Researchers find equation that reveals the density of interstellar clouds

Researchers have discovered a new equation that explains how the brightness and colour of celestial bodies are altered by interstellar clouds. The findings, published in the journal Monthly Notices of the Royal Astronomical Society , provides a more efficient explanation of the phenomenon than has been possible so far. They are the result of research led by Maria Vittoria Legnardi, a Ph.D. student in Physics and Astronomy at the University of Padua, with the collaboration of astronomer Sohee Jang of Seoul University.

Interstellar matter is to be found all over the Milky Way, including in areas that look dark even when observed using large telescopes. Although intangible, these clouds of particles interact with the light emitted by celestial bodies and change its properties, making them appear less bright and altering their colours. The new equation makes it possible to better understand a vast array of astrophysical phenomena.

"The Hubble images we use capture a large number of star clusters, clusters of tens of thousands of twin stars that lie beyond (interstellar) clouds,” says Legnardi. "The clouds are not visible in the images, but we were able to reconstruct them thanks to a painstaking analysis of the light from stars passing through them."

The most surprising result concerns the impact that this discovery will have on the so-called reddening law, namely the mathematical equation that can predict how interstellar matter alters the brightness and colour of stars.
"With this discovery, many studies based on the traditional equation will have to be reviewed,” Legnardi concludes.