STAR, stella , in Astronomy , is a name given in general to all celestial bodies. See Heaven, Heavenly body, etc. [1]

We distinguish the stars by the phenomena of their motion, into fixed and wandering .

Wandering stars are those that continually change location and distance with respect to each other; it is these that are properly called planets. See Planet. We can also put in the same class the heavenly bodies which we call comets. See Comet.

The fixed stars , which are also simply called stars in ordinary usage, are those which perpetually observe the same distance with respect to the others. See Fixed.

The principal points which astronomers examine with respect to the fixed stars are their distance, their size, their nature, their number, and their motion. These different objects will be the subject matter of this article.

Distance of the fixed stars . Fixed stars are bodies extremely distant from us; and so distant that we have no distance in the system of the planets that can be compared with them.

Indeed, astronomical observations tell us that Earth, this mass which at first seems so enormous to us, would be seen from the sun as no more than an imperceptible point. The sun must then be prodigiously distant from us; and nevertheless this distance from Earth to the sun is very small in comparison with that of the fixed stars .

Their immense distance is inferred from the fact that they have no perceptible parallax, in other words that the diameter of the Earth’s orbit has no perceptible proportion to their distance, but that we perceive them in the same manner at every point of this orbit; so that even if from the fixed stars we could see the entire orbit of the Earth described each year, the diameter of which is twice the distance from the sun to the Earth, that orbit would appear only as a point, and the angle it formed with the star would be so small that it is not surprising it has escaped so far the inquiries of the cleverest astronomers. Supposing that angle to be one-half a minute, which is much wider than the true angle, we would find the stars more than12,000 times farther from us than the sun, and beyond.

M. Huygens determines the distance of the stars by another method, which is by making the opening of a telescope so small that the sun seen through it appears no larger than Sirius. In this state, he finds that the diameter of the sun is about the 27,664 ^th part of its diameter when it is seen uncovered. If then the distance from the sun were 27,664 times as great as it is, we would see it under the same diameter as Sirius; consequently, if we suppose that Sirius is the same size as the sun, we will find the distance from Sirius to the Earth is to the distance to the sun as 27,664 is to 1.

It might be said that these methods are too hypothetical to conclude anything from them, but at least we can show that the stars are incomparably farther away than Saturn, since Saturn has a parallax, and the stars have none at all. See Saturn and Parallax. Besides, it follows from what we have just said above, that the distance of the stars is at least 10,000 times as great as that of the sun, a supposition which we may consider incontestable.

This immense distance of the stars serves to explain, in the system of the motion of Earth around the sun, why certain stars do not appear larger at one time of year than at another, and why their apparent distance with relationship to one another could not vary perceptibly with respect to us: for the Earth draws closer to a given star in the space of six months by the whole diameter of its orbit, and by the same reason it distances itself just as much during the other six months of the year. If then we cannot recognize perceptible changes in the apparent position of these stars , that is a sign that they are at an immense distance from the Earth, and that it is precisely the same as if we were not in motion. That is about what occurs when we perceive on earth two towers not very far apart, but more than a ten thousand paces distant from our eyes; for if we take only a single step forward, we will assuredly not for that see the two towers either larger or farther away from each other; for a change to be perceptible we would have to draw closer. Thus, although Earth is a little closer to certain stars at one time of year than six months earlier or six months later, yet as it does not approach it by even one five thousandth [of the distance], there could not possibly be any noticeable changes either in the size or in the apparent distance of those stars .

Let us presently suppose the sun at the same distance as the fixed star closest to Earth: it is easy to see that the angle under which it would appear to us would be at least ten thousand times smaller than the angle under which we see it. Now the angle under which we see the sun is about 30 minutes or one-half degree. It then follows that if we were placed in some fixed star , the sun would appear to us only under an angle equal to the ten millionth part of thirty minutes, in other words about ten tierces. [2]

It might be objected that if the distance of the fixed stars is as considerable as we have just supposed it to be, the stars would necessarily be much larger than the sun; more importantly, it would follow that they would be at least as large as the diameter of the annual cycle of the Earth. That is an objection which we are going to examine in the following article, where we will discuss the size of stars .

Size and number of stars. The sizes of the fixed stars appear to be different, but this difference might come at least in part from the difference in their distances and not from any diversity there might be in their actual sizes.

