Place Jules Janssen

Did Jules Janssen ever imagine a place in Paris bearing his name? Here we are, at Place Jules Janssen, a fitting tribute to a man who chased eclipses across the globe. Place Jules Janssen isn’t just a square in Meudon; it’s a window into the life of a remarkable astronomer. Janssen, born in Paris in 1824, wasn’t destined for a life among the stars. A childhood accident left him with a permanent limp, and he initially worked as a bank clerk. Yet, his passion for science propelled him to earn a degree from the University of Paris and later, a professorship in physics. His real love, however, lay in chasing eclipses. He traveled to Trani, Guntur, Algiers, Siam, the Caroline Islands, and even Alcossebre in Spain to witness these celestial events. In 1868, during an eclipse in Guntur, India, Janssen made a breakthrough. He realized the chromosphere’s spectrum, with its bright lines, could be observed even without an eclipse. This led to more frequent observations of solar prominences. This same year, he observed a mysterious yellow spectral line near sodium’s lines. This, unbeknownst to him at the time, was helium, an element not found on Earth until 1895. During the Franco-Prussian War, Janssen’s dedication to astronomy took a dramatic turn. He escaped besieged Paris in a hot air balloon, determined to observe an eclipse in Algeria. Clouds thwarted his efforts, but the daring escape became legendary. Janssen’s ingenuity extended beyond observations. He invented the “photographic revolver,” capable of capturing 180 images per second, a precursor to motion-picture cameras. He even used it to observe the 1874 transit of Venus in Japan. Later, he became the first director of the Meudon Observatory, where he compiled thousands of solar photographs, culminating in the 1904 publication of his Atlas de photographies solaires. Here at Place Jules Janssen, we stand on the shoulders of a scientific giant. A man who not only broadened our understanding of the Sun but also pioneered new ways of seeing the cosmos.