IN THE STARRY HEAVENS
"Now constellations, Muse, and signs rehearse;
In order let them sparkle in thy verse."--MANILIUS.
Let us imagine ourselves the happy possessors of three properly mounted
telescopes of five, four, and three inches aperture, respectively. A
fine midwinter evening has come along, the air is clear, cool, and
steady, and the heavens, of that almost invisible violet which is
reserved for the lovers of celestial scenery, are spangled with stars
that hardly twinkle. We need not disturb our minds about a few thin
clouds here and there floating lazily in the high air; they announce a
change of weather, but they will not trouble us to-night.
Which way shall we look? Our eyes will answer the question for us.
However we may direct them, they instinctively return to the south, and
are lifted to behold Orion in his glory, now near the meridian and
midway to the zenith, with Taurus shaking the glittering Pleiades before
him, and Canis Major with the flaming Dog Star following at his heels.
Not only is Orion the most brilliant of all constellations to the casual
star-gazer, but it contains the richest mines that the delver for
telescopic treasures can anywhere discover. We could not have made a
better beginning, for here within a space of a few square degrees we
have a wonderful variety of double stars and multiple stars, so close
and delicate as to test the powers of the best telescopes, besides a
profusion of star-clusters and nebulae, including one of the supreme
marvels of space, the Great Nebula in the Sword.
[Illustration: MAP NO. 1.]
Our star map No. 1 will serve as a guide to the objects which we are
about to inspect. Let us begin operations with our smallest telescope,
the three-inch. I may remark here that, just as the lowest magnifying
power that will clearly reveal the object looked for gives ordinarily
better results than a higher power, so the smallest telescope that is
competent to show what one wishes to see is likely to yield more
satisfaction, as far as that particular object is concerned, than a
larger glass. The larger the object glass and the higher the power, the
greater are the atmospheric difficulties. A small telescope will perform
very well on a night when a large one is helpless.
Turn the glass upon beta (Rigel), the white first-magnitude star in
Orion's left foot. Observe whether the image with a high power is clear,
sharp, and free from irregular wisps of stray light. Look at the rings
in and out of focus, and if you are satisfied with the performance, try
for the companion. A good three-inch is certain to show it, except in a
bad state of the atmosphere, and even then an expert can see it, at
least by glimpses. The companion is of the ninth magnitude, some say the
eighth, and the distance is about 9.5", angle of position (hereafter
designated by p.) 199 deg..[1] Its color is blue, in decided contrast with
the white light of its great primary. Sir John Herschel, however, saw
the companion red, as others have done. These differences are doubtless
due to imperfections of the eye or the telescope. In 1871 Burnham
believed he had discovered that the companion was an exceedingly close
double star. No one except Burnham himself succeeded in dividing it, and
he could only do so at times. Afterward, when he was at Mount Hamilton,
he tried in vain to split it with the great thirty-six-inch telescope,
in 1889, 1890, and 1891. His want of success induced him to suggest that
the component stars were in rapid motion, and so, although he admitted
that it might not be double after all, he advised that it should be
watched for a few years longer. His confidence was justified, for in
1898 Aitken, with the Lick telescope, saw and measured the distance of
the extremely minute companion--distance 0.17", p. 177 deg..
[1] The angle of position measures the inclination to the meridian of a
line drawn between the principal star and its companion; in other words,
it shows in what direction from the primary we must look for the
companion. It is reckoned from 0 deg. up to 360 deg., beginning at the north
point and passing around by east through south and west to north again.
Thus, if the angle of position is 0 deg. or 360 deg., the companion is on the
north side of the primary; if the angle is 90 deg., the companion is to the
east; if 180 deg., to the south; if 270 deg., to the west, and so for
intermediate angles. It must be remembered, however, that in the field
of the telescope the top is south and the bottom north, unless a prism
is used, when directions become complicated. East and west can be
readily identified by noticing the motion of a star through the field;
it moves toward the west and from the east.
