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Tycho Brahe’s New Star or “Nova” of 1572

My writing interests are general, with expertise in science, history, biographies, and “how-to” topics. I have written over seventy books.

The constellation Cassiopeia. The yellow star represents what the supernova of 1572 might have looked like to Tycho Brahe.

The constellation Cassiopeia. The yellow star represents what the supernova of 1572 might have looked like to Tycho Brahe.

Tycho Brahe

Tycho Brahe was born into a family of great wealth and political power in 16th century Denmark and went on to become the most prominent observational astronomer of his time. The large number of accurate observations of the stars and planets he accumulated during his many years as an observer were key to generations of astronomers in their quest to understand the cosmos and man’s place within it. As a young man, he was known for his brilliant mind and became interested in all sorts of things, from alchemy to astronomy.

In his second year studying at the University of Copenhagen, Tycho observed an astronomical event that changed the direction of life. In late August 1560, he witnessed a partial eclipse of the Sun, which had a profound effect on the young man. Since he was a law student, he was not allowed to attend lectures on astronomy at the university. He responded by buying books on astronomy and began a self-study.

It was a confusing time for someone studying astronomy, as the movement of the planets and the nature of the stars were poorly understood. Though Polish astronomer Nicholaus Copernicus had introduced a Sun-centered model of the universe decades before, most of the scholars and teachers of the day followed the physics of the ancient Greek philosopher Aristotle and the Earth-centered model of the universe of the second-century astronomer, astrologer, and mathematician Claudius Ptolemy. To complicate matters further, the star charts and tables used to calculate the position of the planets were both terribly inaccurate. Tycho set about learning all he could about astronomy and began taking his own observations of the night sky.

In a time before the invention of the telescope, observations of the positions of the planets and stars were made by the naked eye and a few simple instruments. For five years starting in 1565, Tycho combined travels with his studies while he continued to observe the night sky. He began to acquire accurate instruments while gaining a first-class education at universities in Leipzig, Wittenberg, and Rostock, Germany.

At age 25 he had set up an extensive laboratory for his chemical investigations in the annex to his uncle’s grand estate, the abbey of Herrevad (now in southern Sweden). In the 16th century in northern Europe, it was commonplace for monarchs and powerful courtiers to take control of monasteries from the Church and turn them into palatial estates. It was there that Tycho experienced another astronomical event that solidified his lifelong quest to study the heavens.

Portrait of Tycho Brahe.

Portrait of Tycho Brahe.

The New Star in the Constellation Cassiopeia

On November 11, 1572, while glancing up at the night sky on his way to his evening meal, Tycho noticed a new star or “nova” shining more brightly than all the others in the constellation of Cassiopeia. Tycho later recalled the impact the new star had upon him:

“But when I pointed out the location and learned that others could also see it, I no longer doubted that a star actually appeared there. This was truly the greatest miracle in the whole of Nature since the beginning of the world…All philosophers agree, and reality itself declares unambiguously, that no alteration of generation or corruption occurs in the ethereal regions of the heavenly world, but that the heavens and the ethereal bodies therein neither increase nor decrease in number, magnitude, luminosity, nor in any other way, but are always the same and always will be the same, never worn down by the years, permanent.”

Tycho set aside the chemical experiments and began to take observations of the new star. He enlisted the abbey’s blacksmiths, brass-founders, and cabinet makers to construct a large sextant to accurately measure the position of the new star. The sextant was five feet long with brass tabs at the far ends and interchangeable 60˚ and 30˚ arcs attached to one arm.

By placing his eye along the fulcrum, he could measure angles between two celestial objects along the inner edges of the brass tabs and lock the movable arm in place with a thumbscrew. Using a sextant, he measured the position of the new star relative to the positions of the known stars.

Tycho’s sextant mounted in the window of the abbey in Herrevad.

Tycho’s sextant mounted in the window of the abbey in Herrevad.

Tycho Begins Observing the New Star

Tycho observed the star—today we know it as a supernova—month after month, verifying and refining his position measurements time and again. He repeated the observations many times as he was looking for diurnal parallax; that is, if the new star appeared to shift among the stars in the course of the night, it implies it was much closer to the Earth than the other stars. If the new star shifted in apparent position more than a planet during a night of observation, this would place it in the sphere below the Moon, where followers of Aristotle believed it should reside.

