Tag Archives: astronomer

Annie Jump Cannon: the legend behind stellar classification

It is striking that today, we can not only discover but even classify stars that are light-years from Earth — sometimes, even billions of light-years away. Stellar classification often uses the famous Hertzsprung–Russell diagram, which summarises the basics of stellar evolution. The luminosity and the temperature of stars can teach us a lot about their life journey, as they burn their fuel and change chemical composition.

We know that some stars are made up mostly of ionised helium or neutral helium, some are hotter than others, and we fit the Sun as a not so impressive star compared to the giants. Part of that development came from Annie Jump Cannon’s contribution during her long career as an astronomer. 

The Hertzsprung diagram where the evolution of sun-like stars is traced. Credits: ESO.

On the shoulders of giantesses

Cannon was born in 1863 in Dover, Delaware, US. When she was 17 years old, thanks to her father’s support, she managed to travel 369 miles all the way from her hometown to attend classes at Wellesley College. It’s no big deal for teens today, but back then, this was an imaginable adventure for a young lady. The institution offered education exclusively for women, an ideal environment to spark in Cannon an ambition to become a scientist. In 1884, she graduated and later in 1896 started her career at the Harvard Observatory.

In Wellesley, she had Sarah Whiting as her astronomy professor, who sparked Cannon’s interest in spectroscopy:

“… of all branches of physics and astronomy, she was most keen on the spectroscopic development. Even at her Observatory receptions, she always had the spectra of various elements on exhibition. So great was her interest in the subject that she infused into the mind of her pupil who is writing these lines, a desire to continue the investigation of spectra.”

Whiting’s obituary in 1927, Annie Cannon.

Cannon had an explorer spirit and travelled across Europe, publishing a photography book in 1893 called “In the footsteps of Columbus”. It is believed that during her years at Wellesley, after the trip, she got infected with scarlet fever. The disease infected her ears and she suffered severe hearing loss, but that didn’t put an end to her social or scientific activities. Annie Jump Cannon was known for not missing meetings and participating in all American Astronomical Society meetings during her career.


At Radcliffe College, she began working more with spectroscopy. Her first work with southern stars spectra was later published in 1901 in the Annals of the Harvard College Observatory. The director of the observatory, Edward C. Pickering chose Cannon as the responsible for observing stars which would later become the Henry Draper Catalogue, named after the first person to measure the spectra of a star. 

Annie Jump Cannon at her desk at the Harvard College Observatory. Image via Wiki Commons.

The job didn’t pay much. In fact, Harvard employed a number of women as “women computers” that processed astronomic data. The women computer at Harvard earned less than secretaries, and this enabled researchers to hire more women computers, as men would have need to be paid more.

Her salary was only 25 cents an hour, a small income for a difficult job to look at the tiny details from the spectrographs, often only possible with magnifying glasses. She was known for being focused (possibly also influenced by her deafness), but she was also known for doing the job fast. Simply put,

During her career, she managed to classify the spectra of 225,000 stars. At the time, Williamina Fleming, a Scottish astronomer, was the Harvard lady in charge of the women computers. She had previously observed 10,000 stars from Draper Catalogue and classified them from letters A to N. But Annie Jump Cannon saw the link between the stars’ temperature and rearranged Fleming’s classification to the OBAFGKM system. The OBAFGKM system divides the stars from the hottest to the coldest, and astronomers created a popular mnemonic for it: “Oh Be A Fine Guy/Girl Kiss Me”.


“A bibliography of Miss Cannon’s scientific work would be exceedingly long, but it would be far easier to compile one than to presume to say how great has been the influence of her researches in astronomy. For there is scarcely a living astronomer who can remember the time when Miss Cannon was not an authoritative figure. It is nearly impossible for us to imagine the astronomical world without her. Of late years she has been not only a vital, living person; she has been an institution. Already in our school days she was a legend. The scientific world has lost something besides a great scientist.”

Cecilia Payne-Gaposchkin in Annie Jump Cannon’s obituary.
Annie Jump Cannon at Harvard University. Smithsonian Institution @ Flickr Commons.

Annie Jump Cannon was awarded many prizes, she became honorary doctorate of Oxford University, the first woman to receive the Henry Draper Medal in 1931, and the first woman to become an officer of the American Astronomical Society. 

