Remains of ancient globular clusters found at the heart of the Milky Way

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Ann
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Remains of ancient globular clusters found at the heart of the Milky Way

Post by Ann » Wed Oct 12, 2016 10:53 pm

Remains of ancient globular clusters found at the heart of the Milky Way
Within this image, captured with the VISTA infrared survey telescope
as part of the Variables in the Via Lactea (VVV) ESO public survey,
astronomers detected several ancient stars, of a type known as RR Lyrae.
As RR Lyrae stars typically reside in ancient stellar populations
over 10 billion years old, this discovery suggests that the bulging
centre of the Milky Way likely grew through the merging of primordial
star clusters. Image credit: ESO/VVV Survey/D. Minniti.
Ancient stars, of a type known as RR Lyrae, have been discovered in the centre of the Milky Way for the first time, using ESO’s infrared VISTA telescope. RR Lyrae stars typically reside in ancient stellar populations over 10 billion years old. Their discovery suggests that the bulging centre of the Milky Way likely grew through the merging of primordial star clusters. These stars may even be the remains of the most massive and oldest surviving star cluster of the entire Milky Way...

RR Lyrae stars are typically found in dense globular clusters. They are variable stars, and the brightness of each RR Lyrae star fluctuates regularly. By observing the length of each cycle of brightening and dimming in an RR Lyrae, and also measuring the star’s brightness, astronomers can calculate its distance.

Unfortunately, these excellent distance-indicator stars are frequently outshone by younger, brighter stars and in some regions they are hidden by dust. Therefore, locating RR Lyrae stars right in the extremely crowded heart of the Milky Way was not possible until the public VVV survey was carried out using infrared light. Even so, the team described the task of locating the RR Lyrae stars in amongst the crowded throng of brighter stars as “daunting.”

Their hard work was rewarded, however, with the identification of a dozen RR Lyrae stars. Their discovery indicates that remnants of ancient globular clusters are scattered within the centre of the Milky Way’s bulge.

Rodrigo Contreras Ramos elaborates: “This discovery of RR Lyrae stars in the centre of the Milky Way has important implications for the formation of galactic nuclei. The evidence supports the scenario in which the bulge was originally made out of a few globular clusters that merged...”
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ESO: The Milky Way’s Ancient Heart

Post by bystander » Thu Oct 13, 2016 4:26 am

The Milky Way’s Ancient Heart
ESO VISTA Science Release | 2016 Oct 12

VISTA finds remains of archaic globular star cluster

VVV Survey RR Lyrae in the Nuclear Bulge of the Milky Way and the Formation of the Galactic Nuclei - Dante Minniti et al
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