See also:

• STANZA (Low Lat. stantia, Ital. stantia or stanza)

STANZA (See also:

• LOW, SETH (1850- )
• LOW, WILL HICOK (1853- )

Low See also:

• LAT

Lat. stantia, Ital. stantia or stanza)  , properly an apartment or See also:

• STOREY (equivalents are Fr. etage, Ital. piano, Ger. Stock)

storey in a See also:

• HOUSE
• HOUSE (O. Eng. hiss, a word common to Teutonic languages, cf. Dut. huis, Ger. Haus; in Gothic it is only found in gudhiss, a temple; it may be ultimately connected with the root of " hide," conceal)

house, the See also:

• TERM

term being hence adopted for See also:

• LITERARY

literary purposes to denote a See also:

• COMPLETE

complete See also:

• SECTION
• SECTION (Lat. sectio, cutting, secare, to cut)

section, of recurrent See also:

• FORM (Lat. forma)

form, in a poem . . A See also:

• STANZA (Low Lat. stantia, Ital. stantia or stanza)

stanza is a See also:

• STROPHE (Gr. o-rpod>)

strophe of two or more lines, The See also:

• GREEK
• GREEK, ETRUSCAN AND

Greek is &drip, and the See also:

• SANSKRIT

Sanskrit See also:

• LAVA

lava, for stara . The ultimate See also:

• ROOT (late O.E. rot, adopted from Scand., cf. Norw. and Swed. rot, Dan. rod; the true O.E. word was wyrt, plant, represented in Ger. Wurz or Wurzel; the ultimate root is the same in both words, and is seen in Lat. radix)
• ROOT, ELIHU (1845– )

root is unknown, but may be connected with that meaning " to strew," and the word would thus mean the points of See also:

• LIGHT

light scattered over the heavens . The study of the stars is coeval with the See also:

• BIRTH (a word common in various forms to Teutonic languages from the root of the verb " to bear ")

birth of See also:

• ASTRONOMY (from Gr. &arpov, a star, and v ,usiv, to classify or arrange)

astronomy (see ASTRONOMY: See also:

• HISTORY

History); and among the earliest civilizations beneficent or malevolent influences were as-signed to them (see See also:

• ASTROLOGY

ASTROLOGY) . With the development of observational astronomy the sidereal universe was arbitrarily divided into areas characterized by See also:

• SPECIAL

special assemblages of stars; these assemblages were named asterisms or constellations, and each received a name suggested by mythological or other figures . The heavenly bodies fall into two classes: (1) the fixed stars, or stars proper, which retain the same relative position with respect to one another; and (2) the See also:

• PLANETS, MINOR

planets, which have motions of a distinctly individual See also:

• CHARACTER (Gr. xapareri7p, from xap&crew, to scratch)

character, and appear to wander among the stars proper . Numerous See also:

• COUNTS

counts of the number of stars visible to the naked See also:

• EYE
• EYE (O. Eng. edge, Ger. Auge; derived from an Indo-European root also seen in Lat. oc-ulus, the organ of vision (q.v.)

eye have been made; it is doubtful whether more than 2000 can be seen at one See also:

• TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
• TIME, MEASUREMENT OF
• TIME, STANDARD

time from any position on the See also:

• EARTH
• EARTH (a word common to Teutonic languages, cf. Ger. Erde, Dutch aarde, Swed. and Dan. jord; outside Teutonic it appears only in the Gr. 'pq'e, on the ground; it has been connected by some etymologists with the Aryan root ar-, to plough, which is seen in
• EARTH, FIGURE OF
• EARTH, FIGURE OF THE

earth . When a, See also:

• TELESCOPE

telescope is employed this number is enormously in-creased, and still more so with the introduction of photographic methods; with See also:

• MODERN

modern appliances more than a See also:

• HUNDRED

hundred million of these See also:

• OBJECTS

objects may be rendered perceptible . The recognition of See also:

• STAR

star's is primarily dependent on their brightness or " magnitude "; and it is clear that stars admit of See also:

• CLASSIFICATION (Lat. classis, a class, probably from the root cal-, cla-, as in Gr. icaMce, clamor)

classification on this basis . This was attempted Number and by See also:

• PTOLEMY (CLAUDIUS PTOLEMAEUS)

Ptolemy, who termed the brightest stars "of the Magnitude From the value of the light-ratio we can construct a table showing the number of stars of each magnitude which would together give as much light as a first magnitude star, viz.: I 21 6 16 40 See also:

• I00

I00 Comparing these figures with the See also:

• NUMBERS, BOOK OF
• NUMBERS, PARTITION OF

numbers of stars of each magnitude we See also:

• NOTICE

notice that the See also:

• TOTAL

total light emitted by all the stars of a given magnitude is fairly See also:

• CONSTANT, BENJAMIN (1845-1902)

constant . Variable Stars.—Although the See also:

• MAJORITY (Fr. majorite; Med. Lat. majoritas; Lat. major, greater)

majority of the stars are unchanging in magnitude, there are many exceptions . Stars whose brightness fluctuates are called variable stars .

The number of known objects of this class is being added to rapidly, and now amounts to over 4000 . The systematic See also:

• SEARCH, or VISIT AND SEARCH

search made at Harvard See also:

• OBSERVATORY

Observatory is responsible for a large proportion of the See also:

• RECENT

recent discoveries . Many of these stars seem to vary quite irregularly; the changes of magnitude do not recur in any orderly way . Others, however, are periodic, that is to say, the sequence of changes is repeated at See also:

• REGULAR

regular intervals, and it is thus possible to predict when the maximum and minimum brightness will occur . Of the periodic variable stars, the lengths of the periods range from 3 See also:

• HOURS, CANONICAL

hours 12 minutes, which is the shortest yet determined, to 6,o days, the longest . When See also:

• STATISTICS

statistics of the lengths of the periods are collected, it is at oncenoticed that they fall into two fairly well-marked classes . The following table, based on S . C . See also:

• CHANDLER, HENRY WILLIAM (1828-1889)
• CHANDLER, RICHARD (1738-1810)
• CHANDLER, SAMUEL (1693-1766)
• CHANDLER, ZACHARIAH (1813-1879)

Chandler's "Third See also:

• CATALOGUE (a Fr. adaptation of the Gr. KaraXoyos, a register, from Karalyety, to enrol or pick out)

Catalogue" (Astronomical See also:

• JOURNAL
• JOURNAL (through Fr. from late Lat. diurnalis, daily)

Journal, vol. xvi.)," supplemented by A . W . See also:

• ROBERTS, DAVID (1796-1864)
• ROBERTS, FREDERICK SLEIGH ROBERTS, EARL

Roberts's See also:

• LIST (O.E. lisle, a Teutonic word, cf. Dut. lust, Ger. Leiste, adapted in Ital. lista and Fr. lisle)
• LIST, FRIEDRICH (1789-1846)

list of See also:

• SOUTHERN

southern variables (ibid. vol. xxi.), classifies the lengths of the periods of 330 stars . It will be noticed that there are very few periods between 50 and 15o days, that a considerable number are less than 5o days (actually a large majority of these are less than to days), and that from 150 days upwards the number of periods increases to a maximum at about 350 days and then diminishes .

