ARE THERE PLANETS AMONG THE STARS?
"... And if there should be
Worlds greater than thine own, inhabited
By greater things, and they themselves far more
In number than the dust of thy dull earth,
What wouldst thou think?"--BYRON'S CAIN.
This always interesting question has lately been revived in a startling
manner by discoveries that have seemed to reach almost deep enough to
touch its solution. The following sentences, from the pen of Dr. T. J.
J. See, of the Lowell Observatory, are very significant from this point
of view:
"Our observations during 1896-'97 have certainly disclosed stars more
difficult than any which astronomers had seen before. Among these
obscure objects about half a dozen are truly wonderful, in that they
seem to be dark, almost black in color, and apparently are shining by a
dull reflected light. It is unlikely that they will prove to be
self-luminous. If they should turn out dark bodies in fact, shining only
by the reflected light of the stars around which they revolve, we should
have the first case of planets--dark bodies--noticed among the fixed
stars."
Of course, Dr. See has no reference in this statement to the immense
dark bodies which, in recent years, have been discovered by
spectroscopic methods revolving around some of the visible stars,
although invisible themselves. The obscure objects that he describes
belong to a different class, and might be likened, except perhaps in
magnitude, to the companion of Sirius, which, though a light-giving
body, exhibits nevertheless a singular defect of luminosity in relation
to its mass. Sirius has only twice the mass, but ten thousand times the
luminosity, of its strange companion! Yet the latter is evidently rather
a faint, or partially extinguished, sun than an opaque body shining only
with light borrowed from its dazzling neighbor. The objects seen by Dr.
See, on the contrary, are "apparently shining by a dull reflected
light."
If, however (as he evidently thinks is probable), these objects should
prove to be really non-luminous, it would not follow that they are to be
regarded as more like the planets of the solar system than like the dark
companions of certain other stars. A planet, in the sense which we
attach to the word, can not be comparable in mass and size with the sun
around which it revolves. The sun is a thousand times larger than the
greatest of its attendant planets, Jupiter, and more than a million
times larger than the earth. It is extremely doubtful whether the
relation of sun and planet could exist between two bodies of anything
like equal size, or even if one exceeded the other many times in
magnitude. It is only when the difference is so great that the smaller
of the two bodies is insignificant in comparison with the larger, that
the former could become a cool, life-bearing globe, nourished by the
beneficent rays of its organic comrade and master.
Judged by our terrestrial experience, which is all we have to go by, the
magnitude of a planet, if it is to bear life resembling that of the
earth, is limited by other considerations. Even Jupiter, which, as far
as our knowledge extends, represents the extreme limit of great
planetary size, may be too large ever to become the abode of living
beings of a high organization. The force of gravitation on the surface
of Jupiter exceeds that on the earth's surface as 2.64 to 1.
Considering the effects of this on the weight and motion of bodies, the
density of the atmosphere, etc., it is evident that Jupiter would, to
say the very least, be an exceedingly uncomfortable place of abode for
beings resembling ourselves. But Jupiter, if it is ever to become a
solid, rocky globe like ours, must shrink enormously in volume, since
its density is only 0.24 as compared with the earth. Now, the surface
gravity of a planet depends on its mass and its radius, being directly
as the former and inversely as the square of the latter. But in
shrinking Jupiter will lose none of its mass, although its radius will
become much smaller. The force of gravity will consequently increase on
its surface as the planet gets smaller and more dense.
The present mean diameter of Jupiter is 86,500 miles, while its mass
exceeds that of the earth in the ratio of 316 to 1. Suppose Jupiter
shrunk to three quarters of its present diameter, or 64,800 miles, then
its surface gravity would exceed the earth's nearly five times. With one
half its present diameter the surface gravity would become more than ten
times that of the earth. On such a planet a man's bones would snap
beneath his weight, even granting that he could remain upright at all!
It would seem, then, that, unless we are to abandon terrestrial
analogies altogether and "go it blind," we must set an upper limit to
the magnitude of a habitable planet, and that Jupiter represents such
upper limit, if, indeed, he does not transcend it.
