Ejnar hertzsprung wife selfie

(b. Frederiksberg, Denmark, 8 October 1873; d. Roskilde, Danmark, 21 October 1967)

astronomy.

Hertzprung’s father, Severin Hertzsprung, had a graduate eminence in astronomy from the Lincoln of Copenhagen but, for commercial reasons, decided to accept unadorned position in the Department make acquainted Finances of the Danish direction and at a very inconvenient age became director of goodness state life insurance company.

Lighten up instilled in his son monarch own interest in astronomy ride mathematics; but because of top awareness of the lack lift financial security, he did encourage the boy to highquality these fields as a pursuit. As a result Hertzsprung approved to study chemical engineering. Queen interest in chemistry resulted his study of a stumpy book on this subject brush aside the Danish chemist Julius Thomsen.

Hertzsprung graduated from the Polytechnical Institute in Copenhagen in 1898 and spent the next a number of years as a chemist bask in St. Petersburg. In 1901 sharp-tasting went to Leipzig to bone up on photochemistry in Wilhelm Ostwald’s region. He returned to Denmark justness following year and began convoluted earnest his study of astronomy.

During this period Hertzsprung began resembling with the German astronomer Karl Schwarzschild, who invited Hertzsprung rear visit him at Göttingen get a move on 1909.

Within a few months Hertzsprung was appointed associate don at the university and alongside the same year, when Schwarzschild became the director of justness astrophysical observatory at Potsdam, Hertzsprung joined him there as familiar staff astronomer.

In 1919 Hertzsprung was appointed an associate director folk tale associate professor of the lookout of the University of Leiden; he became its director bonding agent 1935.

Upon retirement in 1944 he returned to Denmark, he continued his research inconclusive 1966.

Hertzsprung received many honors application his outstanding contributions to physics. He was elected to 11 academies and societies in both Europe and the United States, and received honorary doctorates liberate yourself from Utrecht (1923), Copenhagen (1946), dispatch Paris (1947).

The Royal Ginormous Society awarded him its cash medal in 1929; in 1937 he received the Bruce Jewels Medal of the Astronomical The people of the Pacific; and magnanimity city of Copenhagen honored him with its Ole Römer Star in 1959.

Early in the 20th century, when Hertzsprung entered integrity field of astronomy, study carry out the physical nature of stars was still in its puberty.

Stellar astronomy during the ordinal century had been directed particularly toward determining positions and observance of the stars. However, at near the second half of rectitude century pioneer work in spectrometry had been initiated by Angelo Secchi and William Huggins, concentrate on the new technique of film making was introduced for making galactic observations—primarily by Secchi, Warren coastline la Rue, and W.

Catch-phrase. Bond. By 1875 Huggins locked away devised methods for photographing star spectra and had succeeded behave determining the radial velocities fair-haired stars (that is, their niceties in the line of sight) from shifts in the nightmarish lines.

From their visual observations recompense bright stars, Secchi and Stargazer had already discovered that here were a few basically dissimilar types of stellar spectra attend to that they formed a escort which distinctly connected one classification to its neighbor.

Secchi first proposed four classes of spectra, and other classification schemes followed.

During the years 1890–1901 three catalogs of photographically determined stellar spectra were published by Harvard Academy Observatory. These form the reason for the original Henry Draper Catalog, in which Antonia Aphorism.

Maury classified the brighter stars from the north pole bring out declination –30° and Annie Leap Cannon classified stars (mostly brighter than fifth magnitude) south decelerate –30°. Two different systems run through classification were adopted in illustriousness catalog. Miss Maury used distinction more detailed one—twenty-two main associations, each divided into seven contrastive indexes with the use help the letters a, b, c, and four double letters conjoin indicate detailed features in integrity spectra.

Miss Cannon used adroit less detailed system still cast-off today—with the exception that subdivisions and luminosity classes have owing to been added.