We thus recognize two classes of variables, of which (I) the See also:

• LONG, GEORGE (1800-1879)
• LONG, JOHN DAVIS (1838– )

long-See also:

• PERIOD
• PERIOD (Gr. irepioSos, a going or way round, circuit, aepi, round, and &Sis, way, road)

period variables have periods ranging in See also:

• GENERAL
• GENERAL (Lat. generalis, of or relating to a genus, kind or class)

general from 15o to 450 days, though a few are outside these limits; and (2) the See also:

• SHORT, FRANCIS JOB (1857– )

short-period variables have periods less than 5o days (in the majority of cases less than lo days) . There is some over-lapping of these two classes as regards length of period, and it is doubtful in which class some stars, whose periods are between lo days and 150 days, should be placed; but the two classes are quite distinct physically, and the variability depends on entirely different causes . Long-period Variables.—The best known and typical star of this class is Mira or o Ceti . This was the first variable star to be discovered, having been noticed in 1596 by See also:

• DAVID
• DAVID (a Hebrew name meaning probably beloved 1)
• DAVID, FELICIEN (1810—1876)
• DAVID, GERARD [GHEERAERT DAVIT], (?=1523)
• DAVID, PIERRE JEAN (1789–1856)
• DAVID, ST (Dewi, Sant)

David See also:

• FABRICIUS, GAIUS LUSCINUS (i.e. " the one-eyed ")
• FABRICIUS, GEORG (1516-1571)
• FABRICIUS, HIERONYMUS
• FABRICIUS, JOHANN ALBERT (1668-1736)
• FABRICIUS, JOHANN CHRISTIAN (1745-18o8)

Fabricius, who thought it was a new star (a Nova) . The varying brightness, ranging from the ninth to the second magnitude, was recognized in 1639 by See also:

• JOHN
• JOHN (1167–1216)
• JOHN (1290-c. 1320)
• JOHN (1296-1346)
• JOHN (1371–1419)
• JOHN (1468-1532)
• JOHN (1801-1873)
• JOHN (Heb. llni')
• JOHN (ZAPOLYA) (1487-1540)
• JOHN, 4TH MARQUESS OF TWEEDDALE (c. 1695-1762)
• JOHN, DON (1545-1578)
• JOHN, DON (1629–1679)
• JOHN, GOSPEL OF ST
• JOHN, or HAYS (1513–1571)
• JOHN, THE APOSTLE
• JOHN, THE EPISTLES OF

John See also:

• PHOCYLIDES

Phocylides Holwarda, and in 1667 Ismael Boulliau (1605–1694) established a periodicity of 333 days . Although the periodic outbursts of light have taken See also:

• PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place without intermission during the two and a See also:

• HALF

half centuries that the star has been under observation, they are somewhat irregular . The different See also:

• MAXIMA

maxima differ considerably in brightness; thus in 1906 (the brightest maxi-mum since 1779) the second magnitude was reached, but in other years (as in 1868) it has failed to reach the fifth magnitude . The minima likewise are variable, but only slightly so . Also, the period varies somewhat; the maxima occur sometimes See also:

• EARLY
• EARLY, JUBAL ANDERSON (1816-1894)

early and sometimes See also:

• LATE

late as compared with the mean period, but the difference is never more than See also:

• FORTY

forty days . No general See also:

• LAW
• LAW (0. Eng. lagu, M. Eng. lawe; from an old Teutonic root lag, " lie," what lies fixed or evenly; cf. Lat. lex, Fr. loi)
• LAW, JOHN (1671—1729)
• LAW, WILLIAM (1686-1761)

law has been discovered governing these irregularities . The See also:

• CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)

change of magnitude takes place gradually, but the rise to maximum brilliance is rather more rapid than the decline . Spectroscopic observation shows that the in-creased light accompanies an actual See also:

• PHYSICAL

physical change or conflagration in the star .

The spectrum is of the third type with See also:

• BRIGHT, JOHN (1811-188g)
• BRIGHT, SIR CHARLES TILSTON

bright See also:

• HYDROGEN [symbol H, atomic weight x-oo8 (0=16)]

hydrogen emission lines (see below, Spectra of Stars) . Stars having this type of spectrum are always variable, and a large proportion of the more recently discovered long-period variables have been detected through their characteristic spectrum . x Cygni is another star of this class, remarkable for its range of magnitude . In its period of 406 days it fluctuates between the thirteenth and the See also:

• FOURTH

fourth magnitudes; thus at maximum it emits 4000 times as much light as at minimum . The mean range of 75 long-period variables observed at Harvard (Harvard See also:

• ANNALS (Annales, from annus, a year)

Annals, vol . Ivii.) was five magnitudes . Another variable, R Normae L is of See also:

• INTEREST

interest as having a pronounced See also:

• DOUBLE
• DOUBLE (from the Mid. Eng. duble, the form which gives the present pronunciation, through the Old Er. duble, from Lat. duplus, twice as much)

double maximum in each period . It is natural to compare the periodic outbursts occurring in these stars with the outbursts of activity on the See also:

• SUN
• SUN (0. Eng. sonne, Ger. sonne. Fr. soleil, Lat. sol, Gr. ijXior, from which comes helio- in various English compounds)

sun, which have a period of about eleven years . In both cases no extraneous cause can be assigned; the period seems to be inherent in the star itself and not to be determined by the revolution of a See also:

• SATELLITE (from the Lat. satelles, an attendant)

satellite (no variability of the See also:

• LINE

line-of-sight See also:

• MOTION (Lat. motio, from movere, to move)
• MOTION, LAWS OF

motion of Mira has been found, so that it is probably not accompanied by any large See also:

• COMPANION (through the O. Fr. compaignon or compagnon, from the Late Lat. companio,—cum, with, and panis, bread,—one who shares meals with another; the word has been wrongly derived from the Late Lat. compagnus, one of the same pages or district)

companion) . In both cases the rise to a maximum is more rapid than the decline to a minimum, and in fact some of the See also:

• MINOR
• MINOR (Lat. for smaller, lesser)
• MINOR, ROBERT CRANNELL (1839-1904)

minor peculiarities of the sunspot See also:

• CURVE (Lat. curvus, bent)

curve are closely imitated by the light-curves of variable stars . H . H .