It is because of this difference that we divide the stars into seven classes, or seven different magnitudes. [3] See Constellation.

The stars of first magnitude are those whose diameters seem to us the largest; after them come those of the second magnitude, and so forth up to the sixth, which includes the smallest stars that can be seen without a telescope. All those that are beyond this are called telescopic stars . The number of these stars is considerable, and we discover new ones as we use longer glasses; but it was not possible for the Ancients to sort them into the six classes we have just mentioned. See Telescopic.

Not that all the stars in each class appear to be precisely the same size: each class is very broad in this respect, and almost all the stars of the first magnitude seem to differ in brilliance and size. There are other stars of intermediate magnitudes, which astronomers cannot place in one class rather than the next, and which for that reason they place between two classes.

For example, Procyon, which Ptolemy regards as a star of the first magnitude, and Tycho places in the second class, is classified in neither by Flamsteed, who puts it between the first and the second. [4]

To speak properly, one would have to establish as many different classes as there are fixed stars . Indeed, it is very rare to find two that are of precisely the same magnitude; and to speak only of those of first magnitude, here are the principal differences that have been recognized in them: Sirius is the largest and brightest of all; next we find that Arcturus exceeds in magnitude and brightness Aldebaran or the Eye of Taurus, and Spica in Virgo; and yet they are commonly called first-magnitude stars .

Catalogue of stars of different magnitudes, according to Kepler. [5]

Of the first magnitude, 15

Of the second, 58

Of the third, 218

Of the fourth, 494

Of the fifth, 354

Of the sixth, 240

Obscure and nebulous, 13

_____

In all, 1392

.

This number is that of the stars which can be seen with the naked eye; for with the telescope, as we have said, one sees many more.

Some authors assure us that the apparent diameter of stars of the first magnitude is at least one minute; and as we have already said that the Earth’s orbit seen from the fixed stars appears at an angle of less than 30 seconds, from this they have concluded that the diameter of the stars is much greater than that of the whole of Earth’s orbit. Moreover, they say, a sphere with a demi-diameter equal only to the distance from the sun to Earth is ten million times larger than the sun; consequently, they believe that the fixed stars must be much more than ten million times larger than the sun. There is therefore an enormous difference between the size of the sun and that of the fixed stars ; and consequently one could no longer say that they are similar luminous bodies, and to place the sun among the fixed stars would be ill-founded.

But that is a mistake: for the diameters of even the largest stars , seen through a telescope that makes objects, for example, a hundred times larger than they are, do not appear at all to have perceptible size, but are no more than bright points.

Thus this pretended magnitude of stars is based only on highly imperfect observations; and it is true that some astronomers of little skill in this exercise have made great errors in the apparent diameters they have assigned to stars . The angle under which the fixed stars of the first magnitude appear is even less than a second; for when the moon reaches the eye of Taurus, the heart of Leo, or Spica in Virgo, the occultation is so instantaneous, and the star  [6] so brilliant at that instant, that an attentive observer could not be mistaken, nor remain in uncertainty for a half-second of time. Now if these stars had for example a diameter of at least five seconds, we would see them slowly eclipsed, and diminish noticeably in magnitude for close to 10 seconds of time, proportionately to the 13 degrees that the moon covers in 24 hours. There is around these stars , especially at night, a sort of false light, a radiance or twinkling that deceives us, and causes us to think them at least a hundred times larger than they are. Yet most of this false light can be made to disappear by looking at the stars through a hole made in a card with the point of a needle, or rather by using an excellent spyglass which absorbs most of it, since through them one can see the fixed stars only as points of light, and much smaller than with the naked eye. We know however that a spyglass magnifies objects, but it seems the contrary appears with respect to the fixed stars , which proves how nearly imperceptible is the apparent diameter of those stars relative to us. We do not know how Father Riccioli [7] got it so wrong as to ascribe to Sirius a diameter of 18 seconds; for if we assume that to the naked eye the two lines drawn from the extremities of the diameter of Sirius form in our eye an angle of 18 seconds, a glass which multiplied objects 200 times would consequently make us see this star under an angle of 3600 seconds, in other words one degree: whence it would follow that Sirius seen through the glass would appear to have a diameter almost double that of the sun or the moon. Now although even the most excellent glasses are not capable of completely absorbing this false light that surrounds the fixed stars , it is nonetheless certain that Sirius does not appear in them any larger than the planet Mars measured by micrometer or simply by sight; [8] but the diameter of Mars at its shortest distance from Earth is at most 30 seconds: thus, although the glass increases the apparent diameter of Sirius about 200 times, the angle under which one perceives this star is only about the 200 ^th part of 30 seconds, or about nine tierces. You might ask now how we can perceive the fixed stars , since their apparent diameter corresponds to an angle that is imperceptible; but one must note that it is that radiance and twinkling which surround them which causes these luminous bodies to be seen at such prodigious distances, contrariwise to what happens with any other object. Does experience not tell us that a candle or lit torch can be seen during the night at a very perceptible angle at more than two leagues’ distance? Whereas if on the brightest day one exposes any other object of similar size at the same distance, it will be impossible to see it; scarcely could one even distinguish an object that was ten times larger than the candle flame. The reason for this is that luminous bodies cast in every direction a material incomparably more powerful than what is reflected by non-luminous bodies, and that being dimmed by reflection, it becomes dimmer and can hardly be seen at a great distance; the other on the contrary is so bright that it stirs with incomparably greater force the fibers of the retina, which produces a completely different sensation, and makes us for this reason think the luminous bodies much larger than they are. See the Institutions astronomiques by M. Le Monnier. [9] It is not useless to observe here that the twinkling of stars is that much dimmer as the air is less full of vapors; and so in countries where the air is extremely pure, as in Arabia, the stars do not twinkle. See Sparkle, Twinkle, and the Histoire de l’Académie from 1743, page 28. [10]

