Developed by NASA, the James Webb Space Telescope (JWST) is a space observatory with significant contributions from the European Space Agency (ESA) and the Canadian Space Agency (CSA). It is the successor to the Hubble Space Telescope and is designed to study the formation and evolution of galaxies, stars, and planets.
The JWST has several unique capabilities that allow it to study the early universe, including a large mirror that is 6.5 meters in diameter and a spectrograph that can measure the distances and physical properties of distant objects. These capabilities have enabled astronomers to find three of the earliest galaxies ever discovered, which existed less than 400 million years after the Big Bang.
The discovery of these ancient galaxies is an important step in understanding the early universe and how galaxies formed and evolved. The JWST will continue to make observations and provide valuable insights into the origins and evolution of the universe.
New Space Observations
As reported by Forbes, the spectroscopic observations of the three infant galaxies were obtained using the JWST's spectrograph, which is a device that breaks the light into its wavelengths, or colors, and measures their intensities. This allows astronomers to identify the chemical composition and other physical properties of distant objects.
It was important to confirm that these galaxies indeed belong to the early universe. Nearby galaxies can appear as very distant galaxies, said astronomer and co-author Emma Curtis-Lake from the University of Hertfordshire in the United Kingdom. Seeing the spectrum of these galaxies as we hoped, confirming their true distance at the edge of our observable universe, further than what the Hubble Space Telescope can see, is a significant achievement for the mission.
The characteristic and distinctive patterns in the light fingerprints of the infant galaxies were used to confirm that they existed in the early universe, rather than being closer galaxies that were masquerading as distant ones. This was an important step in the confirmation process, as it allowed astronomers to accurately measure the distances and physical properties of the galaxies.
The observations discussed were made by a collaboration of scientists who worked on two instruments aboard the James Webb Space Telescope (Webb): the Near-Infrared Camera (NIRCam) and the Near-Infrared Spectrograph (NIRSpec). The investigation of faint and early galaxies was the main motivation behind the development of these instruments.
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JADES Program
In 2015, the teams behind these instruments came together to propose the JWST Advanced Deep Extragalactic Survey (JADES), an ambitious program that was allocated approximately one month of observing time on the telescope over two years. JADES is an international collaboration involving more than 80 astronomers from 10 countries. These new results are the product of the collaboration between the NIRCam and NIRSpec teams, according to co-author Marcia Rieke, the NIRCam principal investigator at the University of Arizona in Tucson.
The first phase of JADES observations focused on the area around the Hubble Space Telescope's Ultra Deep Field, which has been studied by many telescopes over the last 20 years. The Webb telescope added its unique view, providing some of the faintest and sharpest images yet obtained of this region.
The JADES program began with the NIRCam instrument, which observed the field in nine different infrared colors over 10 days, producing detailed images of the area. The region covered by these images is 15 times larger than the deepest infrared images produced by the Hubble Space Telescope, but they are even sharper and deeper at these wavelengths. The images are only the size of a human when viewed from a mile away, but they contain nearly 100,000 galaxies, each caught at a different stage in their history billions of years ago.
NIRCam Images
From the images produced by NIRCam, the JADES team was able to identify early universe galaxies by their distinctive multi-wavelength colors. The expansion of the universe stretches the wavelength of light, and the light from these very young galaxies has been stretched by a factor of up to 14.
Astronomers search for faint galaxies that are visible in the infrared but whose light abruptly cuts off at a certain wavelength. The location of this cutoff in each galaxy's spectrum is shifted by the expansion of the universe. The JADES team looked for these distinctive signatures in the Webb images.
They then used the NIRSpec instrument to collect light from 250 faint galaxies over three days, totaling 28 hours of data collection. This allowed them to study the patterns in the spectrum of each galaxy, which provided a precise measurement of each galaxy's redshift and revealed the properties of the gas and stars in these galaxies. Four of the galaxies studied were particularly interesting, as they were found to be at an unusually early epoch.
The outcomes delivered spectroscopic confirmation that those four galaxies lie at redshifts beyond 10, including two at redshift 13. This corresponds to a time when the universe was about 330 million years old, setting a new record in the search for distant galaxies. These galaxies are extremely faint because of their great distance from us, but thanks to the sensitivity of Webb, astronomers can now study their properties in detail.
Launched on October 31, 2021, and is currently in orbit around the Sun, it is named after James Webb, the second administrator of NASA and the person who oversaw the Apollo program that put the first humans on the Moon.
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