He was born during the Mexican revolution.
Haro was born in Mexico on March 21, 1913 during the long and bloody revolution that radically transformed Mexican politics and society.
Growing up in that era and watching his home change inspired Haro to study philosophy.
But even though he graduated from the University of Mexico with a degree in philosophy, Haro actually switched his interests to astronomy after meeting Mexican astronomer Luis Enrique Eroz as a student, according to Al Jazeera.
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After graduating, Haro worked with Eroz and launched a notable career in the field, eventually training at observatories in the United States, including the Harvard College Observatory and the Case Institute of Technology.
He returned to the Tonantzintla Observatory in Puebla, Mexico, in 1945.
He met his second wife while working at the Tonantzintla Observatory.
According to Vox, Haro met Mexican journalist Elena Poniatowska, during his time at the Puebla facility.
In 2013, Poniatowska told Milenio.com that his intellect was the big draw.
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“For me, it was very important that a man of this caliber and this intelligence would notice me,” she said. “He flattered me very much.”
The pair married in 1968 and divorced in 1981.
Poniatowska also wrote an award-winning biography of her late ex-husband.
He discovered Herbig-Haro objects and flare stars in Orion’s Belt.
"If you're stargazing tonight, look for three stars, closely aligned. These are known as the 'Three Sisters', and they are part of the constellation Orion, representing Orion's belt. They belong to an astral region that pivoted Mexican astronomer Guillermo Haro to fame," Google wrote in its blog Wednesday.
As Haro studied Orion, he discovered planetary nebulae now named Herbig-Haro objects, which were also observed simultaneously and independently by George Herbig.
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These objects are "small-scale shock regions intimately associated with star forming regions," according to the National Optical Astronomy Observatory.
Haro also co-discovered red and blue flare stars in the region of the Orion constellation, bright flares determined to be caused by changes in the stars’ magnetic fields.
He was the first Mexican elected to the Royal Astronomical Society.
Haro’s contributions to astronomy led to him becoming the first Mexican to join the reputed organization in 1959.
The astronomer was also awarded the Lomonosov Medal from the USSR Academy of Sciences in 1986.
Haro founded the National Institute of Astrophysics, Optics, and Electronics.
In 1960, Haro, one of the founders of the Mexican Academy of Sciences, served as president of the institution. Later, in 1971, he also founded the National Institute of Astrophysics, Optics and Electronics, to help support science students in their careers.
"He wanted the country to be transformed," Manuel Peimbert, one of Haro's students, told Al Jazeera.
He died in 1988.
Haro died at age 75 on April 26, 1988.