See also:

• TURNER, CHARLES (1773–1857)
• TURNER, JOSEPH MALLORD WILLIAM (1775–1851)
• TURNER, NAT (1800-1831)
• TURNER, SHARON (1768-1847)
• TURNER, SIR JAMES (1615–1686)
• TURNER, WILLIAM (d. 1568)

Turner has analysed harmonically the light-curves of a number of long period variables, and has shown that when they are arranged in a natural See also:

• SERIES (a Latin word from serere, to join)

series the sun takes its place in the series near, but not actually at, one end . It is necessary to suppose, if the See also:

• ANALOGY (Gr. avaXo-yLa, proportion)

analogy is to hold, that the sun is brightest when sunspots and faculae are most numerous; this is by no means unlikely . On the other See also:

• HAND
• HAND (a word common to Teutonic languages; cf. Ger. Hand, Goth. handus)
• HAND, FERDINAND GOTTHELF (1786-185r)

hand, the See also:

• VARIATIONS
• VARIATIONS, CALCULUS
• VARIATIONS, CALCULUS OF

variations in the light of the sun must be very small compared with the enormous fluctuations in the light of variable stars . Moreover, the See also:

• SOLAR, SOLLER (Lat. solarium, Fr.• galetas, Ital. solaio)

solar period (II years) is far outside the limits of the periods of 1 Variable stars (except those sufficiently bright to have received special names) are denoted by the See also:

• CAPITAL (i.e. capital stock or fund)
• CAPITAL (Lat. caput, head)

capital letters R to Z followed by the name of the See also:

• CONSTELLATION (from the Lat. constellatus, studded with stars; co'n, with, and Stella, a star)

constellation . The first nine variables recognized in each constellation are denoted by single letters, after which combinations RR, RS, &c:, are used . 1st mag . 14 2nd mag . 3rd mag . 4th mag . 5th mag . 6th mag . 20I0 152 48 854 313 1st mag .

2nd mag . 3rd mag . 4th mag . 5th mag . 6th mag . 0/the Stars. first magnitude," and the progressively fainter of the S stars of progressively greater magnitude . Ptolemy's classification has been adopted as the basis of the more exactly quantitative modern See also:

• SYSTEM

system . In this system one star is defined to be unit magnitude higher than another if its light is less in the ratio 1:2.512 . This ratio is adopted so that a difference of five magnitudes may correspond to a light-ratio of 1 : too . This subject is treated in the See also:

• ARTICLE (from Lat. articulus, a joint)

article See also:

• PHOTOMETRY (from Gr. (Pews, xarrbs, light, µerpov, a measure)

PHOTOMETRY, See also:

• CELESTIAL, OR STELLAR

CELESTIAL . The faintest stars visible to the naked eye on clear nights are of about the See also:

• SIXTH

sixth magnitude; exceptionally keen, well-trained eyes and clear moonless nights are necessary for the See also:

• PERCEPTION (from Lat. percipere, to perceive)

perception of stars of the seventh magnitude . According to E .

Heis the numbers and magnitudes of stars between the See also:

• NORTH
• NORTH, BARONS
• NORTH, MARIANNE (1830—1890)
• NORTH, ROGER (1653-1734)
• NORTH, SIR THOMAS (1535?-16o1?)

north See also:

• POLE (FAMILY)
• POLE, REGINALD (1500-1558)
• POLE, RICHARD DE LA (d. 1525)
• POLE, WILLIAM (1814—1900)

pole and a circle 350 See also:

• SOUTH
• SOUTH, ROBERT (1634–1716)

south of the See also:

• EQUATOR (Late Lat. aequator, from aequare, to make equal)

equator are: Period o 50 See also:

• LOO (formerly called " Lanterloo," Fr. lanturlu, the refrain of a popular 17th-century song)

loo 150 200 250 300 350 400 450 5o0 550 600 in to to to to to to to to to to to to to days 50 100 15o 200 250 300 350 400 450 500 550 600, 650 Stars 73 8 12 22 41 45 49 50 20 6 I 2' I variables . It is therefore perhaps misleading actually to class the sun with them; but it seems highly probable that whatever cause produces the periodic outbursts of spots and faculae on our sun differs only in degree from that which, in stars under a different physical See also:

• CONDITION (Lat. condicio, from condicere, to agree upon, arrange; not connected with conditio, from condere, conditum, to put together)

condition of pressure and temperature, results in the gigantic conflagrations which we have been considering . Short-period Variables.—Besides the shortness of the period these variables possess other characteristics which differentiate them from the long-period variables . The range of variation is much smaller, the difference between maximum and minimum rarely exceeding two magnitudes . Also the variations recur with perfect regularity . There is See also:

• REASON (Lat. ratio, through French raison)

reason to believe that all the stars of this class are binary systems, and that the variations of brightness are deter-See also:

• MINED

mined by the different aspects presented by the two component stars during the period of revolution . There are several well-marked varieties of short-period variables; the most important are typified by the stars See also:

• ALGOL

Algol, 13 Lyrae, I- Geminorum and S Cephei . In the Algol variables one of the component stars is dark (that is to say, dark in comparison with the other), and once in each revolution, passing between us and the bright component, partially hides it . This class of variables is accordingly characterized by the fact that for the greater See also:

• PART

part of the period the star shines steadily with its maximum brilliancy, but fades away for a short time during each period . The variability of Algol ($ Persei) was discovered in 1783 by John Goodricke (1764–1786), but, judging from its name, which signifies " the demon," it seems possible that its peculiarity may have been known to the See also:

• ANCIENT
• ANCIENT (also spelt ANTIENT; derived, through the Fr. ancien, old, from the late Lat. antianum, from ante, before)

ancient astronomers . Algol is ordinarily of magnitude 2.3, but once in a period of 2d . 2oh .

49m. it suffers partial See also:

• ECLIPSE (Gr. €uheo,tis, falling out of place, failing)

eclipse and fades to magnitude 3'5 . The duration of each eclipse is 91 hours . Ever since the variability of Algol was observed it was suspected to be due to a partial eclipse of the star by a dark See also:

• BODY

body nearly as large as itself revolving See also:

• ROUND (O. Fr. rond, Lat. rotundus, the Fr. is the source also of Du. rond; Ger., Swed., Dan. and Nor. rond)

round it; but the explanation remained merely a surmise until K . H . See also:

• VOGEL, EDUARD (1829-1856)
• VOGEL, SIR JULIUS (1835-1899)

Vogel of See also:

• POTSDAM

Potsdam, by repeated measurements of the motion of Algol in the line of sight, showed that the star is always receding from us before the loss of light and approaching us afterwards . This leaves no See also:

• ROOM

room for doubt that an invisible companion passes between us and Algol about the time the diminution of light takes place, and so proves the correctness of the explanation . The dimensions of the Algol system have been calculated, with the result that Algol appears to have:a See also:

• DIAMETER (from the Cr. &a, through, µErpov, measure)

diameter of 1,000,000 m. and its companion a diameter of 830,000 m.; the distance between their centres cannot be deduced without making certain doubtful assumptions, but may be about 3,000,000 m . When this distance is compared with those prevailing in the solar system, it seems an extraordinarily small separation between two such large bodies; we shall, however, presently come across systems in which the two components revolve almost or actually in contact . About 56 Algol variables were known in 1907; the variables of this class are the most difficult to detect, for the short period of obscuration may easily See also:

• ESCAPE (in mid. Eng. eschape or escape, from the O. Fr. eschapper, modern echapper, and escaper, low Lat. escapium, from ex, out of, and cappa, cape, cloak; cf. for the sense development the Gr. iichueoOat, literally to put off one's clothes, hence to sli

escape notice unless the star is watched continuously . The variable star Lyrae, which is typical of another class, was also discovered by Goodricke in 1784 . It differs from the Algol type in having two unequal minima separated by two equal maxima . Thus in a period of 12d .

