The Men Who Mapped The Skies

One of the uses of astronomy is in the work of navigation; by observing the stars it is possible for a person to learn where their location might be, both on land and on sea. It is especially useful on the trackless seas.

In the past, and partly true now England was always one of the greatest nations of seafarers. In 1675 there was established at Greenwich, a suburb of London, what is called the Royal Observatory. The head of the observatory is called the Astronomer royal.

The first man to hold this position was John Flamsteed (1646-1720). His special task was to learn more about the stars in their courses in order to give better aid to sailors. For a very long time the work of the Royal Observatory is devoted to this practical purpose.

The second Astronomer Royal was Edmund Halley (1656-1742), a close friend of Sir Isaac Newton. He kept Newton from forgetting one piece of work while turning aside to do something else. Newton never liked to stop working long enough to write down what he had been doing and Halley was the one who finally arranged for Newton's great book, called the Principia , to be printed and distributed.

However, Halley was far more than just a prod for Newton. He was a very capable astronomer in his own right. when only a young man he saw that it was important to know as much as about the southern sky, invisible from England, as it was to know about the northern sky.

His father gave him a salary and obtained various letters of introduction that made it possible for Halley to go to the island of St. Helena to make observations of the exact positions of the southern stars. However, he found St. Helena was not a very good spot from which to study the heavens, so he remained only one year on the island 9which nearly a century and a half later was Napoleon's place of exile).

During that one year Halley had accomplished much, however, and on his return to England his future as an astronomer was assured. He was the first man to become interested in determining how the compass needle behaves in various parts of the world.

Between 1694 and 1700 he traveled to the South Seas and deep down toward the Antarctic region. He published a map for mariners, indicating the variation of the compass needle from the true geographical north and south. This variation, as you perhaps know, is due to the earth's magnetism.

People who are not astronomers remember Halley's name particularly in connection with a great comet. Halley observed several comets and studied the observations of others that had appeared before his time. He determined their paths and at last was able to say that several comets had followed the same path at intervals of about seventy-six years.

He decided that they were all the same comet, coming back time and again. He announced that the comet he saw in 1682 would come again in 1758. It did return when he said it would, years after this death. It came again in 1835, 1910, and 1986.

Halley was the first man to show that the stars are not really fixed in position as they had been thought to be through all the ages. He saw that a few of them had changed their places with respect to each other in the almost sixteen centuries since the time of Ptolemy. The study of these proper motions, as they are called, has taken much of the time of many astronomers since Halley's day, and now we know all about the motions of many thousands of stars.

Halley was the first man to show that the stars are not really fixed in position as they had been thought to be through all the ages. He saw that a few of them had changed their places with respect to each other in the almost sixteen centuries since the time of Ptolemy. the study of these proper motions, as they are called, has taken much of the time of many astronomers since Halley's day, and now we know all about the motions of many thousands of stars.

The great Danish Astronomer Tycho Brahe had been unwilling to accept the Copernican theory of motion of the earth around the sun. Here was his reason: Tycho saw that if the earth swings from one side of the sun to the other, the stars must appear to shift back and forth. Tycho was unable to observe such shifts with his instruments. Other astronomers were content to say that the stars are so distant that the tiny shifts could not be measured with the instruments of Tycho.

The invention of the telescope, the power to measure tiny distances in the sky was greatly increased and many astronomers tried to discover the annual shifts of the stars.

James Bradley (1693-1762) , the third Astronomer Royal, tried, but, like all the others, he too failed. However, in failing he found something else called the "abberation of light."

Just as we must tilt an umbrella a little ahead of us to avoid getting wet as we walk throught he rain, so the telescope must be tilted a little ahead of the direction of the earth's motion in order to catch the light of a star.

If we were not moving, this would not be true. So Bradley was the first to prove in some way that the earth is in motion around the sun.

The greatest observer of all time was Frederick William Herschel (1738-1822). Born in Hanover, Germany he went to England when he was nineteen years old. He had received a musical education and he earned his living by playing the oboe and the organ and by giving music lessons to others.

He was only an amateur astronomer, looking at the stars because he loved them. He borrowed a telescope, but it was not good enough for him, so he set to work to make one for himself. Even today many astronomers design and sometimes even build their own instruments.

On March 13, 1781, with a telescope that he had made, Herschel discovered a new planet, the first one to be found in historic times. While he at first wanted to call the new planet IGeorgium Sidus -- George's Star -- in honor of King George III, he was finally persuaded by other astronomers to give it a mythological name like the others -- the planet was named Uranus.

William Herschel became famous almost at once. He was called to the court of King George III and persuaded to give up his music and become a professional astronomer. The King gave him a salary, but it was not nearly enough to support William, his brother Alexander and his devoted sister, Caroline.

It would perhaps have been enough if William had not wanted to keep on building bigger and better telescopes. So he built many small telescopes to sell to the rich people of the court and even in foreign lands. This he did until 1788, when he was fortunate in finding a wife who had enough money to care for him and his telescopes.

His sister, Caroline Herschel had been the housekeeper, as well as business manager and general assistant to her brother. She moved to another home when William married, but she continued as his assistant until the end of his life. Sometimes her brother would not stop working on his telescopes even to eat his lunch. On one occasion, when he worked for more than fifteen hours without stopping, Caroline fed him with a spoon as he worked.

By 1780, Sir William Herschel (for he was now knighted by the king) had made a telescope four feet across, by far the largest in the world at the time. On the first night it was used, he discovered a sixth moon of Saturn and three weeks later he found the seventh.

In 1787, with a smaller telescope, he had discovered two moons of Uranus, the new planet he had added to the sun's family.

Such discoveries were to him less important than the things he found as he patiently examined, time after time, every little spot in all the heavens visible from England.

He found 2,500 nebulae and more than 800 double stars. He was looking for double stars because he thought that perhaps because of the earth's motion around the sun he could see one of the stars of such a pair change its position with respect to its companion star. He was surprised to find that many of these pairs were actual binary stars, revolving around each other in perfect accordance with Newton's law of gravitation.

Herschel was even a little disappointed when he saw that his original plan would not work out. Later, however, he saw the importance of binary stars and he said, "I am like Saul, who went out to seek his father's asses and found a kingdom."

It has often happened that an astronomer has been disappointed in one thing, but his work has yielded an even more important result than the one he first sought.

Herschel thought that the proper motions of the stars, discovered by Halley, could be partially explained by a motion of the sun through space.

As a result of his studies, he was able to say that the sun is heading in the direction of the star group Herules, not far from the bright summer star Vega. As it travels along with a speed of almost 45,000 mile an hour, the sun carries with it the earth and all the other planets revolving around it.

Caroline and Lady Herschel (William's wife) were good friends and Caroline was very fond of her nephew, John. After the death of Sir William, Caroline went back to Germany, but she corresponded with John (1792-1871) who became a worthy son to carry on his illustrious father's work.

He became Sir John Herschel. He took a telescope to the Cape of Good Hope so that he could see the sky not visible from England.

He remained in South Africa for five years, discovering 1,200 stars and 1,500 nebulae. Int eh sky of England he found 500 nebulae that his father had missed and 3,000 more double stars.