Rigel has been suspected of a slight degree of variability. It is
evidently a star of enormous actual magnitude, for its parallax escapes
trustworthy measurement. It can only be ranked among the very first of
the light-givers of the visible universe. Spectroscopically it belongs
to a peculiar type which has very few representatives among the bright
stars, and which has been thus described: "Spectra in which the hydrogen
lines and the few metallic lines all appear to be of equal breadth and
sharp definition." Rigel shows a line which some believe to represent
magnesium; but while it has iron lines in its spectrum, it exhibits no
evidence of the existence of any such cloud of volatilized iron as that
which helps to envelop the sun.
For another test of what the three-inch will do turn to zeta, the lower,
or left-hand, star in the Belt. This is a triple, the magnitudes being
second, sixth, and tenth. The sixth-magnitude star is about 2.5" from
the primary, p. 149 deg., and has a very peculiar color, hard to describe.
It requires careful focusing to get a satisfactory view of this star
with a three-inch telescope. Use magnifying powers up to two hundred and
fifty diameters. With our four-inch the star is much easier, and the
five-inch shows it readily with a power of one hundred. The
tenth-magnitude companion is distant 56", p. 8 deg., and may be glimpsed
with the three-inch. Upon the whole, we shall find that we get more
pleasing views of zeta Orionis with the four-inch glass.
Just to the left of zeta, and in the same field of view with a very low
power, is a remarkable nebula bearing the catalogue number 1227. We must
use our five-inch on this with a low power, but with zeta out of the
field in order to avoid its glare. The nebula is exceedingly faint, and
we can be satisfied if we see it simply as a hazy spot, although with
much larger telescopes it has appeared at least half a degree broad.
Tempel saw several centers of condensation in it, and traced three or
four broad nebulous streams, one of which decidedly suggested spiral
motion.
The upper star in the Belt, delta, is double; distance, 53", p. 360 deg.;
magnitudes, second and seventh very nearly; colors, white and green or
blue. This, of course, is an easy object for the three-inch with a low
magnifying power. It would be useless to look for the two fainter
companions of delta, discovered by Burnham, even with our five-inch
glass. But we shall probably need the five-inch for our next attempt,
and it will be well to put on a high power, say three hundred diameters.
The star to be examined is the little brilliant dangling below the
right-hand end of the Belt, toward Rigel. It appears on the map as eta.
Spare no pains in getting an accurate focus, for here is something worth
looking at, and unless you have a trained eye you will not easily see
it. The star is double, magnitudes third and sixth, and the distance
from center to center barely exceeds 1", p. 87 deg.. A little tremulousness
of the atmosphere for a moment conceals the smaller star, although its
presence is manifest from the peculiar jutting of light on one side of
the image of the primary. But in an instant the disturbing undulations
pass, the air steadies, the image shrinks and sharpens, and two points
of piercing brightness, almost touching one another, dart into sight,
the more brilliant one being surrounded by an evanescent circle, a tiny
ripple of light, which, as it runs round the star and then recedes,
alternately embraces and releases the smaller companion. The wash of the
light-waves in the atmosphere provokes many expressions of impatience
from the astronomer, but it is often a beautiful phenomenon
nevertheless.
Between eta and delta is a fifth-magnitude double star, Sigma 725, which
is worth a moment's attention. The primary, of a reddish color, has a
very faint star, eleventh magnitude, at a distance of 12.7", p. 88 deg..
Still retaining the five-inch in use, we may next turn to the other end
of the Belt, where, just under zeta, we perceive the fourth-magnitude
star sigma. He must be a person of indifferent mind who, after looking
with unassisted eyes at the modest glimmering of this little star, can
see it as the telescope reveals it without a thrill of wonder and a cry
of pleasure. The glass, as by a touch of magic, changes it from one into
eight or ten stars. There are two quadruple sets three and a half
minutes of arc apart. The first set exhibits a variety of beautiful
colors. The largest star, of fourth magnitude, is pale gray; the second
in rank, seventh magnitude, distance 42", p. 61 deg., presents a singular
red, "grape-red" Webb calls it; the third, eighth magnitude, distance
12", p. 84 deg., is blue; and the fourth, eleventh magnitude, distance 12",
p. 236 deg., is apparently white. Burnham has doubled the fourth-magnitude
star, distance 0.23". The second group of four stars consists of three
of the eighth to ninth magnitude, arranged in a minute triangle with a
much fainter star near them. Between the two quadruple sets careful
gazing reveals two other very faint stars. While the five-inch gives a
more satisfactory view of this wonderful multiple star than any smaller
telescope can do, the four-inch and even the three-inch would have shown
it to us as a very beautiful object. However we look at them, there is
an appearance of association among these stars, shining with their
contrasted colors and their various degrees of brilliance, which is
significant of the diversity of conditions and circumstances under which
the suns and worlds beyond the solar walk exist.