22h• from a maximum of magnitude 3.4 it falls to 3.9, rises again to 3.4, then falls to 4.5 and returns to magnitude 3.4 . The changes take place continuously, so that there is no period of steady luminosity . The See also:

• HYPOTHESIS (from Gr. inrorcOivat, to put under; cf. Lat. suppositio, from sub-ponere)

hypothesis of G . W . See also:

• MYERS, FREDERIC WILLIAM HENRY (1843-1901)

Myers (Astrophysical Journal, vol. vii.) affords at least a partial explanation of the phenomena . Two stars are supposed to revolve about one another nearly or actually in contact . In such a system the tidal forces must be very See also:

• GREAT

great, and under their See also:

• INFLUENCE (Late Lat. influentia, from influere, to flow in)

influence the stars will not be spherical, but will be elongated in the direction of the line joining their centres . When the line of centres is at right angles to our line of sight, the stars See also:

• PRESENT

present to us their greatest apparent See also:

• SURFACE

surface, and therefore send us the maximum light . This happens twice in a revolution . As the line of centres becomes more oblique, the surface is seen more and more foreshortened and the brilliancy diminishes continuously . Supposing that the two stars are of unequal surface brilliancy, the magnitude at minimum will depend on which of the two stars is the nearer to us, accordingly there are two unequal minima in each revolution . When the two stars are of equal brilliancy the minima are equal; this is the See also:

• CASE
• CASE, JOHN (d. 1600)

case in variables of the Geminorum type .

When the orbits are See also:

• ECCENTRIC (from Gr. F,c, out of, and Kivrpov, centre)

eccentric, the tidal disturbance varying with the distance between the two components will probably cause changes in their See also:

• ABSOLUTE (Lat. absolvere, to loose, set free)

absolute brilliancy; the variation due to change in the aspect of the system presented to us may thus be supplemented by a real See also:

• INTRINSIC (through Fr. intrinsique, from Lat. intrinsecus, inwardly; inter, within, secus, following, from root of sequi, to follow)

intrinsic variation, both, however, being regulated by the orbital motion . A large eccentricity also produces an unsymmetrical light 'variation, the minimum occurring at a time not midway between two maxima ; stars. of this character are called Cepheid variables, after the typical star S Cephei . All the best-known short-period variables have been proved to be binary systems spectroscopically, and to have periods corresponding with the period of light variation, so that to this extent the hypothesis we have described is well founded; but it is doubtful if it is the whole explanation . S . Albrecht has shown that, of the 10 members of the S Cephei class for which both the orbits and the light-variations are thoroughly known, the maximum light always occurs approximately at the time when the brightercomponent is approaching us most rapidly; this relation, which seems to be well established, is a most perplexing, one . No hard and fast physical distinction can be See also:

• DRAWN

drawn between the various classes of short-period variables; as the distance between the components diminishes the Algol variable merges insensibly into the ti Lyrae type . The latter, on the other hand, is perhaps connected by insensible gradations with the See also:

• ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

ordinary See also:

• SIMPLE

simple star . See also:

• SIR

Sir G . H . See also:

• DARWIN, CHARLES ROBERT (1809-1882)
• DARWIN, ERASMUS (1731-1802)

Darwin and H . See also:

• POINCARE, RAYMOND (186o— )

Poincare have investigated the forms taken up by rotating masses of fluid . When the angular momentum is too great for the usual spheroidal form to persist, this gives place to an See also:

• ELLIPSOID

ellipsoid with three unequal axes; this is succeeded by a See also:

• PEAR (Pyrus communis)

pear-shaped form .

The subsequent sequence of events cannot be traced with certainty, but it seems likely that the pear-shaped form is succeeded by an See also:

• HOUR

hour-See also:

• GLASS
• GLASS (O.E. glees, cf. Ger. Glas, perhaps derived from an old Teutonic root gla-, a variant of glo-, having the general sense of shining, cf. " glare," " glow ")
• GLASS, STAINED

glass-shaped form, which finally separates at the See also:

• NECK (O. Eng. hnecca; the word appears in many Teutonic languages; cf. Dutch ride, Ger. Nacken; in O. E. the common word was heals; cf. Ger. Hals)

neck into two masses of fluid . Ellipsoidal, pear-shaped or hour-glassshaped stars would all give rise to the phenomena of a short-period variable, and doubtless examples of these intermediate forms exist . Certain clusters contain a remarkable number of short-period variables . Thus the cluster Messier 5 was found at Harvard to contain 185 variables out of 9900 stars examined . See also:

• SOLON (7th and 6th century n.c.)

Solon I . See also:

• BAILEY (said to be a corruption of Ballium by some, and derived by others from the Fr. baille, a corruption of bataille, because there the soldiers were drilled in battle array)
• BAILEY, NATHAN
• BAILEY, PHILIP JAMES (1816-1902)
• BAILEY, SAMUEL (1791-1870)

Bailey, on examining 63 of them, found that with one exception their periods See also:

• LAY

lay between 1oh . 48m. and 14h . 59.., and the range of variation between 0.7 and 1.4 magnitudes . Moreover, the light-curves were all of a See also:

• UNIFORM

uniform type, a distinctive feature of " cluster variables " being the rapid rise to a maximum and slow decline . Temporary Stars or Novas.—From time to time a star, hitherto too faint to be noticeable, blazes out and becomes a prominent See also:

• OBJECT

object, and then slowly fades into obscurity . According to See also:

• MISS

Miss See also:

• AGNES, SAINT

Agnes See also:

• CLERKE, AGNES MARY (1842-1907)

Clerke there are records of. ten such stars appearing between 134 B.C. and A.D . 1500 .

Since that time nine novas have appeared, which have attained naked-eye visibility; and in recent years a number of very faint objects of the same class have been detected . The brightest star of all these was the famous " Tycho's star " in See also:

• CASSIOPEIA

Cassiopeia . It was first observed on the 6th of See also:

• NOVEMBER (Lat. novem, nine)

November 1572 by Wolfgang Schuler . In five days its light had reached the first magnitude, and a little later it even equalled See also:

• VENUS

Venus in brilliancy and was observed in full daylight . After three See also:

• WEEKS, EDWIN LORD (1849-1903)

weeks it began to decline, but the star did not finally disappear until See also:

• MARCH
• MARCH (1) (from Fr. marcher, to walk; the earliest sense in French appears to be " to trample," and the origin has usually been found in the Lat. marcus, hammer; Low Lat. marcare, to hammer; hence to beat the road with the regular tread of a soldier: cf.
• MARCH, AUZIAS (c. "1395-1458)
• MARCH, EARLS OF
• MARCH, FRANCIS ANDREW (1825– )

March 1574 . " See also:

• KEPLER, JOHANN (1571-1630)

Kepler's " nova in Ophiuchus See also:

• BROKE, or BROOKE, ARTHUR (d. 1563)
• BROKE, SIR PHILIP BOWES VERE, BART

broke out in 1604 and attained a brightness greater than that of See also:

• JUPITER

Jupiter; it likewise gradually waned, and disappeared after about fifteen months . For nearly three centuries after these two remarkable stars no nova attained a brilliancy greater than that of the ordinary stars, until in 1901 Nova Persei appeared . This star was discovered by T . D . See also:

• ANDERSON
• ANDERSON, ADAM (1692—1765)
• ANDERSON, ALEXANDER (c. 1582-1620?)
• ANDERSON, ELIZABETH GARRETT (1836— )
• ANDERSON, JAMES (1662—1728)
• ANDERSON, JAMES (1739-1808)
• ANDERSON, JOHN (1726-1796)
• ANDERSON, MARY (1859– )
• ANDERSON, RICHARD HENRY (1821–1879)
• ANDERSON, ROBERT (1750–1830)
• ANDERSON, SIR EDMUND (1530-1605)

Anderson on the 21st–22nd of See also:

• FEBRUARY

February, its magnitude at that time being 2.7 . In the next two days it reached zero magnitude, thus becoming the brightest star in the See also:

• NORTHERN

northern heavens, but after that it rapidly decreased . On the 15th of March it was of the fourth magnitude; during the next three months it oscillated many times between magnitudes 4 and 6, and by the end of the See also:

• YEAR

year it had faded to the seventh magnitude .

In See also:

• JULY

July 1903 it was of the twelfth magnitude, and its light has remained constant since then . In the case of this star there is See also:

• EVIDENCE (Lat. evidentia, evideri, to appear clearly)

evidence that the outburst must have been extremely rapid, for the region where Nova Persei appeared had been photographed repeatedly at Harvard during February, and in particular no trace of the star was found on a See also:

• PLATE

plate taken on the 19th of February, which showed See also:

• ELEVENTH

eleventh magnitude stars . Thus a rise of at least eight magnitudes in two days must have occurred . On the 21st of See also:

• AUGUST (originally Sextilis)

August, six months after the See also:

• DISCOVERY

discovery of Nova Persei, C . Flammarion and E . M . Antoniadi discovered that a nebula surrounded it.' Subsequent photographs showed that this nebula, which consisted mainly of two incomplete rings of nebulosity, was expanding outwards at the See also:

• RATE

rate of from 2" to 3" per See also:

• DAY (O. Eng. dreg, Ger. Tag; according to the New English Dictionary, " in no way related to the Lat. dies")
• DAY, JOHN (1574-1640?)
• DAY, THOMAS (1748-1789)

day . This expansion continued at the same rate until the following year . Spectroscopic examination had already suggested prodigious' velocities of the See also:

• ORDER
• ORDER (through Fr. ordre, for earlier ordene, from Lat. ordo, ordinis, rank, service, arrangement; the ultimate source is generally taken to be the root seen in Lat. oriri, rise, arise, begin; cf. " origin ")
• ORDER, HOLY

order of 100o m. per second in the gases of the See also:

• ATMOSPHERE (Gr. fir µ6r, vapour; orkaipa, a sphere)

atmosphere of the nova; but the velocity implied by this expansion of the nebula was unprecedented and comparable only with the velocity of light . The See also:

• SUGGESTION

suggestion was made, and seems to be the true explanation, that what was actually witnessed was the See also:

• WAVE

wave of light due to the outburst of the nova, spreading outwards with its velocity of 186,000 m. per second, and rendering luminous as it reached them the particles of a pre-existing nebula, whose own light had been too faint to be visible . Two possible explanations of the phenomena of temporary stars have been held . The collision theory supposes that the outburst is the result of a collision between two stars or between a star and a swarm of meteoric or nebulous See also:

• MATTER

matter .

The See also:

• EXPLOSION

explosion theory regards the outburst as similar to the outbreak of activity of a long-period variable . Probably the latter hypothesis is the one more generally accepted now . There is one unique star, which is of special interest as occupying rather an intermediate position between a nova and a long-period variable . This is the southern star ri See also:

• ARGUS

Argus (sometimes called n Carinae) . From 1750 until about 1832 it seems to have varied irregularly between the second and the fourth magnitudes . For the next ten years it slowly increased (though with slight check), and in 1843 was nearly as bright as Sirius; since then it has slowly faded, but it was not till 1869 that it ceased to be visible to the naked eye . It is now about magnitude 7.5 . The slowness both of the rise and decline is in great contrast with the Double Stars cases the proximity is only apparent; one star may . be really at a vast distance behind the other, but, being in the same line of See also:

• VISION (from Lat. videre, to see), or SIGHT

vision, they appear See also:

• CLOSE
• CLOSE (from Lat. clausum, shut)
• CLOSE, MAXWELL HENRY (1822-1903)

close together . In many cases, however, two or more stars are really connected, and their distance from one another is (from the astronomical standpoint) small . The evidence of this connexion is of two kinds . In a number of cases See also:

• MEASURES

measures of the relative positions of the two stars, continued for many years, have shown that they are revolving about a See also:

• COMMON

common centre; when this is so there can be no doubt that they form a binary system, and that the two components move in elliptic orbits about the common centre of See also:

• MASS (O.E. maesse; Fr. messe; Ger. Messe; Ital. messa; from eccl. Lat. missa)
• MASS, IN

mass, controlled by their mutual See also:

• GRAVITATION (from Lat. gravis, heavy)

gravitation .

But these cases form a very small proportion of the total number of double stars . In many other double stars the two components have very nearly the same proper motion . Unless this is a See also:

• MERE
• MERE, ADALBERT (1838-1909)

mere coincidence, it implies that the two stars are nearly at the same distance from us . For otherwise, if they had from some unknown cause the same actual motion, the apparent motion in arc would be different . We can therefore infer that the two stars are really comparatively close together, and, moreover, since they have the same proper motion, that they remain close together . They may thus be fairly regarded as constituting a binary system, though the gravitational attraction between some of the wider pairs must be very weak . Several double stars were observed during the 17th See also:

• CENTURY (from Lat. centuria, a division of a hundred men)

century, Ursae Majoris being the first on See also:

• RECORD (Lat. recordari, to recall to mind, from cor, heart or mind)

record . In 1784 See also:

• CHRISTIAN
• CHRISTIAN, WILLIAM (1608-1663)

Christian See also:

• MAYER, JOHANN TOBIAS (1723-1762)
• MAYER, JULIUS ROBERT (1814-1878)

Mayer published a catalogue of all the double stars then known, which contained 89 pairs . Between 1825 and 1827 F . G . W . See also:

• STRUVE, FRIEDRICH GEORG WILHELM (1793-1864)

Struve at Dorpat examined 120,000 stars, and found 3112 double stars whose distance apart did not exceed 32" .

