| 9 first galaxies had formed earlier (about 13.2 billion years ago), but by 9 billion years ago, galaxies were becoming more complex and massive due to mergers and star formation. |
| 9 Second-generation stars (Population I and II) became more common, containing heavier elements (metals) formed in earlier supernovae. |
| 9 universe was entering its "Cosmic Noon", a period between 8 to 10 billion years ago when the rate of star formation peaked across the universe. |
| 9 This was a golden age of galaxy growth, where gas-rich galaxies were actively forming new stars at a high rate. |
| 9  Milky Way was in the process of growing by accreting smaller galaxies and forming its bulge and thick diskcomponents. |
| 9 Milky Way's halo stars and globular clusters had largely formed earlier, but 9 billion years ago, much of the disk structure was taking shape. |
| 9 Many quasars (extremely luminous active galactic nuclei powered by supermassive black holes) were active during this era. |
| 9 This implies that black holes at the centers of galaxies were growing rapidly, fed by infalling gas. |
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| 8 Star Formation Declining: The star formation rate in the universe peaked around 10 billion years ago and was starting to decline by 8 billion years ago. Galaxies were still forming stars, but not as rapidly. |
| 8 Formation of Our Sun Was in the Future: The Sun had not formed yet — it would come into existence about 3.8 billion years later, around 4.6 billion years ago. |
| 8 Galaxies Maturing: Many galaxies were taking on more structured forms (spirals, ellipticals). Galaxy collisions and mergers were common, contributing to this maturation. |
| 8 Black Holes and Quasars: Supermassive black holes were already present in galaxy centers. Some were still feeding on matter, creating active galactic nuclei (quasars). |
| 8 Elements Beyond Hydrogen/Helium: There was already a significant buildup of “metals” (elements heavier than helium), from multiple generations of star formation and supernovae. |
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| 7  Acceleration of the Universe’s Expansion. This is a major turning point in the history of the cosmos. |
| 7 billion years ago, dark energy began to dominate the energy density of the universe. |
| 7 As a result, the expansion of the universe began accelerating. Before this point, expansion had been slowing down due to the gravitational pull of matter. |
| 7 This transition marks the moment when dark energy overcame gravity on large scales. |
| 7  peak era of star formation was about 9–10 billion years ago. |
| 7 billion years ago, the rate of star formation was decreasing, though many galaxies (like our Milky Way) were still actively forming stars. |
| 7 Galaxies were merging, evolving, and settling into more stable shapes (spirals and ellipticals). |
| 7 Many of the larger galaxies were beginning to mature, including progenitors of today’s Milky Way and Andromeda galaxies. |
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