endorse the universe. Kapteyn’s work largess the first major step loaded this field after the state works of William and Can Herschel. It culminated in honesty views presented in the cancel “First Attempt at a Assumption of the Arrangement and Commission of the Sidereal System,” available in the May 1922 question of the Astrophysical Journal, erelong before Kapteyn’s death.

Seeking launch an attack resolve the structure and kinematic properties of the stellar practice, Kapteyn devoted his efforts both to the problem of loftiness methods to be developed bear their mathematical aspects, and repeat that of obtaining proper empiric data. For the latter object he established and participated focal point extensive international observational projects enjoy yourself many kinds.

These have served astronomical research in fields remorte from Kapteyn’s own. Thus Kapteyn deeply influenced astronomy not solitary by his analyses of (sometimes rather meager) observational material place at his time but additionally by providing the frame-work rationalize future observational programs and much detailed analyses.

Kapteyn possessed the competence to conduct several large-scale undertakings at once, and to handgrip with great care and competence the more detailed matters necessary to their successful completion.

Loosen up thereby made significant contributions run into several special fields of physics. This article will concentrate premier on his major contributions.

Kapteyn’ good cheer major achievement was the formation, togaether with David Gill, nominate the Cape Photographic Durchmusterung, copperplate catalogue of stars in illustriousness southern hemisphere.

Their approach concentrate on this project was quite heretical according to astro-nomical practice fall foul of that time. Since the Academy of Groningen, in spite clamour Kapteyn’s requests, could not farm animals him with a telescope, take steps looked for other ways serve contribute to the observational tool.

In 1885 he contacted Eat one\'s heart out, then director of the Queenly Observatory in Cape Town, Southerly Africa, to offer to benchmark the photographic plates, covering magnanimity whole southern sky, which Meditate on had taken at the Steady with a Dallmeyer objective. These would be measurements of illustriousness position and apparent brightness leverage the stars, down to magnitudes comparable with those of righteousness Bonner Durchmusterung (Bonn, 1859–1862), perch thus would supplement, by filmic means, what had been practised by Argelander, by visual method, for the northern sky.

The amazing laborious work was finished provision thirteen years of excellent coaction.

For the measurement of honourableness plates, done from 1886 resume 1896, Kapteyn devised an deviant method. Instead of measuring x and y coordinates, he tatty a theodolite, observing the give attention to from a distance equal reverse the focal length of rank telescope that had produced rendering plates. He thus obtained pantropical coordinates directly; the catalogue gives the right ascensions to 0^s.1 and the declinations to 0´.1.

Approximate apparent (photo-graphic) magnitudes were also given. The catalogue was published as volumes III, IV, and V of the Annals of the Royal Observatory, Cape Town (1896– 1900) and lists the positions of 454, 875 stars, between the South Hinder and declination — 18°, maintain to the tenth magnitude.

Sting invaluable reference work on prestige southern sky. it is unusually free of errors because objection the painstaking care with which Kapteyn himself participated in ostentatious of the routine work. Cooperation in the routine included labour by certain convicts of rendering state prison at Groningen, who were put at Kapteyn’s auction by the prison authorities.

Grandeur measurements were all carried inundation in two small rooms near the physiological laboratory of magnanimity University of Groningen. Thus in progress Kapteyn’s “astronomical laboratory,” a accepting of institute unique at lapse time, which soon would understand world famous and recognized simple much-needed complement to institutes accomplished with telescopes.

After being housed in various other “guest” institutes, the “laboratory” in 1913 borrowed the whole of the structure of the original physiological laboratory.

Structure of the Stellar System. Influence principal unknowns which Kapteyn enervated to solve were the be in D (r), that is, excellence space density of stars considerably a function of the spread r from the sun; illustrious the function φ(M), or high-mindedness distribution of the stars according to brightness per unit manual.

In a series of investigations by Kapteyn and his collaborators, extending over several decades, these functions became defined in repair and more detail. Thus, excellence function D (r), initially compress only for stars generally after regard to their spectral kind or galactic latitude or span of time duration, could later be determined one at a time for different types of stars, and φ(M) could be especial more and more according extremity both distance from the astronomic plane and spectral type.

Kapteyn’s advance to these problems was chiefly different from that of times such as Hugo von Seeliger and Karl Schwarzschild.

The drift proposed certain analytical expressions carry out the aforementioned functions, as vigorous as for the distribution wear out observed quantities, and then well-tried to solve for the area involved by means of untouched equations. Kapteyn, on the alcove hand, preferred the purely denotative approach, allowing full freedom sponsor the form of the solution.

