astronomy@iowa

Forensic sketch of Copernicus, age 70.

Nicolaus Copernicus, the 16th century Polish astronomer and canon in the Catholic Church, was reburied in a formal ceremony in Frombork, Poland, on May 22, over 460 years after his death in 1543. In that same year, his greatest work, De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Spheres), was published and legend has it that the dying cleric received a copy on his death bed. Were it not for the efforts of Georg Joachim Rheticus, a young scholar from the University of Wittenberg who traveled to Frombork in 1539, Copernicus’ revolutionary theory that the Sun is the center of the universe and that the earth rotates on its axis might never have been published. Sometime in late 1538 or early 1539, Rheticus became aware of the Polish astronomer’s work and made the decision to visit him and learn all he could of this extraordinary theory.

Choosing to live far from the intellectual hotbeds of Europe, Nicolaus Copernicus chose instead to pursue a life of relative ease. After studying both medicine and astronomy in Italy and serving as his uncle’s assistant for a number of years, he resigned that position and accepted the position of canon in little Frombork. This was not the path to greatness that his uncle, the prince-bishop of Warmia, had in mind for his nephew. In this tiny fishing village that even Copernicus described as “the remotest corner of the world,” is nascent astronomical talents emerged and Dr. Nicolaus began outlining his criticism of Claudius Ptolemy’s earth-centered model of the heavens. In a scant six leaves, Copernicus described in non-technical language what he considered “no small difficulties” and “defects” in the model that had dominated astronomy for 1,300 years. A total of seven assumptions, or axioms, were presented that refuted the Ptolemaic model. Some time before 1514, the anonymous, handwritten manuscript was circulated among friends and scholars from Copernicus’ university days. Eventually copies were made and disseminated throughout astronomical circles and the promised “larger work” that included all of the requisite mathematica detail was eagerly awaited. Although people waited decades, the promised treatise never materialized. Back in little Frombork, however, Copernicus was at work writing the book that would help usher in the scientific revolution.

While it is often said that Copernicus withheld the publication of De Revolutionibus because of concerns he would be labelled a heretic, evidence does not support that conclusion. Shortly after the distribution of the little pamphlet that eventually came to be called Commentariolus, Copernicus’ name became well enough known that Pope Leo X invited him to participate in the calendar reform that had been started in 1475 but never finished. We don’t know how Copernicus responded to the request, but regardless the calendar reform never took place. Additionally as late as 1536, by which time Copernicus would have been putting the finishing touches on his book, Cardinal Nicholas Schönberg, who had discussed Copernicus’ sun-centered model of the heavens with Pope Clement VII in 1533, sent Copernicus a letter in which he praised the Polish astronomer and urged that he publish his new theory in which the earth moves and that “the sun occupies the lowest, and thus the central place in the universe.” The cardinal even offered to send one of his assistants to Frombork and arrange for the copying of all of Copernicus’ notes in preparation for publication of this new theory. Copernicus chose to ignore the appeal. He may have been concerned that some of his calculations still needed refinement and were not yet ready for presentation. Perhaps there were other reasons as well. Unlike astronomers who held university positions, Copernicus had a day job—administration of church business and medicine occupied much of his time as did a growing scandal around Copernicus’ living arrangements with a woman although he had taken a first-order vow of celibacy. While not completely uncommon at the time, at a time when the Catholic Church was growing increasingly sensitive to the influence of the Lutheran Church in Poland, this was just the kind of ammunition enemies seeking the position of canon needed. Evidence of sympathy to some Lutheran doctrine didn’t help matters.

Copernicus’ greatest contribution to science might have been left among his belongings waiting a later scholar to uncover and publish were it not for the efforts of the Lutheran professor from Wittenberg. Rheticus carried the manuscript of De Revolutionibus with him from Frombork and delivered it to Andreas Osiander, a colleague charged with overseeing the publication in Nuremberg. Without the consent of Copernicus or Rheticus, Osiander wrote and inserted a preface in which the sun-centered model is stated to be merely a hypothesis that allows for more accurate calculations and not necessarily the truth sought by natural philosophers. Rheticus was justifiable furious upon learning of the unauthorized insertion. For years it was assumed that Copernicus wrote the preface and that he might not actually believe the bold statements made in his book. Rheticus must also have been devastated by the glaring omission of his own name in the acknowledgements written by Copernicus. While many others were mentioned by name, Rheticus was never mentioned and historians have yet to agree on a satisfactory explanation for the omission.

