Great Astronomers: W. Herschel
Great Astronomers in Modern English
by Sir Robert S. Ball, 1895 (paraphrased by Leslie Noelani Laurio)
To view the table of contents for the rest of this book, click here.
(Frederick) William Herschel, 1738-1822
Founder of sidereal (star) astronomy, and discoverer of the planet Uranus.
William Herschel [Friedrich Wilhelm Herschel], one of the greatest astronomers who ever lived, was born in Hanover [Germany] on November 15, 1738. His father, Isaac Herschel, was a gifted but financially struggling musician. He may not have had money to lavish on his [ten] children, but he passed on to them a splendid inheritance of genius. William, his fourth child, and Caroline, his younger daughter, were both astronomers, and combined perseverance and principles to their genius, and that made them successful. Caroline [1750-1848] later wrote about the way Isaac Herschel educated his sons. At the time, she was an unnoticed little girl of about 5 or 6 years of age [so William would have been about 17].
'My brothers and I often performed [she sang, William played organ] and assisted with the orchestra at Court, and I was often kept awake with lively debates about music after we had returned home from the concert. Sometimes I tried to stay awake just to listen to their enthusiastic discussion -- I was so happy to see them so happy. But usually their talk would branch out to philosophical topics, and my brother William and my father would argue so heatedly that my mother would have to interfere and tell them that they were talking about Euler, Leibnitz, and Newton too loudly and preventing the sleep of the littler ones, who had to be at school by seven in the morning.'
Caroline Herschel later became a famous astronomer herself, and her memoirs, edited by Mary Cornwallis Herschel [1829-1876, she was married to William's grandson, Major John Herschel], provide the best picture we have of her brother William.
This unassuming family was somewhat scattered when the Seven Years' War broke out in 1756 and France invaded British-controlled Hanover. Young William Herschel became part of the Hanoverian Guards regimental band, and saw some fighting action during the disastrous battle of Hastenbeck. He was not wounded, but he had to spend the night after the battle in a ditch -- and the experience turned him off to a soldier's life. So he deserted! He took on various disguises to elude detection and got to England safely. Years later, this offense was sincerely forgiven. When he had become a famous astronomer, he visited King George at Windsor, and the King handed him a pardon written in his own hand.
During the first few years he lived in England, he had trouble supporting himself. He didn't get a regular position until he was appointed as Instructor of Music to the Durham Militia when he was twenty two. Then, after his talents were more widely recognized, he became the organist at the little parish church in Halifax. The Seven Years' War ended, and he was steadily employed, so he decided to take a trip back home to Hanover to visit his father. Old Isaac Herschel must have been delighted to see his son, and very proud when a concert was given where some of William's own compositions were performed. He never got to see his son become famous because he died years before his son became an astronomer.
In 1766, a couple of years after he visited his father, William Herschel was promoted to organist at the Octagon Chapel, at Bath. Bath was a highly fashionable resort, and he gained the attention of many notable people. He wasn't just a skillful musician -- he was handsome, well-dressed, charming, and he was a Hanoverian during the reign of George III [who was from Hanover]. On Sundays he delighted his church with his organ playing, and during the week he gave private lessons and practiced for his performances. So he kept busy and was making enough money to live comfortably.
William Herschel had always been curious and eager to learn. In order to improve himself as a musician, he studied mathematics, and this opened up a whole new region of knowledge -- including astronomy. Astronomy captured his attention, and finally became his absorbing passion. But he still had to earn a living, so he had to devote most of his time to music, but his heart was eagerly focused on the science of astronomy. It wasn't until he was middle aged and earned a reputation as an astronomer that he could afford to give up music for astronomy.
He began his career as an astronomer with a small borrowed telescope. But it wasn't long before he realized that, if he was going to be able to see everything he wanted to observe, he was going to need a more powerful telescope. So he decided to make one. His was very different from Isaac Newton's refracting telescope. He made a reflector. A reflector telescope gets its power from a mirror at the bottom of a tube. The astronomer looks down the tube towards the mirror and views a reflection of the stars. Its usefulness depends on how accurately the image is displayed on the mirror. The mirror's surface has to be slightly hollowed out, and the slightest imperfection will distort the image being reflected.
