- 3770 - EARLIEST GALAXIES - Deep field image of first galaxies: The James Webb Space Telescope lets us see the first galaxies in the universe. The “SMACS 0723” deep field image was taken with only a 12.5-hour exposure. Faint galaxies in this image emitted this light more than 13 billion years ago.
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--------------------- 3770 - EARLIEST GALAXIES - Deep field image
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- These images also raise interesting points about how the expansion of the universe factors into the way we calculate distances at a cosmological scale. Looking back in time might sound like a strange concept, but it's what space researchers do every single day.
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- Our universe is bound by the rules of physics, with one of the best-known "rules" being the speed of light. And when we talk about "light," we're actually referring to all the wavelengths across the electromagnetic spectrum, which travel at 300,000 kilometers per second.
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- Light travels so fast that in our everyday lives it appears to be instantaneous. Even at these break-neck speeds, it still takes some time to travel anywhere across the cosmos.
When you look at the moon, you actually see it as it was 1.3 seconds ago. It's only a tiny peek back in time, but it's still the past. It's the same with sunlight, except the photons which are light particles emitted from the sun's surface travel just over eight minutes before they finally reach Earth.
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- Our galaxy, the Milky Way, spans 100,000 light-years. And the beautiful newborn stars seen in JWST's Carina Nebula image are 7,500 light-years away. In other words, this nebula is seen at a time roughly 2,000 years earlier than when the first ever writing is thought to have been invented in ancient Mesopotamia.
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- Space-based telescopes let us see certain ranges of light that are unable to pass through Earth's dense atmosphere. The Hubble space telescope was designed and optimized to use both ultraviolet (UV) and visible parts of the electromagnetic spectrum.
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- The JWST was designed to use a broad range of infrared light. And this is the reason the JWST can see further back in time than Hubble.
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- Galaxies emit a range of wavelengths on the electromagnetic spectrum, from gamma rays to radio waves, and everything in between. All of these give us important information about the different physics occurring in a galaxy.
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- When galaxies are near us, their light hasn't changed that much since being emitted, and we can probe a vast range of these wavelengths to understand what's happening inside them. When galaxies are extremely far away, we no longer have that luxury. The light from the most distant galaxies, as we see it now, has been stretched to longer and redder wavelengths due to the expansion of the universe.
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- This means some of the light that would have been visible to our eyes when it was first emitted has since lost energy as the universe expanded. It's now in a completely different region of the electromagnetic spectrum. This is the "cosmological redshift".
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- The broad range of infrared wavelengths detectable by JWST allow it to see galaxies Hubble never could. Combine this capability with the JWST's enormous mirror and superb pixel resolution, and you have the most powerful time machine in the known universe.
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- Using the JWST, we will be able to capture extremely distant galaxies as they were only 100 million years after the Big Bang, which happened around 13.8 billion years ago.
What's about to hurt your brain, however, is that those galaxies are not 13.7 billion light-years away. The actual distance to those galaxies today would be 46 billion light-years.
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- This discrepancy is due to the expanding universe. The universe is expending due to something called "dark energy." It's thought to be a universal constant, acting equally in all areas of space-time. The more the universe expands, the greater the effect dark energy has on its expansion. This is why even though the universe is 13.8 billion years old, it's actually about 93 billion light-years across.
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- For the foreseeable future, the JWST will be taking us on a journey through space and time each and every week. You can stay up to date with the latest news as NASA releases it.
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- In clusters of galaxies there is a fraction of stars which wander off into intergalactic space because they are pulled out by huge tidal forces generated between the galaxies in the cluster. The light emitted by these stars is called the intracluster light (ICL) and is extremely faint. Its brightness is less than 1% of the brightness of the darkest sky we can observe from Earth. This is one reason why images taken from space are very valuable for analyzing it.
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- Infrared wavelengths allow us to explore clusters of galaxies in a different way than with visible light. Thanks to its efficiency at infrared wavelengths and the sharpness of the images of the JWST, astronomers have been able to explore the intracluster light from SMACS-J0723.3-7327 with an unprecedented level of detail. The images from the JWST of the center of this cluster are twice as deep as the previous images obtained by the Hubble Space Telescope.
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- These observations not only offer clues about the formation of galaxy clusters, but also about the properties of a mysterious component of our universe: dark matter. The stars which emit the intracluster light follow the gravitational field of the cluster, which makes this light an excellent tracer of the distribution of the dark matter in these structures.
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- The JWST will let us characterize the distribution of the dark matter in these enormous structures with unprecedented precision, and throw light on its basic nature.
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December 4, 2022 EARLIEST GALAXIES - Deep field image 3770
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