Annie Jump Cannon was born in 1863 in Delaware. Her father was a bank director and former state senator. Her mother taught her the constellations at an early age and encouraged her interest in astronomy.

Cannon studied physics at Wellesley College under Sarah Frances Whiting, a protégé of Edward Charles Pickering, director of the Harvard College Observatory. Whiting showed Cannon how to use a four inch telescope to observe the Great Comet of 1882. During college, a bout of scarlet fever took most of Cannon's hearing. She graduated from Wellesley in 1884 as valedictorian of her class and went back home to Dover to continue healing and study photography. Her skills allowed her to travel to Europe and eventually publish photos of Spain. After returning home, she tutored students in math and U.S. history, played organ at her church, and continued her photography.

After 10 years of this and the loss of her beloved mother, Cannon was feeling unfulfilled and depressed. She reached out to Whiting, who was still at Wellesley, and procured an assistantship. Whiting prepared Cannon for advanced physics studies at Radcliffe College. There she was offered an unpaid internship at Harvard Observatory, still under Pickering's direction.

Teaching physics classes and completing astronomical observations gave Cannon a sense of purpose again. With her experience and academic background, Pickering made her the first female assistant to make astronomical observations at the observatory. Night after night she would record the slight fluctuations in brightness of stars by comparing them to nearby stars that were slightly brighter or fainter. She also compiled the observations of citizen scientists across the globe who made similar observations into a large series of tables that anyone could use called “A Provisional Catalogue of Variable Stars.”

Cannon is most known for classifying stellar spectra in a way that lead astronomers to understand why stars had different spectral patterns. Astronomers like Pickering used to observe one star’s spectrum at a time, passing the light through a prism in front of the telescope's eyepiece and drawing the rainbows they saw which were interrupted by dark, vertical lines from atoms within the star. With the invention of photographic plates — glass with a photosensitive liquid painted on — the spectrum could be recorded on a  1-inch square plate of glass but, now, in black and white. While this eliminated the task of drawing , Pickering found that installing the prism at the light gathering end of the telescope, instead of near the eye, sped up the process by creating an image that displayed the spectra for all the stars in the telescope's view on an 8”x10” photographic plate.

Many of the Harvard Computers were tasked with classifying the thousands of spectra obtained using this method, but Cannon was by far the fastest. She would carefully place each photographic plate on a stand with a mirror at the base to catch sunlight that would illuminate the plate, revealing the hundreds of tiny horizontal bands of light where a star should be. The chemical makeup of each star is contained in the horizontal band of light that appeared on the photographic plates. The vertical dark lines that interrupted the stellar rainbow correspond to a specific element on the periodic table. Using a microscope, she would evaluate the patterns of dark vertical lines and call out a classification to an assistant who would record them. According to sources, Cannon could classify spectra in as little as three seconds — as quickly as her assistants could write them down.

Cannon devised a system that combined elements of the classification systems created by two of her fellow computers, Williamina Fleming and Antonia Maury. Fleming had devised a system with 15 separate classifications for the stars based on the strength of their hydrogen lines. Maury had a complex system of 22 separate classifications each with their own subdivisions and placed significance on the helium lines and their widths.

In Cannon’s system, she kept Fleming's lettered designations but reorganized them into just seven classifications. She, like Maury, gave precedence to the helium lines, so stars that had helium with missing electrons were first. The next set of stars had helium with all their electrons in tact. After that, the next category held stars with only hydrogen lines. In under three seconds, Cannon could look at a spectrum, assess the type of lines and their strengths, and choose from the 70 different possibilities for classification.

Cannon’s system is still used today. Astronomers later realized that her order perfectly ranks stars from hottest to coldest. All O stars, Cannon's first designation, are blazing hot stars with temperatures between 25,000-50,000 Kelvin while M stars, the final designation, are the coolest with temperatures less than 3,500 Kelvin.

Astronomers from around the globe recognized and celebrated her work. She was the first woman to receive an honorary doctor of science degree from Oxford University, and became an honorary member of the Royal Astronomical Society (RAS). She was nominated in 1919 for elevated standing as an Associate which would have put her at the same standing as men in the RAS. The Society members declined to do so. Harlow Shapley, who succeeded Pickering as director of the Harvard Observatory, nominated Cannon for the Henry Draper Medal of the National Academy of Science and wrote her a personal congratulatory announcement when she was awarded. 