William Herschel's mirror was made of two parts copper to one part tin. This alloy is very hard, which makes it difficult to cast into the right shape, and challenging to work with afterwards. But when it's polished, it shines almost like silver. He didn't record many specifics about how he cast and polished his reflecting mirrors. But years later, when his telescopes had become famous, he made quite a bit of money by making and selling them. Maybe that's why he never divulged the exact process he used to make them!
Later astronomers, such as the Earl of Rosse, have also experimented to make a better telescope, and have undoubtedly made more powerful and more effective telescopes than Herschel's. But we know how they did it, so amateurs have been able to make their own telescopes by following their instructions. It's possible for anyone with a little bit of mechanical skill and a lot of patience to make a telescope as powerful as the one that made Herschel famous. But the material we now use for the mirror is much easier to work with than what was available to Herschel and Lord Rosse. In our day, we would use a silver-coated glass mirror that's been carefully fitted and polished instead of using the alloy of copper and tin (called speculum metal) [view a video about speculum in telescopes, which includes an image of Herschel's 40-foot telescope, on YouTube]. Mirrors made of silver-coated glass are so much lighter and easier to make that the old-fashioned mirrors are obsolete. However, speculum mirrors last longer. If taken care of, a mirror made of speculum metal will stay bright and untarnished longer than glass with a silver film. On the other hand, it's fairly easy to replace the silver backing on a mirror, so even lasting longer is not a huge advantage.
Years after William Herschel became interested in astronomy, his improved telescope finally paid off. In 1774, at the age of thirty-six, he got his first glimpse of the stars from the telescope he had constructed. Every night, as soon as his music work was done, he would bring out his telescopes and set them up, sometimes in the little garden behind his house in Bath, and sometimes right in the street in front of his hall door. True to his character, he was forever tweaking his apparatus to make improvements. He was incessantly making better mirrors, or trying new lenses, or combining lenses as eye pieces, or trying new ways of mounting the telescope. In fact, his home was always littered with evidence that a workman was busy, much to the distress of his sister Caroline who lived with him and took care of the house. She complained that sometimes he would be so eager to get to his workshop after conducting a concert that he would forget to take off his fancy lace collar -- and his collars would get stained with the pitch he used to polish his mirrors.
Caroline greatly admired her big brother. From childhood and even as an adult, she was delighted to render whatever service she could. No scientist ever had a more capable, eager, or devoted helper. She was always ready to assist him, or, when necessary, work by herself when he allowed her to. She managed his household affairs, ground lenses, polished mirrors -- whatever was needed. There's one step during the construction of a reflector where a workman has to keep pressure on the reflector with his hand for hours. During these times, Caroline would sit with him and keep him company by reading him stories, or even spoon feeding him while his hands were occupied with the reflector.
When there was mathematical work to be done, Caroline was ready for it. She had taught herself enough to be able to do the more basic of the calculations that her brother's work required. In fact, the great work that Herschel contributed to the world of astronomy couldn't have been done without the help of his faithful and devoted little sister. When he looked through his telescope at night, Caroline would be sitting beside him at her desk with her pen in her hand, ready to write down his comments about what he saw. This was no small sacrifice. The telescope was out in the open air, and Herschel frequently continued his observations through the night, even in winter. Not many women could have done the task that she so cheerfully did. Herschel's star-gazing hours were from dusk to dawn every clear night. Caroline later said that there were some nights she had to stop working because the ink had frozen in her pen! At dawn, when the night's work was done, William would tend to his day's duties, and Caroline would carefully transcribe the comments she had jotted down during the night, calculate and reduce the mathematical figures, and get everything ready to begin again at dusk.
But all of that came later. We must now get back to the earlier part of his life, back in 1774 when he first started to observe the skies over Bath with the telescope he had constructed. For years he didn't make any notable observations, but that time wasn't wasted. It gave him practice using his instruments. It wasn't until 1782 that he made the discovery that made him famous.
