You can see Where JWST Took a Direct hit From a Micrometeorite on one of its Mirrors
The world is still reeling from the release of the James Webb Space Telescope‘s (JWST) first images. These provided a comprehensive overview of the kind of science operations that Webb will conduct over its 20-year mission. They included the most sensitive and detailed look at some iconic astronomical objects, spectra from an exoplanet atmosphere, and a deep field view of some of the most distant galaxies in the Universe. Since their release, we’ve also been treated to glimpses of objects in the Solar System captured by Webb‘s infrared instruments.
Meanwhile, the JWST collaboration released a full report titled titled “Characterization of JWST science performance from commissioning,” in which they examined everything Webb has accomplished so far and what they anticipate throughout the mission. This paper recently appeared online and covers everything from the telescope’s navigation and pointing to the performance of its many instruments. An interesting tidbit, which was not previously released, is how Webb suffered a series of micrometeoroid impacts, one of which caused “uncorrectable change” in one mirror segment.
The team behind this study included researchers from the three participating space agencies – NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA) – and from the mission’s many partner agencies. These include the Space Telescope Science Institute (STScI), the Niels Bohr Institute, the Max-Planck-Institut für Astronomie (MPIA), the UK Astronomy Technology Centre (UK ATC), the National Research Council Canada (NRCC), the Instituto Nacional de Técnica Aeroespacial (INTA), the Centro de Astrobiología (CAB), and many aerospace companies, universities, research institutes, and agencies worldwide.
The main components of the JWST’s primary mirror. Credit: NASA/STScI
The paper they compiled assesses the JWST performance during the six-month commissioning period before it entered service on July 12th, 2022. This consisted of characterizing the observatory’s on-orbit performance, the JWST’s design and architecture, and the pre-launch predicted performance. These were then compared to the performance of the spacecraft, telescopes, science instruments, and ground system. Section 4 of the Report, Optical Performance, addresses how Webb’s various instruments functioned during the commissioning period.
The JWST’s primary mirror consists of eighteen hexagonal segments arranged in a honeycomb configuration. Each segment is composed of gold-plated beryllium, and all are aligned to ensure the highest resolution and sensitivity possible. The overall performance is measured in terms of Wavefront Error (WFE), which refers to how light collected by the telescope’s mirrors deviates from the expected wavelength of light. The overall extent is determined by calculating the collected light’s deviation from the Root-Mean-Square (RMS) error – the spherical average of the entire wavefront.
This is expressed mathematically using the units of the particular wavelength, measured in nanometers (nm) when dealing with Infrared wavelengths. Section 4.7 addresses micrometeoroid impacts and their potential effect on Webb’s long-term optical performance. The assessment begins by reminding readers that any spacecraft will inevitably encounter micrometeoroids, then lists how several impacts were expected during the commissioning period:
“During commissioning, wavefront sensing recorded six localized surface deformations on the primary mirror that are attributed to impact by micrometeoroids. These occurred at a rate (roughly one per month) consistent with pre-launch expectations. Each micrometeoroid caused degradation in the wavefront of the impacted mirror segment, as measured during regular wavefront sensing. Some of the resulting wavefront degradation is correctable through regular wavefront control; some of it comprises high spatial frequency terms that cannot be corrected.”
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Michael Lanza of The Big Outside above Macon Lake and Washakie Lake on the Washakie Pass Trail in the Wind River Range, Wyoming.
” data-image-caption=”Me above Macon Lake and Washakie Lake on the Washakie Pass Trail in the Wind River Range, Wyoming; and in Death Hollow in southern Utah (lead photo, above).