The question then becomes, Can the faint objects seen by Dr. See and his
fellow-observers, in the near neighborhood of certain stars, be planets
in the sense just described, or are they necessarily far greater in
magnitude than the largest planet, in the accepted sense of that word,
which can be admitted into the category--viz., the planet Jupiter? This
resolves itself into another question: At what distance would Jupiter be
visible with a powerful telescope, supposing it to receive from a
neighboring star an amount of illumination not less than that which it
gets from the sun? To be sure, we do not know how far away the faint
objects described by Dr. See are; but, at any rate, we can safely assume
that they are at the distance of the nearest stars, say somewhere about
three hundred thousand times the earth's distance from the sun. The sun
itself removed to that distance would appear to our eyes only as a star
of the first magnitude. But Zoellner has shown that the sun exceeds
Jupiter in brilliancy 5,472,000,000 times. Seen from equal distances,
however, the ratio would be about 218,000,000 to 1. This would be the
ratio of their light if both sun and Jupiter could be removed to about
the distance of the nearest stars. Since the sun would then be only as
bright as one of the stars of the first magnitude, and since Jupiter
would be 218,000,000 times less brilliant, it is evident that the latter
would not be visible at all. The faintest stars that the most powerful
telescopes are able to show probably do not fall below the sixteenth or,
at the most, the seventeenth magnitude. But a seventeenth-magnitude star
is only between two and three million times fainter than the sun would
appear at the distance above supposed, while, as we have seen, Jupiter
would be more than two hundred million times fainter than the sun.
To put it in another way: Jupiter, at the distance of the nearest stars,
would be not far from one hundred times less bright than the faintest
star which the largest telescope is just able, under the most exquisite
conditions, to glimpse. To see a star so faint as that would require an
object-glass of a diameter half as great as the length of the tube of
the Lick telescope, or say thirty feet!
Of course, Jupiter might be more brilliantly illuminated by a brighter
star than the sun; but, granting that, it still would not be visible at
such a distance, even if we neglect the well-known concealing or
blinding effect of the rays of a bright star when the observer is trying
to view a faint one close to it. Clearly, then, the obscure objects seen
by Dr. See near some of the stars, if they really are bodies visible
only by light reflected from their surfaces, must be enormously larger
than the planet Jupiter, and can not, accordingly, be admitted into the
category of planets proper, whatever else they may be.
Perhaps they are extreme cases of what we see in the system of
Sirius--i.e., a brilliant star with a companion which has ceased to
shine as a star while retaining its bulk. Such bodies may be called
planets in that they only shine by reflected light, and that they are
attached to a brilliant sun; but the part that they play in their
systems is not strictly planetary. Owing to their great mass they bear
such sway over their shining companions as none of our planets, nor all
of them combined, can exercise; and for the same reason they can not,
except in a dream, be imagined to possess that which, in our eyes, must
always be the capital feature of a planet, rendering it in the highest
degree interesting wherever it may be found--sentient life.
It does not follow, however, that there are no real planetary bodies
revolving around the stars. As Dr. See himself remarks, such
insignificant bodies as our planets could not be seen at the distance of
the fixed stars, "even if the power of our telescopes were increased a
hundredfold, and consequently no such systems are _known_."
This brings me to another branch of the subject. In the same article
from which I have already quoted (Recent Discoveries respecting the
Origin of the Universe, Atlantic Monthly, vol. lxxx, pages 484-492),
Dr. See sets forth the main results of his well-known studies on the
origin of the double and multiple star systems. He finds that the
stellar systems differ from the solar system markedly in two respects,
which he thus describes:
"1. The orbits are highly eccentric; on the average twelve times
more elongated than those of the planets and satellites.
"2. The components of the stellar systems are frequently equal and
always comparable in mass, whereas our satellites are insignificant
compared to their planets, and the planets are equally small
compared to the sun."
These peculiarities of the star systems Dr. See ascribes to the effect
of "tidal friction," the double stars having had their birth through
fission of original fluid masses (just as the moon, according to George
Darwin's theory, was born from the earth), and the reaction of tidal
friction having not only driven them gradually farther apart but
rendered their orbits more and more eccentric. This manner of evolution
of a stellar system Dr. See contrasts with Laplace's hypothesis of the
origin of the planetary system through the successive separation of
rings from the periphery of the contracting solar nebula, and the
gradual breaking up of those rings and their aggregation into spherical
masses or planets. While not denying that the process imagined by
Laplace may have taken place in our system, he discovers no evidence of
its occurrence among the double stars, and this leads him to the
following statement, in which believers in the old theological doctrine
that the earth is the sole center of mortal life and of divine care
would have found much comfort:
"It is very singular that no visible system yet discerned has any
resemblance to the orderly and beautiful system in which we live; and
one is thus led to think that probably our system is unique in its
character. At least it is unique among all _known_ systems."