Sometimes discoveries are made by accident, but not as often as you'd think. Often, those 'lucky accidents' only come to people who have done the work before-hand so that they recognize them when they happen. This was true of William Herschel. He started on a project of closely examining all of the stars above a certain size. Maybe he thought he could complete such a task by limiting his observation to a small section of sky, but, at any rate, he jumped into this project energetically and systematically. He focused his telescope at one star after another. He would carefully examine it and then move on to the next star. Generally these kinds of observations don't yield any new or important discoveries, although, of course, even the smallest star in the heavens would reveal far more than we could imagine if we could find out everything about it. But our observations only give us a small amount of information. All we see is a little point of light, and that's all.
In the course of his work on this project, William Herschel examined hundreds, if not thousands, of stars, without recording any notes or comments. But in March, 1782, he was continuing this project among the stars in the constellation of Gemini. He observed one star after another, dismissing them without any further attention and moving on to the next one. But he noticed that one star looked different from the multitude of others strewn across the sky. Most stars appear as points of light. Even magnified with a telescope, they are just points of light with no discernible outline or shape. But this one star caught his attention, and when he magnified it, he saw that it had an actual definite shape that could be measured! To our educated minds, this sounds like a planet rather than a star. And, after further observation, Herschel saw that this object was shifting its position among the stars -- further evidence that it was something other than a star. Herschel, the organist of Octagon Chapel at Bath, had discovered a new planet [Uranus] with his home-made telescope!
But is that really so amazing? Aren't planets being discovered all the time? The Czech astronomer Johann Palisa, for example, discovered about eighty of them, and there are hundreds of them known nowadays. Yet, without diminishing those sharp-sighted astronomers who made those discoveries, we have to admit that what Herschel did was very different. All of those hundreds of discoveries are minor planets [or dwarf planets, or asteroids], all of them so small that if you lumped them all together into a ball, it wouldn't even be a thousandth of the size of the planet that William Herschel discovered. Even more important, the discovery of Uranus was the very first recorded occasion of anyone discovering a planet in the history of mankind.
Since the most ancient times, star-gazers had been aware of the five old planets -- Jupiter, Mercury, Saturn, Venus, and Mars. It never seems to have occurred to the ancient philosophers that there might be more than five. So it was astonishing when Herschel discovered a sixth one! And what a planet! Admittedly, it wasn't as large as Saturn or Jupiter, but it was much larger than Mercury, Venus, or Mars. The earth was downright puny and insignificant in comparison. This new planet was much more majestic than the others, too -- its orbit swept around all the other known planets in a much larger ellipse, outside anything else known in our Solar System at the time, and it took a full 81 years to complete its orbit.
King George III. heard about the astronomical achievements of this Hanoverian musician, and invited Herschel to visit Windsor with his famous telescope so he could show the new planet to the King and tell him all about it. This visit finally gave Herschel the opportunity he had long wished for -- to be able to devote himself exclusively to science.
King George was impressed with the astronomer. He pardoned his military desertion from twenty-five years earlier. He gave him a title as the King's own astronomer and assigned him a place to live near Windsor, as well as a regular salary, and enough funding to purchase whatever telescopes and equipment he needed to continue his work. Herschel couldn't be nearly as effective without his sister's help, so King George also gave her a salary and a position as Herschel's assistant.
With his characteristic impulsive determination, William Herschel immediately quit all of his musical obligations at Bath and went to work making and setting up the large telescopes at Windsor. For over thirty years, he and Caroline continued their nightly star gazing. They sent articles to the Royal Society describing hundreds, or even thousands, of objects such as double stars, nebulae, and clusters that had never been noticed before. Herschel devoted himself to astronomy for the rest of his life, although he never topped his discovery of Uranus.
William Herschel married late in life, and lived long enough to see his only son, Sir John Herschel, follow in his father's footsteps and become successful as an astronomer. William Herschel died in 1822, and Caroline moved back to Hanover. She lived many years after that and was respected as an astronomer in her own right. She died in 1848 at the age of 90.