His repeated observations revealed that the new star did not appear to move in the sky, implying that the diurnal parallax was zero, which meant that the star was much further from the Earth than the Moon. He continued to observe the star until the end of March 1574 when it finally faded into the black sky, no longer visible to his eye.

Since the new star twinkled like a star, had no tail like a comet, and exhibited no parallax, then Tycho concluded it must be a new star. He wrote, “This new star is not located in the upper regions of the air just under the lunar orb, nor in any place closer to Earth, but far above the sphere of the Moon in the [Aristotle’s] eighth sphere.” His conclusion about the place of the new star in the heavens was in direct opposition to the ancient Greek philosopher Aristotle—how could this be?

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The Placement of the New Star in the Heavens Contradicts Aristotle

The appearance of a new star contradicted the ideas held by the ancients, particularly Aristotle, that the heavens in the region of the stars was fixed and unchanging. Aristotle wrote in De caelo (On the Heavens), 270b12-16: “For in the whole range of time past, so far as our inherited records reach, no change appears to have taken place either in the whole scheme of the outermost heaven or in any of its proper parts.” As far as Aristotle knew, no one had ever witnessed a change in the stars; therefore, they must be unchanging.

In another of Aristotle’s books, Metaphysics (1073), the ancient philosopher developed a physical cosmology of spheres based on the model of his contemporary philosopher Eudoxus of Cnidus. In Aristotle’s celestial model, the spherical Earth is at the center of the universe and the planets are moved by either 47 or 55 interconnected spheres that form a unified planetary system. According to Aristotle, “Eudoxus supposed that the motion of the Sun or of the Moon involves, in either case, three spheres, of which the first is the sphere of the fixed stars, and the second moves in the circle which runs along the middle of the zodiac…”

Aristotle continues (1074),

“But it is necessary, if all the spheres combined are to explain the observed facts, that for each of the planets there should be other spheres (one fewer than those hitherto assigned) which counteract those already mentioned and bring back to the same position the outermost sphere of the star which in each case is situated below the star in question; for only thus can all the forces at work produce the observed motion of the planets.”

For Tycho, the observation of the bright new star was a direct contradiction to the wisdom of the ancients that had been the “gospel” for two thousand years. But how could he explain this new revelation?

Aristotle’s model of the universe.

Aristotle’s model of the universe.

Tycho’s Search for Understanding of the New Star

As the new star slowly faded over several months back into the blackness of space, he pondered the meaning of it all. Being a religious man, he believed the new star was an omen, a sign placed in the sky by God as a warning to humanity.

Tycho wrote up his observations and thoughts on the new star in the brief tract, De nova stella (On the New Star) in 1573. He began another report on the new star just before his death titled Astronomiae instauratae progymnasmata (Exercises for the Reform of Astronomy); however, this work would only be completed after his death, by Johannes Kepler.

Star map from “De nova stella” showing the nova (labeled I) in the constellation of Cassiopeia.

Star map from “De nova stella” showing the nova (labeled I) in the constellation of Cassiopeia.

What Is a Supernova?

When a star explodes, and it becomes many millions of times brighter than before it exploded, astronomers call it a supernova (plural: supernovae). This is to be distinguished from regular novae, which are more common but increase in brightness by only a few thousand times. Supernovae come in two types, called Type I and Type II.

  • Type I Supernova: This type occurs in all types of galaxies, and the lack of hydrogen in its spectrum leads to the conclusion that it is an event in a low-mass star, probably resulting from the collapse and incineration of a white dwarf star in a binary system.
  • Type II Supernova: This type is found in the spiral arms of a galaxy and shows hydrogen in its spectrum. Astronomers believe this type of supernova is associated with the explosion of massive stars.

Supernovae in Our Milky Way Galaxy

Supernovae in our galaxy, the Milky Way, that are bright enough to be seen during daylight have been observed for over a thousand years. In recorded history, five supernovae have been observed. The first three, in the years 1006, 1054, and 1181, were recorded by Chinese observers. The first one was said to be as bright as a full moon, yet there are no records of sightings from European observers. The lack of observations by Europeans may have been influenced by their belief that fixed stars were absolutely unchanging.

There is some evidence that the supernova that occurred in 1054 may have been observed by Native Americans in the American Southwest. Several petroglyphs dated to that period in Arizona and New Mexico depict a bright star next to a crescent Moon, which is the approximate relative position of the supernova and the new star in early July 1054. This supernova remained visible during the daylight for several weeks and was able to be seen at night for about two years.

