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Today's Looking Back can be found here.

Today's bonus story comes from the Feb. 2, 1910 edition of the News-Miner and concerns the passage of Halley's Comet that year. In February, it was still some months away from its closest passage (which took place in April), but it attracted an immense amount of attention around the world.

We know immensely more about comets than they did in 1910 — information garnered in part by its next passage, in 1986 — but this story still provides a fascinating look at what was known and what they had wrong back then.

Look Out for the Comet! It's Coming This Way!

Halley's comet, which has not been visible before since 1835, becomes a potably bright object of intense interest to all star gazers now as the winter advances. It is at present in or near the constellation, Orion, which may be seen late in the evening in the southeastern sky. Although there has not been entire agreement in the computations of the comet's orbit made by different astronomers, the orbit computed by Messrs. Cowell and Crommelin, at Grenwich observatory, is probably a very near approximation to accuracy. Upon the basis of the Greenwich orbit, the Rev. Father George M. Searle, supervisor of the Paulist Fathers, of New York City, has calculated that the comet will make its nearest approach to the earth on May 18th, when it will be 14,000,000 miles distant from us.

What is a Comet?

The return of Halley's comet, discovered on September 18th last by Prof. Max Wolf, of Heidelberg, by photography, has given rise to the question: "What is a comet?"

"One theory concerning the origin of comets," said Prof. J.F. Gould, of the University of Washington, yesterday, "is that they are made of material ejected by the stars in the violent convulsions which their enormous temperatures induce. Another theory is that they have been ejected by the sun, and still another is that they are the products of far remote parts of an original solar nebula. The spectroscope has shown the presence of hydrocarbon compunds, and sometimes sodium and iron.

"A comet," continued the professor, "is usually considered to be made up of three parts. (1) The densest and brightest part, near the center of the head, called the nucleus; and nearly all the mass of a comet lies in the nucleus. (2) The coma, an envelope of small density, surroundig the nucleus. (3) The tail, which always points approximately away from the sun. When the comet approaches the sun the tail follows the head; when it receds, the tail precedes the head. And this shows that some force originating in the sun repels the materials composing the tail.

"There is a theory that the particles composing the tail are driven off by the electric repulsion of the sun, but still another, and a modern theory, is that of radiation pressure. Radiation pressure's action is dependent upon the surface area of the particle in relation to its mass. This results in particles of a certain size being driven away, while others are being obtained by the comet. The constant expulsion of matter along the tail must cause a comet to grow smaller. There can be no doubt that Halley's comet is slowly disintegrating, and after long ages it will disappear."

Why so named.

The name of Halley is not connected with this comet because he was the discoverer of it, but rather because of the fact that he was the first great calculator of comit orbits. He was a young mathematician and astronomer when a brilliant comet appeared in 1682. Halley's friend, Sir Isaac Newton, had but recently announced the law of gravition, and had proved that a comet or other body subject only to the sun's attraction must move in an ellipse about the sun.

This formed the basis for Halley's computation, for he calculated the orbit of the great comet and successfully predicted its return in 1758.

Halley's comet, upon its discovery in September, last, was more than three hundred million miles from the sun. In its motion toward the sun it will continue to approach the earth until about the middle of December, when it will have reduced its distance nearly two-thirds. After that it receds from us, because it moves about the sun in a direction opposite to that of the earth, and the comet reaches the opposite side of the sun during the third week in March, when it turns to meet the earth, and passes between the earth and the sun during the middle of May. After this it moves rapidly away from us, diminishing in brightness until it is lost to sight during the latter part of 1910.

The records show that the comet has been a conspicuous naked eye object of at least 24 of its last 26 returns. The records are not complete with reference to two of the returns.

There is reason to believe, therefore, that the comet will be an interesting sight next May, when it will be for a few days comparatively near us, perhaps within 10,000,000 miles of the earth. At the present time the comet is still too faint to be seen in a small telescope. It has been photographed several times and observed with the largest telescopes. It is expected that it will be bright enough for observation very early in the year. From computations given in Popular Astronomy, it appears very certain that the earth will pass through the tail of the comet about May 18, 1910. No harm will be done, because the matter of which the tail of the comet is composed is extremely rare. We shall probably see a fine meteoric shower.

Origin a Mystery.

The origin of comets is still a mystery, and astronomers are looking forward with interest to the return of Halley's comet, being certain that the photo dry plate and the spectroscope will reveal new facts about hte comet.

The last Halley comet was in 1835, before the discovery of photography. Returns have been found in 1759, 1682, 1607, 1531, 1456, 1378, 1301, 1222, 1145 and 1066, a famous comet which appeared just before the Norman conquest. The return in 989 can be identified, as also the one in 760, 684, 607, 530, 451, 373, 295, 218, 141, 66, B. C. 12 and B. C. 87.

To determine the time of the return of a comet is a problem which presents a number of difficulties. Returning comets, especially those of long period, move in elongated ellipses. Usually the comet can be observed only when it is comparatively near the sun, and therefore the position secured may cover much less than one-tenth of the total orbit. A very small error in an observed position may result in greater error in the computed dimensions of the orbit and the time of return.

A small change in the direction or in the velocity of motion, such a change as may be caused by the attraction of a planet near the orbit of the comet, will often lead to a large error in its period and the elements of its orbit. Observations made at several successive returns will help to correct these errors and permit one to determine the orbit very closely.