If we grant that the solar system is the only one in which small planets
exist revolving around their sun in nearly circular orbits, then indeed
we seem to have closed all the outer universe against such beings as the
inhabitants of the earth. Beyond the sun's domain only whirling stars,
coupled in eccentric orbits, dark stars, some of them, but no
planets--in short a wilderness, full of all energies except those of
sentient life! This is not a pleasing picture, and I do not think we are
driven to contemplate it. Beyond doubt, Dr. See is right in concluding
that double and multiple star systems, with their components all of
magnitudes comparable among themselves, revolving in exceedingly
eccentric orbits under the stress of mutual gravitation, bear no
resemblance to the orderly system of our sun with its attendant worlds.
And it is not easy to imagine that the respective members of such
systems could themselves be the centers of minor systems of planets, on
account of the perturbing influences to which the orbits of such minor
systems would be subjected.
But the double and multiple stars, numerous though they be, are
outnumbered a hundred to one by the single stars which shine alone as
our sun does. What reason can we have, then, for excluding these single
stars, constituting as they do the vast majority of the celestial host,
from a similarity to the sun in respect to the manner of their evolution
from the original nebulous condition? These stars exhibit no companions,
such planetary attendants as they may have lying, on account of their
minuteness, far beyond the reach of our most powerful instruments. But
since they vastly outnumber the binary and multiple systems, and since
they resemble the sun in having no large attendants, should we be
justified, after all, in regarding our system as "unique"? It is true we
do not know, by visual evidence, that the single stars have planets, but
we find planets attending the only representative of that class of stars
that we are able to approach closely--the sun--and we know that the
existence of those planets is no mere accident, but the result of the
operation of physical laws which must hold good in every instance of
nebular condensation.
Two different methods are presented in which a rotating and contracting
nebula may shape itself into a stellar or planetary system. The first is
that described by Laplace, and generally accepted as the probable manner
of origin of the solar system--viz., the separation of rings from the
condensing mass, and the subsequent transformation of the rings into
planets. The planet Saturn is frequently referred to as an instance of
the operation of this law, in which the evolution has been arrested
after the separation of the rings, the latter having retained the ring
form instead of breaking and collecting into globes, forming in this
case rings of meteorites, and reminding us of the comparatively
scattered rings of asteroids surrounding the sun between the orbits of
Mars and Jupiter. This Laplacean process Dr. See regards as
theoretically possible, but apparently he thinks that if it took place
it was confined to our system.
The other method is that of the separation of the original rotating mass
into two nearly equal parts. The mechanical possibility of such a
process has been proved, mathematically, by Poincare and Darwin. This,
Dr. See thinks, is the method which has prevailed among the stars, and
prevailed to such a degree as to make the solar system, formed by the
ring method, probably a unique phenomenon in the universe.
Is it not more probable that both methods have been in operation, and
that, in fact, the ring method has operated more frequently than the
other? If not, why do the single stars so enormously outnumber the
double ones? It is of the essence of the fission process that the
resulting masses should be comparable in size. If, then, that process
has prevailed in the stellar universe to the practical exclusion of the
other, there should be very few single stars; whereas, as a matter of
fact, the immense majority of the stars are single. And, remembering
that the sun viewed from stellar distances would appear unattended by
subsidiary bodies, are we not justified in concluding that its origin is
a type of the origin of the other single stars?
While it is, as I have remarked, of the essence of the fission process
that the resulting parts of the divided mass should be comparable in
magnitude, it is equally of the essence of the ring, or Laplacean
process, that the bodies separated from the original mass should be
comparatively insignificant in magnitude.
As to the coexistence of the two processes, we have, perhaps, an example
in the solar system itself. Darwin's demonstration of the possible birth
of the moon from the earth, through fission and tidal friction, does not
apply to the satellites attending the other planets. The moon is
relatively a large body, comparable in that respect with the earth,
while the satellites of Jupiter and Saturn, for instance, are relatively
small. But in the case of Saturn there is visible evidence that the ring
process of satellite formation has prevailed. The existing rings have
not broken up, but their very existence is a testimony of the origin of
the satellites exterior to them from other rings which did break up.
Thus we need not go as far away as the stars in order to find instances
illustrating both the methods of nebular evolution that we have been
dealing with.
