The Milky Way is a dynamic museum of ancient merging relics, river-like streams of stars stripped from dwarf satellite galaxies that flow through the galaxy revealing its history and structure that allow astronomers to better understand how galaxies in the universe have formed and evolved.
Hubble astronomers found something extraordinary at the heart of nearby globular cluster NGC 6397 –a concentration of smaller black holes lurking there instead of one monster, supermassive black hole. Ancient stellar jewelry boxes, globular star clusters are densely packed objects, glittering with the light of a million stars in a ball only about 100 light-years across dating back almost to the birth of the Milky Way.
Most stars in the universe –including our life-giving Population 1, main-sequence Sun, one of more than 100 billion stars in the Milky Way, that formed approximately 4.6 billion years ago–are formed a massive star clusters created from the violent gravitational collapse of matter within a region of a large molecular cloud. These clusters are the building blocks of galaxies, but their actual formation from these dense clouds is a mystery.
An enormous “something” more massive than a star, appears to have torn a hole in part of the Milky Way’s halo. The “dark substructure” was found in data from Gaia spacecraft observations—a mission producing the most detailed 3D map of our galaxy—with Harvard’s Ana Bonaca noticing a perturbation in a tidal stream. Bonaca is a leading authority on how the tidal field of the Milky Way galaxy disrupts globular clusters, and what the resulting debris can tell us about the underlying distribution of dark matter. (more…)
Our Milky Way Galaxy is surrounded by about 150 globular clusters, formed about 11.5 billion years ago, 2.3 billion years after the Big Bang and shortly before the rate of cosmic star formation reached its peak, 10 billion years ago –a period known as “cosmic high noon.” The largest numbers of globular clusters, over ten to twenty thousand, are found around giant galaxies at the centers of galaxy clusters that contain hundreds to thousands of galaxies bound together by gravity, infused by hot gas (up to ten times hotter than the center of the Sun) that far outweighs all the stars in the galaxies comprising the galaxy cluster combined.
The Galaxy Report newsletter brings you twice-weekly news of space and science that has the capacity to provide clues to the mystery of our existence and add a much needed cosmic perspective in our current Anthropocene Epoch.