From sigma let us drop down to see the wonders of Orion's Sword
displayed just beneath. We can use with advantage any one of our three
telescopes; but since we are going to look at a nebula, it is fortunate
that we have a glass so large as five inches aperture. It will reveal
interesting things that escape the smaller instruments, because it
grasps more than one and a half times as much light as the four-inch,
and nearly three times as much as the three-inch; and in dealing with
nebulae a plenty of light is the chief thing to be desired. The middle
star in the Sword is theta, and is surrounded by the celebrated Nebula
of Orion. The telescope shows theta separated into four stars arranged
at the corners of an irregular square, and shining in a black gap in the
nebula. These four stars are collectively named the Trapezium. The
brightest is of the sixth magnitude, the others are of the seventh,
seven and a half, and eighth magnitudes respectively. The radiant mist
about them has a faint greenish tinge, while the four stars, together
with three others at no great distance, which follow a fold of the
nebula like a row of buttons on a coat, always appear to me to show an
extraordinary liveliness of radiance, as if the strange haze served to
set them off.
[Illustration: THE TRAPEZIUM WITH THE FIFTH AND SIXTH STARS.]
Our three-inch would have shown the four stars of the Trapezium
perfectly well, and the four-inch would have revealed a fifth star, very
faint, outside a line joining the smallest of the four and its nearest
neighbor. But the five-inch goes a step farther and enables us, with
steady gazing to see even a sixth star, of only the twelfth magnitude,
just outside the Trapezium, near the brightest member of the quartet.
The Lick telescope has disclosed one or two other minute points of light
associated with the Trapezium. But more interesting than the Trapezium
is the vast cloud, full of strange shapes, surrounding it. Nowhere else
in the heavens is the architecture of a nebula so clearly displayed. It
is an unfinished temple whose gigantic dimensions, while exalting the
imagination, proclaim the omnipotence of its builder. But though
unfinished it is not abandoned. The work of creation is proceeding
within its precincts. There are stars apparently completed, shining like
gems just dropped from the hand of the polisher, and around them are
masses, eddies, currents, and swirls of nebulous matter yet to be
condensed, compacted, and constructed into suns. It is an education in
the nebular theory of the universe merely to look at this spot with a
good telescope. If we do not gaze at it long and wistfully, and return
to it many times with unflagging interest, we may be certain that there
is not the making of an astronomer in us.
Before quitting the Orion nebula do not fail to notice an
eighth-magnitude star, a short distance northeast of the Great Nebula,
and nearly opposite the broad opening in the latter that leads in toward
the gap occupied by the Trapezium. This star is plainly enveloped in
nebulosity, that is unquestionably connected with the larger mass of
which it appears to form a satellite.
At the lower end of the Sword is the star iota, somewhat under the third
magnitude. Our three-inch will show that it has a bluish companion of
seventh or eighth magnitude, at a little more than 11" distance, p.
142 deg., and the larger apertures will reveal a third star, of tenth
magnitude, and reddish in color, distance 49", p. 103 deg.. Close by iota we
find the little double star Sigma 747, whose components are of five and
a half and six and a half magnitudes respectively, and separated 36", p.
223 deg.. Above the uppermost star in the Sword is a small star cluster, No.
1184, which derives a special interest from the fact that it incloses a
delicate double star, Sigma 750, whose larger component is of the sixth
magnitude, while the smaller is of the ninth, and the distance is only
4.3", p. 59 deg.. We may try the four-inch on this object.
