The Glass Universe

by Dava Sobel

  1956 Cecilia Payne-Gaposchkin becomes the first woman at Harvard promoted to full professor; she is also named chair of the astronomy department.

  1973 Formation of the Harvard-Smithsonian Center for Astrophysics unites the two observatories under a single director.

  1979 Cecilia Payne-Gaposchkin dies.

  2005 Inauguration of plate digitization process, Digital Access to a Sky Century at Harvard (DASC@H).

  GLOSSARY

  American Astronomical Society The first national professional society of astronomers in the United States, founded in 1898 and originally called the Astronomical and Astrophysical Society of America.

  Astronomical unit The distance from Earth to the Sun.

  Astronomische Gesellschaft The second oldest astronomical society (after London’s Royal Astronomical Society), established in Heidelberg in 1863.

  Binary star A pair of stars moving around a common center of gravity.

  Brightness—see magnitude.

  Cepheid A pulsating variable star that changes brightness in a characteristic, predictable cycle, making it useful in estimating cosmic distances.

  Chromatic aberration Blur or haze, caused by the several colors of light coming to focus at different distances from a lens.

  Circumpolar star A star that neither rises nor sets, but circles the celestial pole.

  Clock drive A mechanical or electric device that moves the telescope counter to Earth’s turning, allowing it to stay focused on a given object.

  Cluster A group of associated stars.

  Cosmogony A theory about the origin and evolution of the universe.

  Declination The latitude measure of the heavens; that is, the angular distance of an object above or below the celestial equator (the projection of Earth’s equator onto the sky).

  Doublet A pair of lenses combined for a desired effect.

  Eclipsing binary, or eclipsing variable A pair of associated stars orbiting a common center of gravity, oriented so they pass in front of each other in the observer’s line of sight.

  Electromagnetic spectrum The full range of stellar radiation, from the longest wavelength (radio waves) to the shortest (gamma rays).

  Ephemeris A table of predicted positions for a celestial body such as a planet, a moon, or a comet.

  Epoch A reference date chosen for astronomical observations.

  Flash spectrum The sudden change of the solar spectrum lines from dark to bright in the moments just before (and immediately following) the total phase of a solar eclipse.

  Fraunhofer line A dark absorption line in the continuous (rainbow-colored) spectrum.

  Galaxy A system consisting of billions of stars plus abundant dust and gas.

  Globular cluster A group of many thousand associated stars with a dense central concentration.

  Ion An atom that has lost one or more electrons and has a positive charge.

  Island universe A term originally coined by Immanuel Kant (1724–1804) to denote a star system similar to, but separate from, our own galaxy.

  K line One of the dark absorption lines seen in the solar spectrum and many other stellar spectra; it indicates the presence of ionized calcium.

  Light curve The graphic representation of a variable star’s (or other celestial body’s) changing brightness over time.

  Luminosity The intrinsic brightness of a star, or the total amount of energy it emits per unit of time.

  Magellanic Clouds Two dense conglomerations of stars and nebulae seen from the Southern Hemisphere, now known to be satellite galaxies of the Milky Way.

  Magnitude The brightness of an object, as judged by various standards over the centuries. The higher the number, the dimmer the appearance. Astronomers distinguish between “apparent” magnitude, or the way the object appears to earthly observers depending on its distance, and “absolute” magnitude, its intrinsic brightness.

  Messier numbers (M-31 and others) Identification labels introduced by comet hunter Charles Messier (1730–1817), who needed a way to keep track of nebulous objects that were not comets.

  Metals The term astronomers apply to all elements heavier than hydrogen and helium.

  Meteor A particle, often a bit of comet dust no bigger than a grain of sand, that enters Earth’s atmosphere and burns up by friction, looking like a “shooting star.”

  Milky Way The bright band of starlight stretching across the sky that has meant many things to stargazers over the ages, from the spilled milk of the goddess Hera to the name of the home galaxy where our solar system resides.

  Nebula At the start of this story, any blurred object in space; today, an enormous interstellar cloud of ionized gases.

  North Polar Sequence The forty-six stars (later increased to ninety-six) chosen as standards of comparison for precise determinations of photographic magnitudes.

