- 3634 - JAMES WEBB - what can it see? The $10 billion James Webb Space Telescope (JWST or Webb) is searching the cosmos to uncover the history of the universe's first galaxies and the formation of stars and planets.
--------------------- 3634 - JAMES WEBB - what can it see?
- The Near-Infrared Spectrograph (NIRSpec) on the Webb Telescope is used to study a region close to the center of our Milky Way galaxy. It can pack more than 200 spectra in a single exposure. Each horizontal stripe represents a spectrum that scientists will be able to analyze to better understand the composition and properties of the gas found between the stars in this region.
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- NIRSpec is designed to disperse infrared light from the distant universe into spectra, astronomical "rainbows" that measure how much light is present at which wavelengths. It reveals the physical properties of observed objects, including their temperature, mass and chemical composition.
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- In multi-object spectroscopy mode, NIRSpec can individually open and close about 250,000 small shutters, all just the width of a human hair, to view some portions of the sky while blocking others. This allows observation of multiple specific targets while reducing interference from others.
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- The missing piece of technology was infrared detectors that would be able to collect the faint light coming from those early stars and galaxies more than 13 billion light-years away. Hubble was built to detect visible and ultraviolet light. These early galaxies do emit visible light, but because of their distance, the wavelength of this light gets stretched into the infrared part of the electromagnetic spectrum by the redshift.
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- In the 1980s, infrared pictures were taken with one detector scanning the sky one pixel at a time. The detectors on JWST have 2000 by 2000 pixels. We have many more infrared pixels on JWST than Hubble had optical pixels when it was launched.
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- The giant mirror will feed the light of stars and galaxies into four cutting edge instruments designed not only to take images, but also to analyze the chemical composition of the near and distant universe.
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- “Spectroscopy” looks at how matter in the universe absorbs light. As different chemical elements absorb light at different wavelengths, astronomers will be able to reconstruct what stars, nebulas, galaxies and planets are made of.
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- These improvements in the resolution of infrared imaging are critical for imaging the furthest reaches of the universe. Where the Hubble Space Telescope, or the recently retired infrared telescope Spitzer, could provide only a rough estimate of an ancient galaxy's age and chemical composition, Webb delivers with precision including the Wide Field Camera 3 installed during the final servicing mission in 2009.
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- When it comes to these distant galaxies, the Wide Field Camera 3 runs out of wavelength. Webb will be able to do that kind of thing, to say exactly that we see this particular galaxy 250 million years after the Big Bang.
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- If we are seeing that material some 500 million years after the Big Bang, it must have been made even earlier by stars we haven't yet seen. Big stars form and die quickly, in only a few million years, so after 500 million years, you may have had lots of generations of massive stars.
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- The early universe had a very different chemical composition from what we see today. It consisted only of hydrogen, helium and a little bit of lithium. All the other chemical elements that we see now, including those that make life possible, were cooked up throughout eons inside those stars, then exploded as supernovae.
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- A lot of the chemical synthesis in the universe is around massive stars when they explode, or low mass stars in their final stages of evolution. It's fascinating to me how we can go from having only three chemical elements to the vast array of diversity we see around us today.
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- The James Webb spectroscopes will be able to probe the chemical kitchens of those early galaxies, seeing what was cooking inside individual stars and what they fertilized the wider cosmos with when they exploded in powerful supernovas.
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- Hubble's strength is imaging the visible universe, Webb's infrared superpowers will enable the telescope to see through dust right into the heart of nebulas, galaxies and star-forming regions that are hidden from Hubble's view.
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- Previous infrared observatories with NASA's Spitzer Space Telescope, were much smaller than Webb and they couldn't see as far as Webb, and when they did, they only glimpsed those star-forming regions in a limited resolution.
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- Previously, we could only see stars about 8 times the mass of the sun but now we should be able to see the formation of stars about as big as the sun and that process has never been observed before.
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- But, it will not all be about far away places. JWST can look at planets like Mars, Jupiter, Saturn, Uranus and Neptune but also into the Kuiper Belt.
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- The Kuiper Belt is a repository of comets, asteroids and other debris that encircles the outer solar system beyond the orbit of Neptune. It's a dark and cold region that is very difficult to explore because these objects reflect very little light.
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- Exoplanets have atmospheres that have various molecules in them. Like carbon dioxide, oxygen and nitrogen.
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- The Near Infrared Camera (NIRCAM) is fitted with extra implements called coronographs, which block out the light of a star to see more clearly what is happening around it. That might involve alien systems of planets, some of which might be habitable, with water and atmosphere that could support life just like Earth.
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- The James Webb Space Telescope will change our view of the universe. NIRCam will be crucial for accomplishing Webb's flagship goal: detecting the light from the earliest stars and galaxies. It's not just a simple infrared camera, but is fitted with some extra implements called coronographs. The coronographs will enable astronomers to block out the light of a star and look at what's happening around it, which makes it great for discovering orbiting exoplanets.
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- NIRSpec is the main tool for cracking the chemistry of the universe. It will split the light coming from the distant universe into spectra, revealing the properties of the observed objects, including their temperature, mass and chemical composition.
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- Because some of these objects are extremely distant and the light coming from them will be extremely faint, the James Webb Space Telescope, despite its giant mirror, will have to stare at them for hundreds of hours. To make those observations more efficient, NIRSPec will be able to observe 100 such distant galaxies at the same time.
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- It basically lets you open little doors and let the light through from one galaxy, but then block off all the light from everything else. But you can open 100 doors at once.
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- The Mid-Infrared Instrument (MIRI)is a combination of a camera and a spectrograph, but unlike the previous two, it observes in the longer wavelengths of the mid-infrared part of the electromagnetic spectrum, which will make it a go-to instrument for everyone looking to study everything from comets and asteroids at the outskirts of the solar system to newly born stars and distant galaxies.
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July 22, 2022 JAMES WEBB - what can it see? 3634
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