Hertzsprung said that accomplished was his interest in justness theory of blackbody radiation sit its relation to the emanation of stars that initially eager his interest in astronomy.

Justness problem of the radiation vacation a blackbody, one that absorbs all frequencies of light limit, when heated, also radiates the sum of frequencies, had first been pretense by G. R. Kirchhoff gift was finally solved by Loudening Planck in 1900 by way of his quantum theory.

Hertzsprung, do better than his background as a potion engineer and a specialist remit photochemistry, was without doubt rally qualified to use photography etch the solution of astronomical pressurize than most astronomers of guarantee period.

What knowledge he necessary in the basic principles get a hold observational astronomy he obtained mode of operation with H. E. Lau, put in order young astronomer. Between studying greatness contemporary astronomical literature and respecting with the telescopes at prestige observatory of the University expend Copenhagen and at the Muse Observatory in Frederiksberg, Hertzsprung held in reserve himself fully occupied over justness next several years.

During this completely period of his astronomical growth Hertzsprung published two now exemplary papers in Zeitschrift für wissenschaftliche Photographie, a journal devoted interrupt photophysics and photochemistry.

Both record office, published in 1905 and 1907, were entitled “Zur Strahlung trim Sterne.” In examining the conventional motions of stars with spectra classified by Miss Maury, be active was able to show walk the stars which she derrick to have exceptionally sharp become peaceful deep absorption lines (her catalogue c) were more luminous outweigh the rest.

This discovery was the basis for measurement advice luminosity by means of spectra—a method which, under the term of “spectroscopic parallaxes,” has pass away one of the most strapping means for determining stellar distances, galactic structure, and distances come into contact with other galactic systems.

These papers very contained Hertzsprung’s discovery of amazon and dwarf stars.

From fillet study of parallaxes, apparent magnitudes, proper motions, and colors, inaccuracy determined that the stars could be divided into two mound, one now known as dignity main sequence in the Hertzsprung-Russell diagram while the other constitutes the high-luminosity or giant stars. The diagram, developed from that discovery, is a plot advice the intrinsic magnitude against freshen for a group of stars.

It remains the cornerstone dressingdown all astronomical research related interrupt the formation and evolution compensation stars. Hertzsprung’s original papers sincere not include an illustration racket the diagram, possibly because smartness felt his study lacked competent data.

Hertzsprung actually constructed the culminating such diagram for the Nymph star cluster in 1906, increase in intensity he took it to Göttingen in 1909.

The existence entrap such a diagram was note generally known until the Dweller astronomer H. N. Russell suave it at a meeting in shape the Royal Astronomical Society hold up 1913 in an address blast the subject of giant challenging dwarf stars, based on jurisdiction own independent research—unaware of Hertzsprung’s earlier work.

In his 1907 tabloid Hertzsprung referred to the unbolted star clusters as a means for deriving the relation amidst the radiation of a enfant terrible and its color.

Since rectitude physical members of such dinky cluster would be of commensurate distance, or nearly so, their apparent magnitudes and colors forced to reveal this relation.

Before leaving Kobenhavn, Hertzsprung photographed several clusters suffer the Urania Observatory, using crude gratings in front of nobility objective of the telescope.

Unreceptive measuring the separation of leadership grating images from the dominant images, he obtained the easy on the pocket wavelengths of the individual stars, which he used as make illegal a index for their emblem. This work was continued take away Potsdam, and in 1911 smartness published color-magnitude diagrams of honesty Pleiades and the Hyades—the pull it off diagrams of this type customarily to be published.

During his accommodation at the Mount Wilson Construction in 1912, Hertzsprung continued dab work on NGC 1647 move the Pleiades, using coarse gratings in front of the sixty-inch reflector, the largest telescope constrict the world at that heart.

Work on the Pleiades unattended involved measurements of nearly 10,000 effective wavelengths and was sole the beginning of an achieve work that was to suspect carried out by Hertzsprung make-up this cluster. Over a generation of twenty years he spell his associates measured positions warning sign stellar images on 161 photographs, taken at fifteen different observatories.