The Association to Aid Scientific Research by Women awarded Cannon a $1000 prize in 1932, then dissolved claiming that since “women are given opportunities in research equally as men the objectives of the association have been achieved.” Cannon thanked them for the prize money but questioned their dissolution. She decided to use the money to endow the Annie Jump Cannon Prize which is still given every three years to a woman of any nationality by the American Astronomical Society. The first Prize went to Cecilia Payne-Gaposchkin. Cannon had a jeweler, Marjorie Blackman, fashion a beautiful gold pin in the shape of a spiral galaxy for the prize. When she saw the result, she said, “Isn’t it the first universe ever made by a woman?” Even to this day, Cannon Prize winners receive an individualized piece of jewelry created by a different craftswoman.

In 1938, Cannon was finally recognized by Harvard as the William Cranch Bond Astronomer and Curator of Astronomical Photographs. Cannon reported to the Observatory six days a week until mid-March of 1941 when she became ill. She died in April of 1941, age 77.

Rubin was one of Massive’s first Science Heroes. According to Kepler’s laws, bodies that orbit close to massive objects move faster than those that are further away. So, Mercury orbits the Sun  at a higher speed than Jupiter. But when Rubin measured the speed of stars orbiting at the edges of galaxies, she saw that they were moving just as fast as stars near the center. But if we add up all the mass that we can see in a galaxy, it’s not enough to explain the high speeds. She surmised that there must be mass we cannot see - dark matter - driving this motion.

In the 40 years since Rubin’s discovery, astronomers and physicists have come up with many clever ways to try to understand dark matter, but we’re still no closer to knowing what it is. The LSST will use a more traditional approach. It’s 8.4-meter (27.6-foot) mirror can take images of the entire night sky. Over a 10-year period, the telescope will map galaxies across both time and space, measure their masses, and uncover how the extra mass from dark matter bends space. 

Rubin’s perseverance and dedication to scientific pursuit revealed one of the cosmos’ greatest mysteries. She deserves to have this telescope named for her, especially since she passed before she could be awarded a Nobel Prize.  

(Banner image by Daniela Sherer)

Minor planets are large asteroids orbiting the Sun somewhere between the orbits of Mars and Jupiter. They come in various sizes and we've identified thousands of the biggest ones using telescopes on the ground. There is actually one object in this region large enough to be considered dwarf planet: Ceres.  We recently sent the Dawn probe to take some images. Sadly, Mariakirch probably won't get its own probe. It's one of the millions of minor planets, orbiting in the void between Mars and Jupiter. 

Mariakirch was discovered at the Palomar Observatory on September 24, 1960 during a collaborative minor planet survey involving the Palomar Observatory and the Dutch Leiden Observatory. It is 2.8 AU from the Sun and takes 4.7 years to make a full orbit. For reference, Mars is 1.5 AU from the Sun and Jupiter is 5 AU. 

You can learn more about all the minor planets in our solar system by visiting the International Astronomical Union’s Minor Planet Center. It’s where I got the image for the orbit of Mariakirch. As incentive, check out this cool gif of all the known asteroids moving around the asteroid belt.

Last week, NASA and ESA released a wide-field view of  our universe. To create this image, they stitched together over 7500 separate exposures taken over the past three decades. Astronomers picked a seemingly empty patch of sky and took multiple lengthy exposures with Hubble's camera. Then they stacked, or added up, the images to enhance the brightness of faint galaxies.

Due to the vast distances we are dealing with and the finite speed of light, galaxies that are farther away are also from an earlier time. The particles of light we receive at our telescopes left these distant galaxies billions of years ago. The longer we keep the camera shutter open the more of these particles we can accumulate and the further back in time we can look. This image contains around 265,000 galaxies, the faintest of which are revealed by light they emitted over 13 billion years ago.

It's a really cool image to download and zoom into different areas. I recommend downloading the highest resolution PNG or TIFF image. Galaxies pop into view that weren't visible when you were zoomed out. There are galaxies of all shapes, sizes, and colors. It's a fun way to get lost in the cosmos.

See anything interesting in your zooms? Take a screen shot and send it to me on Twitter! We can talk about what you are seeing. 

When I noticed that she wasn’t given credit for the discovery of Comet 1702 H in the textbook I referenced, it reminded me of recent news stories about women in the sciences showing up in the acknowledgments for work that deserves authorship.  

Winkelmann-Kirch and her husband worked as a team. The only significant difference between them was that she did not attend a university — forbidden for women at the time. Both had discovered comets. Both could make accurate calendars and perform the necessary calculations. When the Academy of Sciences in Berlin denied her petition to take over her husband’s position after his death, all I could think about was those studies where researchers changed the names on resumes from male to female and found that hiring committees were less likely to hire the woman. Or reports that women in the biomedical sciences need to publish 2.5 times more than men to earn the same postdoctoral positions.

As a woman who became a mother during graduate school, the way Winkelmann-Kirch was treated throughout her career felt all too familiar. Today, research has shown that close to half of women leave full-time STEM work after having children — I’m one of them. I may not have been actively pushed out as Winkelmann-Kirch was, but the lack of support made it difficult to be productive with a family. 

