Faraway blue star cluster shines in Hubble Space Telescope photo

Blue stars are commonly associated with young stars. Here is an interesting report on star formation and molecular clouds.

Molecular clouds extend their lives by constantly reassembling themselves, say astronomers, https://phys.org/news/2023-01-molecular-clouds-constantly-reassembling-astronomers.html

ref - Clouds of Theseus: long-lived molecular clouds are composed of short-lived H2 molecules, https://arxiv.org/abs/2301.10251, 24-Jan-2023.

My observation. The arxiv.org report indicates host molecular cloud lifetimes range 1-90 Myr so the upper limit or max age is about 90 Myr for a GMC type gas cloud. Other reports I have in my home database suggested perhaps 30 Myr. Consider the age of the Universe using Hubble time, 13.8 Gyr and the age of the Milky Way galaxy with globular clusters dated some 12 Gyr or older. Star formation to proceed in our galaxy would require just how many GMC and molecular clouds to be recreated with max lifetimes now about 90 Myr? I enjoy views of M42 in Orion using my telescopes. How many M42s evolved in the galaxy since its origin and then lasted perhaps 90 Myr, creating new stars?

Anytime we see blue stars commonly considered as youth, just how many were regenerated in the Milky Way or another galaxy over Gyr time spans?
My observation. This NASA reports indicates NGC 2031 is 140 Myr and with many blue stars, a problem for stellar evolution modeling to explain. Hubble Beholds Brilliant Blue Star Cluster, https://www.nasa.gov/image-feature/goddard/2022/hubble-beholds-brilliant-blue-star-cluster, 07-Dec-2022. "...The NGC 2031 cluster lives in an extremely dense and starry region of the LMC. Its location in this crowded area results in “stellar contamination,” a phenomenon where the atmospheres and surface features of nearby stars affect the measurements of objects under study. Stellar contamination is one theory that could explain observations of bright blue stars in the cluster center. Stars like these typically burn very hot and have short lifespans, but globular clusters are known for housing only ancient stars. Another theory is that these bright blue stars are in fact blue stragglers, a type of star that forms later than its neighbors, enabling astronomers to observe them in older globular clusters such as NGC 2031. Blue stragglers are thought to form from the merging of two old, red stars, resulting in a star with greater mass and therefore bluer color – a theory developed with Hubble’s help from imaging another globular cluster, 47 Tucanae. NGC 2031 is estimated to be 140 million years old and has a mass more than 3,000 times that of our Sun. Astronomers studied this cluster using Hubble’s ultraviolet capabilities."

Finding blue stars in clusters that should be old is a problem and various methods are used to explain age dating issues like this, efforts to reconcile different ages. Molecular clouds and lifetimes of 90 Myr runs into this too.

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