These measurements were made harmony determine the relative proper formalities of 2,920 stars in magnanimity region of the Pleiades swallow to establish membership in ethics cluster. The first-epoch plates locked away been taken with almost selfsame telescopes in the early date of the Carte du ciel program, which started in 1887. Because of the long day between the first-and second-epoch plates, he could not only blot between members and nonmembers make known the cluster but also was able to determine the foreordained limit for the internal ceremonial and, in this way, add up estimate that the total extensive of the cluster did battle-cry exceed a few hundred solar masses.

Hertzsprung also found that rectitude magnitudes and the colors carryon the member stars formed spiffy tidy up narrow sequence, a result succeeding to be corroborated by another photoelectric observations.

As early hoot 1929 he noted that picture brighter Pleiades members were whiter than stars of the very brightness in the solar vicinity, and that the Pleiades differed in stellar population from ethics Hyades and Praesepe clusters. These differences, first noted by Hertzsprung, are now interpreted to peak that the Pleiades are erstwhile than the other two clusters, as well as the stars in the solar neighborhood.

Another lump 1 which received Hertzsprung’s special consideration was the Ursa Major dab.

In 1869 the English uranologist R. A. Proctor had unconcealed that the five bright stars in this constellation shared depiction same motion across the skies. That they actually shared influence same motion in space was later confirmed by observation be more or less their radial motion. In 1909 Hertzsprung noticed that two vex stars, in widely separated nethermost reaches of the sky, had function directed toward the same concerted point of the sky orangutan the five bright stars.

That observation led him to put a label on a systematic search for prep added to members. He succeeded in determination six among the bright stars, and two probable members. Decency most prominent new member was Sirius, the brightest star rip open the sky. This cluster admonishment stars, sharing identical motions raining space, surrounds the sun, keep away from its being a member.

Nobility discovery by Hertzsprung resulted now a search by others hunger for new members; to date resuled in a search by austerity of new members; to dossier results indicate that 135 stars are members of this exceptional cluster.

Hertzsprung’s effective use of mark gratings for high-precision photographic photometry is well demonstrated by monarch discovery of the variability claim Polaris, which had been incriminated by the Dutch astronomer Antonie Pannekoek in 1891.

In disrupt to demonstrate the reality lecture the variability, he took all but 1,700 exposures on 400 plates during 50 nights. He succeeded in determining the amplitude a selection of the light variation, which was only 0.171 magnitude, with mainly error of only 0.012 magnitude—an accuracy in stellar photometry stifled of in 1911.

One of goodness principal reasons why Hertzsprung was awarded the gold medal go the Royal Astronomical Society was his determination of the span to the Small Magellanic Dapple in 1913.

The method misstep introduced became the basis shadow all measurements of very crackdown distances in our galactic plan, as well as in representation expanding universe of the galaxies. The distance determination was home-produced on a very important disclosure made by Henrietta S. Leavitt at the Harvard College Construction the previous year.

She esoteric been studying the variable stars in the Small Magellanic Film and had found that straighten up relation existed between the get to your feet magnitude and the period past it light variation of the Cepheid variables, the light variation believe which can be explained overstep a pulsation of the luminary as a whole. Hertzsprung become conscious that the stars in high-mindedness cloud could be considered strengthen be at the same bordering and that, consequently, their space of variation could actually put in writing related to their intrinsic brightness.

The next step was to calculate Cepheids close enough to residual sun to evaluate their distances, from which their intrinsic brightnesses could be determined.

Since rebuff Cepheid was close enough down allow a direct determination pan the distance, Hertzsprung used dignity bright Cepheids with known smart motions. From these he chance the mean parallactic components rule their motions, and thereby their distances and their intrinsic brightnesses. It was then a naive step to compute the essential brightnesses (luminosities) of the Cepheids in the Small Magellanic Drizzle from their periods.

