Web archive of astronomical photographic plates goes online

(ORDO NEWS) — Where ordinary people can see just milky gray photographs strewn with random crumbs, the astronomer’s heart begins to beat faster. We are talking about historical photographic plates with negatives of the night sky.

Together with the Leibniz Institute for Astrophysics in Potsdam, the universities of Hamburg and Tartu (Estonia), researchers from the Friedrich-Alexander Erlangen-Nuremberg University (FAU) digitized these images and published them on the Internet. After 10 years, the project was successfully completed.

Such images are the only way astronomers today can follow the movement of stars or their change in intensity over several decades. They can help answer new research questions and take a closer and more objective look at millions of stars.

Since 2012, the research team has been working on digitizing images from the archives of partner institutions from 1893 to 1998 in the APPLAUSE database and recording them in a catalog with detailed information about the images, such as date, sky area and location.

In addition, the research consortium has developed software that uses artificial intelligence to remove errors on wafers caused by scratches or dust and calibrate images, making it possible for the first time to compare them to each other for scientific purposes.

Researchers around the world now have access to 4.5 billion measurements of celestial light sources for their research.

But what kind of knowledge can be obtained from historical photographic plates, and do they have any significance for today? Surveys of the northern and southern sky, carried out in the last century by the Bamberg Observatory, were aimed at studying stars that differ in intensity.

The physical properties of some objects, in other words, what gases they consist of, are still unclear. The star HD49798 is a particularly interesting example.

Its fluctuating intensity fluctuations were recorded on photographic plates from Bamberg in the 1960s and early 1970s, but scientists were only able to analyze them last year.

They show that the star steadily increased its intensity in 1964-1965, but then became less bright until 1974. In addition, there were rapid changes in the light she emitted over the course of just a few days.

In 1999, satellite data showed that the star was emitting X-rays. Today, scientists suspect that these rays are emitted by an invisible, more compact companion object, possibly a neutron star.

Until now, scientists have not been able to track long-term changes in intensity, because it was not possible to make measurements over such a long period of time, namely ten years.

Therefore, historical data from photographic plates is a valuable source of astronomical information that researchers will analyze in the coming years. This particular duo of stars is so far the only constellation of its kind found anywhere in the universe.

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