Her work in stellar classification was followed by Cecilia Payne-Gaposchkin, another dame of stellar spectroscopy. Payne improved the system with quantum mechanics and described what stars are made of

Very few scientists have such a competent and exemplary career as Cannon. Payne continued the work left from Cannon, her advisor, Henry Norris Russell, then improved it with minimum citation. From that, we got today’s basic understanding of stellar classification. Her beautiful legacy has been rescued recently by other female astronomers who know the importance of her life’s work.

Amateur astronomer finds and christens Clyde’s Spot — a new storm on Jupiter

Although NASA has sent a craft to Jupiter’s orbit — the Juno probe — a newly-named region of the planet was recently spotted by an amateur astronomer.

Clyde’s Spot, seen here in the center as a white maelstrom, just below and to the right of the Great Red Spot. Image processed by Kevin Gill using JunoCam data.
Image credits NASA/JPL-Caltech/SwRI/MSSS / Kevin M. Gill.

The structure, a swirl not far from the planet’s infamous Great Red Spot, has been christened the somewhat anticlimactic ‘Clyde’s Spot‘. At the time it was observed, Juno was flying between 28,000 miles and 59,000 miles (45,000 to 95,000 kilometers) above Jupiter’s southern cloud tops.

Long-distance spotting

“The feature is a plume of cloud material erupting above the upper cloud layers of the Jovian atmosphere,” according to a NASA description of the new imagery. “These powerful convective ‘outbreaks’ occasionally erupt in this latitude band, known as the South Temperate Belt.”

After it was spotted by Clyde Foster from Centurion, South Africa on May 31, Juno moved in to take some better-quality pictures of the structure on June 2 — which is, as far as we know, a storm.

It rages in swirls not far off from Jupiter’s centuries-old Great Red Spot. Unlike the iconic storm, however, Clyde’s Spot is young, having just popped up. It’s not the first time such a storm appeared out of the brown and orange clouds: Juno captured another similar system at this latitude back in February of 2018.

An image of Jupiter taken by Clyde Foster. The new storm sits just below and to the right of the Great Red Spot.
Image credits Clyde Foster.

Juno orbits Jupiter on an elliptical orbit, so it does most of its data-gathering every 53.3 (Earth) days as it comes closest to the gas giant. Its latest fly-by luckily placed it at the ideal angle to capture Clyde’s Spot on its JunoCam. NASA makes JunoCam images available to the public, and citizen scientist Kevin Gill processed five of its images into a composite view of Clyde’s Spot. Gill is responsible for many of the striking NASA images you’ve seen online.

Both his work and that of Foster shows that there’s enough space in space exploration for everybody down here on terra firma — and an amazing wealth of beauty and science to share with us.

An astronomer thought he discovered a new, bright star — turns out, it was just Mars

Peter Dunsby thought he made a groundbreaking discovery. He noticed a bright object in the night sky, only visible for a few moments. Excited, he wanted to share his discovery with the world, so he Dunsby posted a note on the Astronomer’s Telegram. Unfortunately, as it turns out… Dunsby had re-discovered Mars.

Dunsby quickly issued a correction. Image credits: Astronomer’s Telegram.

Dunsby is a well-known cosmologist who has published extensively in the fields of cosmology and gravitation and is a key member of the South African National Astrophysics and Space Science Programme. But no one is spared of blunders, not even proficient scientists. Despite detailed maps of the night sky, planets move around quite a lot, and it’s easy to overlook even something as elementary as Mars.

The sad thing is, you can even feel the excitement in his words — he just wanted to share his finding with other astronomers, and encourage them to also look for it:

“The object was visible throughout the full duration of the observations and not seen when this field was observed previously (08 March 2018),” Dunsby wrote.

“The optical transient is the brightest star in the field. Further observations are strongly encouraged to establish the nature of this very bright optical transient.”

It didn’t take long for Dunsby to realize and admit his error — no later than 40 minutes after the original submission, he submitted the correction you see above. Astronomer’s Telegram took the chance to poke a little fun at Dunsby:

Dunsby took it well, replying:

Ok ok …. very funny. ?

Lesson learned. Check check and triple check and then check some more!!