Carnegie Institution for Science | 2020 Jul 29
A team of astronomers ... discovered a stellar stream composed of the remnants of an ancient globular cluster that was torn apart by the Milky Way’s gravity 2 billion years ago, when Earth’s most-complex lifeforms were single-celled organisms. This surprising finding ... upends conventional wisdom about how these celestial objects form.
- Artist’s impression of the thin stream of stars torn from the Phoenix globular cluster, wrapping around our Milky Way (left). For the study, the astronomers targeted bright Red Giant stars, to measure the chemical composition of the disrupted Phoenix globular cluster (artist’s impression on right). Credit: James Josephides (Swinburne Astronomy Productions) and the S5 Collaboration.
Imagine a sphere made up of a million stars bound by gravity and orbiting a galactic core. That’s a globular cluster. The Milky Way is home to about 150 of them, which form a tenuous halo that envelops our galaxy.
But the globular cluster that spawned this newly discovered stellar stream had a lifecycle that was very different from the globular clusters we see today. ...
Using the Anglo-Australian Telescope, the stream was revealed by S5, the Southern Stellar Stream Spectroscopic Survey Collaboration. ... the initiative aims to map the motion and chemistry of stellar streams in the Southern Hemisphere.
In this study, the collaborative focused on a stream of stars in the Phoenix constellation. ... The team measured the abundances of heavier elements—what astronomers call a star’s metallicity. ... the Phoenix Stream progenitor is well below this predicted minimum metallicity, posing a significant problem for previous ideas about how globular clusters are born. ...
Scientists Find Remnant of Strange Dismembered Star Cluster at Galaxy's Edge
Lowell Observatory | 2020 Jul 29
The Phoenix stellar stream rose from the ashes of an ancient star cluster
Nature | News & Views | 2020 Jul 29
The tidal remnant of an unusually metal-poor globular cluster ~ Zhen Wan et al
- Nature 583(7818):768 (2020 Jul 30) DOI: 10.1038/s41586-020-2483-6