The only difference 300 years has given us is that the sexism is sometimes more subtle. What is still painfully clear is that women and minorities can never be ‘good enough’ for a system that both actively and passively pushes them out. That needs to change. 

She woke her husband up to show him. The very next day, he wrote a report for King Leopold I describing the celestial newcomer. But Winkelmann Kirch’s name was left off the report. It wasn’t until just before Kirch's death in 1710 that he revealed his wife was the one who made the discovery, when he published the finding in the first journal for the Academy of Science in Berlin.

Though not initially acknowledged, Winkelmann Kirch was actually the first woman to discover a comet — dubbed the Comet of 1702. (Two other astronomers in Rome independently found the comet hours before she did. So she is technically a co-discoverer.) But it seems the message still hasn't sunk in. While doing research on this comet, I came across a book Cometography: Volume 1, Ancient-1799: A Catalog of Comets,published in 1999, which describes the parabolic orbit of Comet 1702 H. In this text, the discovery is attributed to the two astronomers in Rome and ….Gottfried Kirch.

The Stars Aligned

Winkelmann Kirch had a nontraditional childhood for a kid in Germany during the late 1600s. Her father, a Lutheran minister, wanted his daughter to have the same education as men, so he oversaw her studies.

Winkelmann Kirch soon showed a strong interest in astronomy, and became the unofficial apprentice of Christoph Arnold, a farmer in Sommerfield, who was also a self-taught astronomer. After working with him for a few years, Arnold promoted her to his assistant.

Arnold was also friends with Gottfried Kirch, one of the most famous German astronomers of the time. Arnold introduced his assistant and Kirch, and they married in 1692. They had four children, who were all taught astronomy. The couple worked as a team, making observations and doing calculations to produce incredibly accurate calendars and positions of celestial objects — including planets, comets, and stars. Their calendars also contained the phases of the moon, sunrise and sunset times, and the timing of eclipses. When Kirch joined the newly created Academy of Science in Berlin in 1700, Winkelmann Kirch joined him there as his assistant. Two years later, she would discover her comet.

This wasn't Winkelmann Kirch's only contribution to astronomy. She went on to publish many well-received papers on a number of topics before Kirch’s death. In 1709, for example, she wrote a pamphlet on the approaching conjunction of Saturn and Venus with the Sun that garnered her respect within the German astronomical community. There was only one other woman —Maria Cunitz, a Silesian astronomer — in the entire Holy Roman Empire that was self published at the time.

Same credentials, different names

After her husband’s death in 1710, Winkelmann Kirch wanted to take over his position as the astronomer and calendar maker for the Academy of Science — as was common during that era in other trades, where widows often took over their husbands’ businesses. But the Academy of Science didn’t consider Winkelmann Kirch for the position until she petitioned them. She was allowed to continue her work while the Academy considered her petition — even receiving an Academy medal for her accomplishments. The president of the Academy, Gottfried Wilhelm Leibniz, supported and encouraged Winkelmann Kirch, bringing her to the Prussian royal court to explain sunspots.

But the Academy didn’t want to set a precedent, and even the president’s word wasn’t enough. The secretary Johann Theodor Jablonski cautioned Leibniz that having Winkelmann Kirch "kept on in an official capacity to work on the calendar or to continue with observations simply will not do. Already during her husband's lifetime, the academy was burdened with ridicule because its calendar was prepared by a woman. If she were now to be kept on in such a capacity, mouths would gape even wider."

Kirch knew the reason she was kept out of the Academy was her gender. Some members went as far as advising her to return to her “distaff” and “spindle.”

Instead, the Academy hired an inexperienced man, Johann Heinrich Hoffmann, to take over the calendar making in 1711, while Winkelmann Kirch's petition was still technically under consideration. She and Hoffman worked independently during this time. Winkelmann Kirch published another well-received pamphlet predicting a new comet, as well as a defense of women’s intellectual abilities, where she argued that the “female sex as well as the male possesses talents of the mind and spirit." It was clear to Winkelmann Kirch that with experience and study a woman could be “as skilled as a man at observing and understanding the skies.”

After she was officially dismissed in 1712, Hoffmann fell behind in his observations, and the Academy asked Winkelmann Kirch to come back as his assistant. In a letter, she described her reluctance, saying “Now I go through a severe desert, and because … water is scarce … the taste is bitter.”

Persistence doesn’t always pay off

Fortunately, at the same time, Winkelmann Kirch was offered a position at the personal observatory of a friend, Baron von Krosigk. There, she reached the rank of master astronomer, and published another pamphlet on the conjunction of Saturn and Jupiter.  She continued to make calendars there, with the help of her children, until von Krosigk’s death in 1714. She was offered a position as astronomer for the Russian czar in 1716, but refused so she could stay in Berlin with her son, Christfried, who had just been hired as a director of the new observatory of the Academy of Science.

