globular clusters<\/a>: immense, roughly spherical collections of tens of thousands to a few million stars. Globular clusters contain some of the oldest stars in our galaxy, and they can act as cosmic archaeological sites that preserve stars from other galaxies the Milky Way galaxy has collected.<\/p>\n\u201cThanks to the high resolution and depth of Hubble imaging, we could measure the age and the metal content of these clusters with unprecedented precision,\u201d said Chiara Zerbinati, study co-author, University of Bologna in Italy. \u201cCoupled with measurements from Gaia, this made it possible to distinguish a population of globular clusters that are different from the others. These are the clusters that were born in LKH, and they tell us when that galaxy was devoured by ours, and how massive it was.\u201d<\/p>\n
The team analyzed Hubble observations of 39 globular clusters in the inner 20,000 light-years of our galaxy, where evidence of the most ancient mergers should be preserved. They expected this sample to contain globular clusters that formed within the young Milky Way galaxy as well as those collected from the Gaia-Sausage-Enceladus dwarf galaxy about 10 billion years ago.<\/p>\n
Using Hubble\u2019s sensitive observations to determine each cluster\u2019s precise age and associated metallicity \u2014 the abundance of elements heavier than helium \u2014 they determined there was a third population of globular clusters in the inner regions of our galaxy. The team found that these clusters are older than the group collected in the Gaia-Sausage-Enceladus merger, but younger than those born in the Milky Way, regardless of their metal content. These\u00a0 clusters, therefore, came from a separate and even earlier merger \u2014 in which the Milky Way galaxy absorbed a dwarf galaxy containing roughly 500 million times the mass of the Sun in stars, a significant fraction of our galaxy\u2019s mass at the time. They named this dwarf galaxy Low-energy-Kraken-Heracles, or LKH, in honor of three earlier research papers that championed the idea of a merger early in our galaxy\u2019s history.<\/p>\n
Such a large merger so early in the Milky Way galaxy\u2019s formation has profound implications for the evolution of our galaxy.<\/p>\n
\u201cSome past studies have argued that the earliest phases of our galaxy\u2019s evolution were defined by stars born only in our galaxy,\u201d says Massari. \u201cHere, we have shown that stars born in external galaxies also need to be considered.\u201d<\/p>\n
The team plans to continue their work to unravel the history of the Milky Way galaxy by studying its globular clusters, aiming to characterize all the massive mergers that our galaxy has experienced across cosmic history.<\/p>\n
\u201cHubble is observing globular clusters that have never been studied before, and this will help us characterize the merger events that are far back in time in the Milky Way galaxy\u2019s history,\u201d said Fernando Aguado-Agelet, co-author, University of Vigo and the University of La Laguna in Spain.<\/p>\n
The Hubble Space Telescope has been operating for more than three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA\u2019s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.<\/p>\n","protected":false},"excerpt":{"rendered":"About 12 billion years ago, a dwarf galaxy known as LKH collided with a young Milky Way and…\n","protected":false},"author":2,"featured_media":642172,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[270],"tags":[1025,3093,18,3094,163840,5198,3095,19,17,133,451,42129,47693],"class_list":["post-642171","post","type-post","status-publish","format-standard","has-post-thumbnail","category-space","tag-astrophysics","tag-astrophysics-division","tag-eire","tag-galaxies","tag-globular-clusters","tag-goddard-space-flight-center","tag-hubble-space-telescope","tag-ie","tag-ireland","tag-science","tag-space","tag-star-clusters","tag-the-milky-way"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/117112108497676909","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/642171","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=642171"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/642171\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/642172"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=642171"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=642171"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=642171"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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