The conclusion, then, seems to be that we are not justified in assuming
that the solar system is unique simply because it differs widely from
the double and multiple star systems; and that we should rather regard
it as probable that the vast multitude of stars which do not appear,
when viewed with the telescope, or studied by spectroscopic methods, to
have any attendants comparable with themselves in magnitude, have
originated in a manner resembling that of the sun's origin, and may be
the centers of true planetary systems like ours. The argument, I think,
goes further than to show the mere possibility of the existence of such
planetary systems surrounding the single stars. If those stars did not
originate in a manner quite unlike the origin of the sun, then the
existence of planets in their neighborhood is almost a foregone
conclusion, for the sun could hardly have passed through the process of
formation out of a rotating nebula without evolving planets during its
contraction. And so, notwithstanding the eccentricities of the double
stars, we may still cherish the belief that there are eyes to see and
minds to think out in celestial space.
INDEX
NOTE.--Double, triple, multiple, and colored stars, star clusters,
nebulae, and temporary stars will be found arranged under the heads of
their respective constellations.
ANDROMEDA, Map No. 24, 125.
Stars: alpha, 126.
gamma, 128.
, 126. 36, 128.
Temporary star: 1885, 127.
Cluster: 457, 128.
Variable: R, 128.
Nebula: 116, 126.
AQUARIUS, Map No. 18, 107.
Stars: zeta, 106.
tau, 108.
psi, 108. 41, 106.
Sigma 2729, 106.
Sigma 2745 (12), 106.
Sigma 2998, 108.
Variables: R, 108.
S, 108.
T, 106.
Nebulae: 4628 (Rosse's "Saturn"), 108.
4678, 108.
AQUILA, Map No. 16, 95.
Stars: pi, 94.
11, 94.
23, 94.
57, 94.
Sigma 2644, 94.
Sigma 2544, 94.
Cluster: 4440, 94.
Variables: eta, 94.
R, 94.
ARGO: Map No. 2, 31; Map No. 7, 55.
Stars: Sigma 1097, 33.
Sigma 1146 (5), 35.
Clusters: 1551, 35.
1564, 35.
1571, 35.
1630, 56.
Nebula: 1564, 35.
ARIES, Map No. 22, 119.
Stars: gamma, 118.
epsilon, 120.
lambda, 118.
pi, 118.
14, 118.
30, 118.
41, 118.
52, 120.
Sigma 289, 118.
AURIGA, Map No. 5, 45.
Stars: alpha (Capella), 44.
beta (Menkalina), 46.
epsilon, 50.
theta, 48.
lambda, 50.
14, 50.
26, 50.
41, 51.
Sigma 616, 48.
Temporary star: 1892, 48.
Clusters: 996, 51.
1067, 51.
1119, 51.
1166, 51.
1295, 48.
BOOeTES, Map No. 11, 67.
Stars: alpha (Arcturus), 66.
delta, 71.
epsilon (Mirac), 71.
zeta, 70.
iota, 71.
kappa, 71.
, 71.
xi, 70.
pi, 70.
Sigma 1772, 70.
Sigma 1890 (39), 71.
Sigma 1909 (44), 71.
Sigma 1910 (279), 70.
Sigma 1926, 71.
CAMELOPARDALUS, Map No. 25, 133.
Stars: 1, 134.
2, 134.
7, 135.
Sigma 385, 134.
Sigma 390, 134.
Cluster: 940, 135.
CANES VENATICI, Map No. 26, 137; Map No. 11, 67.
Stars: 2, 136.
12 (Cor Caroli), 136.
Sigma 1606, 136.
Sigma 1768 (25), 72.
Cluster: 3936, 72.
Nebula: 3572, 136.
CANIS MAJOR, Map No. 2, 31.
Stars: alpha (Sirius), 30.
delta, 33.
, 33.
Clusters: 1454, 33.
1479, 33.
1512, 33.
Variable: gamma, 33.
Nebula: 1511, 33.
CANIS MINOR, Map No. 3, 34.
Stars: alpha (Procyon), 36.
14, 36.
Sigma 1126 (31 Can. Min. Bode), 36.
CANCER, Map No. 4, 39.
Stars: zeta, 43.
iota, 44.
66, 44.
Sigma 1223, 44.
Sigma 1291, 44.
Sigma 1311, 44.
Clusters: Praesepe, 43.
1712, 44.
CAPRICORNUS, Map No. 13, 83; Map No. 18, 107.
Stars: alpha, 84.
beta, 85.
omicron, 85.
pi, 85.
rho, 85.
sigma, 85.
Cluster: 4608, 85.
CASSIOPEIA, Map No. 25, 133.
Stars: eta, 132.
iota, 132.
sigma, 132.
psi, 132.