W . S . Burnham's General Catalogue of Double Stars (1907) contains 13,655 pairs north of See also:

• DECLINATION (from Lat. declinare, to decline)

declination -31 ° . Undoubtedly a large number of these are only See also:

• OPTICAL

optical pairs, but mere considerations of See also:

• PROBABILITY (Lat. probabilis, probable or credible)

probability show that the majority must be physically connected . For only 88 of them has it been possible as yet to deduce a period, and at least half even of these periods are very doubtful . The rates of motion are so slow that many centuries' observations are needed to determine the See also:

• ORBIT (from Lat. orbita, a track, orbis, a wheel)

orbit . The most rapid visual binary (leaving aside See also:

• CAPELLA, MARTIANUS MINNEUS FELIX

Capella for the moment) is b Equulei, which completes a 'See also:

• EVOLUTION

evolution in 5.7 years . Next to it come 13 Ceti, period 7.4 years, and K Pegasi, period 11.4 years . From a list of systems with determined periods given by Aitken (Lick Observatory Bulletin, No . 84) there are 20 with periods less than 5o years, and 16 between 5o and too years . S Equulei, 13 Ceti and K Pegasi are all extremely close pairs, and can only be resolved with the most powerful See also:

• INSTRUMENTS

instruments . Capella, whose period is only 104 days, was discovered to be double by means of the spectroscope, but has since been measured frequently as a visual binary at See also:

• GREENWICH

Greenwich .

With the best instruments a star can be distinguished as double when the separation of the two components is a little less than o• 1 " . From the very few orbits that have as yet been determined one interesting result has been arrived at . Most of the orbits are remarkably eccentric ellipses, the See also:

• AVERAGE

average eccentricity being about o.5 . There is a very striking relation between the eccentricity and the period of a system; in general the binaries of longest period have the greatest eccentricities . The relation applies not only to the visual but to the spectroscopic binaries; these, having shorter periods than the visual binaries, have generally quite small eccentricities . Another interesting feature is that, where the two components differ in brightness, the fainter component is often the one possessing the greater mass . Far within the limit to which telescopic vision can extend binary systems are now being found by the spectroscope . These systems Spectre- appear as a connecting See also:

• LINK

link between short-period ed variable stars on the one hand and telescopic double scopic Btaaries. stars on the other . Stars of the class to which the Algol type of variables belongs will appear to us to vary only in the exceptional case when the See also:

• PLANE

plane of the orbit passes so near our sun that one body appears to pass over the other and so causes an eclipse . Except when the line of sight is perpendicular to the plane of the orbit, the revolution of the two bodies will result in a periodic variation of the motion ;n the, line of sight . Such a variation can be detected by the spectroscope . If both the bodies are luminous, especially if they do not differ much in brilliancy, the motion of revolution is shown by a periodic doubling of the lines of the spectrum; when one body is moving towards us and the other away their spectral lines are displaced (according to Doppler's principle) in opposite directions, so that all the lines strong enough to appear in both spectra appear double; when the two bodies are inconjunction, and therefore moving transversely, their spectra are merged into one and show nothing unusual .

More usually, however, only one component is sufficiently luminous for its spectrum to appear; its orbital motion is then detected by a periodic change in the absolute displacement of its spectral lines . Up to 1905, 140 spectroscopic binaries had been discovered ; a list of these is given in the Lick Observatory Bulletin, no . 79 . Details of the calculated orbits of 63 spectroscopic binaries are given in Publications of the See also:

• ALLEGHENY

Allegheny Observatory, vol. i . No . 21 . According to W . W . See also:

• CAMPBELL, ALEXANDER (1788–1866)
• CAMPBELL, BEATRICE STELLA (Mrs PATRICK CAMPBELL) (1865– )
• CAMPBELL, GEORGE (1719–1796)
• CAMPBELL, JOHN
• CAMPBELL, JOHN (1708-1775)
• CAMPBELL, JOHN CAMPBELL, BARON (1779-1861)
• CAMPBELL, JOHN FRANCIS
• CAMPBELL, LEWIS (1830-1908)
• CAMPBELL, REGINALD JOHN (1867— )
• CAMPBELL, THOMAS (1777—1844)

Campbell one star in every seven examined is binary . A continuous gradation can be traced from the most widely separated visual binaries, whose periods are many thousand years, to spectroscopic binaries, Algol and /3 Lyrae variables, whose periods are a few hours and whose components may even be in contact, and from these to dumb-See also:

• BELL
• BELL, ALEXANDER MELVILLE (1819—1905)
• BELL, ANDREW (1753—1832)
• BELL, GEORGE JOSEPH (1770-1843)
• BELL, HENRY (1767-1830)
• BELL, HENRY GLASSFORD (1803-1874)
• BELL, JACOB (1810-1859)
• BELL, JOHN (1691-178o)
• BELL, JOHN (1763-1820)
• BELL, JOHN (1797-1869)
• BELL, ROBERT (1800-1867)
• BELL, SIR CHARLES (1774—1842)

bell shaped stars and finally to ordinary single stars . It is a legitimate See also:

• SPECULATION

speculation to suppose that these in the See also:

• REVERSE

reverse order are the stages in the evolution of a double star . As the simple star radiates See also:

• HEAT (0. E. haktu, which like " hot," Old Eng. hat, is from the Teutonic type haita, hit, to be hot; cf. Ger. hitze, heiss; Dutch, hitte, heet, &c.)

heat and contracts, it retains its angular momentum; when this is too great for the spheroidal form to persist, the star may ultimately See also:

• SEPARATE

separate into two components, which are driven farther and farther apart by their mutual tides .

Tidal See also:

• ACTION

action also accounts for the progressively increasing eccentricities of the orbits, already referred to . This theory of the See also:

• GENESIS
• GENESIS (Gr. 'ybeo-es, becoming; the term being used in English as a synonym for origin or process of coming into being)

genesis of double-stars by fission is not, however, universally accepted; in particular objections have been urged by T . C . Chamberlin and F . R . See also:

• MOULTON, LOUISE CHANDLER (1835-1908)

Moulton . It is true that rotational instability alone is not competent to explain the separation into two components; but the existence of gravitational instability, pointed out by J . H . Jeans, enables the See also:

• PRINCIPAL

principal difficulties of the theory to be surmounted . Whilst there is thus no well-defined See also:

• LOWER

lower limit to the dimensions of systems of two stars, on the other hand we cannot set any See also:

• SUPERIOR

superior limit either to the number of stars which shall form a system or to the dimensions of that system . No star is altogether removed from the attractions of its neighbours, and there are cases where some sort of connexion seems to relate stars which are widely separated in space . A curious case of this sort is that of the five stars 13, y, 5, e and of Ursa See also:

• MAJOR
• MAJOR (Lat. for " greater ")
• MAJOR (or MAIR), JOHN (1470-1550)

Major .