Catalogue of the stars . Stars are also divided up with respect to their position in asterisms or constellations, which are nothing other than an assemblage of several neighboring stars which are considered as forming some determinate figure, for example an animal, etc., and which takes its name; this division is at least as ancient as the book of Job, in which there is mention of Orion and the Pleiades, etc. See Constellation and Arcturus.

Besides the stars which are thus grouped by different magnitudes or constellations, there are others that belong to none. Those which are not included in constellations are called unformed , or stars without form . Modern astronomers have formed new constellations out of several stars which the Ancients regarded as unformed stars , like the heart of Charles, Cor Caroli , which was formed into a constellation by Halley, and the shield of Sobieski, Scutum Sobiesci by Hevelius, etc. See Heart, Shield, etc.

Those which are not put into classes or magnitudes are called nebulous stars , because they appear only dimly and in the shape of small, shining clouds. See Nebula.

The number of stars appears very great and almost infinite; yet astronomers have long since determined the number of those the eyes can see, which they have found much smaller than would be imagined. 125 years B.C., Hipparchus made a catalogue, which is to say an enumeration of the stars with the exact description of their magnitudes, positions, longitude, latitude, etc. That catalogue is the first we know about, and Pliny does not shrink from calling that enterprise rem etiam deo improbam . [11] Hipparchus increased the number of visible stars to 1022; they were distributed into 48 constellations. Ptolemy added four stars to Hipparchus’s catalog, and increased the number to 1026. In the year 1437, Ulugh Beg, the grandson of Tamerlane, counted only 1017 in a new catalogue which he made, or had made. [12]

But in the sixteenth and seventeenth centuries, when astronomy began to flourish, it was found that the number of stars was much larger. They added to the 48 constellations of the Ancients twelve more new ones, which were observed toward the South Pole, and two others towards the North Pole, etc. See Constellation.

Tycho Brahé published a catalogue of 777 stars which he himself observed. Kepler, on the observations of Ptolemy and others, increased the number to 1163; Riccioli to 1468, and Bayer to 1725. [13] Halley added 373 more, which he observed himself toward the Antarctic pole; Hevelius, on the observations of Halley and his own, made a catalogue of 1888 stars; [14] and since then, Flamsteed made one containing 3000 stars, all of which he himself observed with precision.