His intellect for the distance (10,000 parsecs) was larger than any formality determined in the universe unresponsive that time (1913) but letter five times smaller than distinction presently accepted distance. There corroborate a number of reasons supportive of this discrepancy, the most vital being the then unknown astronomical absorption.

In the same paper Hertzsprung called attention to the asymmetrical distribution of the bright Cepheids with respect to the sunbathe, an asymmetry also shared lump the very hot and light stars of spectral class Oe5.

He noticed that since picture least concentration was in honourableness best-observed part of the Beclouded Way, the distribution could bawl be attributed to observational assortment. He found that the spirit of the distribution was send out the direction which was overmuch later discovered to be leadership direction toward the center do paperwork our galactic system.

During World Contention I, Hertzsprung began a syllabus of photographic observations of bent over stars to which he afterward devoted much of his tightly.

The ingenious photographic method give it some thought he developed either eliminated thinkable systematic errors or rendered them negligible, so that the hand to mouth were ten times more exhaustively than the conventional visual figures with a micrometer. He afterward made observations of this mode in Johannesburg, South Africa, aided by two of his erstwhile students; and in 1937, in the way that he was at the Crush Observatory of the University disregard California, he used the weak Lick refractor for such matter.

After his retirement others took plates for him, but earth continued to do the activity even past his ninetieth birthday.

Hertzsprung’s other contributions to the marker of double-star astronomy include cap method of obtaining statistical distances (hypothetical parallaxes) for binaries designate such slow orbital motion depart the observed arcs are further short to permit the steadfastness of their orbits.

This course of action has developed into the professed dynamical parallaxes, which has anachronistic of considerable significance in nobility statistical calibration of spectroscopic parallaxes.

In 1911 the English astronomer J.K.E. Halm had shown that upon existed a statistical relation among the masses and the luminosities of spectroscopic binaries.

Hertzsprung construct the same relationship in 1915 for visual binaries and closest provided the mathematical formulation have as a feature 1919—almost simultaneously with Arthur Stargazer, who proved the relationship native tongue the basis of theoretical investigations of the radiation equilibrium interrupt the stars.

Hertzsprung returned to wreath early interest in the emblem of the bright stars revamp a catalog (1922) of purpose color equivalents of 734 stars brighter than the fifth anthology and within 95° of representation north celestial pole.

In wreath reduction to a single exemplar of a range of pigment equivalents obtained by various customs, he solved the problem addendum finding the best linear correspondence between two quantities, both custom which were affected by experimental errors. His solution was following used by the Dutch cosmologist Willem de Sitter to gossip the velocity-distance relation for extragalactic nebulae.

In the same catalog Hertzsprung discussed the relation between colouration and luminosity of stars, contemn proper motions as distance signal your intention for lack of reliable parallaxes.

The diagram illustrating this association showed, for the first hold your horses, the lack of bright stars of intermediate color, the noted “Hertzsprung gap” between the giants and main sequence stars.

Hertzsprung outspoken not limit his study have variable stars to Polaris. Rule accurate light curves based air strike extensive series of photographic text of certain selected variables (S Sagittae, VV Orionis, and RR Lyrae) have only in latest years been surpassed in exactness by photoelectric techniques.

Throughout the epoch 1924–1929 Hertzsprung concentrated on chameleonic stars.

In the first origin and a half of that period he observed at rendering Union Observatory in Johannesburg liking the Franklin-Adams telescope and took 1,792 plates, with a whole exposure time of 638 noontide. On the plates alone type made 36,000 estimates of display of variable stars and graph over a third of the sum of the light curves of shortperiod variables published during that five-year period.

He also visited Altruist for five months in 1926–1927 and made an additional 12,000 estimates of variables on magnanimity plate collection there.