Copernicus died on May 24, 1543, months after suffering a stroke and falling into decline. According to reports of the time, he received a printed copy of De Revolutionibus the day he died.

Although the general location of where Copernicus’ body was buried has been known, the exact location and identification of his remains was not made until 2005 when a team of archaeologists and historians discovered the remains of a man that matched the age of Copernicus. A forensic analysis of the skull provided a sketch (see above) that seemed to match contemporary paintings of Copernicus, but DNA recovered from the body awaited verification from another source. Finally scientists had a lucky break when several hairs were found in a book once owned by Copernicus. The DNA samples from several of the hairs matched the DNA of a tooth in the skeletal remains found in the cathedral at Frombork. Copernicus’ remains now rest in the alter of the Cathedral he presided over and under a 10-foot granite monument depicting his sun-centered model of the heavens.

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For further reading, check out Copernicus’ Secret by Jack Repcheck and The Book Nobody Read: Chasing the Revolutions of Nicolaus Copernicus by Owen Gingerich.

At 13:40 UT (that’s 7:40 a.m. CST) on March 2, the near-Earth asteroid 2009 DD45 zipped past Earth at a distance of only 0.00048 A.U. Considering that the average Earth-Sun distance is 1 Astronomical Unit, 0.00048 A.U. works out to be a mere 45,000 miles! That’s a close shave by anyone’s standards. The Moon’s average distance is 240,000 miles and the geosynchronous satellites monitoring our weather and blanketing Earth with a global positioning and communication network orbit the earth at 23,000 miles. Having an Apollo group asteroid careen past the planet at twice the distance of the geosynchronous satellites is certainly something to note.

This kind of celestial fly-by is not entirely unprecedented, however. In 1972 a small asteroid (or meteoroid, if you prefer) skimmed through Earth’s upper atmosphere as if it were a stone skipping off a pond. That object entered the atmosphere over the Northwest United States and exited somewhere over Canada. Estimated to be about the size of an SUV, an impact or airburst of an rock this size would have been very impressive. Not the kind of event that would spell doom for civilization, but enough to get your attention. The most recent event of this type was the Tunguska blast over a remote area of Siberia in 1908 when a loose-aggregate meteoroid, or perhaps a comet fragment, entered the atmosphere and exploded in the upper atmosphere. Trees were stripped of branches and felled for many square miles around the spot directly below the blast. On a bit larger scale, anyone standing in the desert Southwest 50,000 years ago might have been in for a shock when a 100-foot meteoroid slammed into the ground (becoming a meteorite in the process) and created the Barringer meteor crater. At over 3/4 mile in diameter and nearly 600 feet deep, Barringer crater is the best preserved example of what happens when big rocks cross Earth’s orbit.

Thought to be about the same size as the Tunguska event’s object and just  bit smaller than the meteorite responsible for the Barringer crater, 2009 DD45 is over 100 feet in size and could have potentially unleashed many dozens of times the explosive force of the atomic bombs used at the end of World War II. Sleep well.

For further information: 2009 DD45 orbital parameters from NASA’s Jet Propulsion Laboratory (JPL) and a movie on YouTube showing the asteroid’s fly-by.

The Full Moon of February occurred at 8:49 a.m. CST this morning. Known as the Snow Moon, it is the second Full Moon of the northern hemisphere’s winter. As far as the lunar calendar is concerned, February is unique in that it is the only month in which is it not possible to have two Full Moons and it is that prospect of two Full Moons in a month that brings up an interesting historical oddity referred—incorrectly, as I’ll discuss in a few moments—as a Blue Moon. It is impossible for February to have two Full Moons, incidentally, due to the 29.5 day synodic period of lunar phases. Thus, the interval between Full Moons is over one day longer than the length of a typical February (and one-half day longer than a leap year February.)