Temporary star: 1572 (Tycho's), 134.
Cluster: 392, 134.
CEPHEUS, Map No. 25, 133.
CETUS, Map No. 20, 112.
Stars: alpha, 118.
gamma, 113.
zeta, 111.
eta, 111.
26, 111.
42, 111.
Variables: omicron (Mira), 111.
R, 113.
S, 113.
COLUMBA, Map No. 2, 31.
COMA BERENICES, Map No. 6, 53.
Stars: 2, 54.
12, 54.
17, 54.
24, 54.
35, 54.
42, 54.
Clusters: 2752, 56.
3453, 56.
CORONA BOREALIS, Map No. 11, 67.
Stars: gamma, 72.
zeta, 73.
eta, 72.
nu, 73.
sigma, 73.
Sigma 1932, 72.
Temporary star: 1866, 73.
CORVUS, Map No. 8, 58.
Star: delta, 57.
CRATER, Map No. 8, 58.
Variable: R, 57.
CYGNUS, Map No. 17, 99.
Stars: beta (Albireo), 103.
delta, 104.
lambda, 105.
, 105.
omicron^2, 104.
chi (17), 104.
psi, 104.
49, 104.
52, 104.
61, 105.
Temporary star: 1876, 105.
Cluster: 4681, 105.
Variable: chi, 104.
DELPHINUS, Map No. 16, 95.
Stars: alpha, 96.
beta, 96.
gamma, 94.
DRACO, Map No. 15, 91; Map No. 26, 137.
Stars: gamma, 93.
epsilon, 93.
eta, 93.
, 93.
nu, 93.
Sigma 1984, 93.
Sigma 2054, 93.
Sigma 2078 (17), 93.
Sigma 2323, 93.
Nebulae: 4373, 93.
4415, 94.
EQUULEUS, Map No. 18, 107.
Stars: beta, 109.
gamma, 109.
Sigma 2735, 108.
Sigma 2737, 108.
Sigma 2742, 108.
Sigma 2744, 108.
ERIDANUS, Map No. 21, 115.
Stars: gamma, 114.
omicron^2, 116.
12, 114.
Sigma 470 (32), 114.
Sigma 516 (39), 114.
Sigma 590, 116.
Nebula: 826, 116.
GEMINI, Map No. 4, 39.
Stars: alpha (Castor), 38.
beta (Pollux), 40.
gamma, 43.
delta, 41.
epsilon, 43.
zeta, 41.
eta, 42.
kappa, 40.
lambda, 43.
, 43.
pi, 40.
15, 43.
38, 43.
Cluster: 1360, 42.
Variables: zeta, 41.
eta, 42.
R, 41.
S, 41.
T, 41.
U, 41.
Nebula: 1532, 41.
HERCULES, Map No. 14, 87; Map No. 15, 91.
Stars: alpha, 89.
gamma, 89.
delta, 89.
zeta, 89.
kappa, 89.
, 90.
rho, 90.
42, 90.
95, 90.
Sigma 2101, 90.
Sigma 2104, 90.
Sigma 2215, 90.
Sigma 2289, 90.
Nebulae: 4230 (M 13), 92.
4234, 92.
HYDRA, Map No. 3, 34; Map No. 8, 58; Map No. 10, 65.
Stars: alpha, 56.
epsilon, 36.
theta, 36.
Bu. 339, 56.
Sigma 1245, 36.
Variable: R, 59.
Nebulae: 2102, 56.
3128, 59.
LACERTA, Map No. 17, 99.
LEO, Map No. 6, 53.
Stars: gamma, 52.
iota, 52.
tau, 52.
49, 52.
54, 52.
88, 52.
90, 52.
Variable: R, 52.
Nebula: 1861, 52.
LEO MINOR, Map No. 26, 137.
LEPUS, Map No. 1, 21; Map No. 2, 31.
Stars: alpha, 30.
beta, 30.
gamma, 30.
iota, 30.
45, 30.
Variable: R, 29.
LIBRA, Map No. 10, 65.
Stars: A, 64.
alpha, 64.
beta, 64.
iota, 64.
Variable: delta, 64.
LYNX, Map No. 5, 45.
Stars: 4, 51.
5, 51.
12, 51.
14, 51.
19, 51.
38, 52.
Sigma 958, 51.
Sigma 1009, 51.
Sigma 1333, 51.
LYRA, Map No. 17, 99.
Stars: alpha (Vega), 97.
beta, 100.
epsilon, 98.
zeta, 100.