” data-medium-file=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2022/11/Wind9-53-Me-above-Macon-Lake-and-Washakie-Lake-on-the-Washakie-Pass-Trail-in-the-Wind-River-Range-WY.jpg?fit=300%2C200&ssl=1″ data-large-file=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2022/11/Wind9-53-Me-above-Macon-Lake-and-Washakie-Lake-on-the-Washakie-Pass-Trail-in-the-Wind-River-Range-WY.jpg?fit=900%2C600&ssl=1″ src=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2022/11/Wind9-53-Me-above-Macon-Lake-and-Washakie-Lake-on-the-Washakie-Pass-Trail-in-the-Wind-River-Range-WY.jpg?resize=900%2C600&ssl=1″ alt=”Michael Lanza of The Big Outside above Macon Lake and Washakie Lake on the Washakie Pass Trail in the Wind River Range, Wyoming.” class=”wp-image-61100″ srcset=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2022/11/Wind9-53-Me-above-Macon-Lake-and-Washakie-Lake-on-the-Washakie-Pass-Trail-in-the-Wind-River-Range-WY.jpg?resize=1024%2C683&ssl=1 1024w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2022/11/Wind9-53-Me-above-Macon-Lake-and-Washakie-Lake-on-the-Washakie-Pass-Trail-in-the-Wind-River-Range-WY.jpg?resize=300%2C200&ssl=1 300w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2022/11/Wind9-53-Me-above-Macon-Lake-and-Washakie-Lake-on-the-Washakie-Pass-Trail-in-the-Wind-River-Range-WY.jpg?resize=768%2C512&ssl=1 768w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2022/11/Wind9-53-Me-above-Macon-Lake-and-Washakie-Lake-on-the-Washakie-Pass-Trail-in-the-Wind-River-Range-WY.jpg?resize=150%2C100&ssl=1 150w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2022/11/Wind9-53-Me-above-Macon-Lake-and-Washakie-Lake-on-the-Washakie-Pass-Trail-in-the-Wind-River-Range-WY.jpg?w=1200&ssl=1 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />Me above Macon Lake and Washakie Lake on the Washakie Pass Trail in the Wind River Range, Wyoming; and in Death Hollow in southern Utah (lead photo, above).
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The Early Universe Had No Problem Making Barred Spiral Galaxies
Spiral galaxies like the Milky Way are like cosmic snowflakes—no two are exactly alike. For many years, astronomers thought spirals couldn’t exist until the universe was about half its present age. Now, a newly discovered galaxy in the early Universe is challenging that idea.
CEERS-2112 is an early “cosmic snowflake” with spiral arms and a bar across its middle. The amazing thing is that it’s showing this structure when the Universe was only 2 billion years old. That’s about five billion years earlier than astronomers expected something like that to exist. The fact that a perfectly formed spiral exists so early tells us that our ideas about galaxy formation in early cosmic history need some re-tuning.
Surveying the Early Universe
This galaxy showed up in a survey done by the JWST called “Cosmic Evolution Early Release Science” (CEERS). It uses JWST imaging and spectroscopy to do a survey of the early Universe to find the earliest galaxy. The analysis of the CEERS-2112 galaxy was done by an international team led by astronomer Luca Constantin of the Centro de Astrobiología in Spain.
CEERS results should show astronomers the early populations of galaxies at high redshifts (distances). They will also help them estimate related star-formation conditions and black hole growth. Finally, the work should give some insight into the formation of galaxy disks and bulges. Essentially, CEERS data should add to our store of knowledge about first light and reionization (which occurred after the Big Bang) and explain the formation and evolution of early galaxies.
Early deep-field images of very distant galaxies show shreds of galaxies and irregular clumps of stars in the early Universe. That was evident in some of the first Hubble Deep-Field images. The most distant ones in the images looked more blobby and indistinct. And, some of them appeared to be colliding, which fits into the collisional model of galaxy formation.
This view of nearly 10,000 galaxies is called the Hubble Ultra Deep Field. It shows some galaxies in the early Universe, (which appear as red blobs). Credit: NASA/ESA/HUDF
Forming Galaxies in the Early Universe
Prior to the Hubble and JWST eras, astronomers really felt that it would take a long time to form spiral galaxies. They often describe a hierarchical model of galaxy formation. That’s where smaller clumpy galaxies collide to form larger ones. Over time, those objects begin to develop structures like spiral arms and bars.