  Objective lens The light-gathering lens of a telescope, at the opposite end from the eyepiece.

  Open cluster A group of a few hundred associated stars.

  Orion Nebula The bright object in the sword of Orion, the Hunter, designated M-42.

  Parallax The shift, or difference in apparent position, of an object against its background when viewed from two separate vantage points. Astronomers use parallax measures to estimate distances up to a few hundred light-years from the Sun.

  Period The time span in which a variable star cycles through its brightness changes.

  Personal equation An astronomer’s reaction time.

  Proper motion Movement of a celestial body across the line of sight.

  Radial velocity An object’s speed of approach or recession along the line of sight.

  Radio astronomy A complement to optical astronomy; the study of electromagnetic radiation at wavelengths much longer than those of visible light.

  Redshift The shift of known spectral lines toward the red end of the spectrum, caused by the object’s motion away from the observer.

  Right ascension The celestial equivalent of longitude for stating star positions.

  Royal Astronomical Society The world’s first organization of astronomers, founded in 1820 as the Astronomical Society of London.

  Seeing The quality of the observing conditions, ideally cloudless skies and minimal movement of air. Astronomers rate seeing on a scale ranging from one (very poor) to ten (perfect).

  Spectrum The rainbow of colors (and Fraunhofer lines) contained in visible light.

  Spiral nebula An early term for a spiral galaxy.

  Visible light A small portion of the electromagnetic spectrum, bordered by infrared and ultraviolet rays.

  A CATALOGUE OF HARVARD ASTRONOMERS, ASSISTANTS, AND ASSOCIATES

  George Russell Agassiz (July 21, 1862–February 5, 1951), like his famous father and grandfather, held a faculty position with Harvard’s Museum of Comparative Zoology. He became an influential and generous member of the observatory’s Visiting Committee. After his death, his wife, Mabel Simpkins Agassiz, continued that generosity.

  Adelaide Ames (June 3, 1900–June 26, 1932), a Vassar alumna, was the observatory’s first graduate student in astronomy, earning her master’s degree from Radcliffe in 1924. She worked with Director Harlow Shapley to catalogue galaxies.

  Solon Irving Bailey (December 29, 1854–June 5, 1931) extended the reach of the observatory by reconnoitering good locations for high-altitude satellite stations, first in South America and later in South Africa. He identified and studied the variable stars in globular clusters, which he called “cluster variables.”

  Bartholomeus Jan Bok (April 28, 1906–August 5, 1983) chose the structure and evolution of the Milky Way as his subjects while still a student in Leiden, and continued to work on them at Harvard. The dark, nebulous knots he suspected of being stellar birthplaces are now called Bok globules.

  George Phillips Bond (May 20, 1825–F
ebruary 17, 1865), the son of the observatory’s founding director, William Cranch Bond, assisted in all his father’s discoveries before taking over as director himself in 1859. He extended the early experiments in stellar photography and was the first American astronomer to win the gold medal of the Royal Astronomical Society.

  Selina Cranch Bond (December 4, 1831–November 25, 1920), George’s sister and the sixth child of William Cranch Bond, began working at the observatory as a teenager, was later hired as a computer, and continued lifelong in that profession.

  William Cranch Bond (September 9, 1789–January 29, 1859), a successful chronometer maker before he became founding director of the observatory, established its time service, discovered (with son George) Saturn’s inner ring and eighth satellite (Hyperion), and aided in taking the first-ever photograph of a star (Vega) in 1850.

  Catherine Wolfe Bruce (January 22, 1816–March 13, 1900), a New York heiress who became an astronomy enthusiast in her later years, funded numerous research projects, journals, and instruments with the guidance of observatory director Edward Pickering, and also endowed a prestigious lifetime achievement award, the Bruce Medal.

  Leon Campbell (January 20, 1881–May 10, 1951) traced light curves of variable stars and taught others the techniques. For many years he collected, collated, and published reports for the American Association of Variable Star Observers.

  Annie Jump Cannon (December 11, 1863–April 13, 1941) classified the spectra of several hundred thousand stars for the nine-volume Henry Draper Catalogue and its Extension. Her system, with its “OBAFGKM” order of spectral classes, was internationally adopted in 1922 and remains in use today.

