The value of historical star records
DOI: 10.1063/PT.5.023387
To study the object further, researchers delved into a trove of the astronomical past: a collection of photographic plates at Harvard University dating as far back as the 1860s. They spotted 3C 273 on some 600 photographs taken with a variety of telescopes over 70 years, some of them days apart.
The images showed fluctuations in the object’s brightness on time scales as short as a week. Because the object could not be dimming or brightening faster than light could traverse it, the researchers inferred that in spite of being more luminous than a billion suns, the object had to be less than a light-week across—the size of the solar system. The finding helped characterize 3C 273 as a new type of object known as a quasar, one of the most powerful energy sources in the universe.
The discovery shows the value of historical sky observations, says Harvard astronomer Jonathan Grindlay, who is leading an initiative to scan the 500,000 plates in the university’s collection and put them online. The project—called Digital Access to a Sky Century at Harvard (DASCH)—is part of a movement by a small but persistent group of astronomers to preserve, digitize, and study old astronomical photographs in hope of doing new science.
Related Physics Today articles
Astronomers Save Historic Plates (June 2003)
North Carolina institute offers to archive old astronomy data (March 2009)
