Giant star cluster in the dark

(ORDO NEWS) — The very young cluster Westerlund 1 (Wd 1) stands out in the Milky Way. Less than ten million years old – by comparison, the Sun is five billion years old – it is considered the most massive cluster in our galaxy.

A team of scientists “broke through the darkness” to accurately estimate the distance to the cluster and analyze its environment.

The stellar population of Westerlund 1 includes all kinds of massive stars. They range from giants and O-type supergiants to red supergiants, several extremely luminous B-type hypergiants, several yellow hypergiants, and others.

However, the exact determination of the masses and ages of stars depends on several parameters: one of the main unknowns so far has been their distance, as well as the effect of light attenuation due to dust in these regions.

According to Ignacio Negeruela, head of the study and professor of astronomy and astrophysics at the University of Alicante, Wd 1 is without a doubt one of the most interesting objects in our galaxy.

Due to the sheer amount of dust along our line of sight, even a modern telescope like Gaia is struggling to provide us with high quality data.

Therefore, in order to obtain such an accurate distance value, it was necessary to apply complex statistical processing of observations.

However, Gaia gave us much more information, as it revealed the true size of the cluster and allowed us to identify stars in it that were not known before.

The cluster is about thirteen thousand light-years from the Sun, and its mass is probably closer to a hundred thousand solar masses, making it the most massive young star cluster in the Local Group, with the exception of R136 in the Large Magellanic Cloud.

The Gaia-EDR3 data, together with new spectroscopic observations, has enabled the team to detect a large cluster of blue stars that may lie about six and a half thousand light-years from the Sun, representing a hitherto unknown star-forming complex or spiral arm segment.

All the stars that we can see in this cluster are much more massive and brighter than the Sun. Some of them are so huge that if we placed them in the center of the solar system, they would reach almost to the orbit of Saturn. In fact, one of them claims to be the biggest star known.

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