Having looked at alpha (Betelgeuse), the great topaz star on Orion's
right shoulder, and admired the splendor of its color, we may turn the
four-inch upon the star Sigma 795, frequently referred to by its number
as "52 Orionis." It consists of one star of the sixth and another of
sixth and a half magnitude, only 1.5" apart, p. 200 deg.. Having separated
them with a power of two hundred and fifty diameters on the four-inch,
we may try them with a high power on the three-inch. We shall only
succeed this time if our glass is of first-rate quality and the air is
perfectly steady.
The star lambda in Orion's head presents an easy conquest for the
three-inch, as it consists of a light-yellow star of magnitude three and
a half and a reddish companion of the sixth magnitude; distance 4", p.
43 deg.. There is also a twelfth-magnitude star at 27", p. 183 deg., and a tenth
or eleventh magnitude one at 149", p. 278 deg.. These are tests for the
five-inch, and we must not be disappointed if we do not succeed in
seeing the smaller one even with that aperture.
Other objects in Orion, to be found with the aid of our map, are: Sigma
627, a double star, magnitude six and a half and seven, distance 21", p.
260 deg.; Omicron Sigma 98, otherwise named iota Orionis, double, magnitude
six and seven, distance 1", p. 180 deg., requires five-inch glass; Sigma
652, double, magnitudes six and a half and eight, distance 1.7", p.
184 deg.; rho, double, magnitudes five and eight and a half, the latter
blue, distance 7", p. 62 deg., may be tried with a three-inch; tau, triple
star, magnitudes four, ten and a half, and eleven, distances 36", p.
249 deg., and 36", p. 60 deg.. Burnham discovered that the ten-and-a-half
magnitude star is again double, distance 4", p. 50 deg.. There is not much
satisfaction in attempting tau Orionis with telescopes of ordinary
apertures; Sigma 629 otherwise _m_ Orionis, double, magnitudes five and
a half (greenish) and seven, distance 31.7", p. 28 deg., a pretty object;
Sigma 728, otherwise A 32, double, magnitudes five and seven, distance,
0.5" or less, p. 206 deg., a rapid binary,[2] which is at present too close
for ordinary telescopes, although it was once within their reach; Sigma
729, double, magnitudes six and eight, distance 2", p. 26 deg., the smaller
star pale blue--try it with a four-inch, but five-inch is better; Sigma
816, double, magnitudes six and half and eight and a half, distance 4",
p. 289 deg.; psi 2, double, magnitudes five and a half and eleven, distance
3", or a little less, p. 322 deg.; 905, star cluster, contains about twenty
stars from the eighth to the eleventh magnitude; 1267, nebula, faint,
containing a triple star of the eighth magnitude, two of whose
components are 51" apart, while the third is only 1.7" from its
companion, p. 85 deg.; 1376, star cluster, small and crowded; 1361, star
cluster, triangular shape, containing thirty stars, seventh to tenth
magnitudes, one of which is a double, distance 2.4".
[2] The term "binary" is used to describe double stars which are in
motion about their common center of gravity.
Let us now leave the inviting star-fields of Orion and take a glance at
the little constellation of Lepus, crouching at the feet of the mythical
giant. We may begin with a new kind of object, the celebrated red
variable R Leporis (map No. 1). This star varies from the sixth or
seventh magnitude to magnitude eight and a half in a period of four
hundred and twenty-four days. Hind's picturesque description of its
color has frequently been quoted. He said it is "of the most intense
crimson, resembling a blood-drop on the black ground of the sky." It is
important to remember that this star is reddest when faintest, so that
if we chance to see it near its maximum of brightness it will not
impress us as being crimson at all, but rather a dull, coppery red. Its
spectrum indicates that it is smothered with absorbing vapors, a sun
near extinction which, at intervals, experiences an accession of energy
and bursts through its stifling envelope with explosive radiance, only
to faint and sink once more. It is well to use our largest aperture in
examining this star.
We may also employ the five-inch for an inspection of the double star
iota, whose chief component of the fifth magnitude is beautifully tinged
with green. The smaller companion is very faint, eleventh magnitude, and
the distance is about 13", p. 337 deg..
