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Cosmic dust factories: variable stars and the origin of life

It was found that stars with variable light intensity influence the production of the interstellar dust and its enrichment in heavy elements from which life was created

V838 Monocerotis A red variable star in the Monocros group. Illustration: depositphotos.com
V838 Monocerotis A red variable star in the Monocros group. Illustration: depositphotos.com

Of all the different types of stars, stars in the asymptotic giant branch (AGB), which are usually a little bigger and older than our Sun, and are known to produce interstellar dust. Dusty AGBs are particularly prominent dust producers, and the light they emit is highly variable. In a long-term study it was found for the first time that the changing intensity of dusty AGB stars corresponds to the changes in the amount of dust these stars produce. Since this dust can lead to the formation of planets, its study can shed light on our origin.

The Webb Space Telescope is the largest and most sensitive space telescope for infrared (IR) light observations, but long before it, two other IR space telescopes, AKARI and WISE, surveyed the cosmos. Both have already completed their mission and provided a lot of valuable data that astronomers are still making new discoveries in. The new findings could have implications for the study of the origin of life itself.

"We study stars, and the AA light from them is an important source of information that helps us crack their secrets," said Kengo Tachibana, from the Institute of Astronomy of the University of Tokyo. "Until recently, most of the AA data were short surveys due to the lack of advanced dedicated platforms. But missions like AKARI and WISE have allowed us to do longer surveys of things. This means we can see how things change over a longer period of time, and what the consequences of those changes can be. Recently we have been dealing with a type of stars that belong to the "asymptotic giant branch", which are interesting because they are the main producers of interstellar dust.

The interstellar dust is not the same stuff that accumulates on the floor at home when you don't vacuum for a few days. It is a name given to heavy elements that are scattered from stars and lead to the formation of solid objects, including planets. Although it has long been known that AGB, especially the so-called dusty ones, are the main dust producers, it is not known what the main causes of dust production are and where we should look for the answer.

"Our latest research pointed us in the right direction," Tachibana said. Thanks to long AA observations, we found that the light from dusty AGB varies in cycles longer than a few hundred days. We also found that the concentrations of dust in the globular dust envelopes that these stars produce and emit vary according to changes in their light intensity. In the 169 dusty AGBs surveyed, regardless of the periodicity, the dust concentrations around them will overlap. Therefore, we are sure that they are related."

for the scientific article

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