Astronomer

The first Cassini to explore Saturn was a person

Saturn
TWO CASSINIS The Cassini spacecraft has become famous for its stunning views of Saturn, including this image of the unlit side of the rings taken in 2012. But what do we know about the man Cassini was named for?

As the Cassini spacecraft plunges toward its death on Saturn, the world’s knowledge of the famous ringed planet continues to accumulate. Thanks to years of observations by the versatile probe, astronomers now know Saturn as intimately as macaroni knows cheese. But still hardly anyone outside the world of astronomy knows anything about Cassini — and I don’t mean the spacecraft, but the guy it was named for.

Gian Domenico Cassini was an Italian astronomer, born in Perinaldo in 1625, around the time that Galileo was battling the church over Copernicus’ revelation that the Earth orbits the sun. Cassini was attracted to poetry but was also good at math. He got his start in science via astrology, which back then was not considered quite as completely idiotic as it is today. In fact, astronomy itself was often supported by wealthy people in order to get better astrological forecasts. One such wealthy Italian, an amateur astronomer, was impressed with a pamphlet on astrology that Cassini had written; it earned him an invitation to work at the amateur’s observatory, near Bologna.

From the leading scientists at Bologna, Cassini learned the importance of using high-quality instruments to make the most precise measurements possible. His talents were soon recognized; by 1650 Cassini’s accomplishments and reputation earned him the chair in astronomy at the university in Bologna. He continued his research during the 1650s, taking a particular interest in comets.

Gian Domenico Cassini was an Italian astronomer who studied comets, the sun and solar eclipses. After mastering the moons of Jupiter, he turned to Saturn.

Cassini was an old-school conservative kind of scientist, not even inclined to take Galileo’s side on the Earth-orbiting-the-sun issue. Cassini preferred Tycho Brahe’s position that the other planets orbited the sun, but the sun then orbited the Earth. (Later Cassini accepted the Copernican sun-centered solar system, but only half-heartedly.) Cassini also was no fan of Newton’s law of gravity.

Cassini’s work as an eminent Italian scientist was not limited to astronomy. Called on to referee a…

Stitching a Supernova: A Needlepoint Celebration of Science by Cecilia Payne, the First Person to Earn a Ph.D. in Astronomy

Stitching a Supernova: A Needlepoint Celebration of Science by Cecilia Payne, the First Person to Earn a Ph.D. in Astronomy

“The eye that directs a needle in the delicate meshes of embroidery will equally well bisect a star with the spider web of the micrometer,” astronomer Maria Mitchell, who paved the way for women in science, wrote in a beautiful 1878 diary meditation on the needle as an instrument of the mind. “I am an instrument in the shape of a woman,” the poet Adrienne Rich channeled Caroline Herschel a century later in her sublime ode to the world’s first professional woman astronomer, who spent her mornings in needlework.

But nowhere is this strangely fertile intersection of needlepoint and astronomy more striking than in a forgotten labor of love by the English-American astronomer and astrophysicist Cecilia Payne-Gaposchkin (May 10, 1900–December 7, 1979) — the first person to earn a Ph.D. in astronomy and the first woman to chair a department at Harvard.

Cecilia Payne, Harvard College Observatory

In her autobiography, Cecilia Payne-Gaposchkin: An Autobiography and Other Recollections (public library), Payne recounts that she first fell in love with astronomy as a small child, when she saw a meteorite blaze across the sky. Her mother, wheeling young Cecilia in the pram, explained what the celestial sighting was and made up a rhyme to help the little girl remember it:

As we were walking home that night
We saw a shining meteorite.

The seed planted that night blossomed when Payne won a scholarship to Cambridge at the age of nineteen, plunging herself into the sciences. After attending a lecture by the great astronomer and mathematician Sir Arthur Eddington on his solar eclipse expedition confirming Einstein’s theory of relativity, she experienced “a complete transformation of [her] world picture,” as she recounted in her autobiography, and resolved to become an astronomer.

But although Payne completed her studies at Cambridge, she was not awarded a degree — the university wouldn’t accredit women until 1948, nearly half a century after Austrian universities began admitting women. Disheartened by her prospects in England, Payne applied for a fellowship at the Harvard College Observatory — home to the Harvard Computers, the trailblazing women who made major astronomical discoveries decades before they could vote — and went on to earn a Ph.D. in astronomy from Radcliffe College, now part of Harvard.