“In such galaxies, bars can form spontaneously due to instabilities in the spiral structure or gravitational effects from a neighboring galaxy,” according to astronomer and team member Alexander de la Vega. He is a post-doctoral researcher currently at the University of California Riverside. “In the past, when the Universe was very young, galaxies were unstable and chaotic. It was thought that bars could not form or last long in galaxies in the early universe.”
The spiral arms are likely the result of density waves moving through the galaxy. The bars also form from density waves radiating out from the center. That compresses material in the arms and bars, leading to bursts of star formation. That could explain why these regions in galaxies seem brighter, with their populations of hot young stars. All of this takes time to accomplish. That’s why astronomers suggested that it would take about half the age of the Universe to form spiral galaxies.
CEERS-2112 is Part of the Early Universe
CEERS-2112 upends the discussion about spiral formation, according to de la Vega. “Finding CEERS-2112 shows that galaxies in the early Universe could be as ordered as the Milky Way,” he said. “This is surprising because galaxies were much more chaotic in the early Universe and very few had similar structures to the Milky Way.”
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Apollo Samples Contain Hydrogen Hurled from the Sun
According to the U.S. National Academies of Sciences, Engineering, and Medicine, men should drink 3.7litres of water a day and women 2.7litres. Now imagine a crew of three heading to the Moon for a 3 week trip, that’s something of the order of 189 litres of water, that’s about 189 kilograms! Assuming you have to carry all the water rather than recycle some of it longer trips into space with more people are going to be logistically challenging for water carriage alone. Researchers from the U.S. Naval Research Laboratory (NRL) have discovered lunar rocks with hydrogen in them which, when combined with lunar oxygen provide a possibly supply for future explorers.
A total of 382 kilograms of rock was brought back from the Moon by the Apollo program (I weigh about 80kg so that’s almost five of me in weight – and its all muscle I promise!) Some of the samples were immediately studied while others were sealed for future research hoping that future instrumentation would be more sensitive.
A research team from NRL, led by Katherine D. Burgess and team members Brittany A. Cymes and Rhonda M. Stroud, have recently announced their findings whilst studying some of the lunar rock. They wanted to understand the source of water on the Moon and to understand its formation. Future lunar exploration especially permanent lunar bases will rely heavily upon existing lunar resources. The paper articulates “Effective use of the resource depends on developing an understanding of where and how within the regolith the water is formed and retained”.
Buzz Aldrin’s footprint in the lunar regolith – the soft powdery material found over the surface of the Moon (Credit – NASA)
Transmission electron microscopy was used as part of the study to explore lunar sample 79221. The technique utilises a particle beam of electrons to visualise specimens and generate a highly magnified image. In particular, the team looked at grains of the minerals apatite and merrillite and discovered signs of ‘space’ weathering due to the solar wind. The solar wind is a stream of charged particles that rush outward from the Sun at speeds of up to 1.6 million km per hour!
They found hydrogen signatures in samples in vesicles – small holes left behind after lava cools. The discovery confirms that solar wind is being trapped in detectable quantities proving a potential reservoir that could be accessible to future explorers.
Hydrogen itself is a tremendously useful resource and if that can be mined from the lunar surface material it can aide many aspects of exploration. The real buzz around the discovery is that it may finally resolve the mystery about the origins of lunar water and that it might well be the result of chemical interactions between the solar wind and lunar rocks. If we can understand the origins of the lunar water – and we may finally be close to that now – then we can be sure we use it effectively to reach out further into the Solar System.
Source : Hydrogen detected in lunar samples, points to resource availability for space exploration
The post Apollo Samples Contain Hydrogen Hurled from the Sun appeared first on Universe Today.
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