Astronomy Goes Old School – REALLY Old School

[Left: Medieval scholars learn how to use a cardboard astrolabe at the 2017 International Congress on Medieval Studies in Kalamazoo, MI; Right: CCSU Students in a Cultural Astronomy class learn how to use astrolabes]

Astronomy has rightly been called the oldest science. From using the phases of the moon to record the passage of time and make calendars to monitoring the position of the sun at sunrise to determine the summer solstice, humans have been studying the heavens throughout recorded history. Technology such as the telescope and sensitive cameras (not to mention space probes!) has greatly enhanced our ability to understand the universe around us. But one particular type of astronomical technology is decidedly old school – really old school! The origins of the astrolabe are lost to history, but probably date back to around the 6th century CE. Part calculator, part star map, part surveying and navigational tool, and part work of art, the astrolabe has been used for centuries to calculate the time from the position of the sun or stars, estimate one’s latitude, and measure the heights of buildings and trees, among other uses. Although they were largely replaced by more “modern” technologies by the 18th century, they are still an excellent tool that can be used to teach basic astronomical concepts, as well as demonstrate the close connections between astronomy, history, art, and religion (as they were used to calculate prayer times by both Christians and Muslims in medieval times).

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[So-called Chaucer Astrolabe in the British Museum]

I have greatly enjoyed teaching students how to use simple cardboard astrolabes, both in a Cultural Astronomy course as well as as a guest lecturer in a Medieval History class, as well as giving lectures and workshops at other universities and numerous conferences. If you ever get the chance, peruse the astrolabe collections at the Adler Planetarium in Chicago and the Oxford University Museum of the History of Science. I have been fortunate to have seen both these collections in person and they are quite simply out of this world!

— Kris Larsen

Kudos to Kepler for a Job Well Done!

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[The Kepler Space Telescope Main Mission’s 4000+ exoplanet haul!]

NASA recently announced the final planet-finding tally for the main mission of the Kepler Space Telescope: a whopping 2335 verified planets outside our solar system and another 1699 candidate planets yet to be verified. Among these 4000+ potential planets are 49 potentially habitable bodies – rocky planets about the size of earth that inhabit the so-called Goldilocks Zone of their star (you know, not too hot, not too cold, just right!)

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[Exoplanet discoveries by year (does not include recent Kepler announcement)]

Take a minute and consider what this means. When I started teaching at CCSU back in 1989 there were NO planets known orbiting sun-like stars outside our solar system. None. Nada. Zippo. By the time I became tenured we finally knew of a single planet around a sun-like star. By the time I became a full professor we had discovered a handful. In fact, until Kepler started staring at over 100,000 stars in one area of the sky (near Cygnus) in 2010 the number of known planets outside of our solar system was only a few 100.

And then everything changed. Not only did we discover that planets were relatively common, but that there are more types of planets than astronomers ever imagined! Superearths, mini Neptunes, hot Jupiters, lava planets…. Suddenly our original sample size of 1 known solar system wasn’t so representative of the universe as a whole.

While the main Kepler mission has ended (thanks to failing systems that point the telescope), the extended K2 mission is still making discoveries, including new exoplanets. The TESS satellite will likely reveal another slew of exoplanets after its launch next March. But Kepler will always have a place in my heart as the telescope that COULD and DID change the way we think about the universe and our own pale blue dot of a world.

— Kris Larsen

Seeing Spots Safely

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[Sunspot observation by Kris Larsen. Groups of sunspots are labeled]

It might surprise you to learn that the sun is actually variable star – it varies (albeit very slightly) in the amount of light that it sends earthward. The complex and ever-changing magnetic field of the sun creates both brighter than average (faculae) and dimmer than average (sunspots) regions on its visible “surface” (called the photosphere) that are continually changing in size and number. While a given sunspot group or faculae region may last for as little as a day or as long as two months, over a roughly 11-year period the numbers of these active regions waxes and wanes, creating the so-called sunspot cycle. Since the time of Galileo, observers have been monitoring sunspot activity. While this is a fun and scientifically useful activity, it must be done safely, as the sun is the only variable star that poses a danger to your eyesight if you aren’t careful. You should never look directly at the sun with your eyes or any optical equipment unless you are properly using an approved solar filter.

To this end, the Solar Section of the American Association of Variable Star Observers (which I am currently fortunate to serve as president) has recently released a Solar Observing Guide. Written by long-time AAVSO solar observer Frank Dempsey (with additional content by fellow Solar Section members and solar safety experts), this guide is a must for anyone contemplating solar observing. Anyone interesting in taking up this task should also seek the aid of a seasoned mentor to help them get started.

