Gaia discovers half a million new stars in the core of the Omega Centauri star cluster

For about 10 years Gaia has been providing ESA researchers with new information on the universe around us, this time the satellite has outdone itself by providing us with unpublished images of over half a million stars never seen before.

Milky Way
There are over half a million additional stars within the Omega Centauri globular cluster.

ESA's Gaia mission had a very specific objective: to obtain a three-dimensional map of our galaxy, revealing its composition, formation and evolution. Thus, since 19 December 2013 it has continuously scanned the sky surrounding it, exploiting rotation and precession motions to achieve its purpose, observing each area of the sky approximately seventy times during its operational life.

In recent years, Gaia has obtained astrometric data of over a billion stars with a precision 200 times greater than that of its predecessor Hipparcos. Furthermore, thanks to the astrophysical information on brightness in the different spectral bands, it will allow us to study in detail the formation, dynamics, chemistry and evolution of the Milky Way.

Gaia was able to provide us with previously unpublished images

In the latest release of Gaia (DR3, Data Release 3) there were data regarding over 1.8 billion stars but the map still had some gaps. There were areas of the sky particularly rich in stars that had not been thoroughly investigated. Furthermore, attention had not yet been focused on those stars that shone less than their neighbours.

It is precisely for this reason that it was decided to make Gaia do something not originally foreseen for scientific purposes: to select a star cluster and instead of concentrating only on the individual stars, as is usual, observe a smaller portion of the sky through a special mode to map in detail a vast area surrounding the core of the cluster.

Gaia's gaze then turned towards Omega Centauri, the largest and brightest globular cluster observable from Earth, located in our galaxy and about 18,000 light years away from us.

This cluster is made up of several million stars and now, thanks to Gaia, we know that in its nucleus there are 526,587 new ones, which means that there are 10 times more stars in the nucleus than we thought.

Some of these stars are too close together to be measured in the telescope's normal operating mode, and the stars in Omega Centauri's core are up to 15 times fainter than those observed so far.

The history of Omega Centauri is still not entirely clear

The nature of Omega Centauri has long been debated. Initially it was thought to be a single star in the constellation of Centaurus (which is why in 1677 Edmond Halley gave it this name, with a Greek letter, typical for star names), then in 1830 John Herschel realised that it was a globular cluster, until a few years ago when some researchers came to the conclusion that it was the heart of a dwarf galaxy that had lost the most peripheral stars within the Milky Way, a decidedly more massive galaxy.

These additional very high resolution images will certainly be useful for carrying out further studies on this dwarf galaxy.

Furthermore, given the excellent results obtained with the observations of the Omega Centauri nucleus, it was decided to have Gaia explore 8 other regions using this same modality. Any results will be included in Gaia Data Release 4.

We therefore just have to wait to find out what new and incredible images Gaia will be able to provide us in the future.

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