It is true that of these 3000 stars there are many which one can see only with a telescope. If it often occurs on fine winter nights that one sees an innumerable quantity, that is because our sight is deceived by the dazzle of their brightness; because we see them only confusedly, and we do not examine them in order, whereas when one begins to contemplate them more attentively, and even to make them out one after the other, it would be quite difficult to find any that have not been marked on the maps or in the catalogues of Hevelius or Flamsteed. Further, if we have before our eyes one of those great globes like those of Blaue, [15] and compare it with the heavens, however excellent our eyesight may be, we will never be able to discover any, even among the smallest stars , which has not been located on the surface of that globe. Yet the number of the stars is almost infinite. Riccioli (which is perhaps exaggerated) asserts in his Almageste that were someone to say there are more than 20,000 times 20,000, he would only be stating what is probable.  [16]

Indeed, a good telescope aimed at any point in the sky reveals an immense multitude of them, which the eye alone cannot perceive; particularly in the Milky Way, which could well be nothing but than an assemblage of stars too distant to be seen separately, but arranged so close together that they give a luminous appearance to the part of the sky which they occupy. See Galaxy and Milky Way.

In the Pleiades constellation alone, instead of six or seven stars which the sharpest eye perceives, Dr. Hooke, with a telescope twelve feet long, counted 78; and with larger lenses, an even larger number of different magnitudes. Father Rheita, Capuchin, assures us that he has observed more than two thousand stars in the constellation of Orion alone; it is true that this last point has not been confirmed. The same author found 188 stars in the Pleiades, and Huygens, studying the star which is in the middle of Orion’s sword, found that instead of one there were twelve. Galileo found 80 in Orion’s sword, 21 in the nebulous star of his head, and 36 in the nebulous star called Praesepe. [17]

In 1603 Johann Bayer, a German astrologer, published engraved celestial maps where all the constellations are drawn with the visible stars of which each is composed. He designated these stars by Greek letters, calling one α, another β, etc., which abbreviates the names they are given; thus one says star η of the Great Bear instead of the second-magnitude star at the end of the Great Bear’s tail, etc.

The changes which the stars have undergone are very considerable, which overturns the opinion of the Ancients, who maintained that the heavens and the heavenly bodies were incapable of any change; that their matter was permanent and eternal, infinitely harder than a diamond, and could not take another form. Indeed, until the time of Aristotle, and even 200 years later, no change had been observed.

The first was noticed in the year 125 B.C. Hipparchus noticed the appearance of a new star , which committed him to making his catalogue of stars of which we have spoken so that posterity could perceive the changes of this sort that could occur in the future.

In 1572 Tycho Brahé observed yet another new star in Cassiopeia, which similarly afforded him the opportunity to make his new catalogue. Its magnitude at first surpassed that of Sirius and the glowing star in Lyra, which are the largest of our stars; it even equaled that of Venus when it is closest to the Earth, and it was seen in full daylight. It was visible for sixteen months; in the latter times it began to dim, and finally disappeared entirely without changing position for the whole time it lasted.

Leovicius speaks of another star that appeared in the same constellation about 945 A.D. and resembled the star of 1572; and he cites another ancient observation by which it appears that a new star had been seen in the same place in 1264.

Keill asserts that it was the same star , and does not doubt that it should reappear again in 150 years.

Fabricius discovered another new star in the neck of the Whale, [18] which appeared and disappeared at various times in the years 1648 and 1662. Its course and motion were described by Bouillaud. [19]

Simon Marius discovered another one in the belt of Andromeda in 1612 and 1613. Bouillaud asserts that it had already appeared in the fifteenth century. Kepler observed another in Serpentarius, and another of the same magnitude near the bill of Cygnus in the year 1601, which disappeared in 1626; which was also observed by Hevelius in 1659 until the year 1661, and which reappeared a third time in 1666 and in 1671 as a star of the sixth magnitude.

It is certain from the ancient catalogues that several of the ancient stars are no longer visible today; this is noted particularly in the Pleiades or seven stars , of which there are no longer but six which the eye can see: this is an observation which Ovid made long ago, witness this verse by this author:

What is most remarkable is that there are stars the light of which, after dimming little by little, finally is absolutely extinguished only to reappear subsequently; among these last stars , the one in the neck of the Whale is famous among astronomers. It happens that for eight or nine months one cannot see the star at all, and the three or four other months of the year it is seen to increase or decrease in size. Some philosophers have believed that that was solely because the surface of that star is covered, for the most part, with opaque bodies or spots similar to those of the sun; that only an exposed or luminous part remains; and that the star completing its successive revolutions or rotations on its axis still cannot directly show its luminous part, in such a way that we must see it sometimes larger and sometimes smaller, and cease completely to see it, when its luminous part is no longer turned towards us. What led to a suspicion that it was spots that principally caused these changes was that in some years the star does not preserve a constant regularity or is not precisely of the same magnitude: sometimes it equals in light the finest stars of the second magnitude, sometimes those of the third: in a word, the increase or decrease of its light does not correspond to equal intervals. Sometimes it is visible only during three full months, whereas it has often been seen for four months and more. However, this opinion of the philosophers on the appearance and disappearance of stars is hardly likely if we consider that despite some irregularities the star of the Whale appears and disappears fairly regularly in the same seasons of the year, which should not reasonably be suspected in the hypothesis of spots that can vanish or recur while observing no order either in time or in seasons. It is far simpler to suppose, as did M. de Maupertuis in his book on the shape of heavenly bodies, that these sorts of stars are not round like the sun, but considerably flattened because they rotate no doubt very rapidly around their axis. This supposition is all the more legitimate in that we see among our planets those that turn the most rapidly around their axis being more flattened than the others. Jupiter, as M. Picard observed in 1668, and as MM. Cassini and Pound measured, is considerably flattened, which one cannot say of the other planets; Jupiter also turns very rapidly on its axis. Why then would it not be permitted to suppose more or less flattened fixed stars , according to whether they rotate more or less rapidly? Moreover, as large planets can themselves turn around these stars , and change with respect to us the position of the axis of these luminous bodies, it follows that according to their greater or lesser inclination they will appear more or less brilliant, to the point of sending us only a very small quantity of their light. See M. de Maupertuis’s figure des astres, chapter vii, page 114 , second edition. [21]

Montanari, in a letter which he wrote to the Royal Society in 1670, observes that there were then two fewer stars of the second magnitude in the ship Argo, which appeared until the year 1664; he does not know when they began to disappear, but he assures that not the slightest appearance of them remained in 1668. He adds that he has observed many other changes in the fixed stars , and counts these changes at more than one hundred. However, we do not believe that these supposed observations of Montanari deserve much attention, since it is true, according to M. Kirch, that the two fine stars that Montanari claims to have lost sight of have been sighted continually from the time of Ptolemy to this day one sign beyond, or 30 degrees from the spot in the sky where they were being sought. These stars , says Montanari, are marked β and γ in Bayer near Canis Major. The error in Bayer’s maps is doubtless owing to the fact that the author relied on Latin translations of Ptolemy’s texts, whereas the Greek edition of Basel tells us that these stars needed to be sought in the old catalogue around the 15 ^th degree of Leo, and not the 15 ^th of the Crayfish [Cancer].

As there are stars which never set for us ( see Circumpolar), there are others that never rise: these are those which as at less distance from the austral pole than our latitude. Mr. Halley had already put together a catalogue of them ( see Constellation). M. de la Caille in his recent voyage to the Cape of Good Hope asserts that in very little time he made a catalogue of more than 9800 stars between the South Pole and the Tropic of Capricorn; [22] he constructed a planisphere of 1930 of these stars ; time will tell how accurate it is.

The nature of fixed stars . Their immense distance does not allow us to advance our discoveries very far on this object; everything certain we can learn about it from its phenomena comes down to the following.

1. The fixed stars shine with their own light; for they are much farther away from the sun than Saturn, and appear smaller than Saturn, yet we note that they are much brighter than Saturn: whence it is evident that they cannot borrow their light from the same source as Saturn, which is to say the sun. Now since we know no other luminous body other than the sun from which they could draw their light, it follows that they shine with their own light.

We conclude from this 2. that the fixed stars are so many suns: for they have all the characteristics of the sun, that is, immobility, their own light, etc. See Sun.

3. That it is most probable that the stars are not smaller than our sun.

4. That it is highly probable that these stars must not be in a single spherical surface of the sky; for in that case they would all be at the same distance from the sun, and variously distant from each other, as they appear to us. Now why this regularity in one way, and this irregularity in the other? Moreover, why should our sun not occupy the center of that sphere of stars ?