The sun changes every day, and safely observing these changes is an experience that will have you coming back again and again. But “safety first” is a must!

– Kris Larsen

 

 

Celebrating International Women’s Day through the Life of Astronomer Dorrit Hoffleit

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Dorrit Hoffleit (1907 – 2007) receiving an Honorary Doctorate from CCSU in 1998

If you are fortunate, you encounter a special mentor in your life, someone who helps to shape not only your career, but your entire life. I have been fortunate to have had several such individuals while a college student and young academic. One of the most influential was Dorrit Hoffleit. If it were not for her, I would not be President of the AAVSO today. In celebration of Dorrit’s remarkable life and career, I offer here a summary of her achievements. – Kristine Larsen

 

The daughter of German immigrants Fred and Kate Sanio Hoffleit, Ellen Dorrit Hoffleit was born on her father’s farm in Alabama on March 12, 1907. According to Dorrit, her father named her Ellen, her mother named her Dorrit, and in her words, “the woman in the house always has her way.” After a suspicious fire destroyed the family farmhouse when Dorrit was still an infant, Fred moved the family to New Castle, Pennsylvania, where he had been working as a bookkeeper for the Pennsylvania Railroad. The marriage eventually fell apart and Fred moved back to the farm by himself when Dorrit was nine years old.

Dorrit recounted that watching Perseid meteors with her older brother Herbert was an important step towards becoming an astronomer. As a child, Dorrit fell into her brilliant older brother’s shadow, facing constant comparisons from teachers who were impressed with his natural talent for languages. As she explained, “One of my grade school classes I had the same teacher that my brother had had a few years previously. My mother and I were walking down the street one day and we bumped into my teacher and Mother and teacher started talking … and the teacher says ‘Dorrit isn’t as bright as her brother, is she?’ where upon my mother says, ‘What can you expect, she’s only a girl.’” Dorrit was deeply hurt by that remark but years later her mother explained that she was referring to the teacher’s intelligence, not her daughter’s. Dorrit was deeply proud of her brother, who received a Ph.D. from Harvard in Classics at the young age 21, and subsequently became a professor at UCLA. She later explained that “The contrast between my brother and me is an exemplification of the childhood tale of the tortoise and the hare. Herb learned quickly and achieved early in life. I was slow but deliberate and finally made the grade. It is hard to say whose influence was the greater on our respective students.”

Dorrit was sent to Radcliffe College by her mother “so that her brilliant son wouldn’t be ashamed of his ‘dumb’ sister.” At Radcliffe, Dorrit became a mathematics major as Radcliffe only offered two astronomy courses at the time. Dorrit learned her first taste of independent research quite by accident at Radcliffe when she incorrectly conducted an astronomical transit experiment. For her, it was a valuable learning experience but in her words “I don’t think my professor appreciated the educational value of that experiment. I think I got a lot more out of the pole star than I did out of what the thing was intended for. So you see, independence wasn’t appreciated even then.” Dorrit graduated Radcliffe cum laude in 1928 and began taking graduate classes while looking for work. Through a classmate she landed a job as a research assistant at the Harvard College Observatory for 40 cents per hour, half of a man’s salary. She turned down a higher paying statistician job to work there, and several times subsequently turned down other, higher paying offers because of her growing love for the HCO and respect for its Director, Harlow Shapley, who encouraged independent thinking. Her original position was working as an assistant to Henrietta Swope, daughter of the president of General Electric Company. Henrietta had discovered a large number of variable stars, and her father was so proud of her that he funded the assistant position that Dorrit filled. Dorrit proved herself to be an expert discoverer of variable stars in her own right, finding approximately 1200 over her career.

At Harvard Dorrit came into contact with the American Association of Variable Star Observers, or AAVSO, an organization of amateur and professional astronomers that had been founded at Harvard in 1911 by Observatory Director E.C. Pickering and variable star observer William Tyler Olcott. She became an official member of the organization in 1930, and a life member in 1943. Of her eventual 450+ professional publications, her first two (published in 1930) were directly related to variable stars: the first was on variable stars in Centaurus, and the second was a collaboration with AAVSO Recorder Leon Campbell on the color curve of the variable star RV Centauri. Thus began Dorrit’s lifelong love for the AAVSO and its members.