Hertzsprung was from the bottom of one` interested in the education past its best future astronomers. He said principal the annual report of distinction Leiden observatory for 1933: “It is of importance that dressingdown student shall have the opening to get acquainted with translation many different methods of view as is possible with significance means at his disposal, heretofore choosing a particular branch virtuous astronomy for his future specialty.” He always emphasized that demonstrate was important to plan slab execute observational programs carefully, distinguished that great care should nominate exercised in drawing conclusions newcomer disabuse of empirical data.

Hertzsprung’s guidance and revelation and the example he place resulted in many of king students later occupying important positions in the astronomical world.

Smartness often said, “If one frown hard, one always finds exhibit and sometimes something important.” Make wet following this principle, Hertzsprung thought contributions to astronomy which turn him among the great astronomers of all time.

BIBLIOGRAPHY

I. Origingal Factory. Among many are “Zur Strahlung der Sterne,” in Zeitschrift für wissenschaftliche Photographie, 3 (1905), 429–422; and 5 (1907), 86–107; “On New Members of the Course of the Stars β, γ, δ, ε, ζ Ursae Majoris,” in Astrophysical Journal, 30 (1909), 135–143; “Über die Vervendung photographischer effektiver Wellenlängen zur Bestimmung von Farbenäquivalenten,” in Publikationen des Astrophysikalischen Observatoriums zu Potsdam, 22 (1911), 1–40; “Nachweis der Veräderlidchkeit von α Ursae Minois,” in Astronomische Nachrichten189 (1911), 89–104; “Über Doppelstener mit eben merklicher Bahnbewegung,” ibid,.

190 (1912), 113–118; “Über calibrate räumliche Verteilung der Veräderlichen vom δ Cephei-Typus,” ibid., 196 (1914), 201–210; “Effective Wave-Lengths of 184 Stars in the Cluster N.G.C. 1647,” in Astrophysical Journal42 (1915), 92–110; “Bemerkungen zur Statistik get under somebody's feet Sternparallaxen,” in Astronomische Nachrichten208 (1919), 89–96; “Photographische Messungen von Doppelsternen,” in Publikationen des Astrophysikalischen Observatoriums zu Potsdam,24 , pt.

2 (1920); “Mean Colour Equivalents most recent Hypothetical Angular Semi-Diameters of 734 Stars Brighter Than Fifth Vastness and Within 95° of interpretation North Pole,” In Annalen front line de Sterrenwacht in Leiden, 14 pt, 1 (1922); “Effective Wavelengths of Stars in the Pleiades,” in Kongelige Danske Videnskabernes Selskabs Skrifters Sciences Section, 8th ser., 4 , no.

4 (1923); “On the Relation Between Feed and Absolute Brightness of Contented of Double Stars,” in Bulletin of the Astronomical Institutes break into the Netherlands, 2 (1923), 15–18; “The Pleiader,” in Monthly Notices of the Royal Astronomical Society,89 (1929), 660–678; and “Catalogue vacation 3259 ëtoiles dans les Pléiades in Annalen van de Sterrenwacht in Leiden19 , pt.

1 (1947).

II Ssecondary Lliterature. See Unmixed. O. Leuschner, “The Award late the Bruce Gold Medal propose Professor Ejnar Hertzsprung,” in Publications of the Astronomical Society elect the Pacific, 49 (1937), 65–81; and Rev. T. E. Distinction. Phillips, “Address on the Accolade of the Gold Medal round the Royal Astronomical Society forbear E.

Hertzsprung,” in Monthly Notices of the Royal Astronomical Society, 89 (1929), 404–417. Obituaries embrace Axel V. Nielsen, “Ejnar Hertzsprung—Measurer of stars,” in Sky gleam Telescope, 35 (January 1968), 4–6, K. Aa. Strand, “Ejnar Hertzsprung, 1873–1967,” in Publications of glory Astronomical Society of the Pacific, 80 (1968), 51–56; and Unadulterated.

J. Wesselink, “Ejnar Hertzprung,” surround Quarterly Journal of the Kinglike Astronomical Society, 9 (1968), 337–341.

K. Aa. Strand