A long time ago, back when telephones had cords, photographs weren’t stored on the cloud or even on computers.
Instead, they were recorded on something called film, and when you filled up one roll of film, you took it to the photo clerk at the drugstore, waited a while, and then got back a slim envelope of 4-by-6-inch glossies, which you took home and tucked into a shoebox or album.
Sometimes you scribbled names and dates on the photos, and sometimes you didn’t. After all, it was hard to imagine that you might ever forget the name or face of Cousin Ingrid, or Morris from down the street, so the labeling seemed nonessential, the sort of thing you’d get around to on a rainy day after you’d finished crocheting that blanket you started back during the Clinton era.
Then, time passed. Your memory got a little wobbly. Maybe those albums and shoeboxes were passed on to a child or a grandchild, and the familiar faces that you thought were so unforgettable got forgotten and lost their place in the geography and history of your personal universe.
Okay, we’re getting a little maudlin here, so let’s talk astronomy. Old astronomical images have the same problem as those shoebox photos: though they hold a treasure-trove of information about how our universe looked decades and even centuries ago, we’ve lost their context.
Today, astronomers make a habit of “labeling” their photos. They tag images and other datasets with essential “metadata” — sky coordinates, camera specs, telescope information — so that those images can be searched and sorted by computers.
That metadata also makes it possible for images taken by different telescopes, using different…