[Edward S. Holden, who wrote The Sciences, also wrote The Life and Works of Sir William Herschel. It can be read online for free at Project Gutenberg.]
by Sir Robert S. Ball, 1895 (paraphrased by Leslie Noelani Laurio)
To view the table of contents for the rest of this book, click here.
(Frederick) William Herschel, 1738-1822
Founder of sidereal (star) astronomy, and discoverer of the planet Uranus.
William Herschel [Friedrich Wilhelm Herschel], one of the greatest astronomers who ever lived, was born in Hanover [Germany] on November 15, 1738. His father, Isaac Herschel, was a gifted but financially struggling musician. He may not have had money to lavish on his [ten] children, but he passed on to them a splendid inheritance of genius. William, his fourth child, and Caroline, his younger daughter, were both astronomers, and combined perseverance and principles to their genius, and that made them successful. Caroline [1750-1848] later wrote about the way Isaac Herschel educated his sons. At the time, she was an unnoticed little girl of about 5 or 6 years of age [so William would have been about 17].
'My brothers and I often performed [she sang, William played organ] and assisted with the orchestra at Court, and I was often kept awake with lively debates about music after we had returned home from the concert. Sometimes I tried to stay awake just to listen to their enthusiastic discussion -- I was so happy to see them so happy. But usually their talk would branch out to philosophical topics, and my brother William and my father would argue so heatedly that my mother would have to interfere and tell them that they were talking about Euler, Leibnitz, and Newton too loudly and preventing the sleep of the littler ones, who had to be at school by seven in the morning.'
Caroline Herschel later became a famous astronomer herself, and her memoirs, edited by Mary Cornwallis Herschel [1829-1876, she was married to William's grandson, Major John Herschel], provide the best picture we have of her brother William.
This unassuming family was somewhat scattered when the Seven Years' War broke out in 1756 and France invaded British-controlled Hanover. Young William Herschel became part of the Hanoverian Guards regimental band, and saw some fighting action during the disastrous battle of Hastenbeck. He was not wounded, but he had to spend the night after the battle in a ditch -- and the experience turned him off to a soldier's life. So he deserted! He took on various disguises to elude detection and got to England safely. Years later, this offense was sincerely forgiven. When he had become a famous astronomer, he visited King George at Windsor, and the King handed him a pardon written in his own hand.
During the first few years he lived in England, he had trouble supporting himself. He didn't get a regular position until he was appointed as Instructor of Music to the Durham Militia when he was twenty two. Then, after his talents were more widely recognized, he became the organist at the little parish church in Halifax. The Seven Years' War ended, and he was steadily employed, so he decided to take a trip back home to Hanover to visit his father. Old Isaac Herschel must have been delighted to see his son, and very proud when a concert was given where some of William's own compositions were performed. He never got to see his son become famous because he died years before his son became an astronomer.
In 1766, a couple of years after he visited his father, William Herschel was promoted to organist at the Octagon Chapel, at Bath. Bath was a highly fashionable resort, and he gained the attention of many notable people. He wasn't just a skillful musician -- he was handsome, well-dressed, charming, and he was a Hanoverian during the reign of George III [who was from Hanover]. On Sundays he delighted his church with his organ playing, and during the week he gave private lessons and practiced for his performances. So he kept busy and was making enough money to live comfortably.
William Herschel had always been curious and eager to learn. In order to improve himself as a musician, he studied mathematics, and this opened up a whole new region of knowledge -- including astronomy. Astronomy captured his attention, and finally became his absorbing passion. But he still had to earn a living, so he had to devote most of his time to music, but his heart was eagerly focused on the science of astronomy. It wasn't until he was middle aged and earned a reputation as an astronomer that he could afford to give up music for astronomy.
He began his career as an astronomer with a small borrowed telescope. But it wasn't long before he realized that, if he was going to be able to see everything he wanted to observe, he was going to need a more powerful telescope. So he decided to make one. His was very different from Isaac Newton's refracting telescope. He made a reflector. A reflector telescope gets its power from a mirror at the bottom of a tube. The astronomer looks down the tube towards the mirror and views a reflection of the stars. Its usefulness depends on how accurately the image is displayed on the mirror. The mirror's surface has to be slightly hollowed out, and the slightest imperfection will distort the image being reflected.
