How were the oldest galaxies formed? Astronomers are looking for a light that has an answer
Features of some of the oldest galaxies in the universe come into sharper focus.
The Big Picture: Data from telescopes in space and on Earth – including the new and powerful James Webb Space Telescope (JWST) – will give astronomers their best picture yet of how the universe’s first stars and galaxies formed and evolved.
- Several hundred million years after the Big Bang is a mysterious and defining moment in the universe. During that period, e first stars gave birth to gas made mostly of hydrogen and helium. These stars died and formed heavier elements scattered throughout the universe, planting the next generation of stars.
- A billion years after the Big Bang, supermassive galaxies and black holes have existed throughout the universe. The universe was also going to ionize until then, transforming it from a place filled with dark and dense primeval gas to a place where light could shine.
- Astronomers want to know what role the first stars and galaxies played in that critical process — and how these early astronomical objects formed.
motivating news: NASA released a stunning image this week showing thousands of galaxies – some of which formed less than a billion years after the Big Bang – as part of JWST’s first five science images.
- The telescope is also designed to connect the elements that formed the first galaxies to understand their evolution.
- “This is how oxygen is formed in our bodies — in stars, in galaxies,” said Jane Rigby, an astrophysicist at NASA’s Goddard Flight Center and an Operations Project Scientist at JWST. We are seeing this process begin.”
How does this work: JWST looks at the universe in infrared (IR) light, giving astronomers access to distant stars and galaxies that emit light that would normally be obscured by cosmic dust.
- As the universe expands, the wavelength of optical light from early galaxies increases and shifts into the infrared spectrum as it moves through space and time. These galaxies are too weak to be seen with the naked eye, but can still be captured by lenses and detectors with sensitive telescopes.
- JWST data will be combined with optical observations from the Hubble Space Telescope, radio data from the Atacama Large Millimeter/ Submillimeter Array (ALMA) and the Very Large Array (VLA), and Chandra X-ray observatories to give scientists a more comprehensive view of the universe.
The big question: Combining this data, astronomers are looking for clues about how the first galaxies ever formed.
One theory proposes early galaxies It generated huge clouds of gas and dust that collapsed on themselves, creating dense clouds that began to coalesce and spin to form galaxies.
- Another theory, backed by Smith’s data, says that smaller clumps of gas and dust merged to form larger galaxies and clusters interconnected by intense gravity.
- Cumulative evidence points to merger as the dominant way galaxies grow, but observations are still sparse and details are unclear.
- “Galaxies are just a chaotic process,” says Chris Carrelli, a radio astronomer at the National Science Foundation Observatory and a researcher in early galaxy formation.
- “[It’s] Much like weather,” similar to cloud research, the goal is to identify biophysical phenomena visible across galaxies and separate them from the details of a single galaxy to understand when and how the universe transformed primordial gas into stars.
Between the lines: About 10 billion years ago, the mass of galaxies appears to have been controlled by gases, not stars, according to data from ALMA. In newer galaxies, the opposite is true.
- This molecular inventory provides clues about how galaxies — and their star-forming activities — have changed over time. Carrelli says that the amount of gas in galaxies has risen and fallen over the course of the universe’s history as the rate at which stars are forming.
Where do you stand: Scientists were able to use JWST to analyze the molecules – including oxygen, neon and hydrogen – that formed one of the galaxies in the deep field image this week as they existed 13.1 billion years ago.
- Spectra is the astronomical equivalent of a DNA sponge. Tweet on Twitter Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics. “What the galaxies have done is code in their light”.
what are you expecting: Comparing the properties of gas in nearby and distant galaxies can help astronomers study how the interstellar medium itself has changed over time.
- “I think we can better understand this evolution in the coming years, especially with the JWST,” says Brian Traces, an astrophysicist and postdoctoral fellow at the Center for Astrophysics.
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