Another fine double in Lepus is kappa, to be found just below iota; the
components are of the fifth and eighth magnitudes, pale yellow and blue
respectively, distance 2.5", p. 360 deg.; the third-magnitude star alpha has
a tenth-magnitude companion at a distance of 35", p. 156 deg., and its
neighbor beta (map No. 2), according to Burnham, is attended by three
eleventh-magnitude stars, two of which are at distances of 206", p. 75 deg.,
and 240", p. 58 deg., respectively, while the third is less than 3" from
beta, p. 288 deg.; the star gamma (map No. 2) is a wide double, the distance
being 94", and the magnitudes four and eight. The star numbered 45 is a
remarkable multiple, but the components are too faint to possess much
interest for those who are not armed with very powerful telescopes.
[Illustration: MAP NO. 2.]
From Lepus we pass to Canis Major (map No. 2). There is no hope of our
being able to see the companion of alpha (Sirius), at present (1901),
even with our five-inch. Discovered by Alvan Clark with an eighteen-inch
telescope in 1862, when its distance was 10" from the center of Sirius,
this ninth-magnitude star has since been swallowed up in the blaze of
its great primary. At first, it slightly increased its distance, and
from 1868 until 1879 most of the measures made by different observers
considerably exceeded 11". Then it began to close up, and in 1890 the
distance scarcely exceeded 4". Burnham was the last to catch sight of it
with the Lick telescope in that year. After that no human eye saw it
until 1896, when it was rediscovered at the Lick Observatory. Since
then the distance has gradually increased to nearly 5". According to
Burnham, its periodic time is about fifty-three years, and its nearest
approach to Sirius should have taken place in the middle of 1892. Later
calculations reduce the periodic time to forty-eight or forty-nine
years. If we can not see the companion of the Dog Star with our
instruments, we can at least, while admiring the splendor of that
dazzling orb, reflect with profit upon the fact that although the
companion is ten thousand times less bright than Sirius, it is half as
massive as its brilliant neighbor. Imagine a subluminous body half as
ponderous as the sun to be set revolving round it somewhere between
Uranus and Neptune. Remember that that body would possess one hundred
and sixty-five thousand times the gravitating energy of the earth, and
that five hundred and twenty Jupiters would be required to equal its
power of attraction, and then consider the consequences to our
easy-going planets! Plainly the solar system is not cut according to the
Sirian fashion. We shall hardly find a more remarkable coupling of
celestial bodies until we come, on another evening, to a star that
began, ages ago, to amaze the thoughtful and inspire the superstitious
with dread--the wonderful Algol in Perseus.
We may remark in passing that Sirius is the brightest representative of
the great spectroscopic type I, which includes more than half of all the
stars yet studied, and which is characterized by a white or bluish-white
color, and a spectrum possessing few or at best faint metallic lines,
but remarkably broad, black, and intense lines of hydrogen. The
inference is that Sirius is surrounded by an enormous atmosphere of
hydrogen, and that the intensity of its radiation is greater, surface
for surface, than that of the sun. There is historical evidence to
support the assertion, improbable in itself, that Sirius, within
eighteen hundred years, has changed color from red to white.
With either of our telescopes we shall have a feast for the eye when we
turn the glass upon the star cluster No. 1454, some four degrees south
of Sirius. Look for a red star near the center. Observe the curving rows
so suggestive of design, or rather of the process by which this cluster
was evolved out of a pre-existing nebula. You will recall the winding
streams in the Great Nebula of Orion. Another star cluster worth a
moment's attention is No. 1479, above and to the left of Sirius. We had
better use the five-inch for this, as many of the stars are very faint.
Not far away we find the double star , whose components are of the fifth
and eighth magnitudes, distance 2.8", p. 343 deg.. The small star is pale
blue. Cluster No. 1512 is a pleasing object with our largest aperture.
In No. 1511 we have a faint nebula remarkable for the rows of minute
stars in and near it. The star gamma is an irregular variable. In 1670
it is said to have almost disappeared, while at the beginning of the
eighteenth century it was more than twice as bright as it is to-day. The
reddish star delta is also probably variable. In my "Astronomy with an
Opera Glass" will be found a cut showing a singular array of small stars
partly encircling delta. These are widely scattered by a telescope, even
with the lowest power.