But just what is a Blue Moon, anyway? Not what most people believe when you ask them for a definition. The earliest known usage of the phrase “blue moon”, however, appears to be a 1528 pamphlet entitled Rede Me and Be Not Wrothe in which the author wrote “Yf they say the mone is belewe We must beleve that it is true.” The expression seems to refer to something so absurd as to be unbelievable. According to common lore, however, a Blue Moon is usually described as the second Full Moon in a month, but in reality they are not so rare as to warrant the phrase “Once in a Blue Moon.” In fact, there are two Full Moons in a month about once every two years—hardly a rarity. Believe it or not, this particular usage of the phrase appears to stem from a misinterpretation of the original meaning and can be traced to the original Trivial Pursuit game of the 1980s.

The modern usage of Blue Moon appears to have its origin in the Maine Farmer’s Almanac. Editors at Sky & Telescope, with the assistance of several librarians, obtained 40 copies of the Almanac dating back to the early 1800s and found numerous citations that referred to Blue Moons, but not one of them referred to the second Full Moon of the month. In fact, the Blue Moons always occurred on the 20th – 23rd days of February, May, August, or November! These Full Moons always occur about one month before a seasonal change. A further nuance discovered with additional research revealed that the almanac definition relied on the use of the tropical year, which is measured from one winter solstice (Yule) to the next, instead of using the traditional calendar year. Most tropical years have 12 Full Moons—three per season—but occasionally there are 13 Full Moons with one season having four Full Moons.

Why is the third Full Moon significant? Because historically the name of the fourth Full Moon must be in accordance with the seasonal change as the name of that Full Moon relates to the impending equinox or solstice. Thus, the Full Moons of this winter are: the January (Moon After Yule) Full Moon, the February (Snow) Full Moon, and the March (Lenten) Full Moon. Occasionally, however, the first Full Moon of winter occurs just hours after the winter solstice and is therefore in December and not January. In those years, the occurrence of Full Moons will be: the December (Moon After Yule) Full Moon, the January (Snow) Full Moon, the February (Blue) Full Moon, and the March (Lenten) Full Moon. In both cases, the sequence of Full Moons occurs prior to the arrival of the vernal equinox and the start of spring. Thus, Easter won’t occur until after the first Full Moon of spring—referred variously as the Egg, Grass or Hare Full Moon.

A complete description of how Blue Moons are determined is quite convoluted, but is an interesting example of how calendar reform, religious observances (namely Lent and Easter), and astronomical events are joined together.

Read the full Sky & Telescope article for a detailed explanation of the calculation and how the editors traced the history of the Blue Moon definition.

In the early morning hours of January 26, the Moon will slip in front of the Sun producing a solar eclipse visible to observers on the Indian Ocean. This  eclipse is a bit unusual, however, in that the Moon will be near the apogee of its orbit around Earth. As discovered by Johannes Kepler in the 17th century, orbits are not circular as the prevailing wisdom of thousands of years assumed, but are instead elliptical. The Full Moon of two weeks ago occurred when the Moon was at the closest point in its orbit around earth—perigee—and the New Moon of January 26 will occur near the farthest point from Earth (apogee.) Since the Moon will be slightly farther from Earth than usual, it will cover a smaller area of the sky. Add to this the fact that Earth is near the closest point in its orbit around the Sun (perihelion) at this time of year and the circumstances result in the Moon appearing just a bit too small to cover the visible disk of the Sun. The result is a ring of the Sun’s disk remaining visible producing a annular eclipse.

Note: Because the Sun’s visible disk is not completely obscured (the maximum coverage will be about 93%), it is NOT safe to look directly at the eclipse without protective filters. If protective filters are not available, the Sun’s image can be projected so that the projected image can be observed.

Fred Espenak’s “Mr. Eclipse” graphic for the January 26 annular eclipse.

Visit spaceweather.com for animations, videos and photo galleries of the eclipse.

Early this morning physicists at the CERN—the European Center for Nuclear Research that straddles the French–Swiss border—activated the world’s most powerful particle accelerator. After a quarter century of dreaming and nearly 15 years of construction, several beams of protons were sent through the 17-mile beam ring that is buried 300 feet below the shores of Lake Geneva. Today’s test is a crucial first step on the path leading scientists to the unimaginably energy a mere trillionth of a second after the Big Bang. Eventually counter-circulating beams of protons (the proton is one member of a class of particles called hadrons) will collide to recreate those conditions.