Dorrit completed a MA in Astronomy from Radcliffe in 1932, as she put it, “the highest degree for which I felt qualified.” She continued her work on variable stars during the day and worked on independent research projects at night on her own time, including a pioneering study of the light curves of meteors using the accidental photographs of meteors in the Harvard plate collection. She brought her completed paper to Shapley, who submitted it for publication and then called Dorrit into his office, where colleague Bart Bok was also waiting. As Dorrit described it, Shapley said “‘We were wondering why you were not continuing to work for your Ph.D. Go back to your office and think it over.’ I had never been particularly bright, and this was the greatest expression of confidence in my abilities I had ever heard.”

With more prodding from Bart Bok, Dorrit went back for her Ph.D. at Radcliffe, which she completed in 1938 with work on determining the absolute magnitudes of stars from their spectra. Her thesis was awarded the Caroline Wilby Prize for the best original work in any department by a student that year. Dorrit continued her work at the HCO as a research associate and then astronomer with tenure, continuing her research on variable stars and other astronomical objects. She came into contact with some of the biggest names in astronomy and made a reputation for herself as a diligent worker. For example, Ejnar Hertzsprung sent her so many requests for observations of variable stars that Shapley had to finally put his foot down because it was taking too much time away from Dorrit’s Harvard assignments.

At Harvard, Dorrit met and worked with many of the now-famous female “computers” and astronomers, including Antonia Maury, Annie Jump Cannon and Cecilia Payne-Gaposchkin, all of whom made contributions to variable star astronomy. But her favorite was undoubtedly Antonia Maury, with whom she became good friends. After Antonia’s death, Dorrit became a champion for her and the rightful place of her work in astronomical history, and wrote numerous articles about her friend.

Dorrit also developed an overall passion for the history of astronomy, seen most tangibly in a later work she was quite proud of, The History of Astronomy at Yale. She was also interested in illuminating the important role played by women in astronomy, as seen in her short works Maria Mitchell’s Famous Students and Comets Over Nantucket (1983), Women in the History of Variable Star Astronomy (1993), and The Education of American Women Astronomers Before 1960 (1994).

During World War II, Dorrit, like many Harvard astronomers, became involved in “war work.” She felt more compelled than more to become involved because of her German heritage, and because during World War I young classmates had taunted her as one of the enemy. In 1943 she took a leave from Harvard and began work at the Aberdeen Proving Ground in Maryland, preparing aircraft firing tables. There she found herself in a private war against gender discrimination. As an academic with a Ph.D., she was clearly eligible for a professional rating but was instead relegated to a subprofessional class even though she was assigned to do professional class work. This led to a conflict which Dorrit rates as a defining experience in her career. In her words, “After I’d been there for about a year the inspector general of the Baltimore district, where Aberdeen is, discovered there was a woman Ph.D. with the subprofessional rating, and he came around on a day when the colonel was down at Washington instead of in Aberdeen and he wanted to find out all about the story about why I was on a subprofessional [rating]…So when the colonel came back the next day and heard about what had happened …[he]told the major to tell me that there was no room for professional women …, that I’d have my choice – either I could transfer to the Pentagon where women were welcome, … or the poor major was to make sure that I did nothing but subprofessional work because if I didn’t do anything but subprofessional work then it would be all right to keep me on subprofessional rating. So I told the poor quaking major that… since the colonel wouldn’t talk to me himself, he, the major, could go back and tell the colonel ‘thanks, I don’t accept either alternative, that isn’t what I came down here for.’” Dorrit eventually won her “war” with the military brass and afterwards returned to Harvard, but continued as a consultant – with the proper professional rating – at the Proving Ground until 1961.

Dorrit’s life was drastically changed by Shapley’s retirement from Harvard in 1952. His replacement, Donald Menzel, did not apparently value independence, so despite having tenure at Harvard, Dorrit was forced to follow her conscience and “defected” to Yale in 1956 where she worked on large astrometric catalogue projects and where, to her unhappy surprise, she was not afforded the same independence she had enjoyed at Harvard. Fortunately, at the same time, she was offered the Directorship of Nantucket’s Maria Mitchell Observatory. Due to the financial situation of the observatory, she held a split 6 month/6 month appointment between Yale and Nantucket.

Dorrit’s two decades on Nantucket allowed her to encourage a new generation of astronomers through her summer variable star research program for undergraduates. Over the years 102 young women (and 3 young men) conducted research on approximately 650 variable stars, presented their findings at the AAVSO Fall conference, and often published their results in the Journal of the AAVSO. As Dorrit reflected, at least thirty five of her former students became professional astronomers “and their achievements are a joy to behold.” To this day, being called “one of Dorrit’s girls” is considered a supreme honor.

