Recently, a new study published in the Astrophysical Journal Letters questioned astronomers previously believed that spiral galaxies formed about 6 billion years ago
- The universe is about 13.8 billion years old and is home to different kinds of galaxies, from spiral to elliptical and those with or without bulges.
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Types of Galaxies
Spiral Galaxies
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Elliptical Galaxies
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Quasars
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- These galaxies resemble giant rotating pinwheels with a pancake-like disk of stars and a central bulge or tight concentration of stars.
- The spiral arms can be wound tightly or loosely.
- Thease are surrounded by halos, mixtures of old stars, star clusters, and dark matter
- The youngest stars form in gas-rich arms, while older stars can be found throughout the disk and within the bulge and halo.
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- They have shapes that range from completely round to oval.
- Unlike spirals, elliptical galaxies usually contain little gas and dust and show very little organization or structure.
- The stars orbit around the core in random directions and are generally older than those in spiral galaxies since little of the gas needed to form new stars remains.
- Scientists think elliptical galaxies originate from collisions and mergers with spirals.
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- Quasars are the most luminous type of active galaxy.
- They emit light across the electromagnetic spectrum, produce powerful particle jets, and can radiate thousands of times the energy emitted by a galaxy like the Milky Way.
- The nearest quasar, called Markarian 231, is located some 600 million light-years away.
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Significance Of Findings
- The new findings could also affect what astronomers understand about the rate of the formation of stars in the universe.
Key Findings
Following are the key findings of the research:
- Older Theory Of Formation & Evolution Is Now Suspected
- Popular Belief In Astronomy: As the universe cooled down from a dense plasma state, it contained more and more hot gas.
- They formed clumps of matter that eventually gravitated to become galaxies.
- These early galaxies had irregular shapes and lacked disks.
- Spiral ‘arms’: But as they cooled as well, they formed hot, thick disks that later became thinner and finally spiral ‘arms’ — a process that took billions of years.
- Findings: Recent work shows that this cooling down and spiral formation occur around the same cosmic time
- Increased Fraction of Spiral Galaxies
- Researchers compared the number of spiral galaxies to the total number of galaxies.
- Between 3 billion and 7 billion years after the Big Bang, the fraction of spiral galaxies increased from about 8% to 48%.
- As the universe aged: Spiral galaxies became more populous even around the time star formation peaked.
- Prior observations: It indicated an increase from 5% to 30%.
- Future Galaxy Evolution
- Gas Depletion: Over time, spiral galaxies have less gas in their arms, slowing new star formation.
- Galactic Collisions: Predicted collisions, such as between the Milky Way and Andromeda, could restart star formation and create elliptical galaxies.
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Detecting Galaxies In The Early Universe
Methodology: Since light takes time to travel, scientists can use light from these galaxies as a way to peer back in time to study black hole growth and galaxy evolution
Usage of Telescope: James Webb Space Telescope (JWST) vs Hubble Space Telescope (HST)
- Initiation and collaboration: The JWST project began in 1996 as a collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA).
- Successor to Hubble: It has been conceived as the next-generation space telescope succeeding the Hubble Space Telescope, with a focus on infrared astronomy.
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July 4, 2024
