The four asteroids first discovered, Ceres, Pallas, Juno, and Vesta, are naturally the largest, ranging in diameter from four hundred to one hundred and eighteen miles. Vesta, though not the largest, is considerably the brightest of the minor planets, and is occasionally visible to the naked eye.
None of the other asteroids has a diameter so great as one hundred miles, and probably the majority of them are only ten or twenty miles in diameter. In addition to the planets and their satellites, the sun is attended by numerous other bodies, moving with far less regularity, and generally much less conspicuous in the heavens. These are known as comets and meteorites or shooting stars.
One of the most interesting of recent astronomical discoveries is that an intimate physical connection exists between these two classes of bodies. Comets have been known from the earliest times, because every now and then a very large and conspicuous one hastens up to the sun from the remote regions of space, and perplexes monarchs with the fear of change.
Such bright comets are sometimes as brilliant as Venus; their tails have been known to stretch halfway across the visible sky.
These comets are very beautiful and conspicuous objects, which usually appear in the sky without any warning from astronomers, and invariably create a great popular sensation. By far the greater number of comets, however, are only visible through a telescope, and it is rare that a year passes without at least half a dozen of these being reported. Up to the present time nearly a thousand comets of all sizes have been recorded. Not more than one in five of these visitors is visible to the naked eye.
Cometary Orbits. In all cases in which a comet has been observed sufficiently often for its orbit to be calculated, it is found that it moves in one of the curves which are known to the geometer as conic sections.
- Friendship: A Gift to Give (Sacred Mundane Book 4).
- Other Features.
- Airborne Armour: Tetrarch, Locust, Hamilcar and the 6th Airborne Armoured Reconnaissance Regiment 1938-50!
- Texts, Bodies, Entanglement;
- 10 Interesting Things About Kenneth Oppel?
Less than a hundred of the known comets move like the planets in elliptical orbits, and consequently their periodical return to visibility can be predicted. As a rule the eccentricity of these cometary orbits is very much greater than that of any planetary orbit, which means that the comet approaches fairly close to the sun at one end of its orbit, but at the other flies away far beyond the outermost planet, and for a long period disappears from the view of our most powerful telescopes.
The great majority of comets have only been seen once, and their orbits appear to be either parabolic or hyperbolic. Neither of these is a closed curve, and what seems to happen in such cases  is that a comet travelling in such an orbit dashes up to the sun from the remote parts of space, swings round it, often at very close quarters, and flies away again forever.
Only those comets which have elliptical orbits can be said to belong to the solar system. Of the comets which move in elliptical orbits, about twenty have been observed at more than one return to the sun. The Constitution of Comets. The nature of comets was long in doubt, and even today their physical characteristics are not fully understood. They are certainly formed of gravitational matter, because they move in orbits which are subject to the same laws as those of the planets. But they also appear to be acted upon by powerful repulsive forces emanating from the sun, to which is due the remarkable phenomenon of cometary tails.
Perhaps there is not much exaggeration in the statement once made by a well-known astronomer that the whole material of a comet stretching halfway across the visible heavens, if properly compressed, could be placed in a hatbox. The old fear that the earth might suddenly be annihilated by a comet striking it is thoroughly dispelled by modern investigation, which leads us to believe that the worst results of such an encounter would be an extremely beautiful display of shooting stars.
Meteors , or Fireballs , are bodies which do not belong to the earth, but come from other parts of space into our atmosphere, and are seen as bright balls of fire crossing the sky, with a train of light behind. Suddenly they are seen to go out, and very often a fall of stones occurs. Sometimes they are observed to break in two, and loud explosions like thunder are heard. They move very fast—ten or twelve miles per second, and are visible when between forty and eighty miles above the earth.
Other meteors dart across the sky and disappear, all in a very short time. These are known as shooting stars, and are sometimes big and bright, like planets. It is estimated that about six or eight meteors which drop stones come into our atmosphere every year; but some 20,, of small bodies pass through the air every day—these would all appear as shooting stars if they occurred at night. At some periods of the year there are so many shooting stars that they appear like a shower of fire. On November 14th this happens, the shower being greatest every thirty-three years.
A stream of meteors is travelling round the sun, and every thirty-three years the earth just comes through them. Meteoric showers also occur about August 9th to 11th, and smaller ones in April. The luminosity of meteors is due to the intense heat caused by the resistance of the air to their passage, and in support of this theory it is found that meteoric stones are always covered, either wholly or in part, with a crust of cement that has recently been melted. We shall now study the so-called fixed stars, those stars, namely, which preserve the same relative position and configuration from night to night, only varying, and that with perfect regularity, in the times at which they reach the meridian.
For this reason they have been known from the dawn of astronomy as fixed stars, in contrast with the planets or wandering stars. The observer who watches the nightly changes in the sky with close attention will soon perceive that all these fixed stars appear to move in circles or parts of circles. Some of them describe larger circles than others, and the further south a star is when it passes the meridian, the larger circle will it describe. It cannot be too often repeated that this motion of the stars is only apparent, being due to the real rotation of the earth, along with the observer on its surface, in the contrary direction.