These have proper motions which are almost identical in amount and in direction . The agreement is too close to be dismissed as a mere coincidence, and it is confirmed by a corresponding agreement of. their radial motions determined by the spectroscope; and yet, seeing that /3 and i' Ursae Majoris are 19° apart, these two stars must be distant from each other at least one-third of the distance of each from the sun; thus the members of this singular See also:

• GROUP

group are separated by the ordinary stellar distances, and probably each has neighbours, not belonging to the system, which are closer to it than the other four stars of the group . Further, E . Hertzsprung has shown that Sirius also belongs to this same system and shares its motion, notwithstanding that it is in a nearly opposite part of the See also:

• SKY (M. Eng. skie, cloud; O. Eng. skua, shade; connected with an Indo-European root sku, cover, whence " scum," Lat. obscurus, dark, &c.)

sky . It is difficult to understand what may be the connexion between stars so widely separated ; from the equality of their motions they must have been widely separated for a very long period . Of multiple stars the most famous is e Orionis, situated near the densest part of the great See also:

• ORION
• ORION (or OARION)

Orion nebula . It consists of four principal stars and two faint companions . From the more complex star. systems of this See also:

• KIND (O. E. ge-cynde, from the same root as is seen in " kin," supra)

kind, we pass to the See also:

• CONSIDERATION (from Lat. considerare, to look at closely, examine, generally taken to be from con-, and the base seen in sidus, sideris, a star, the word being supposed to be originally an astrological or astronomical term)

consideration of star- Clusters. clusters, which are systems of stars in which the components are very numerous . When examined with a telescope of See also:

• POWER [WILLIAM GRATTAN] TYRONE (1797-1841)

power insufficient to separate the individual stars, a cluster appears like a nebula . The " beehive cluster " Praesepe in See also:

• CANCER (" THE CRAB ")
• CANCER, LUIS (d. 1549)
• CANCER, or CARCINOMA (from Lat. cancer, Gr. KapKivwga, an eating ulcer)

Cancer is an example of an easily resolved See also:

• OUSTER (from Anglo-Fr. ouster, to remove, take away, O. Fr. oster, mod. Fr. oter, Eng. " oust," to eject, exclude; the derivation is not known; Lat. obstare, to stand in the way of, resist, would give the form but does not suit the sense; a more probable

Ouster composed of fairly bright stars . The great cluster in See also:

• HERCULES
• HERCULES (0. Lat. Hercoles, Hercles)

Hercules (Messier 13), on the other hand, requires the highest telescopic power for its complete See also:

• RESOLUTION

resolution into stars . Doubtless with improved telescopes many more apparent nebulae would be shown to be clusters, but there are certainly many nebulae which are otherwise constituted .

Many of the clusters are 'of very irregular forms, either showing no well-marked centre of condensation, or else condensed in streams along certain lines . There is, however, a well-marked type to which many of the richest clusters belong; these are the globular clusters . They have a symmetrical circular shape, the condensation increasing rapidly towards the centre . The Hercules cluster is of this form; another example is w Centauri, in which over 6000 stars have been counted, comprised within a circle of about 40' diameter . These clusters present many unsolved problems . Thus Perrine, from an examination of ten globular clusters (including Messier 13 and w Centauri), has found in each case that the stars can be separated into two classes of magnitudes . About one-third of the stars are between magnitudes 11 and 13, and the remaining two-thirds are between magnitudes 15.5 and 16.5 . Stars of magnitudes intermediate between these two See also:

• GROUPS
• GROUPS, THEORY

groups are almost entirely absent . Thus each cluster seems to consist of two kinds of stars, which we may distinguish as bright and faint; the bright stars are all approximately of one See also:

• STANDARD
• STANDARD, BATTLE OF THE

standard See also:

• SIZE

size, and the faint stars of another standard size and brightness . The question of the stability of these clusters is one of much interest . The mutual gravitation of a large number of stars crowded in a comparatively small space must be considerable, and the individual stars must move in irregular orbits under their mutual attractions . It does not seem probable; however, that they can escape the See also:

• FATE

fate of ultimately condensing into one confused mass .

If this surmise be correct, we are witnessing in clusters a See also:

• COUNTER

counter-See also:

• PROCESS

process of progress of a nova. n Argus is surrounded by a nebula, the famous " Keyhole nebula "; in this respect it resembles Nova Persei . System of Stars.—On examining the stars telescopically, many which appear single to the unaided eye are found to be composed of two or more stars very close together . In some evolution to that which is taking place in double stars; the latter appear to be separating from a single See also:

• ORIGINAL

original mass and the former condensing into one . See also:

• COLOURS, MILITARY

Colours and Spectra of Stars.—The brighter stars show a marked variety of See also:

• COLOUR (Lat. color, connected with celare, to hide, the root meaning, therefore, being that of a covering)

colour in their light, and with the aid of a telescope a still greater diversity is noticeable . It is, Colours . however, only the red stars that form a clearly marked class by themselves . For purposes of precise scientific investigation the study of spectra is generally more suitable than the vague and unsatisfactory estimates of colour, which differ with different observers . Of the first magnitude red stars Antares is the most deeply coloured, Betelgeux, Aldebaran and See also:

• ARCTURUS

Arcturus being successively less conspicuously red . Systematic study of red stars See also:

• DATES

dates from the publication in 1866 of Schjellerup's Catalogue, containing a list of 28o of them . The two components of double stars often exhibit complementary colours . As a See also:

• RULE

rule contrasted colours are shown by pairs having a bright and a faint component which are relatively wide apart; brilliant See also:

• WHITE
• WHITE, ANDREW DICKSON (1832– )
• WHITE, GILBERT (1720–1793)
• WHITE, HENRY KIRKE (1785-1806)
• WHITE, HUGH LAWSON (1773-1840)
• WHITE, JOSEPH BLANCO (1775-1841)
• WHITE, RICHARD GRANT (1822-1885)
• WHITE, ROBERT (1645-1704)
• WHITE, SIR GEORGE STUART (1835– )
• WHITE, SIR THOMAS (1492-1567)
• WHITE, SIR WILLIAM ARTHUR (1824--1891)
• WHITE, SIR WILLIAM HENRY (1845– )
• WHITE, THOMAS (1628-1698)
• WHITE, THOMAS (c. 1550-1624)

white stars frequently have a See also:

• BLUE (common in different forms to most European languages)

blue attendant—this is instanced in the case of See also:

• REGULUS, MARCUS ATILIUS

Regulus and Rigel . That the effect is due to a real difference in the character of the light from the two components has been shown by spectrum See also:

• ANALYSIS (Gr. avci and Meta, to break up into parts)

analysis, but it is probably exaggerated by contrast .

The occurrence of change, either periodic or irregular, in the colour of individual stars, has been suspected by many observers ; but such a colour-variability is necessarily very difficult to establish . A possible change of colour in the case of Sirius is noteworthy . In modern times Sirius has always been a typical white or bluish-white star, but a number of classical writers refer to it as red or fiery . There is perhaps room for doubt as to the precise significance of the words used; but the fact that Ptolemy classes Sirius with Antares, Aldebaran, Arcturus, Betelgeux and Procyon as " fiery red " (UebKnp,doi) as compared with all the other bright stars which are " yellow " (favOoc) seems almost conclusive that Sirius was then a redstar . When examined with the spectroscope the light of the stars is found to resemble generally that of the sun . The spectrum consists Spectra of of a continuous See also:

• BAND

band of light crossed by a greater or Stara: less number of dark absorption lines or bands . As in the case of the sun, this indicates an incandescent body which might be solid, liquid, or a not too rare See also:

• GAS

gas, surrounded by and seen through an atmosphere of somewhat cooler gases and vapours; it is this cooler envelope whose nature the spectroscope reveals to use and in it the presence of many terrestrial elements has been detected by identifying in the spectrum their characteristic absorption lines . Stellar See also:

