Galaxies may have formed earlier and faster than previously thought
The James Webb Space Telescope lives up to its promise as a return machine. The impressively sensitive observatory finds and confirms galaxies that are more distant, and therefore existed earlier in the universe’s history, than any seen before.
The telescope, also known as JWST, has confirmed the extraordinary distance to four galaxies, one of which set a cosmic distance record by shining about 13.475 billion years ago, astronomers announced on December 12 at a conference First Science Results from JWST . Dozens of other galaxies may have been spotted because they were only 550 million years or less after the Big Bang, meaning light from these galaxies traveled at least 13.1 billion years before reaching the telescope.
Taken together, the new observations suggest that galaxies formed earlier and faster than previously thought. “We are entering a new era,” says astronomer Swara Ravindranath of the Space Telescope Science Institute in Baltimore.
This new era happened in part thanks to JWST’s ability to see very faint infrared light. For the most distant objects, such as the first stars and galaxies, their visible light is stretched by the universe’s relentless expansion into longer infrared wavelengths, invisible to the human eye and some earlier space telescopes. But now measurements that were not long ago impossible are suddenly easy with JWST, the researchers say.
“JWST is the most powerful infrared telescope ever built,” astrophysicist Jane Rigby told the conference. Rigby, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, is a JWST project scientist. “In almost every area, scientific results are better than expected.”
Even in the first image published in July, astronomers noticed galaxies whose light originated 13 billion years ago or more But these distances were approximate. To accurately measure distances, astronomers need spectra, measurements of the amount of light emitted by galaxies at many wavelengths. These measurements are slower and more difficult to perform than imaging.
“With this amazing telescope, we are now getting spectra … for hundreds of galaxies at once,” said astronomer Emma Curtis-Lake of the University of Hertfordshire in England.
Including the four oldest galaxies ever seen , some of which existed less than 400 million years after the Big Bang, Curtis-Lake and colleagues reported at the meeting and in a paper submitted Dec. 8 to arXiv.org. The team spotted these record holders in a section of the sky that once explored the Hubble Space Telescope in search of extremely distant galaxies.
Previous distance record holder existed between 13.3 billion and 13.4 billion years ago, or about 400 million years after the Big Bang. JWST confirmed the distance to this galaxy and returned with three others whose light originates 325 million years after the Big Bang.
Galaxies are also surprisingly pristine, chemically speaking, with no elements heavier than hydrogen and helium.
“We don’t see that in the modern universe,” says Ravindranath, who was not involved in the new discovery. This could mean that few of the galaxy’s stars died in supernova explosions that spread heavy elements throughout the universe, suggesting that the galaxy’s original stars were not extremely massive.
In another part of the sky, JWST observed 26 galaxies which may have existed about 550 million years or earlier after the Big Bang, astronomer Steven Finkelstein and colleagues reported at the meeting and in a paper submitted Nov. 10 to arXiv.org.
“On an emotional, intuitive level, looking at these images is overwhelming,” said Finkelstein of the University of Texas at Austin.
As the researchers reported on December 1 Astrophysical Journal Letters the first of them that was opened, called the Maisie Galaxy on honor of Finkelstein’s daughter, arose only 380 million years after the Big Bang. The most distant galaxy in the team’s study may lie 130 million years earlier than Macy. The distances to these galaxies have yet to be confirmed by spectra, but the team expects to have that data in the next few weeks.
And the distant galaxies that lie behind a massive galaxy cluster called Abell 2744 are also more numerous and more distant than expected, astrophysicist Guido Roberts-Borsani of the University of California, Los Angeles told the meeting.
Before JWST observed the cluster, astronomers predicted that it should reveal virtually zero galaxies 13.2 billion years ago. “But we found two,” said Roberts-Borsani, who reported the results at the meeting. “So something’s a little weird.” This could mean that galaxies are forming earlier and faster than previously thought, he said, although it could also mean that JWST was just looking at a particularly galaxy-rich patch of sky.
All of these new galaxies are exciting because they could be responsible for that the universe becomes transparent to visible light , a process astronomers call reionization. Before the first stars erupted, the universe was filled with a hot, thick soup of particles. The first stars and galaxies bathed the universe in ultraviolet light, stripping electrons from hydrogen atoms and allowing the light to pass through until it reached JWST.
The new data, Roberts-Borsani said, “gives us constraints on when this process started, when it ended, and which galaxies were responsible for this process.”