One of Dorrit’s most beloved “girls” was Janet Mattei, who unexpectedly assumed the responsibility of hosting the October 1969 meeting of the AAVSO on Nantucket at the last minute when Dorrit was unable to travel back to the island due to extreme fog. As Dorrit has often recounted, “my girl Janet had done such a marvelous thing running the meeting for me that when Margaret Mayall [Director of the AAVSO] was looking for an assistant… I got the two of them together again and Margaret of course grabbed Janet… and then when Margaret was ready to retire there were a half a dozen people who wanted her job and [Janet] was unanimously elected to that job, all because of the Nantucket fog.” It should be noted that Janet also made an equally deep impression on a young AAVSO member at that meeting, Michael Mattei, who became her husband.

Dorrit remained an untenured research associate and astronomer at Yale (supported entirely through grants – a feat she was especially proud of) even after her “official” retirement in 1975. Her main contributions at Yale include the first paper on the light variability of quasars, catalogues containing the proper motions of 30,000 stars, and the 3rd and 4th editions of the Bright Star Catalogue and its Supplement.

Dorrit received numerous awards over her life, some of which are shown on this slide, including an asteroid named in her honor, the George van Biesbroeck award from the University of Arizona for outstanding service to astronomy, the Annenberg Foundation Award from the American Astronomical Society for “service to the community in education,” and the AAVSO’s William Tyler Olcott Distinguished Service Award.

Dorrit’s service to astronomy is impressive and wide-reaching, but her service to variable star astronomy was perhaps nearest and dearest to her heart. Of her approximately 450 professional publications, 41% were related to variable stars, and over 50 were published by the AAVSO. She served the AAVSO in many capacities (as shown on this slide), including two years as President, and several terms on the Council. She was undoubtedly the organization’s greatest cheerleader.

But the AAVSO was not Dorrit’s only avenue for interacting with amateur astronomers and the general public. For example, she was active with the Bond Astronomical Club at Harvard (serving as President in 1952) as well as the Astronomical Society of New Haven, which is where I met her while a teenager. An honorary member of the Society, Dorrit spoke at nine meetings between 1957-1987, including keynote speeches at the 1973-5 annual banquets. At the Maria Mitchell Observatory she held public observing nights, exposing her research students to the joys of public outreach. And she also penned many popular level articles on astronomy over her career, in such journals as Sky and Telescope, Mercury, Popular Astronomy, and The Scientific Monthly.

In everything she did, Dorrit’s work ethic was simple, and straightforward: “Work for the work’s sake and it will become a part of you.” Not only was her work a part of her, but through her work she became an integral part of the astronomical community. In honor of her lifetime of accomplishments, Yale University hosted special symposia for her 90th birthday in 1997, and in honor of her Centenary year in 2006. She continued to be active in research on topics of her choice until shortly before her death on April 9, 2007, at the age of 100, and often remarked of her later years “I have become as happy and independent as I had been in my youth at Harvard.”

Those who were blessed to have known Dorrit treasured her for her intelligence, work ethic, loyalty, sense of humor, and her hearty full-body laugh. I once asked her what she liked to do outside of astronomy – she replied without hesitation “eat and sleep,” and then laughed with gusto. She was a mentor to many, and a role model to countless more. She will not be matched, and she is dearly missed.

I had the honor of introducing Dorrit when she was inducted into the Connecticut Women’s Hall of Fame, and nominated her for the Honorary Doctorate she received from my home institution, Central Connecticut State University. Dorrit liked my introduction of her at both events so much she included it in her autobiography, Misfortunes as Blessings in Disguise, and I am honored to think that she felt it did a reasonable job of summing up her career:

It is a basic tenet of stellar astronomy that those stars which burn hottest and brightest and draw the most attention to themselves also burn out the quickest, rapidly becoming nothing more than fading memories. Meanwhile, those unassuming stars which steadily shine in the background, content to diligently produce energy at a more modest pace, continue to influence the universe with their light and heat for many generations to come. Such is the record of your long and amazingly productive career.

But I think that Janet Mattei did a far better job of summarizing Dorrit’s impact on the universe, when she said “It is rare that a human being can touch many lives and make the world a better place – as Dorrit Hoffleit has.”

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Note: This summary was heavily based on two prior publications, and I invite the interested reader to consult those for relevant citations and references:

“Whistling Meteors, Vibrating Cameras, and the Moon-Struck Iris: Popular-level Writings of Dorrit Hoffleit.” In The Hoffleit Centennial, eds. A. G. Davis Philip, William F. van Altena and Rebecca A. Koopmann. L. Davis Press, 21-6, 2008.

“Variable Stars and Constant Commitments: The Stellar Career of Dorrit Hoffleit.” Journal of the American Association of Variable Star Observers 40(1): 44-50, 2012.