An 11th century pictograph at Chaco Canyon, New Mexico, may depict the supernova of AD 1054. The supernova and the Moon were in this configuration when the supernova was near its brightest.

An 11th century pictograph at Chaco Canyon, New Mexico, may depict the supernova of AD 1054. The supernova and the Moon were in this configuration when the supernova was near its brightest.

Tycho’s Supernova: SN 1572

Modern astronomers have given the designation SN 1572, which means the supernova of the year 1572, to the supernova Tycho first observed on November 11, 1572. Tycho was by no means the only person to report the observation of the new star; some records indicate it may have been visible as early as August of that year. Based on European and Chinese observations, astronomers have been able to piece together a light curve that shows the change in brightness of the exploding star with time. From this they have concluded it was a Type I supernova.

Based on observations from that period, the new star suddenly appeared in early November 1572, and by the middle of the month it was as bright as Jupiter or Venus. According to Tycho, the star was “brighter than Venus.” The supernova faded over the subsequent months, remaining visible to the naked eye until early 1574. Today, only remnants of the exploding star are visible in the world’s largest and most sophisticated telescopes.

The red circle visible in the upper left part of this infrared image is the remnant of Tycho’s supernova of 1572.

The red circle visible in the upper left part of this infrared image is the remnant of Tycho’s supernova of 1572.

The image of Tycho’s supernova of 1572 is a composite of an X-ray image taken by the orbiting Chandra X-ray Observatory, an infrared image taken by the orbiting Spitzer Space Telescope, and an optical telescope.

The image of Tycho’s supernova of 1572 is a composite of an X-ray image taken by the orbiting Chandra X-ray Observatory, an infrared image taken by the orbiting Spitzer Space Telescope, and an optical telescope.

Tycho Brahe After the “New Star” of 1572

The observations and his publication of De nova stella propelled Tycho to the level of a first-rate astronomer in Europe. In 1576, King Frederick II of Denmark offered Tycho the island of Hven in the Danish Sound and asked him to build an observatory and a laboratory to continue his research into astronomy and alchemy. The king told Tycho: “It occurred to me that it would be very well suited to your experience in astronomy and distillation, because it is high and has an isolated location…If you want to live on the island, I would gladly grant it to you.”

Tycho accepted the king’s offer, which came with a handsome yearly stipend and startup money, and set to work building a world-class observatory and research facility. By 1584 he had built two observatories: Uraniborg (heavenly castle) and Stjerneborg (cast of the stars) on the island. To support the observatories and people working for Tycho, the island’s facilities eventually included workshops for the construction of the instruments, a printing press, a windmill, a paper mill, numerous fishponds, and indoor running water. The instruments Tycho had constructed were large and well built, allowing him and his observers to keep measurement error to a minimum.

Toward the end of Tycho’s life, a young German mathematician and astronomer, Johannes Kepler, began to work for him. After the death of Tycho, Kepler was instrumental in using the observations to develop the laws of planetary motion, which have come to be known as Kepler’s Three Laws of Planetary Motion. Tycho’s observations of the heavens were key to the work of astronomers like Kepler and then Isaac Newton in unlocking the secrets of the universe.

References

Abell, George O., David Morrison, and Sidney C. Wolff. Realm of the Universe. Philadelphia: Saunders College Publishing, 1988.

Christianson, John R. Tycho Brahe and the Measure of the Heavens. London: Reaktion Books Ltd., 2020.

Concise Dictionary of Scientific Biography. New York: Charles Scribner’s Sons, 1981.

Couper, Heather and Nigel Henbest. The History of Astronomy. Buffalo, New York: Firefly Books Ltd., 2007.

Dictionary of Scientific Biography. New York: Charles Scribner’s Sons, 1981.

McKeon, Richard (Editor). The Basic Works of Aristotle. New York: The Modern Library, 2001.

The New Encyclopedia Britannica. 15th Edition. Chicago: Encyclopedia Britannia, Inc., 1994.

West, Doug. Nicholaus Copernicus: A Short Biography: The Astronomer Who Moved the Earth. Missouri: C&D Publications, 2018.

West, Doug. The Astronomer Tycho Brahe: A Short Biography. Missouri: C&C Publications, 2022.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Doug West

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