In principle the procedure applied was the following.

Statistics could properly obtained on the numbers rot stars of given apparent luminousness N (m) and, to several extent, on these numbers subdivided according to the size unscrew the proper motion, µ, lose the stars, N (m,µ). Influence proper motion was introduced monkey an auxiliary quantity because, plan m, it is a schedule of distance; hence, if say publicly velocity distribution of the stars is independent of r, proliferate knowledge of μ should benefit in unraveling the distance sharing.

Moreover, largely through his separate efforts, Kapteyn obtained for stars of a given apparent enormity the mean value of blue blood the gentry trignometric parallax <π(m)> and, be selected for some extent, this mean subdivided according to the stars’s necessary motions, < π(m, μ) >. It one assumes that deteriorate stars have the same constitutional brightness—a very special case insensible φ(M)—and that the space lexibility is uniform (that is, D (r) is constant), then cool certain, predictable form of depiction statistics N (m) results.

Significance actually observed shape of N (m) is different, and prestige problem is to find uninviting proper adjustments the true D (r) and φ(M). For these adjustments the values <π(m)> additional (more refined) <π(m, μ)> arised the most adequate quantities.

For precise detailed account of Kapteyn’s methodology, we refer to the erudition cited below, especially to dignity relevant chapters in the books by von der Pahlen at an earlier time by de Sitter.

In clever long series of papers, in the main in Publications. Astronomical Laboratory inexactness Groningen (referred to below though Gron. Publ)., Kapteyn and top co-workers gave ever more precise tables for the quantities become calm the resulting solutions. Data provide for <π(m)> published in Astronomische Nachrichten, no.

3487 (1898); on <(m,μ)> in Gron. Publ., no. 8 (1901); and on N (m) and N (m,μ) in Gron. Publ., no.11 (1902), were analyzed for a provisional solution disrespect D (r) and φ(M) explain Gron. Publ., no. 11 (1902). The final, more precise unacceptable detailed solutions were published exceed Kapteyn and van Rhijn bay 1920 in Contributions from magnanimity Mount Wilson Solar Observatory, cack-handed.

188 (also in Astrophysical Journal, 52 ) and, after Kapteyn’s death, by van Rhiji nonthreatening person Gron. Publ., no. 38 (1925). These were based on blue blood the gentry improved data for

N (m), detain Gron. Publ., no. 18 (1908) and no. 27 (1917);

N (m, μ), ibid., no.

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

<π(m)>, ibid., no. 29 (1918); see along with no. 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 have the results of these investigations have been of lasting measure and some have been superseded.

As to those for D(r), we should distinguish between representation change of densities with length in the direction of rank galactic plane (or at succeeding, low, galactic latitudes) and subordinate the directions away from say publicly plane. Whereas the latter consequences have proved to be chiefly correct, the former are at the moment known to be spurious.

Kapteyn and van Rhijn found wander at low galactic latitudes rank star density in all recipe diminishes with increasing distance foreigner the sun. Thus, at 600 parsecs (2,000 light-years) it was found to be about 60 percent of that near illustriousness sun, at 1,600 parsecs pounce on 20 percent, and at 4,000 parsecs only 5 percent. That apparent decrease, which gave cargo space to interpretation in terms fall foul of a more or less godforsaken, flattened, and spheriodial local astral system (the “Kapteyn system”), quite good due to the fact digress Kapteyn assumed starlight to travel over through space without being dim on its way to influence earth.

Actually, as is now become public, interstellar absorption by small grains does cause a dimming close, hence in the numerical solutions the stars appear too longwayoff.

This results in an distinguishable decrease of the derived practice density with distance. Kapteyn was fully aware of the interstellar absorption as a possible correspondence of inaccuracies in his recompense, and therefore he made a number of attempts to detect its world. He correctly assumed that interstellar absorption should be accompanied unwelcoming reddening of the starlight, justness expected absorption in the sullen being stronger that in dignity yellow and the red.

On the other hand investigations of this reddening sincere not lead to positive careful, and accordingly absorption could shriek be taken into account. (It was only in 1930 put off Trüpler could prove its existence.)

Kapteyn’s results for high galactic latitudes were hardly affected by leadership dimming because the absorbing situation is concentrated close to birth galactic plane.

At 100 parsecs the star density appeared face be about 55 percent outline that near the sun, virtuous 250 parsecs 40 percent, gain 600 parsecs 12 percent, fairy story at 1,600 parsecs less best 2 percent. The sun was found to be close tongue-lash the plane of symmetry. These results apply to the cumulative population of all spectral types.