In order to recreate those exotic conditions, the beams of protons must be accelerated to within a tiny fraction of the speed of light. Because Einstein’s special theory of relativity dictates that an object gains mass as its velocity increases (a hypothesis that has been experimentally verified time and time again) and also that mass and energy are equivalent. Thus, extremely high velocities are needed to produce the energies needed to test our theories of the early universe and the fundamental nature of mass itself. The LHC is expected to eventually accelerate protons to energies of 7 trillion electron-volts (7 TeV) where each electron-volt is the kinetic energy gained by a single electron as it moves through an electric field of 1 volt. The eV is the fundamental unit of energy used in nuclear physics.

By recreating conditions shortly after the Big Bang, physicists hope to glimpse evidence of the Higgs boson—a particle hypothesized to exist in those rarified conditions that is responsible for giving the property of mass, and thus inertia, to matter—as well as learn more about the elusive dark matter that accounts for anomalies in the rotation rates of galaxies and holds clusters of galaxies together. Dark matter is thought to account for as much as a quarter of the matter in the universe. One thing that the LHC is not expected to produce is an Earth-swallowing black hole. While “mini” black holes that are sub-atomic in size may be produced, if in fact they exist at all, the production of black holes that would spell doom for the earth is the stuff of fiction not science. No credible scientific evidence predicts that sort of scenario. In fact, Earth’s upper atmosphere is bombarded by cosmic rays of even greater energy every day and no mini black holes have been observed in those collisions.

One thing that is inescapable, however, is the bittersweet moment the test firing of the Large Hadron Collider represents. Even though the LHC is an international effort, the United States has relinquished its position as a leader in basic high-energy physics. Construction of the Superconducting Supercollider in Texas ended in 1993 when Congress looked for ways to save money and eliminated the funding after $2 billion dollars had already been spent. The SSC was to be an even bigger project than the Large Hadron Collider, whose construction was undertaken the year after the Superconducting Supercollider was killed. Although its budget eventually ballooned to $11 before being defunded, the SSC represented a mere 0.6% of the federal R&D budget for FY1992.

Given the politically-charged environment in which basic scientific research must be conducted today, CERN’s approach, with over 20 countries providing funding that is governed by treaty, may be the reality for the foreseeable future. Gone are the days of national pride in scientific achievement like those when physicist Robert Wilson was asked in a congressional hearing about the proposed FermiLab’s benefit to the United States’ national security. His reply: “It has nothing to do directly with defending this country except to make it worth defending.”

Two years ago the International Astronomical Union (IAU) angered a lot of people when the Solar System’s ninth planet Pluto was demoted and designated a “dwarf planet” along with the asteroid Ceres and the recently discovered trans-neptunian object Eris. Well, the IAU has now come up with an official designation for Pluto and Eris that is almost guaranteed to upset people all over again. While some may think it’s a silly exercise to spend so much energy coming up with classification schemes (years ago the physicist Enrico Fermi complained about the number of sub-atomic particles saying “If I could remember the names of all these particles, I’d be a botanist.”), it is important for scientists to make classifications of the objects they study. The Greeks used the term “planetes astrum” to describe the wandering stars—as opposed to the “fixed” stars—but that definition did not really distinguish the actual planets from the Moon and Sun. But “Plutoid?”

The IAU Committee on Small Body Nomenclature defines a plutoid as “celestial bodies in orbit around the Sun at a semimajor axis greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighbourhood around their orbit.” For naming purposes, any body that meets these criteria and have an absolute magnitude brighter than H = +1 where H is the magnitude of the planet, asteroid, comet, etc. at one Astronomical Unit from the Sun.

In the above image, Pluto and its three moons are shown on the left while Eris is on the right.

Image Credit: IAU, NASA/ESA Hubble Space Telescope, H. Weaver (JHU/APL), A. Stern (SwRI), the HST Pluto Companion Search Team and M. Brown.

The following Oo-Ed piece by physicist Brian Greene appeared in the New York Times today:

Put a Little Science in Your Life