Found stars surrounded by iron dust

Found stars surrounded by iron dust
Found stars surrounded by iron dust

Researchers have discovered a curious group of stars in the Large Magellanic Cloud, shrouded in iron dust.


Researchers from the Canary Institute of Astrophysics (IAC) participated in a study that found a group of low-metal stars enveloped in large amounts of iron dust in the Large Magellanic Cloud. The study involved theoretical models of dust formation in circumstellar envelopes and images taken by the Spitzer space telescope. The work also includes some predictions for the James Webb telescope. The study is published in the Astrophysical Journal.

Stars between one and eight solar masses evolve along the asymptotic giant branch before ending up as white dwarfs. It is during this short but important phase that stars expand to enormous sizes and cool down, losing most of their mass due to strong stellar winds. The low temperature and high density of the wind provide ideal conditions for the condensation of dust particles in their circumstellar envelopes.

The dust produced by stars during the phase of the asymptotic giant branch and ejected into interstellar space is important for the life of galaxies, since it contains the component necessary for the formation of new stars and planets. Understanding exactly what dust is made of - solid-state organic components or inorganic components - and determining its amount are significant for the astronomical community.

In the new study, astronomers looked at a curious group of asymptotic giant branch stars located in the Large Magellanic Cloud. By comparing infrared observations from the Spitzer space telescope with theoretical models developed by the research team, scientists have found that these stars have about five solar masses and were formed about 100 million years ago, in addition, they have very few metals like iron., magnesium and silicon.

Surprisingly, the researchers found that such a distribution of energy in the infrared range can be obtained only if iron dust is the main component of the circumstellar envelopes. This is an unusual phenomenon for stars in the asymptotic giant branch. It was previously known that such stars mainly produce silicates, magnesium, as well as large amounts of oxygen and silicon. However, the new data turned out to be much more surprising, given the low metal content in the environment surrounding the stars under study. As a result of the study, this class of stars with unique spectral properties was characterized for the first time.

“The low metal content of these giant stars creates an interesting environment, allowing large amounts of stardust to form,” explains Esther Marini, lead author of the study at Roma Tre University. "In fact, in a low-metal environment, the complex nuclear fusion within massive stars of the asymptotic giant branch is so advanced that it burns off almost all the magnesium and oxygen needed to form other types of dust, such as silicates."

Under these special conditions, iron dust becomes the main component in the dust generated by these stars.

"This confirms the theory of iron dust in low metal environments that has been previously pointed out by independent observations," says IAC researcher and co-author Anibal García Hernandez.

“The launch of the James Webb Space Telescope will open up new possibilities for studying this discovery in detail,” said Flavia Del'Agli of the IAC and also co-author of the study. "This telescope will help find more extragalactic stars in the asymptotic giant branch."

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