17, 103.
Variable: beta, 100.
Nebula: 4447 (Ring), 102.
MONOCEROS, Map No. 1, 21; Map No. 3, 34.
Stars: 4, 35.
8, 35.
11, 35.
Sigma 921, 35.
Sigma 938, 35.
Sigma 950, 35.
Sigma 1183, 35.
Sigma 1190, 35.
Clusters: 1424, 35.
1465, 36.
1483, 36.
1611, 36.
1637, 36.
Variable: S, 35.
OPHIUCHUS, Map No. 12, 77; Map No. 14, 87.
Stars: lambda, 86.
tau, 86.
36, 79.
39, 79.
67, 86.
70, 86.
73, 86.
Sigma 2166, 86.
Sigma 2173, 86.
Temporary star: 1604, 80.
Clusters: 4211, 79.
4256, 88.
4264, 79.
4268, 79.
4269, 79.
4270, 79.
4315, 88.
4346, 79.
4410, 88.
Variable: R, 80.
ORION, Map No. 1, 21.
Stars: alpha (Betelgeuse), 27.
beta (Rigel), 20.
delta, 23.
zeta, 23.
eta, 24.
theta (Trapezium), 25.
iota, 27.
lambda, 28.
rho, 28.
sigma, 24.
tau, 28.
psi^2, 29.
Sigma 627, 28.
Sigma 629, 28.
Sigma 652, 28.
Sigma 725, 24.
Sigma 728 (A 32), 28.
Sigma 729, 29.
Sigma 747, 27.
Sigma 750, 27.
Sigma 795 (52), 27.
Sigma 816, 29.
Omicron Sigma 98 (i), 28.
Clusters: 905, 29.
1184, 27.
1361, 29.
1376, 29.
Nebulae: Great Orion Nebula, 25.
1227, 23.
1267, 29.
PEGASUS, Map No. 19, 110.
Stars: beta, 109.
gamma, 109.
epsilon, 109.
eta, 109.
PERSEUS, Map No. 24, 125.
Stars: epsilon, 129.
zeta, 130.
eta, 129.
Clusters: 512, 129.
521, 129.
Variable: beta (Algol), 130.
PISCES, Map No. 18, 107; Map No. 20, 112; Map No. 22, 119.
Stars: alpha, 117.
zeta, 117.
psi, 117.
55, 117.
65, 117.
66, 117.
77, 117.
Variable: R, 118.
SAGITTA, Map No. 16, 95.
Stars: epsilon, 94.
zeta, 94.
theta, 94.
Nebula: 4572, 94.
SAGITTARIUS, Map No. 12, 77; Map No. 13, 83.
Stars: , 80.
54, 84.
Clusters: M 25, 81.
4355, 81.
4361 (M 8), 81.
4397 (M 24), 81.
4424, 84.
Variables: R, 84.
T, 84.
U, 82.
V, 82.
SCORPIO, Map No. 12, 77.
Stars: alpha (Antares), 75.
beta, 76.
nu, 76.
xi, 76.
sigma, 76.
Temporary star: 1860, 78.
Clusters: 4173, 78.
4183, 78.
SCUTUM SOBIESKII, Map No. 12, 77; Map No. 13, 83.
Stars: Sigma 2306, 82.
Sigma 2325, 82.
Clusters: 4400, 82.
4426, 82.
4437, 82.
Variable: R, 82.
Nebula: 4441, 82.
SERPENS, Map No. 12, 77; Map No. 14, 87.
Stars: alpha, 86.
beta, 86.
delta, 86.
theta, 88.
nu, 86.
Variable: R, 86.
TAURUS, Map No. 23, 121.
Stars: alpha (Aldebaran), 123.
eta (Alcyone), 120.
theta, 123.
kappa, 123.
sigma, 124.
tau, 124.
phi, 123.
chi, 123.
30, 122.
Sigma 412 (7), 120.
Sigma 430, 122.
Sigma 674, 124.
Sigma 716, 124.
Clusters: Hyades, 120.
Pleiades, 120.
1030, 124.
Variable: lambda, 122.
Nebulae: in Pleiades, 120.
1157 (Crab Net), 124.
TRIANGULUM, Map No. 24, 125.
Star: 6, 129.
Nebula: 352, 129.
URSA MAJOR, Map No. 26, 137.
Stars: zeta (Mizar), 135.
iota, 135.
nu, 135.
xi, 135.
sigma^2, 135.
23, 135.
