Astronomers have uncovered evidence showing how ancient star-forming galaxies evolved into the massive elliptical galaxies we see today. By analyzing over 100 galaxies from the universe’s most active period of star formation, researchers found that these early galaxies were already forming into spherical shapes through intense star formation at their cores.
The discovery resolves a long-standing mystery about how the universe’s oldest galaxies formed. Modern elliptical galaxies contain very old stars but lack new star formation, leaving questions about their origins. This research demonstrates the direct transformation process from ancient star-forming cores to modern elliptical giants.
Key Takeaways
- First solid evidence of how massive elliptical galaxies formed in early universe
- Star formation at galaxy cores directly created spherical shapes
- Findings date from “Cosmic noon” era, 1.6 to 5.9 billion years after Big Bang
Published in Nature | Estimated reading time: 4 minutes
The international research team, led by Associate Researcher Qinghua Tan from Chinese Academy of Sciences Purple Mountain Observatory, analyzed data from over 100 Submillimeter Bright Galaxies (SMGs) using the Atacama Large Millimeter/submillimeter Array (ALMA). These galaxies date from the universe’s most active star-forming period, known as “Cosmic noon.”
Using statistical analysis of dust emission patterns, researchers found that most sample galaxies showed very compact submillimeter emission with brightness profiles unlike typical disk galaxies. This indicates these early galaxies were already developing spheroidal shapes characteristic of modern elliptical galaxies.
The team’s 3D geometric analysis revealed these galaxies had an average ratio of shortest to longest axis of about one-half, increasing with spatial compactness. This demonstrates they were inherently spherical rather than disk-shaped, like today’s spiral galaxies such as our Milky Way.
The study leveraged data from A3COSMOS and A3GOODSS archival projects, though researchers note that future observations using new technologies like the James Webb Space Telescope and China Space Station Telescope will provide even more detailed insights into early galaxy formation processes.
Key Terms
- Submillimeter Bright Galaxies (SMGs)
- Ancient galaxies from the early universe that emit strong radiation in submillimeter wavelengths, indicating intense star formation activity.
- Elliptical Galaxies
- Older galaxies with spheroidal shapes, containing mostly ancient stars and little new star formation, representing the end stage of galaxy evolution.
- Cosmic Noon
- Period between 1.6 and 5.9 billion years after the Big Bang when the universe experienced peak star formation activity.
Test Your Knowledge
What distinguishes ancient star-forming galaxies from modern elliptical galaxies?
Ancient star-forming galaxies were actively forming new stars at their cores, while modern elliptical galaxies contain very old stars and lack new star formation.
How did researchers analyze these ancient galaxies?
They used the ALMA telescope to study dust emission patterns in over 100 Submillimeter Bright Galaxies, analyzing their brightness profiles and 3D geometry.
What evidence showed these galaxies were becoming spherical?
The galaxies showed compact submillimeter emission unlike disk galaxies, and 3D analysis revealed they had an average shortest-to-longest axis ratio of one-half, indicating spherical rather than disk shapes.
Why is this discovery significant for understanding galaxy evolution?
It provides the first solid observational evidence showing how massive elliptical galaxies formed directly through intense star formation in early galaxy cores.
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