William Herschel's mirror was made of two parts copper to one part tin. This alloy is very hard, which makes it difficult to cast into the right shape, and challenging to work with afterwards. But when it's polished, it shines almost like silver. He didn't record many specifics about how he cast and polished his reflecting mirrors. But years later, when his telescopes had become famous, he made quite a bit of money by making and selling them. Maybe that's why he never divulged the exact process he used to make them!
Later astronomers, such as the Earl of Rosse, have also experimented to make a better telescope, and have undoubtedly made more powerful and more effective telescopes than Herschel's. But we know how they did it, so amateurs have been able to make their own telescopes by following their instructions. It's possible for anyone with a little bit of mechanical skill and a lot of patience to make a telescope as powerful as the one that made Herschel famous. But the material we now use for the mirror is much easier to work with than what was available to Herschel and Lord Rosse. In our day, we would use a silver-coated glass mirror that's been carefully fitted and polished instead of using the alloy of copper and tin (called speculum metal) [view a video about speculum in telescopes, which includes an image of Herschel's 40-foot telescope, on YouTube]. Mirrors made of silver-coated glass are so much lighter and easier to make that the old-fashioned mirrors are obsolete. However, speculum mirrors last longer. If taken care of, a mirror made of speculum metal will stay bright and untarnished longer than glass with a silver film. On the other hand, it's fairly easy to replace the silver backing on a mirror, so even lasting longer is not a huge advantage.
Years after William Herschel became interested in astronomy, his improved telescope finally paid off. In 1774, at the age of thirty-six, he got his first glimpse of the stars from the telescope he had constructed. Every night, as soon as his music work was done, he would bring out his telescopes and set them up, sometimes in the little garden behind his house in Bath, and sometimes right in the street in front of his hall door. True to his character, he was forever tweaking his apparatus to make improvements. He was incessantly making better mirrors, or trying new lenses, or combining lenses as eye pieces, or trying new ways of mounting the telescope. In fact, his home was always littered with evidence that a workman was busy, much to the distress of his sister Caroline who lived with him and took care of the house. She complained that sometimes he would be so eager to get to his workshop after conducting a concert that he would forget to take off his fancy lace collar -- and his collars would get stained with the pitch he used to polish his mirrors.
Caroline greatly admired her big brother. From childhood and even as an adult, she was delighted to render whatever service she could. No scientist ever had a more capable, eager, or devoted helper. She was always ready to assist him, or, when necessary, work by herself when he allowed her to. She managed his household affairs, ground lenses, polished mirrors -- whatever was needed. There's one step during the construction of a reflector where a workman has to keep pressure on the reflector with his hand for hours. During these times, Caroline would sit with him and keep him company by reading him stories, or even spoon feeding him while his hands were occupied with the reflector.
When there was mathematical work to be done, Caroline was ready for it. She had taught herself enough to be able to do the more basic of the calculations that her brother's work required. In fact, the great work that Herschel contributed to the world of astronomy couldn't have been done without the help of his faithful and devoted little sister. When he looked through his telescope at night, Caroline would be sitting beside him at her desk with her pen in her hand, ready to write down his comments about what he saw. This was no small sacrifice. The telescope was out in the open air, and Herschel frequently continued his observations through the night, even in winter. Not many women could have done the task that she so cheerfully did. Herschel's star-gazing hours were from dusk to dawn every clear night. Caroline later said that there were some nights she had to stop working because the ink had frozen in her pen! At dawn, when the night's work was done, William would tend to his day's duties, and Caroline would carefully transcribe the comments she had jotted down during the night, calculate and reduce the mathematical figures, and get everything ready to begin again at dusk.
But all of that came later. We must now get back to the earlier part of his life, back in 1774 when he first started to observe the skies over Bath with the telescope he had constructed. For years he didn't make any notable observations, but that time wasn't wasted. It gave him practice using his instruments. It wasn't until 1782 that he made the discovery that made him famous.