Winkelmann Kirch and her daughter, Christine, became Christfried’s assistants. Shortly thereafter, Academy members complained that Winkelmann Kirch made herself too prominent during public visits, and demanded that she stay in the background and not speak when visitors came around. She refused, and the Academy forced her to leave her position, saying they hoped she would stay close by so that “Herr Kirch could continue to eat at her table.” Winkelmann Kirch tried to continue her work in private, but no longer had access to the proper instruments. Her daughter stayed on as Christfried’s assistant at the observatory. Winkelmann Kirch died of fever in 1720.

When astronomers look out into the universe, we see that galaxies commonly live in these types of groups — gravitationally bound to each other in the slowest do-si-do ever performed. But to galaxies, the millions of light years between them are trivial compared to their sizes. If you shrank our galaxy down to the size of a person six feet tall, Andromeda would only be about 150 feet away. So, although stars and planets rarely run into each other, galaxies do all the time. It's hard for astronomers to see this in real-time because the immense distances mean we only get a snapshot of the added light from all the stars. The faint debris from these galactic hoe-downs is rarely detectable with even our most powerful telescopes.

Andromeda is so close, though, that astronomers can measure individual stars' age and composition by looking at spectra. Just as light from the Sun can be spread out into separate colors by raindrops, the light from other stars can be spread out into their own rainbows. Each element in a star absorbs specific colors of light, leaving a fingerprint of missing colors in the spectrum.

Stars' spectra also provide an upper limit to their ages. Stars that are five or more times as massive as the Sun have to be much hotter in order to exist. They live much shorter lives than the Sun as they burn through their material. Higher temperatures also make it more difficult for atoms to interact with light, so fewer colors are missing in the spectrum. If you look in a given area of a galaxy and see these hot stars, then you can conclude the stars there were created tens or hundreds of millions of years ago. But if you look in a region and see only cooler stars, that means they've been around for a few billion years; all the younger, hotter stars have had time to live out their lives and disappear.

Armed with this information, astronomers turned to the stars in Andromeda. Most of Andromeda lies in a flat disk surrounding a central bulge of stars, like a sunny-side-up egg. There are, however, a smattering of stars surrounding the main structure. In this outer region, most stars have very different spectra than the stars in the main structure...almost as if they came from somewhere else.

A destructive past

Researchers at the University of Michigan set out to determine what conditions could create the structures surrounding Andromeda, and published their findings in Nature Astronomy earlier this year. Because we cannot rewind the clock on the universe, the best way to test what happened in the past is to use computer simulations. These models treat the stars and gas within galaxies as fluids and provide initial conditions that reflect what we see happen to fluids under known physical constraints, such as gravity.

Richard D'Souza and Eric Bell identified galaxies that had the same number of stars remaining in their outer regions as presently seen in Andromeda. Once they identified these analogs, they rewound their simulation to see what type of galaxy could create something like Andromeda. They found that the most common way for the simulated galaxies to end up with enough stars in their outer regions is through an interaction with another large galaxy. In the simulations, the two galaxies don't tear each other apart and settle down into a single galaxy. Instead, there's a clear winner: the Andromeda-like galaxy slowly unravels the other galaxy like a ball of yarn, leaving a distinct trail of stars. 

So, what galaxy did Andromeda attack? The researchers found the remnants of a large galaxy nearby: M32, a dense sphere of stars nestled close to Andromeda. Its stars have the same chemical makeup and age as the stars in Andromeda’s outer regions. Combining these observations with their simulations, researchers came up with a hypothetical scenario that can be tested with future data.

Around five billion years ago, as our solar system started to form, Andromeda began unraveling M32. The gas in M32 got disrupted and compressed, causing a burst of star birth as it unwound. This explains the unique atoms of the stars in the outer regions of Andromeda and their ages. After 3 billion years passed, the star birth stopped, which is why we don’t see any young, hot stars in M32 or surrounding Andromeda. 

Is the Milky Way next?

Our own galaxy is currently on a collision course with Andromeda. In 4 billion years, our galaxy could suffer the same fate as M32, but this depends on a lot of factors. The Milky Way is 2.5 times more massive than M32 was when it tangled with Andromeda and it's expected to make new stars over time, getting even larger. The rotation and trajectory of our galaxy will ultimately determine whether Andromeda and the Milky Way collide head-on or if our galaxy is slowly unwound.

We have time to make these predictions. In the meantime, astronomers can continue to use Andromeda and the Milky Way to better understand how cannibalizing other galaxies influences both the overall structure of a galaxy and the properties of their stars.