5. Besides, it is quite natural to think that each star is the center of a system and has planets that make their revolutions around it in the same manner as our sun; in other words, it has opaque bodies which it illuminates, heats, and sustains with its light: for why would God have placed so many luminous bodies at such great distances from one another, unless there were some opaque bodies around them which receive light and heat from them? Nothing assuredly seems more suited to divine wisdom which does nothing uselessly. In any case, we offer this only as a slight conjecture. See Plurality of worlds. [23] The planets imagined around certain stars could serve to explain the particular motion we note in some of them, and which could be caused by the action of these planets when the theory of precession and nutation ( see these words ) does not suffice to explain it. Thus is the sun ever so slightly disturbed by the action of the seven planets, especially by Jupiter and Saturn. See my recherches sur le système du monde, part II, chapter iv. [24]

Motion of the stars . The fixed stars have in general two sorts of apparent motion: the one, which we can call first , common , or daily motion , or motion of the primum mobile : it is by this motion that they appear to be carried with the sphere or firmament to which they are attached, around the Earth from east to west in the space of twenty-four hours. This apparent motion results from the real motion of Earth around its axis.

The other, which we call the second motion , it that by which they seem to move following the order of the signs, turning so slowly around the poles of the ecliptic that they describe no more than one degree of their circle in the space of 71 or 72 years, or 51 seconds per year.

Some have imagined, who knows on what basis, that when they will have reached the end of their circle at the point where they began it, the heavens will remain still, unless the Being who first imparted to them their motion should order them to make another revolution.

On this supposition the world should end after lasting about 30,000 years, according to Ptolemy; 25,816 according to Tycho, 25,920, according to Riccioli, and 24,800 according to Cassini. See Precession of the equinoxes. But this calculation is based on an illusion.

By comparing the observations of the ancient astronomers with those of the moderns, we find that the latitudes of most of the fixed stars are still substantially the same, leaving aside the almost imperceptible nutation of the Earth’s axis ( See Nutation); but that their longitude continually increases more and more because of precession.

Thus, for example, the longitude of the heart of Leo was found by Ptolemy in 138 A.D. as 2° 3'; in 1115 the Persians observed it at 17° 30'; in 1364 it was found by Alfonso at 20° 40'; [25] in 1586, by the Prince of Hesse at 24° 11'; in 1601, by Tycho, 24° 17'; and in 1690, by Flamsteed, 25° 31' 20"; from which is it easy to infer the motion of the stars themselves, following the order of the signs, on circles parallel to the ecliptic.

It was Hipparchus who first suspected this motion, by comparing the observations of Timocharis and Aristillus with his own. Ptolemy, who lived 300 years after Hipparchus, demonstrated it by incontestable arguments. See Longitude.

Tycho Brahé asserts that the increase in longitude is one degree 25' per century; Copernicus, one degree 23' 40" 12'"; Flamsteed and Riccioli, one degree 23' 20"; Boulliaud, one degree 24' 54"; Hevelius, one degree 24' 46" 50"': whence it results, following Flamsteed, that the annual increase in longitude of the fixed stars must be set at 50".

That settled, it is easy to determine the increase in the longitude of a star for any given year; and from there the longitude of a star for any year being given, it is easy to find its longitude for any other year: for example the longitude of Sirius, in the tables of Mr. Flamsteed for the year 1690 being 9° 49' 1", we will have its longitude for the year 1724, by multiplying the time interval, in other words 34 years by 50": the product, which is 1700" or 28' 20", added to the given longitude, will give the longitude, 10° 17' 21".

Also, the longitude of the stars is subject to a little equation which I gave in my Recherches sur le système du monde , Part II, page 189 ,  [26] and I shall remark on this occasion that below the following table ( page 190 of the same work), for the correction of the obliquity of the ecliptic, the words added and taken away were put accidentally in each other’s place.

The principal phenomena of the fixed stars that come from their common motion and their apparent individual motion, besides their longitudes, are their heights, right ascensions, declinations, occultations, culminations, risings and settings. See Height, Ascension, Declination, Occultation, etc.

I shall now observe that the method given at the word Ascension for finding the right ascension applies properly only to the sun; what is called in this article the cosine of the declination of the heavenly body is the cosine of the obliquity of the ecliptic. To find the right ascension of stars in general, one can use methods explained and detailed in M. Le Monnier’s Astronomical Institutions , pages 383 and 387 .  [27] We refer the reader there.

The number of different stars that make up each constellation, for example Taurus, Boötes, Hercules, etc., can be seen under the specific article for each constellation: Taurus, Boötes, Hercules, etc.

To learn to identify the different fixed stars with the globe, see Globe.