Eastward from Canis Major we find some of the stars of Argo Navis. Sigma
1097, of the sixth magnitude, has two minute companions at 20" distance,
p. 311 deg. and 312 deg.. The large star is itself double, but the distance,
0.8", p. 166 deg., places it beyond our reach. According to Burnham, there
is yet a fourth faint star at 31", p. 40 deg.. Some three degrees and a half
below and to the left of the star just examined is a beautiful star
cluster, No. 1551. Nos. 1564, 1571, and 1630 are other star clusters
well worth examination. A planetary nebula is included in 1564. With
very powerful telescopes this nebula has been seen ring-shaped. Sigma
1146, otherwise known as 5 Navis, is a pretty double, colors pale yellow
and blue, magnitudes five and seven, distance 3.25", p. 19 deg.. Our
three-inch will suffice for this.
[Illustration: MAP NO. 3.]
North of Canis Major and Argo we find Monoceros and Canis Minor (map No.
3). The stars forming the western end of Monoceros are depicted on map
No. 1. We shall begin with these. The most interesting and beautiful is
11, a fine triple star, magnitudes five, six, and seven, distances 7.4",
p. 131 deg., and 2.7", p. 103 deg.. Sir William Herschel regarded this as one of
the most beautiful sights in the heavens. It is a good object to try our
three-inch on, although it should not be difficult for such an aperture.
The star 4 is also a triple, magnitudes six, ten, and eleven, distances
3.4", p. 178 deg., and 10", p. 244 deg.. We should glance at the star 5 to
admire its fine orange color. In 8 we find a golden fifth-magnitude
star, combined with a blue or lilac star of the seventh magnitude,
distance 14", p. 24 deg.. Sigma 938 is a difficult double, magnitudes six
and a half and twelve, distance 10", p. 210 deg.. Sigma 921 is double,
magnitudes six and a half and eight, distance 16", p. 4 deg.. At the spot
marked on the map 1424 we find an interesting cluster containing one
star of the sixth magnitude.
The remaining stars of Monoceros will be found on map No. 3. The double
and triple stars to be noted are S, or Sigma 950 (which is also a
variable and involved in a faint nebula), magnitudes six and nine,
distance 2.5", p. 206 deg.; Sigma 1183, double, magnitudes five and a half
and eight, distance 31", p. 326 deg.; Sigma 1190, triple, magnitudes five
and a half, ten, and nine, distances 31", p. 105 deg., and 67", p. 244 deg..
The clusters are 1465, which has a minute triple star near the center;
1483, one member of whose swarm is red; 1611, very small but rich; and
1637, interesting for the great number of ninth-magnitude stars that it
contains. We should use the five-inch for all of these.
Canis Minor and the Head of Hydra are also contained on map No. 3.
Procyon, alpha of Canis Minor, has several minute stars in the same
field of view. There is, besides, a companion which, although it was
known to exist, no telescope was able to detect until November, 1896. It
must be of immense mass, since its attraction causes perceptible
perturbations in the motion of Procyon. Its magnitude is eight and a
half, distance 4.83", p. 338 deg.. One of the small stars just referred to,
the second one east of Procyon, distant one third of the moon's
diameter, is an interesting double. Our four-inch may separate it, and
the five-inch is certain to do so. The magnitudes are seven and seven
and a half or eight, distance 1.2", p. 133 deg.. This star is variously
named Sigma 1126 and 31 Can. Min. Bode. Star No. 14 is a wide triple,
magnitudes six, seven, and eight, distances 75, p. 65 deg., and 115", p.
154 deg..
PROCYON AND ITS NEIGHBORS.
In the Head of Hydra we find Sigma 1245, a double of the sixth and
seventh magnitudes, distance 10.5", p. 25 deg.. The larger star shows a fine
yellow. In epsilon we have a beautiful combination of a yellow with a
blue star, magnitudes four and eight, distance 3.4", p. 198 deg.. Finally,
let us look at theta for a light test with the five-inch. The two stars
composing it are of the fourth and twelfth magnitudes, distance 50", p.
170 deg..
The brilliant constellations of Gemini and Taurus tempt us next, but
warning clouds are gathering, and we shall do well to house our
telescopes and warm our fingers by the winter fire. There will be other
bright nights, and the stars are lasting.