  Seth Carlo Chandler (September 16, 1846–December 31, 1913), though only briefly on staff, maintained a close association with Harvard for thirty years. He worked as an actuary, pursuing variable stars in his spare time, and also wrote a code for sending astronomical announcements by telegraph.

  Anna Palmer Draper (September 19, 1839–December 8, 1914) partnered with her husband, Dr. Henry Draper, in his telescope making and astrophotography. After his early death she assured his legacy by funding the continuation of his work at Harvard, which resulted in the classification system that bears his name.

  Henry Draper, M.D. (March 7, 1837–November 20, 1882), followed his father, Dr. John William Draper, into medicine, astronomy, and photography. He was the first, in 1872, to capture the spectrum of a star on film, and followed that feat by imaging the faint stars in the Orion Nebula in 1882.

  Sir Arthur Stanley Eddington (December 28, 1882–November 22, 1944), one of the first to appreciate Einstein’s theories, traveled to Príncipe Island, off the west coast of Africa, for the 1919 total solar eclipse, and returned with proof of general relativity. The leader in efforts to describe the internal constitution of the stars, Eddington was knighted in 1930.

  Priscilla Fairfield (later Bok) (April 14, 1896–November 19, 1975) taught astronomy at Smith College while measuring the widths of spectral lines on plates at Harvard. With her husband, Bart Bok, she coauthored The Milky Way, a book intended for nonspecialists; the couple revised and updated the 1941 original through a fourth edition in 1974.

  Williamina Paton Stevens Fleming (May 15, 1857–May 21, 1911), the first woman to hold an official title at Harvard University, built a stellar classification scheme and also discovered ten novae and more than three hundred variable stars, all from her study of spectra on glass plates.

  Caroline Furness (June 24, 1869–February 9, 1936) was the sixth individual and first woman to earn a doctorate in astronomy at Columbia University, in 1900. She taught the subject for twenty years at Vassar, her alma mater, where her students included Adelaide Ames and Harvia Wilson.

  Boris Petrovič Gerasimovič (March 31, 1889–November 30, 1937), director of the Pulkovo Observatory in Russia, spent the years 1926 to 1929 at Harvard, and visited again in 1932. Accused at home of “servility” toward foreign science, he was executed in the Stalinist purges of that period.

  Willard Peabody Gerrish (August 31, 1866–November 11, 1951), the observatory’s resident mechanical genius, designed telescopes and clock drives that controlled the instruments’ motion during long-exposure photography. The “Gerrish code” he devised replaced Seth Carlo Chandler’s telegraphic announcement code in 1906.

  George Ellery Hale (June 29, 1868–February 21, 1938), who spent a year as a young apprentice to Edward Pickering, later pursued solar spectroscopy. He established the Astrophysical Journal, and helped found both the American Astronomical Society and the International Astronomical Union, as well as the Yerkes, Mount Wilson, and Palomar observatories.

  Margaret Harwood (March 19, 1885–February 6, 1979) became the first Astronomical Fellow of the Nantucket Maria Mitchell Association, and later the director of that association’s observatory, a post she retained for forty-one years while studying asteroids of variable brightness.

  Ejnar Hertzsprung (October 8, 1873–October 21, 1967), a native of Denmark long affiliated with the Leiden Observatory in the Netherlands, was first to seize on Henrietta Leavitt’s period-luminosity relation to measure the distance to the Small Magellanic Cloud. He uncovered the existence of both giant and dwarf red stars, demonstrated the variability of Polaris (the North Star), and helped chart the general course of stellar evolution.

  Lydia Swain Mitchell Hinchman (November 4, 1845–December 3, 1938) established the Nantucket Maria Mitchell Association in memory of her famous cousin, and furthered many of its activities, most notably the funding of fellowships for young women pursuing careers in astronomy.

  Frank Scott Hogg (June 26, 1904–January 1, 1951) became Harvard’s first Ph.D. in astronomy in 1928, following Cecilia Payne’s 1925 Ph.D. from Radcliffe. As director of the David Dunlap Observatory near Toronto, he edited Canadian astronomy journals and studied the radial velocities of stars.