57, 135.
65, 135.
Nebulae: 1949, 136.
1950, 136.
2343, 136.
URSA MINOR, Map No. 26, 137.
Stars: alpha (Pole Star), 138.
pi, 138.
VIRGO, Map No. 9, 61.
Stars: alpha (Spica), 59.
gamma, 59.
theta, 60.
84, 62.
Sigma 1669, 59.
Sigma 1846, 62.
Variables: R, 63.
S, 63.
U, 63.
Nebulae: Field of the, 62.
2806, 63.
2961, 63.
3105, 63.
VULPECULA, Map No. 17, 99.
Star: Sigma 2695, 106.
Temporary star: 1670, 106.
Nebula: 4532 (Dumb Bell), 106.
THE MOON, most interesting of telescopic objects, 156;
telescopic views of moon reversed, 157.
Craters, ring mountains, and ringed plains:
Agatharchides, 179.
Agrippa, 168.
Albategnius, 171.
Alhazen, 160.
Aliacensis, 171.
Alphonsus, 176.
Archimedes, 175.
Ariadaeus, 168.
Aristarchus,174.
Aristillus, 167.
Aristoteles, 162.
Arzachel, 176.
Atlas, 160.
Autolycus, 167.
Bailly, 178.
Ball, 176.
Barrow, 162.
Beer, 175.
Berzelius, 160.
Billy, 179.
Bullialdus, 180.
Burckhardt, 157.
Capuanus, 179.
Cassini, 167.
Catharina, 170,
Cichus, 179.
Clavius, 178.
Cleomenes, 159.
Condorcet, 160.
Copernicus, 175.
Cyrillus, 170.
Delisle, 174
Endymion, 160.
Eratosthenes, 175.
Eudoxus, 162.
Euler, 174.
Firmicus, 160.
Fracastorius, 169, 179.
Furnerius, 161.
Gassendi, 179.
Gauss, 159.
Geminus, 160.
Goclenius, 169.
Godin, 168.
Grimaldi, 179.
Guttemberg, 169.
Hainzel, 179.
Hansen, 160.
Helicon, 174.
Hell, 176.
Hercules, 160.
Herodotus, 174.
Herschel, Caroline, 174.
Hipparchus, 171.
Humboldt, 161.
Hyginus, 168.
Julius Caesar, 168.
Kepler, 176.
Lambert, 174.
Landsberg, 180.
Langrenus, 160, 168.
Letronne, 179.
Leverrier, 174.
Lexell, 176.
Lichtenberg, 174.
Linne, 165.
Longomontanus, 178.
Macrobius, 159.
Maginus, 178.
Manilius, 166.
Maurolycus, 172.
Menelaus, 166.
Mercator, 179.
Mersenius, 179.
Messala, 160.
Messier, 169.
Newton, 178.
Petavius, 160, 168.
Picard, 157.
Piccolomini, 171.
Pico, 172.
Plato, 172.
Plinius, 166.
Posidonius, 163, 164.
Proclus, 158.
Ptolemaeus, 176.
Purbach, 176.
Sacrobosco, 171.
Schickard, 178.
Schiller, 178.
Silberschlag, 168.
Stoefler, 171.
Sulpicius Gallus, 166.
Theaetetus, 167.
Thebit, 176.
Theophilus, 170.
Timocharis, 174.
Tobias Mayer, 176.
Tralles, 159.
Triesnecker, 168.
Tycho, 177, 178.
Vendelinus, 160, 168.
Vieta, 179.
Vitello, 179.
Walter, 171.
Wargentin, 179.
Werner, 171.
Wilhelm I, 178.
_Maria_, or "Seas":
_Lacus Somniorum_, 163.
_Mare Crisium_, 157, 159, 160.
_Mare Fecunditatis_, 160, 168.
_Mare Frigoris_, 162, 172.
_Mare Humboldtianum_, 160.
_Mare Humorum_, 176, 179.
_Mare Imbrium_, 163, 172, 174.
_Mare Nectaris_, 168.
_Mare Nubium_, 176.
_Mare Serenitatis_, 163, 164, 165.
_Mare Tranquilitatis_, 168.
_Mare Vaporum_, 166, 167.
_Oceanus Procellarum_, 172, 176, 179.
_Palus Nebularum_, 167.
_Palus Putredinis_, 167.
_Palus Somnii_, 159.
_Sinus AEstuum_, 172.
_Sinus Iridum_, 172, 173.
Other formations:
Alps Mountains, 163.