Sometimes discoveries are made by accident, but not as often as you'd think. Often, those 'lucky accidents' only come to people who have done the work before-hand so that they recognize them when they happen. This was true of William Herschel. He started on a project of closely examining all of the stars above a certain size. Maybe he thought he could complete such a task by limiting his observation to a small section of sky, but, at any rate, he jumped into this project energetically and systematically. He focused his telescope at one star after another. He would carefully examine it and then move on to the next star. Generally these kinds of observations don't yield any new or important discoveries, although, of course, even the smallest star in the heavens would reveal far more than we could imagine if we could find out everything about it. But our observations only give us a small amount of information. All we see is a little point of light, and that's all.
In the course of his work on this project, William Herschel examined hundreds, if not thousands, of stars, without recording any notes or comments. But in March, 1782, he was continuing this project among the stars in the constellation of Gemini. He observed one star after another, dismissing them without any further attention and moving on to the next one. But he noticed that one star looked different from the multitude of others strewn across the sky. Most stars appear as points of light. Even magnified with a telescope, they are just points of light with no discernible outline or shape. But this one star caught his attention, and when he magnified it, he saw that it had an actual definite shape that could be measured! To our educated minds, this sounds like a planet rather than a star. And, after further observation, Herschel saw that this object was shifting its position among the stars -- further evidence that it was something other than a star. Herschel, the organist of Octagon Chapel at Bath, had discovered a new planet [Uranus] with his home-made telescope!
But is that really so amazing? Aren't planets being discovered all the time? The Czech astronomer Johann Palisa, for example, discovered about eighty of them, and there are hundreds of them known nowadays. Yet, without diminishing those sharp-sighted astronomers who made those discoveries, we have to admit that what Herschel did was very different. All of those hundreds of discoveries are minor planets [or dwarf planets, or asteroids], all of them so small that if you lumped them all together into a ball, it wouldn't even be a thousandth of the size of the planet that William Herschel discovered. Even more important, the discovery of Uranus was the very first recorded occasion of anyone discovering a planet in the history of mankind.
Since the most ancient times, star-gazers had been aware of the five old planets -- Jupiter, Mercury, Saturn, Venus, and Mars. It never seems to have occurred to the ancient philosophers that there might be more than five. So it was astonishing when Herschel discovered a sixth one! And what a planet! Admittedly, it wasn't as large as Saturn or Jupiter, but it was much larger than Mercury, Venus, or Mars. The earth was downright puny and insignificant in comparison. This new planet was much more majestic than the others, too -- its orbit swept around all the other known planets in a much larger ellipse, outside anything else known in our Solar System at the time, and it took a full 81 years to complete its orbit.
King George III. heard about the astronomical achievements of this Hanoverian musician, and invited Herschel to visit Windsor with his famous telescope so he could show the new planet to the King and tell him all about it. This visit finally gave Herschel the opportunity he had long wished for -- to be able to devote himself exclusively to science.
King George was impressed with the astronomer. He pardoned his military desertion from twenty-five years earlier. He gave him a title as the King's own astronomer and assigned him a place to live near Windsor, as well as a regular salary, and enough funding to purchase whatever telescopes and equipment he needed to continue his work. Herschel couldn't be nearly as effective without his sister's help, so King George also gave her a salary and a position as Herschel's assistant.
With his characteristic impulsive determination, William Herschel immediately quit all of his musical obligations at Bath and went to work making and setting up the large telescopes at Windsor. For over thirty years, he and Caroline continued their nightly star gazing. They sent articles to the Royal Society describing hundreds, or even thousands, of objects such as double stars, nebulae, and clusters that had never been noticed before. Herschel devoted himself to astronomy for the rest of his life, although he never topped his discovery of Uranus.
William Herschel married late in life, and lived long enough to see his only son, Sir John Herschel, follow in his father's footsteps and become successful as an astronomer. William Herschel died in 1822, and Caroline moved back to Hanover. She lived many years after that and was respected as an astronomer in her own right. She died in 1848 at the age of 90.
[Edward S. Holden, who wrote The Sciences, also wrote The Life and Works of Sir William Herschel. It can be read online for free at Project Gutenberg.]
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