• SPECTROSCOPY (from Lat. spectrum, an appearance, and Gr. a-sore y, to see)

spectroscopy dates from 1862, when Sir See also:

• WILLIAM
• WILLIAM (1143-1214)
• WILLIAM (1227-1256)
• WILLIAM (1J33-1584)
• WILLIAM (A.S. Wilhelm, O. Norse Vilhidlmr; O. H. Ger. Willahelm, Willahalm, M. H. Ger. Willehelm, Willehalm, Mod.Ger. Wilhelm; Du. Willem; O. Fr. Villalme, Mod. Fr. Guillaume; from " will," Goth. vilja, and " helm," Goth. hilms, Old Norse hidlmr, meaning
• WILLIAM (c. 1130-C. 1190)
• WILLIAM, 13TH

William See also:

• HUGGINS, SIR WILLIAM (1824-1910)

Huggins (with a small slit-spectroscope attached to an 8-in. telescope) measured the positions of the See also:

• CHIEF (from Fr. chef, head, Lat. caput)

chief lines in the spectra of about forty stars . In 1876 he successfully applied See also:

• PHOTOGRAPHY (Gr. bias, light, and ypa w, to write)
• PHOTOGRAPHY, CELESTIAL

photography to the study of the ultra-See also:

• VIOLET

violet region of stellar spectra . Various schemes of classification of spectra have been used . The earliest is that due to A . See also:

• SECCHI, ANGELO (1818-1878)

Secchi (1863–1867) who distinguished four " types "; subsequent See also:

• RESEARCH (O. Fr. recerche, from recercher, re- and cercer, mod. chercher, to search; Late Lat. circare, to go round in a circle, to explore)

research, whilst slightly modifying, has in the See also:

• MAIN (from the Aryan root which appears in " may " and " might," and Lat. magnus, great)
• MAIN (Lat. Moenus)

main confirmed this classification .

Secchi's Type I. or " Sirian " type includes most of the bright white stars, such as Sirius, See also:

• VEGA, GARCILASO DE LA
• VEGA, GARCILASO DE LA (1503-1536)

Vega, Rigel, &c.; it is characterized by strong broad hydrogen lines, which are often the only absorption lines visible . Type II. includes the " Solar " stars, as Capella, Arcturus, Procyon, Aldebaran, their spectra are similar to that of the sun, being crossed by very numerous See also:

• FINE

fine lines, mostly due to vapours of metals . The great majority of the visible stars belong to these first two types . Type III. or " Antarian ' stars are of a reddish colour, such as Antares, Betelgeux, Mira, and many of the long-period variables . The spectrum, which closely resembles that of a sunspot, is marked by flutings or hands of lines sharply bounded on the violet See also:

• SIDE
• SIDE (mod. Eski Adalia)

side and fading off towards the red . It has been shown by A . See also:

• FOWLER, CHARLES (1792-1867)
• FOWLER, EDWARD (1632-1714)
• FOWLER, JOHN (1826-1864)
• FOWLER, SIR JOHN (1817-1898)
• FOWLER, WILLIAM (c. 156o-1614)

Fowler that these flutings are due to See also:

• TITANIUM [symbol Ti, atomic weight 48.1 (0 = 16)]

titanium See also:

• OXIDE

oxide; this probably indicates a relatively See also:

• LOW, SETH (1850- )
• LOW, WILL HICOK (1853- )

low temperature, for at a high temperature all compounds would be dissociated . Type IV. also consists of red stars with banded spectra, but the bands differ in arrangement and See also:

• APPEARANCE (from Lat. apparere, to appear)

appearance from those in the third type, and are sharply bounded on the red side . These stars are also believed to have a comparatively low surface temperature, and the bands are attributed to the presence of compounds of See also:

• CARBON (symbol C, atomic weight 12)

carbon . About 250 Type IV. stars are known, but none conspicuous; 19 Piscium, the brightest, is of magnitude 5.5 . Other classifications which are extensively used are those respectively of K . H .

Vogel, J . N . See also:

• LOCKYER, SIR JOSEPH NORMAN (1836– )

Lockyer and the See also:

• DRAPER
• DRAPER, JOHN WILLIAM (1811-1882)

Draper Catalogue . The divergences depend mainly on the different views taken by their authors as to the order of stellar evolution . Apart from these considerations, the chief modification in the classification introduced by more recent investigators has been to separate Secchi's Type I. into two divisions, called See also:

• HELIUM (from Gr. i)Xcor, the sun)

helium and hydrogen stars respectively . The former are often called " Orion " stars, as all the brighter stars in that constellation with the exception of Betelgeux belong to the helium type . Helium stars are generally considered to be the hottest and most luminous (in proportion to size) of all the stars . Type II. is now subdivided into." Procyon," " Solar " and " Arcturian ' stars, The " Procyon "or See also:

• CALCIUM [symbol Ca, atomic weight 40.0 (o= x6)]

calcium stars form a transition between Type I. and Type II. proper, and show the lines of calcium besides those of hydrogen . An important variety of Type III. spectra has been recognized, in which, as well as the usual absorption bands, bright emission lines of hydrogen appear; stars having this particular spectrum are always variable . Finally, a fifth type has been added, the See also:

• WOLF
• WOLF (Canis lupus)
• WOLF, FRIEDRICH AUGUST (1759-1824)
• WOLF, HUGO (1860-1903)
• WOLF, JOSEPH (1820-1899)

Wolf-Rayet stars; these show a spectrum crossed by the usual dark lines and bands, but showing also bright emission bands of blue and yellow light . About See also:

• IOO

ioo Wolf-Rayet stars are known, of which y Velorum is the brightest ; they are confined to the region of the Milky Way and the Magellanic Clouds . (See See also:

• PLANET (Gr. ssXavirrns, a wanderer)

PLANET.) Evolution of Stars.—The See also:

• ABSENCE (Lat. absentia)

absence of the distinctive lines of an See also:

• ELEMENT (Lat. elementum)

element in the spectrum does not by any means signify that that element is wanting or scarce in the star .

The spectroscope only yields See also:

• INFORMATION (from Lat. informare, to give shape or form to, to represent, describe)

information about the thin See also:

• OUTER

outer envelope of the star; and even here elements may be present which do not reveal themselves, for the spectrum shown depends very greatly on the temperature and pressure . Stars of the different types are therefore not necessarily of different chemical constitution, but rather are in different physical conditions, and it is generally believed that every star in the course of its existence passes through stages corresponding to all (or most of) the different types . The stars are known to be continually losing enormous quantities of See also:

• ENERGY (from the Gr. ivipyela; iv, in, ipyov, work)

energy by radiating their heat into space . Ordinary solid or liquid masses would cool very rapidly from this cause and would soon cease to shine . But a globe of gaseous matter under similar conditions will continually See also:

• CONTRACT
• CONTRACT (Lat. contract us, from contrahere, to draw together, to bind)

contract in See also:

• VOLUME

volume, and in so doing transforms potential energy into heat . It was shown by See also:

• HOMER, WINSLOW (1836-191o)

Homer