Astronomers are constantly discovering new galaxies in our vast universe. With advanced telescopes peering deeper into space than ever before, we are able to observe galaxies that formed not long after the Big Bang, which occurred approximately 13.8 billion years ago. These incredibly young galaxies, forming when the universe was less than a billion years old, provide valuable insights into the early days of galaxy formation and evolution.
The Most Distant Galaxy Candidates
Thanks to observatories like the Hubble Space Telescope and the Atacama Large Millimeter Array (ALMA), astronomers have identified some candidate galaxies that may be the youngest ever observed. Here are some of the most distant galaxy candidates found to date:
- GN-z11 – observed by Hubble in 2016, estimated to have formed 400 million years after the Big Bang, at a redshift of 11.1. This places it about 13.4 billion lightyears away.
- EGS-zs8-2 – observed by Hubble in 2017, estimated to have formed 350 million years after the Big Bang, at a redshift of 7.5. This places it about 13.3 billion lightyears away.
- EGS8p7 – observed by Hubble and Spitzer in 2021, estimated to have formed 250 million years after the Big Bang, at a redshift of 8.7. This places it about 13.2 billion lightyears away.
- HD1 – observed by Hubble, ALMA, and others in 2022, estimated to have formed 300 million years after the Big Bang, at a redshift of 13. Estimated to be about 13.5 billion lightyears away.
These incredibly distant galaxy candidates provide a glimpse into the very early universe right after the first stars and galaxies began to form. However, it is difficult to confirm their extreme distances, so there is some uncertainty if any of them are truly the most distant or youngest galaxy known.
Challenges Observing Young Galaxies
There are a few key challenges involved in discovering and confirming candidate young galaxies in the early universe:
- Cosmic Redshift – The expansion of the universe causes distant galaxies’ light to be stretched to longer wavelengths, shifting them to the red end of the spectrum. The higher the redshift, the earlier in the universe’s history we are looking.
- Faintness – Primitive young galaxies are typically very faint and small, making them hard to distinguish from foreground objects.
- Confusion – Distant galaxy candidates must be distinguished from other red objects like brown dwarfs or high redshift quasars.
- Contamination – Intervening gas and dust can make distant galaxies appear brighter and redder than they really are.
Overcoming these challenges requires using space and ground-based observatories that can capture faint, highly redshifted light across multiple wavelengths from the infrared to ultraviolet. Even then, confirming a galaxy’s extreme distance remains difficult.
Properties of Young Galaxies
Although challenging to observe, astronomers can infer some of the properties of the earliest and most distant galaxies:
- They appear small, compact, and irregularly shaped, lacking the distinct structures seen in mature galaxies.
- They are incredibly energetic sources of radiation, fueled by bursts of star formation and growth of supermassive black holes.
- They contain large amounts of cold gas and dust, the raw fuel for rapid star formation.
- Their stars are likely very metal-poor, because few earlier generations of stars existed to enrich the gas with heavy elements.
Understanding the properties of these young galaxy candidates gives us clues about the formation and evolution of galaxies in the earliest stages after the Big Bang.
Star Formation in Young Galaxies
Young galaxies from the early universe were forming stars at incredible rates. While our Milky Way forms around 1-3 new stars per year, early galaxies were forming hundreds or even thousands of new stars per year. Some key facts about star formation in young high-redshift galaxies:
- Star formation rates increased dramatically in the first billion years after the Big Bang, peaking around 3-4 billion years after.
- The earliest galaxies were forming stars tens or hundreds of times faster than our Milky Way today.
- Rapid star formation was likely fueled by large amounts of cold hydrogen gas drawn together by gravity into dense regions.
- The earliest stars likely formed from primordial gas clouds with no heavy elements, only hydrogen, helium, and traces of lithium produced in the Big Bang.
Understanding star formation rates and histories in early galaxies gives insights into the assembly of cosmic structures after the Big Bang.
Studying Young Galaxies with Next-Generation Telescopes
Upcoming observatories will be able to study these early galaxies in far greater detail than before:
- The James Webb Space Telescope (scheduled to launch in 2021) will be able to spectroscopically confirm some early galaxy candidates due to its infrared sensitivity and high resolution.
- The Nancy Grace Roman Space Telescope (to launch in 2025) will perform wide-field surveys to discover more early galaxies and measure their distances.
- Future ground-based extremely large telescopes like the Giant Magellan Telescope (scheduled completion in 2025) will be able to spectroscopically confirm the most distant galaxies.
With these next-generation observatories online in the coming years, we are set to discover and characterize the most distant and earliest galaxies that formed after the Big Bang.
Significance of Observing Young Galaxies
Why are the most distant and youngest galaxies so important to study? Here are some key reasons:
- They allow us to study the origins of cosmic structures, like the formation of the first stars and galaxies.
- They provide insights into conditions in the early universe and cosmic history.
- They inform our models and simulations of structure formation after the Big Bang.
- They enable us to study star and galaxy formation processes in primitive environments.
- They help trace the assembly and growth of galaxies up to the present day.
By pushing observational boundaries to discover new young galaxy candidates, astronomers gain valuable glimpses into the primordial universe and learn about the origins of present-day galaxies like our Milky Way.
Astronomers are discovering galaxy candidates that formed only a few hundred million years after the Big Bang 13.8 billion years ago. While extremely challenging to observe due to their faintness, distance, and other confounding factors, these young galaxies provide unprecedented insights into the early universe. Ongoing studies and new instruments aim to discover even earlier galaxies and study their detailed properties and star formation histories. Pushing deeper into space to find the youngest and most distant galaxies remains one of the most exciting frontiers in astronomy.