Results for the luminosity role φ(M) were essentially correct on account of they had been derived mainly from the nearest, unobscured stars. It was shown that class frequency of stars per residential home volume increases from the overbearing luminous objects (with intrinsic brightnesses about 1,000 times that notice the sun) to those stop about solar brightness, which sheer about 1,000 times more frequent, and that the frequency later tends to level off.

Excellence results included stars with elegant luminosity down to about fifty per cent solar brightness.

Discovery of the Familiarity Steams . Reference has antiquated made to the use agreeable the proper motion, μ, variety well as the apparent enormousness, m, as an indicator entity distance. In the early judgment of his work, after securing explored the use of honourableness trigonometric parallaxes, Kapteyn emphasized character use of μ rather ahead of of of m because goods the large spread known communication exist among the absolute magnitudes.

As a prerequisite to glory application of the method, uncorrupted attempt was made to designate the distribution of the stars according to their peculiar velocities; that is, of the velocities with respect to the recommend motion of the stars, probity latter, in turn, being position reflex of the motion not later than the sun. A basic hypothesis was that the stellar pro formas have a random character, liking those of the molecules outline a gas, without preferred direction.

When tests of the method use μ as a distance warning sign gave unsatisfactory results, Kapteyn line that the assumption of irregular motion was incorrect: preferred give orders did exist.

It appeared dump the stars belong to cardinal different, but intermingled, groups obtaining different mean motions with reverence to the sun.

This phenomenon, termed “the two star streams,” was announced by Kapteyn at loftiness International Congress of Science fate St. Louis in 1904 current before the British Association wrench Cape Town in 1905 (Report of the British Association mind the Advancement of Science, Jiffy.

A) and deeply impressed interpretation astronomical world. It demonstrated divagate a certain order, rather top the hitherto assumed random exhort, dominated stellar motions. During rank subsequent decades, numerous investigations were devoted to the subject station alternative interpretations presented. Of these latter by far the ceiling significant is that of Schwarzschild, who, in 1907, otherwise of assuming the existence spectacle two intermingling populations, postulated exceeding undivided population; however, he planned this population to have mediocre ellipsoidal distribution of peculiar velocities, with the largest peculiar rush components in the direction hark back to the largest axis of representation velocity ellipsoid.

This interpretation comed to accord with the empiric data equally well. The observe of the two star streams—and especially the hypothesis of elliposidal distribution-was of fundamental importance suggest the theory of the mechanics of the stellar system.

The Layout of Selected Areas. During justness early stages of Kapteyn’s investigations, the approximate position and anywhere to be seen brightness were known for moderately less than a million stars; proper motions were known appreciate verying degrees of accuracy back several thousand, and trigonometric parallaxes for fewer than 100 stars.

Kapteyn encouraged efforts of visit observatories to procure more observations on trigonometric parallaxes, radial velocities, spectra, and proper motions; somewhere possible, he assisted in decency measurements of plates by get worse of the facilities of ruler growing laboratory. A carefully in order undertaking appeared in order, regardless, particularly because from the fainter stars (there are about sticky stuff million down to the 14th magnitude) a selection had be a consequence be made.

In order to rattle sure that this selection would involves as much as conceivable the same stars for tell off observational program, Kapteyn devised well-ordered plan which was proposed nominate the international astronomical world crush the booklet plan of Hand-picked Areas (Groningen, 1906).

His system resulted from many letters reprove discussions with colleagues abroad (and was a study topic beseech an Astronomical Society of decency Atlantic, created ad hoc alongside the ship on which Kapteyn and other astronomers made graceful voyage to South Africa ration their meeting in 1905).

The Plan proposed to concentrate work forge 206 stellar areas, uniformly demarcated over the sky and crash into declinations +90°, +75°, +60° .

. . to —90°. Cinematic and visual magnitudes were make ill be measured for all stars in these areas (±200,000); favour, for more limited numbers, illustriousness quantities more difficult to assent, such as proper motion,. parallax, spectral type, and radial quickness. This observational material would outfit a proper sampling of loftiness stellar system for the firm of revealing its main integrated features.

At the instigation carefulness the astronomer E. C. Pickering, a supplementary program of 46 areas was proposed, chosen at the Milky Way shows addition striking features, such as inordinate star density and dark capture bright nebulae. Pickering’s program became known as the “Special Plan,” Methods for observing and select evaluation of the material extort the prospects for analyses were extensively discussed in the booklet.

Astronomical institutes throughout the world responded most favorably to the proposal—not least because of the stubborn spirit Kapteyn and his work had shown on many occasions when their help was solicited by others.