It is estimated that there are about three thousand stars visible to the naked eye  in our latitude, though not all these are visible at the same time, many of them being below the horizon, while others are elevated in the sky at different times and seasons. In beginning our study of the stars, let us put ourselves in the position of the earliest observers. Let us first, like them, watch the stars, and see how they appear from night to night. We see, at the first glance, that the stars vary much in brightness. The brightest ones—like Sirius, Capella, Arcturus, and Vega—are called stars of the first magnitude.
All the stars which can be seen with the unaided eye are thus divided into six classes or magnitudes , according to their brightness. We also see that the stars are not uniformly distributed over the sky. They seem to be arranged in groups, some of which take the form of familiar objects.
All the stars in the heavens have been divided into groups called constellations. Many of these were recognized and named at a very early period. We should become familiar with these constellations in order to study the stars with any profit. It is necessary, in the first place, to have some way of designating the stars in each constellation.
Many of the brighter stars have proper names as Sirius, Arcturus, and Vega; but the great majority of them are marked by the letters of the Greek alphabet. The characters and names of the Greek alphabet are as follows:. These letters are followed by the Latin name of the constellation.
If there are more stars in a constellation than can be named from the Greek alphabet, the Roman alphabet is used in the same way; and when both alphabets are exhausted, numbers are used. Circumpolar Constellations. One of the most important constellations, and one easily recognized, is the Great Bear, or Ursa Major. It is represented in Plate 1 on the Star Chart.
These and the star in the nose can be readily found by means of the lines drawn on the chart. It may be remarked here, that in all cases the stars thus connected by lines are the leading stars of the constellation. On the opposite side of the Pole Star from the Great Bear, and at about the same distance, is another conspicuous constellation, called Cassiopeia.
- Dating For the Shy Guy: Told From a Single Woman;
- 18 Stories That Show What Humans Consider Normal Is Actually Very Strange.
- Grace Infusions: A Nurses Life: From the Crazy to the Heart Wrenching.
- Eagle & birds of prey.
- Be Not Afraid: A Novel.
- The Signalman of Cemetery Station.
Its five brightest stars form an irregular W, opening towards the Pole Star Plate 2. About half-way between the two Dippers three stars of the third magnitude will be seen, the only stars at all prominent in that neighborhood. These belong to Draco, or the Dragon. The chart will show that the other stars in the body of the monster form an irregular curve around the Little Bear, while the head is marked by four stars arranged in a trapezium.
- Stay Organized - Make Personal Organization a Part of your Life?
- Botany Classes!
- Reclaiming Our Souls: A Womans Guide to Healing the Spirit after Sexual Abuse.
- Save this Search.
A little less than half-way from Cassiopeia to the head of the Dragon is a constellation known as Cepheus, five stars of which form an irregular K. These five constellations never set in our latitude, and are called circumpolar constellations. Constellations Visible in September. Of its other conspicuous stars, four form a cross. These and the remaining stars of the constellation can be readily traced with the aid of Plate 3.
Hercules is about half-way between the Crown and Vega. This constellation is marked by a trapezoid of stars of the third magnitude.
Eagle & birds of prey
This star marks the constellation Aquila, or the Eagle, and may be recognized by a small star on each side of it. These are the only important stars in this constellation. Six of its stars form a large cross, by which it will be readily known. It forms a large isosceles triangle with Altair and Vega.
10 Interesting Things About Kenneth Oppel
Low down in the south, on the edge of the Milky Way Plate 6 , is a constellation called Sagittarius, or the Archer. The other stars, as seen by the map, may be grouped so as to represent a bow and an arrow. The head of the Serpent is near the Crown, and marked by a small triangle.
The head of Ophiuchus is close to the head of Hercules, and may be known by a star of the second magnitude. Each shoulder is marked by a pair of stars. His feet are near the Scorpion. This is the only prominent star in the constellation of Canes Venatici, or the Hunting Dogs. Cassiopeia is almost due east of the Pole Star. These, with two others farther to the south, form a large square, called the Square of Pegasus. Three of these, as seen by the chart Plate 5 , belong to the constellation Pegasus, or the Winged Horse.
The bright stars in the neck and nose can be found by the chart. The fourth star in the Square of Pegasus belongs Plate 8 to the constellation Andromeda. The stars in her belt may be found by the chart. This star has one of the third magnitude on each side of it. The other stars in Perseus may be found by the chart.
boundfipopaty.ml These mark the urn of Aquarius, the Water-bearer. His body consists of a trapezium of four stars of the third and fourth magnitudes. Small clusters of stars show the course of the water flowing from his urn. This stream enters the mouth of the Southern Fish, or Piscis Australis.