  Edward Skinner King (May 31, 1861–September 10, 1931) supervised stellar photography at Harvard for four decades. He helped establish a uniform photometric scale, devised tests for the quality and consistency of photographic plates, and tried to discern the effects of interstellar dust on stellar magnitudes.

  Henrietta Swan Leavitt (July 4, 1868–December 12, 1921) discovered thousands of variable stars. She was the first to note a relation between certain variables’ peak brightness and the period over which their brightness varied—a relation that proved a valuable means for measuring distances across space.

  Percival Lowell (March 13, 1855–November 12, 1916), brother of Harvard president Abbott Lawrence Lowell and poet Amy Lowell, built an observatory in Flagstaff, Arizona, where he studied Mars and pursued a ninth planet beyond Neptune.

  Antonia Coetana de Paiva Pereira Maury (March 21, 1866–January 8, 1952), niece of Henry and Anna Draper, was the first female college graduate to work at the observatory. She discovered an early spectroscopic binary and devised a spectral classification scheme capable of distinguishing giant stars from dwarf stars.

  Donald H. Menzel (April 11, 1901–December 14, 1976) was drawn to astronomy after seeing a total solar eclipse in 1918, and traveled to observe more eclipses than anyone before him. He first visited Harvard as Princeton professor Henry Norris Russell’s graduate student in 1923, and succeeded Shapley as director in 1952.

  Maria Mitchell (August 1, 1818–June 28, 1889) discovered a comet in 1847, the first American woman to do so. After family friend William Cranch Bond of Harvard announced her find, she won a gold medal from the king of Denmark. In 1865 Matthew Vassar invited her to become the first professor of astronomy at his new college for women, where she taught Antonia Maury.

  John Stefanos Paraskevopoulos (June 20, 1889–March 15, 1951), known internationally as “Dr. Paras,” guided the transfer of the Boyden Station from Arequipa, Peru, to South Africa, where he and his wife, Dorothy Block, added one hundred thousand plates to Harvard’s collection.

&nb
sp; Cecilia Helena Payne (later Gaposchkin) (May 10, 1900–December 7, 1979), among the first women to achieve a Ph.D. in astronomy—and the first person to earn one at Harvard—ascertained the temperatures of the different classes of stars and estimated the great abundance of hydrogen in them while doing the research for her dissertation.

  Edward Bromfield Phillips (October 5, 1824–June 21, 1848), a Harvard classmate of George Bond, died a suicide, leaving the observatory $100,000. The Phillips Professorship and Phillips Library honor his memory.

  Edward Charles Pickering (July 19, 1846–February 3, 1919), fourth and longest-presiding director of the observatory from 1877 to 1919, burnished its reputation while innovating in photometry, photography, and spectroscopy. He initiated the Draper Memorial spectral classification and the program of nightly all-sky photography. Elected president of the American Astronomical Society in 1905, he retained the office through repeated reelection until his death.

  William Henry Pickering (February 15, 1858–January 16, 1938), younger brother of Edward, brought photography expertise from MIT to Harvard and served as first director of the Boyden Station at Arequipa. He focused his attention on observing the planets and their moons, discovering a satellite of Saturn, Phoebe, in 1899.

  William Augustus Rogers (November 13, 1832–March 1, 1898) ascertained the positions of stars through a decade of observing the times at which each one crossed Harvard’s local north-south meridian, and also performed two decades of calculations, in which he was assisted by his wife, née Rebecca Jane Titsworth.

  Henry Norris Russell (October 25, 1877–February 18, 1957) of Princeton University, regarded as the dean of American astronomers during his lifetime, supervised the graduate work of Harlow Shapley and Donald Menzel. Industrious and influential, he studied stellar composition and evolution, the relationship of magnitude to classification, and the distinctions between giant and dwarf stars.

  Helen B. Sawyer (later Hogg) (August 1, 1905–January 28, 1993) took up the study of globular clusters with Harlow Shapley. After completing her doctoral work at Harvard, she moved with her husband, Frank, to Canada, becoming the first woman to observe with large telescopes in British Columbia and Ontario. She popularized astronomy through her newspaper column and other writing.