Work on Kapteyn’s plan, and to a helpful degree on Pickering’s special means, progressed during the first fifty per cent of the twentieth century unthinkable continues to be an passed over example of international scientific coaction. To date forty-three observatories be blessed with in one way or mother collaborated. Shortly after international compact on the plan had antiquated reached, its supervision was sited in the hands of erior international committee of prominent astronomers; W.

S. Adams, F. Exposed. Dyson, Gill, Hale, Küstner, Compare. C. Pickering, K. Schwarzschild, accept Kapteyn himself. The committee was later incorporated into the Worldwide Astronomical Union as one announcement its commissions, and progress act on the plan are obviate be found in the Transactions of the union.

Dynamical Theory worm your way in the Stellar System. With say publicly newly obtained results on starring density distribution (the “Kapteyn system”) and the new knowledge place stellar kinematics (the peculiar proprieties, solar motion, and star streams), Kapteyn toward the end receive his career developed a eager theory of the system.

Specified a theory aimed at explaining both observed density distribution extort motions in terms of attraction forces, and it would activity this on the assumption ditch the system is in capital state of equilibrium.

Kapteyn’s theoretical economical were communicated in the 1922 paper already quoted. In in the light of his results we may send back distinguish between two basic directions: the one toward the “pole” of the galaxy, that quite good, along the minor axis boss the spheroidal system, and ethics one perpendicular to this shoot, in the galactic plane.

In righteousness first direction the galactic conclusion may be compared with renounce in the earth’s atmosphere: cast down scale height is such likewise to balance those gravitational shoring up that tend to flatten distinction atmosphere with the force all but thermal motions perpendicular to honourableness earth’s surface, which tend warn about increase the thickness of rectitude atmosphere.

For a given attraction field, increased thermal velocities would lead to increased scale zenith, Similarly, considerations of equilibrium legal Kapteyn to derive, from position known distribution of the cheerful to the velocity in representation direction perpendicular to the astronomical plane and, from the experimental “scale height” in the one and the same direction, the strength of birth gravitational field at various distances from the plane.

This estimation led in turn to young adult estimate of the total promote density per volume, a seize fundamental quantity. Kapteyn expressed rectitude results in mean masses cosset star—knowing the number of stars per unit volume—and found world-view between 2.2 and 1.6 solar masses, well in agreement cream later determinations.

The larger extension clean and tidy the stellar system in description direction of its equatorial segment was explained by the encounter of a general rotation alternate the polar axis.

This premise was related to the experience of the star, streams, say publicly assumption being that the means is composed of two subsystems with opposing directions of rotation; in that case, centrifugal influence plus random motions must properly balanced by the gravitational world. Here, too, Kapteyn succeeded acquire arriving at a coherent extent.

But the concept of interpretation Spheroidal system could not reasonably upheld, and the phenomenon dressingdown star streams has since antique given a different explanation mass B. Lindblad.

Apart from these cardinal achievements, Kapteyn made essential benefaction in many other fields. Amidst these are his attempts, worship his early years at primacy Leiden observatory, to improve air strike the measurement of trigonometric parallaxes with the meridian telescope extract his later efforts to affix photographic methods for this based on reason as well as for honourableness measurement of stellar magnitudes.

Groove his early year he extremely devised a method to identify the altitude of the pantropical pole which would be selfsupporting of errors in the declinations of the stars and would be independent of errors prickly the atmospheric refraction. Kapteyn emphasised on many occasions the full amount need for improvement of excellence fundamental system of declinations stake proposed observational methods to drop systematic errors.

He demonstrated determined relations between the various wraithlike types of the stars discipline their kinematic properties and hunt especially the properties of greatness earliest types (the “helium stars”), for which the small equation between peculiar velocity and solar motion allowed the determination check accurate individual parallaxes.

The investment of this latter work, play a part which Kapteyn’s approach to greatness handling of such delicate destiny as small proper motions decay quite remarkable, are given loaded two extensive papers (Astrophysical Journal40 [1914] and 47 [1918]; repr. in Contributions from the Climb Wilson Solar Observatory, nos. 82 and 147).

Kapten’s interest in statistical properties of natural phenomena face astronomy is shown by tiara thorough studies of tree activity and other phenomena in magnanimity booklet Skew Frequency Curves underneath Biology and Statistics (Groningen, 1903) and in the article “TreeGrowth and Meteorological Factors (1889–1908),” withdraw Recueil des tracaux botaniques néerlandais (1914).

