The Night Sky: Past and Present

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Nowadays, all you need is a smartphone, an astronomy app and a clear night to identify the stars and planets that populate the night sky. The days of trying to impress your friends with names of random constellations are behind us. Today’s backyard amateur astronomer relies more on signal strength than stellar smarts.

Which begs the question, how did they do that before cell phones? As the saying goes, behind every good digital astronomy app is an analog photographic plate. Beginning in the mid-19th century, astronomers began utilizing the art of photographic emulsion to capture images of celestial objects. For the first time, astronomers were able to etch their discoveries onto thick glass plates ushering in a new era of data analysis that would help unlock the mysteries of the universe.

But don’t take my word for it. If it’s good enough for Einstein, it’s good enough for me.

Photographic plates helped scientists determine the size, distance and composition of celestial objects such as stars, comets, meteors and planets. Galileo Galilei would be proud. By the early 1990s, the once highly esteemed “analog” plates had fallen out of favor for images captured by new, charged-coupled devices such as digital cameras. Many of the old plates were put on the shelf and stored in basements and barns.

PARI to the rescue: the Pisgah Astronomical Research Institute (PARI) is a non-profit astronomy, research and education facility located in western North Carolina. PARI scientists recognized the archival value in saving the old astro-photographic plates and created the Astronomical Photographic Data Archive, or ADPA, to be housed at PARI’s vast campus.

I recently had the opportunity to visit PARI, poke around their archives and find out why it’s worth saving the old data. What I discovered was that these plates - which a lay-person like me can easily mistake for a dirty windshield {include pic here} – contain a lot data that’s not only historic, but vital to today’s research.

During our visit we spoke with scientists from NASA (link to web extra) as well as the European Space Agency who attribute the success of current and future space missions to data gleamed from APDA.

It turns out there is no expiration date on these invaluable snapshots of the night sky. The plate’s spectral images act as a time-stamp for what the night sky looked like before it was polluted with what one NASA scientists described as “space junk.”

The scientists at PARI compared their collection to the Library of Alexandria. Science Director Michael Castelaz told me, “If that library hadn’t been destroyed, the knowledge that could have been passed on from the philosophers and the Greeks from three millennia ago would just have benefited us greatly. So I think we’re in the same situation.”

Castelaz believes the hidden potential inscribed in the plates have yet to be fully realized. He and his PARI colleagues are stewards of history, preserving the pates for future generations and ensuring that the next Einstein has the resources to turn the world on its axis once again. After all, the proof is in the plates.