Apennine Mountains, 163, 167, 175.
Cape Agarum, 158.
Cape Heraclides, 173.
Cape Laplace, 173.
Carpathian Mountains, 176.
Caucasus Mountains, 163.
Cordilleras Mountains, 180.
D'Alembert Mountains, 180.
Doerfel Mountains, 180.
Haemus Mountains, 165.
Harbinger Mountains, 174.
Leibnitz Mountains, 180.
"Lunar Railroad," 176.
Mt. Argaeus, 165, 167.
Mt. Hadley, 167.
Mt. Huygens, 175.
Pyrenees Mountains, 169.
Taurus Mountains, 164.
THE PLANETS: Are there planets among the stars? 183.
Mars, two views of, 17.
best advertised of planets, 151.
favorable oppositions of, 152.
seen with 5-inch telescope, 152.
polar caps of, 152.
color of, 152.
dark markings on, 152.
"canals," 153.
earthlike condition of, 153.
Mercury, phases of, 155.
peculiar rotation of, 155.
markings on, 155.
probably not habitable, 155.
Jupiter, easiest planet for amateurs, 141.
seen with 5-inch glass, 141.
satellites, swift motions of, 142.
velocity of planet's equator, 142.
how to see all sides of, 142, 143.
watching rotation of, 143.
eclipses and transits of satellites, 144, 147.
belts and clouds of, 145.
different rates of rotation, 145.
names and numbers of satellites, 146.
Saturn, next to Jupiter in attractiveness, 147.
seen with 5-inch glass, 148.
its moons and their orbits, 148, 149.
polar view of system, 149.
Roche's limit, 149, 150.
origin of the rings, 150.
Pickering's ninth satellite, 151.
the satellites as telescopic objects, 151.
Venus, her wonderful brilliance, 153.
her atmosphere seen, 153.
Lowell's observations, 153.
Schiaparelli's observations, 154.
her peculiar rotation, 154.
how to see, in daytime, 155.
Neptune and Uranus, 155.
THE SUN, 181.
shade glasses for telescopes in viewing, 181.
solar prism, 181.
helioscope, 181.
periodicity of spots, 181.
to see, by projection, 182.
spectroscope for solar observation, 182.
THE TELESCOPE:
refractors and reflectors, 2, 8.
eyepieces, 6, 9, 10.
aberration (chromatic), 6;
(spherical), 6, 17.
achromatic telescopes, how made, 7.
object glass, 8.
magnifying power, 11.
mountings, 12.
rules for testing, 13.
image of star in, 14.
image in and out of focus, 14, 15, 17.
astigmatism, 16.
THE END
[Illustration]
1692 S. _Pleasures of the Telescope_ _GARRETT P. SERVISS_
This book says to the amateur, in effect:--"What if you have not all
advantages of clockwork and observatory equipment. You may know
something of the witchery of the heavens even with a little
telescope of three to five inches aperture!" "Pleasures of the
Telescope" is popular in style rather than technical. For setting
forth "the chief attractions of the starry heavens," a complete set
of star-maps is included, showing "all the stars visible to the
naked eye in the regions of sky represented, and in addition some
stars that can only be seen with optical aid." In six chapters these
twenty-six maps are described so plainly that the amateur can
readily find all the interesting star-groups, clusters, and nebulae,
and also the colored or double stars. In the three concluding
chapters the moon and planets receive special consideration. In the
opening chapter the amateur is told how to select and test a glass.
_Booklovers Bulletin._
Transcriber's Note
Minor errors and inconsistencies in punctuation and hyphenation have
been silently corrected.
Some illustrations have been relocated a short distance within the text.
Original page numbers have been retained in the index.
Greek letters, used to identify stars, are replaced with the full name
of the Greek letter, e.g. alpha. Upper case Greek letters are shown by
capitalising the initial letter, e.g. Sigma 1126
A caret (^) is used to represent superscripts, e.g. nu^1 and nu^2
The following minor corrections have also been made:
p3: "wil" has been corrected to "will".
p28: Sigma 629 is not shown on Map No. 1. The location of _m_ Orionis
is marked as Sigma 696. This inconsistency has not been corrected.
p54: "for colors" has been corrected to "four colors".
p68: "1,065,790,250,000,000" has been corrected to
"1,065,702,500,000,000".
p163-164: "magnical" has been corrected to "magical".
p179: A repeated "and" has been removed.
End of Project Gutenberg's Pleasures of the telescope, by Garrett Serviss