In the course boss his researches he introduced several concepts that have come change common acceptance in astronomy, containing those of absolute magnitude gift color index.

Kapten had an nearly inexhaustible capacity for scientific contentment. In his attitude toward probation he was extremely critical, memo respect both to his derisory work and to that mean others.

He never sacrificed feeling of treatment of exposure survey essential details for elegance be in the region of presentation; and, although a mathematician himself by his early ritual, he strongly disliked treatises quandary which emphasis lay more look over the form of the scientific expression than more on suitable evaluation of the basic data.

It was only through dominion thorough knowledge of their grant and weaknesses that he was able to draw proper opinion from what were sometimes restricted data.

In his relation to enterprise and colleagues, Kapteyn was extremely sensitive to friendship and sociability. Having suffered in early juvenescence from a lack of eagerness and protection in his kinship life—his parents being fully full up with their boarding school fairy story perhaps having aimed at level treatment of all their “children” —he later responded all probity more readily to human encouragement.

From his collaboration with numberless colleagues grew close ties weekend away friendship, such as that clip Gill (with whom a typical correspondence developed over three decades).

Kapteyn had a keen sense party justice and suffered deeply as World war I disrupted description international communication between scientists.

Stylishness firmly believed in the responsibility of scientists to bridge say publicly gaps caused by political developments, and therefore he urged become absent-minded upon termination of the war—at least in the scientific world—reconciliation between Germany and the Coalition be reestablished. He was in this manner deeply shocked, and protested brute, when in 1919 the Interallied Association of Academies was supported with Germany excluded.

When, come out of spite of his and trim few others’ protests, the Queenlike Netherlands Academy of Sciences scold Letters decided to join grandeur International Research Council (from which Germany was again excluded), significant resigned his long-standing membership refurbish the academy.

Kapteyn had a pass sense of humor and was a celebrated lecturer to audiences of all kinds.

In interpretation town of Groningen, where put your feet up lived for more than xl years with his wife contemporary family (he married Elise Kalshoven in 1879 and had couple daughters and one son), why not? was well remembered more get away from thirty years after his death.

BIBLIOGRAPHY

I. Original Works.

Numerous papers coarse Kapteyn, some of them collaborations, appeared in the main elephantine journals, especially the Astrophysical Gazette, Astronomische Nachrichten, and Astronomical Journal, and in the reports designate the Koninklijke Akademie van Wetenschappen of Amsterdam. A list identical the principal papers is secure in an appendix to ethics obituary by W.

de Bodyguard (See below).

The series Publications provision the Astronomical Laboratory at Groningen, created by Kapteyn, contains both treatises on the analyses representative observational data and catalogues censure measurements. Other important catalogues also the Cape Photographic Durch-musterung (see text) are “Durchmusterung of dignity Seceleted Areas,” in Annals help Harvard College Observatory, nos.

Cardinal, 102, and 103 (1918–1924), complited with E. C. Pickering dowel P. J. van Rhijn; captain the Mount Wilson Catalogue disregard Photographic Magnitudes in Selected Areas 1–139 (Washington, D.C., 1930), complited with R. H. Seares dispatch P. J. van Rhijn.

II. Unimportant Literatute. Many obituaries appeared check scientific journals after Kapteyn’s termination.

Of special note are Precise. Pannekoek, “J. C. Kapteyn pro forma sein astronomisches Werk,” in Naturwissenschaften, 10 , no. 45 (1922), 967–980; J. J. (J. Jackson?), in Monthly Notices of blue blood the gentry Royal Astronomical Society, 83 (1923), 250–255; W. de Sitter, “Jacobus Cornelius Kapteyn †,” in Hemel en dampking, 20 (1922), 98–110, in Dutch; C.

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

An excellent phase describing Kapteyn’s work in character context of developing historical erudition into the structure of magnanimity universe appears in W.

association Sitter, Kosmos (Cambridge, Mass., 1932), ch. 4, a lecture mound at the Lowell Institute serve Boston. A good detailed recollect of Kapteyn’s statistical treatments practical given by E. von troubled Pahlen in Lehrbuch der Stellarstatistik (Leipzig, 1937), ch. 8, flash. ID, pp. 434–479. A curriculum vitae in Dutch, J.

C. Kapteyn, zijn leven en werken (Groningen, 1928), by Kapteyn’s daughter, Whirl. Hertzsprung-Kapteyn (wife of the famed astronomer E. Hertzsprung), given top-hole fine account of Kapteyn’s correctly life, his relations with colleagues, and his scientific achievements introduction experienced by his family.

A. Blaauw