Star clusters are only the tip of the iceberg
Finding lost star siblings

Date:
October 15, 2020
Source:
University of Vienna
Summary:
Star clusters have been part of the Imaginarium of human
civilization for millennia. The brightest star clusters to Earth,
like the Pleiades, are readily visible to the naked eye. A team
around astronomer has now revealed the existence of massive stellar
halos, termed coronae, surrounding local star clusters.



FULL STORY ==========================================================================
Star clusters have been part of the Imaginarium of human civilization
for millennia. The brightest star clusters to Earth, like the Pleiades,
are readily visible to the naked eye. A team around astronomer has
now revealed the existence of massive stellar halos, termed coronae, surrounding local star clusters.


========================================================================== "Clusters form big families of stars that can stay together for large
parts of their lifetime. Today, we know of roughly a few thousand star
clusters in the Milky Way, but we only recognize them because of their prominent appearance as rich and tight groups of stars. Given enough
time, stars tend to leave their cradle and find themselves surrounded
by countless strangers, thereby becoming indistinguishable from their neighbours and hard to identify" says Stefan Meingast, lead author of
the paper published in Astronomy & Astrophysics. "Our Sun is thought to
have formed in a star cluster but has left its siblings behind a long
time ago" he adds.

Thanks to the ESA Gaia spacecraft's precise measurements, astronomers
at the University of Vienna have now discovered that what we call a
star cluster is only the tip of the iceberg of a much larger and often distinctly elongated distribution of stars.

"Our measurements reveal the vast numbers of sibling stars surrounding
the well-known cores of the star clusters for the first time. It appears
that star clusters are enclosed in rich halos, or coronae, more than 10
times as large as the original cluster, reaching far beyond our previous guesses. The tight groups of stars we see in the night sky are just a
part of a much larger entity" says Alena Rottensteiner, co-author and
master student at the University of Vienna. "There is plenty of work
ahead revising what we thought were basic properties of star clusters,
and trying to understand the origin of the newfound coronae." To find
the lost star siblings, the research team developed a new method that
uses machine learning to trace groups of stars which were born together
and move jointly across the sky. The team analyzed 10 star clusters and identified thousands of siblings far away from the center of the compact clusters, yet clearly belonging to the same family. An explanation for
the origin of these coronae remains uncertain, yet the team is confident
that their findings will redefine star clusters and aid our understanding
of their history and evolution across cosmic time.

"The star clusters we investigated were thought to be well-known
prototypes, studied for more than a century, yet it seems we have to
start thinking bigger.

Our discovery will have important implications for our understanding of
how the Milky Way was built, cluster by cluster, but also implications for
the survival rate of proto-planets far from the sterilizing radiation of massive stars in the centers of clusters," says Joa~o Alves, Professor
of Stellar Astrophysics at the University of Vienna and a co-author
of the paper. "Dense star clusters with their massive but less dense
coronae might not be a bad place to raise infant planets after all."
Video: https://www.youtube.com/watch?v=nnGVL9LEVDE&feature=emb_logo

========================================================================== Story Source: Materials provided by University_of_Vienna. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. S. Meingast, J. Alves, A. Rottensteiner. Extended stellar systems
in the
solar neighborhood. V. Discovery of coronae in nearby star clusters.

Astronomy & Astrophysics, 2020; DOI: 10.1051/0004-6361/202038610 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201015092429.htm

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