In her 1925 doctoral thesis, Payne theorized that stars were made primarily of hydrogen, which rendered it by far the most abundant element in the universe — a landmark discovery illuminating the chemical composition of the cosmos. But when her dissertation was reviewed, a male astronomer persuaded her not to publish her conclusion because it challenged the era’s accepted theories. When that same astronomer changed his mind and came to the same conclusion himself four years later, he published it in a paper barely giving Payne credit for the discovery — a misattribution that persists to this day and is, of course, far from singular in the history of science: The same fate befell Beatrix Potter’s revolutionary theory of lichen reproduction, mathematician Sophie Germain’s work on elasticity,…

The Measure of All Things: How Two French Astronomers Nearly Lost Their Lives Revolutionizing the World with the Invention of the Meter

“The fundamental fallacy of utopianism is to assume that everyone wants to live in the same utopia.”

The Measure of All Things: How Two French Astronomers Nearly Lost Their Lives Revolutionizing the World with the Invention of the Meter

In her memoir, the trailblazing astronomer Caroline Herschel recounted frequently having to “measure the ground with poles” when she first began making astronomical observations in the 1780s. It seems odd that something as grand and lofty as studying the heavens would necessitate something this humble and earthbound, but this seemingly mundane task is important for two reasons — it reminds us that astronomers were the original measurers of everything we know, but it also raises the question of what the ground was measured in. For it wasn’t until a generation later that the measures of the world were standardized, thanks to the French astronomers Pierre Méchain and Jean Baptiste Joseph Delambre, who set out to unite humanity by creating a single measure: the meter, arguably the most impactful mathematical concept since the invention of zero, central to everything from the speed of light and our basic understanding of the universe to the daily practicalities of shoe sizes, doorframe dimensions, and driving speed limits. Over and over during their seven-year quest for peace through mathematical perfection, they stumbled and fell and got back up, nearly losing their heads to the guillotine on multiple occasions as they toiled to create an equalizing measurement that would “encompass nothing that was arbitrary, nor to the particular advantage of any people on the planet.”

Jean Baptiste Joseph Delambre and Pierre Méchain

Historian Ken Alder tells the story of Delambre and Méchain’s ambitious, improbable, and heroic feat in The Measure of All Things: The Seven-Year Odyssey and Hidden Error That Transformed the World (public library). He casts the stakes:

In June 1792 — in the dying days of the French monarchy, as the world began to revolve around a new promise of Revolutionary equality — two astronomers set out in opposite directions on an extraordinary quest. The erudite and cosmopolitan Jean-Baptiste-Joseph Delambre made his way north from Paris, while the cautious and scrupulous Pierre-François-André Méchain made his way south. Each man left the capital in a customized carriage stocked with the most advanced scientific instruments of the day and accompanied by a skilled assistant. Their mission was to measure the world, or at least that piece of the meridian arc which ran from Dunkerque through Paris to Barcelona. Their hope was that all the world’s peoples would henceforth use the globe as their common standard of measure. Their task was to establish this new measure — “the meter” — as one ten-millionth…

Astronomers detect oldest known stardust in distant galaxy

illustration of galaxy dust
DISTANT DUST Observations from an array of telescopes in Chile show that a distant, young galaxy (illustrated above) is filled with dust probably produced by the first supernova explosions in the universe.

Astronomers may have spotted some of the earliest stardust ever created in the cosmos.

Astrophysicist Nicolas Laporte of University College London and colleagues detected the dust in a galaxy seen as it was when the universe was only 600 million years old. “We are probably seeing the first stardust of the universe,” Laporte says. The observations, published online March 8 in the Astrophysical Journal Letters, could help astronomers learn more about an early period known as cosmic reionization, when ultraviolet radiation stripped electrons from hydrogen atoms.

“Dust is ubiquitous in nearby and more distant galaxies, but has, until recently, been very difficult to detect in the very early universe,” says University of Edinburgh astrophysicist Michal Michalowski, who was not involved in the study. “This paper presents the most distant galaxy for which dust has been detected.”

The galaxy, called A2744_YD4, lies behind a galaxy cluster called Abell 2744. That cluster acts as a gravitational lens, magnifying and brightening the distant galaxy’s light by about a factor of two. Laporte and colleagues observed the galaxy with ALMA, the Atacama Large Millimeter/submillimeter Array in Chile, which revealed the dust.

ALMA observations reveal that the galaxy A2744_YD4 (inset) is rich…