See Wolf’s Elements of Astronomy , [28] the dictionaries of Harris and Chambers, the memoirs of Academy of Sciences , and M. Le Monnier’s Astronomical Institutions , from which we have drawn a large part of this article.

1. Parts of this article are translated or adapted from the article “Star” in Chambers’s Cyclopaedia (1743 edition).

2. A tierce is the sixtieth part of a second.

3. Grandeurs . In French magnitude (technically, a logarithmic scale) was not used until the nineteenth century, but Chambers uses it.

4. The ancient astronomer Ptolemy (c. 100 – c. 170); the Danish astronomer Tycho Brahe (1546-1601); and the English astronomer John Flamsteed (1646-1719).

5. Johannes Kepler (1571-1630, German astronomer.

6. The moon, the word star being applicable (as stated at the outset) to any celestial body.

7. Giovanni Battista Riccioli (1598–1671), Italian Jesuit and author of many books on astronomy.

8. A micrometer is a measuring device used in telescopes that employs a calibrated screw to measure the apparent diameter of celestial bodies. It was invented by the English astronomer and instrument maker William Gascoigne (1612-1644) in the seventeenth century.

9. Pierre Charles Lemonnier (1715-1799), Institutions astronomiques (1746), mainly a translation of John Keill’s Introductiones ad veram Physicam et veram Astronomiam (1725). Lemonnier had earlier published a Théorie des comètes, translated from Halley.

10. The unsigned article referenced in the Histoire de l’Académie des Sciences (1743), pp. 28–32 (Histoire), is entitled “Sur la scintillation des étoiles fixes.”

11. “Which even a god would not dare to undertake.”

12. Mīrzā Muhammad Tāraghay bin Shāhrukh, known as Ulugh Beg (1394-1449), was a Timurid sultan as well as an astronomer. He built an observatory in Samarkand between 1424 and 1429, one of the greatest in the Islamic world at that time.

13. Johann Bayer (1572-1625), German celestial cartographer. He published his star atlas Uranometria Omnium Asterismorum in 1603.

14. Johannes Hevelius (1611-1687), Prodromus Astronomiae (1690).

15. Willem Janszoon Blaeu (1571–1638), Dutch cartographer, made such globes and published a user’s manual for celestial and terrestrial globes, first in Dutch (1620), then in Latin (1634), and then in this French edition (1642): Institution astronomique de l’usage des globes et sphères célestes et terrestres. Here is one of his celestial globes, made in 1603 and now in the Science Museum (London).

16. Almagestum novum, 1651.

17. Also known as the Beehive Cluster.

18. Cetus.

19. Ismaël Boulliau (1605-1694), French astronomer and author of Astronomia philolaica (Paris, 1645), on the motion of the planets.

20. “There are said to be seven, but there are only six” Fasti , book IV, v. 170.

21. Pierre Louis Moreau de Maupertuis (1698–1759), had published Discours sur les differentes figures des astres in 1732; the second edition of 1742 added to its title: “Des étoiles qui paraissent s’allumer et s’éteindre” (“on stars that seem to turn on and off”).

22. Nicolas-Louis de Lacaille (1713-1762) was a French astronomer whose voyage to the Cape of Good Hope in 1750 was extremely fruitful. Among other scientific accomplishments he catalogued nearly 10,000 stars and introduced 14 new constellations.

23. Some such article must have been projected, but was it never written, possibly because Fontenelle, for whom the article is “named,” died in 1757, well before the publication of vol. XV, in which it would have been published. In 1686, Fontenelle (1657-1757), who was d’Alembert’s predecessor as permanent secretary of the Academy of Sciences, had written the extremely influential Entretiens sur la pluralité des mondes . Here is an eighteenth-century English translation: A Plurality of Worlds (London, 1702).

24. Jean Le Rond d’Alembert, Recherches sur différents points importants du système du monde [ Research on different important points in the system of the world ] (1754–1756).

25. The reference is to King Alfonso X of Castile, also known as Alfonso the Wise (1221-1284), who encouraged science and the arts in a cosmopolitan court that brought together learned Arabs, Jews, and Christians and produced a set of astronomical tables which bear his name.

26. See note 24.

27. See note 9.

28. German philosopher Christian Wolff (1679–1754), whose numerous works in German and Latin led to a French translation, Cours de mathématiques in 1747.