 

A Lesson on Luni-solar Calendars for Losar

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[A Tibetan mandala, representing the orbits of the moon, sun, and planets]

February 27, 2017 marks Losar, the beginning of the Year 2144 on the Tibetan Calendar, a year of the Fire Bird. You might be saying, hey, wasn’t the Chinese New Year last month, and you would be correct. The Chinese New Year indeed fell on January 28 this year. Both the Han Chinese and Tibetans traditionally follow what we call luni-solar calendars, but despite their geographical proximity, these two cultures have very distinct rules for calculating their calendars.

Unlike our solar calendar of 365.25 days (called solar because it is based on the orbit of the earth around the sun), luni-solar calendars use the 29.5 day cycle of the moon’s phases to define 12 lunar months (normally 6 each of 29 and 30 day lengths) in their year. This means that a luni-solar year is too short, by about 11 days, and in response the holidays will drift earlier and earlier each year. To prevent this, every few years, an extra lunar month (called an intercalary month) is added, and the holidays move back to their original starting point relative to the seasons. You might have noticed that the Jewish holidays can drift somewhat relative to our solar calendar, but you never celebrate Hanukkah in July, for example. This is because the traditional Jewish calendar is also a luni-solar one. In contrast, the Islamic calendar is strictly lunar, so Islamic holidays (such as Ramadan) continually shift earlier and earlier relative to the solar year, occurring in different seasons as the decades pass.

But if both the Chinese and Tibetan calendars are luni-solar, why don’t their New Years occur on the same day relative to each other? This is because they have different calendars with very different rules. For example, the Chinese calendar adds an intercalary month about every 3 years. The lunar month begins at the astronomical New Moon, and there are specific rules for which months have 29 or 30 days based on the exact time of the New Moon relative to a specific longitude line (120 East). Chinese New Year falls on the day after the second New Moon after the Winter solstice (so it is often in February but sometimes in January, like this year). In contrast, in Tibetan Buddhism the phases of the moon are calculated by different rules, and the Full Moon must fall on the 15th day of any month, with the New Moon on the 30th day. So the Tibetan calendar uses skip days (tsi chad-pa) and doubled days (tsi lhag-pa) to accomplish this. Therefore a particular month might have two 19ths and no 23rd (roll that around in your head for a while!). Intercalary months are added about every thirty lunar months, and which months have 29 versus 30 day months are decided by the phase of moon at sunrise. New Year (Losar) is traditionally the first day of the first lunar month of the year. It does not always fall on Chinese New Year because the rules for calculating intercalary months, phases, and defining which months have 29 and 30 days differ. It will not surprise you to learn that the rules for calculating the Tibetan calendar are complex, and passed down from master to student.

So Tashi Losar to all my Tibetan friends, and if you want to learn more about Tibetan cultural astronomy, peruse the following page.

-Kris Larsen

 

Astronomy is “above the fold” today!

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Astronomy is front and center today, appearing “above the fold” on the front page of The New York Times. Unless you’ve been spacing out, already know about the discovery of seven earth-sized planets orbiting the relatively nearby (39 light years) star TRAPPIST-1. What you might not know is what it all means. TRAPPIST-1 is only the second known star to host a stellar system of seven planets, and also has (by far) the largest number of small, rocky, earthlike planets. While the inner three planets (dubbed b, c, and d) are probably too hot for liquid water to be prevalent, and the outermost (called h) is too cold, the other three (e, f, g) are, to steal from Goldilocks, “Just Right.” But before you start packing for a visit, you should know that there is a big difference between this star system and our own, namely the star itself! TRAPPIST-1 is barely a star, what we call an “ultra cool red dwarf.” It is barely massive enough to “shine,” to create energy via nuclear fusion of hydrogen into helium (the actual definition of a true star). At only 8% the mass of our sun, this is surely no “superstar!” In order for these planets to be in the Goldilocks zone (also called the habitable zone), they are so close to their star that they are almost certainly tidally locked. This means that they always keep one side facing the star (in eternal daylight) while the other side is always facing away (in eternal night – sounds like a vampire paradise, doesn’t it?). This means that IF the planets have atmospheres, their climates are pretty darned complicated, to say the least. But regardless of whether or not TRAPPIST-1’s planets really could support life as we know it, they have taught us an extremely important lesson, one that Copernicus himself tried to instill in us – we are NOT the center of the universe, and we should never make the mistake of thinking that our “normal” is the same as every other star system’s “normal.” Variety really is the spice of life, at least as far as the universe is concerned.