Micrometeoroid strikes are an unavoidable aspect of operating any spacecraft. NASA’s James Webb Space Telescope was engineered to withstand continual bombardment from these dust-sized particles moving at extreme velocities, to continue to generate groundbreaking science far into the future.
“We have experienced 14 measurable micrometeoroid hits on our primary mirror, and are averaging one to two per month, as anticipated. The resulting optical errors from all but one of these were well within what we had budgeted and expected when building the observatory,” said Mike Menzel, Webb lead mission systems engineer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “One of these was higher than our expectations and prelaunch models; however, even after this event our current optical performance is still twice as good as our requirements.”
To ensure all parts of the observatory continue to perform at their best, NASA convened a working group of optics and micrometeoroid experts from NASA Goddard‘s Webb team, the telescope’s mirror manufacturer, the Space Telescope Science Institute, and the NASA Meteoroid Environment Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama. After thorough analysis, the team concluded the higher-energy impact observed in May was a rare statistical event both in terms of energy, and in hitting a particularly sensitive location on Webb’s primary mirror. To minimize future impacts of this magnitude, the team has decided that future observations will be planned to face away from what is now known as the ‘micrometeoroid avoidance zone.’
“Micrometeoroids that strike the mirror head on (moving opposite the direction the telescope is moving) have twice the relative velocity and four times the kinetic energy, so avoiding this direction when feasible will help extend the exquisite optical performance for decades,” said Lee Feinberg, Webb optical telescope element manager at NASA Goddard. This does not mean that these areas of the sky cannot be observed, only that observations of those objects will be more safely made at a different time in the year when Webb is in a different location in its orbit. Observations that are time critical, such as solar system targets, will still be done in the micrometeoroid avoidance zone if required. This adjustment to how Webb observations are scheduled will have a long-term statistical benefit.
The team will implement the micrometeoroid avoidance zone starting with Webb’s second year of science, or “Cycle 2.” More information and guidance for Cycle 2 is available on JWST Observer News.
-Thaddeus Cesari, NASA’s Goddard Space Flight Center
Editor’s Note: This post highlights data from Webb science in progress, which has not yet been through the peer-review process.
We spoke with Kristen McQuinn of Rutgers University, one of the lead scientists on Webb Early Release Science (ERS) program 1334, focused on resolved stellar populations. These are large groups of stars – including stars within the dwarf galaxy Wolf–Lundmark–Melotte (WLM) – that are close enough for Webb to differentiate between individual stars, but far enough for Webb to capture a large number of stars at once.
A portion of the dwarf galaxy Wolf–Lundmark–Melotte (WLM) captured by the Spitzer Space Telescope’s Infrared Array Camera (left) and the James Webb Space Telescope’s Near-Infrared Camera (right). The images demonstrate Webb’s remarkable ability to resolve faint stars outside the Milky Way. The Spitzer image shows 3.6-micron light in cyan and 4.5-micron in orange (IRAC1 and IRAC2). The Webb image includes 0.9-micron light shown in blue, 1.5-micron in cyan, 2.5-micron in yellow, and 4.3-micron in red (filters F090W, F150W, F250M, and F430M). Download the full-resolution version from the Space Telescope Science Institute. SCIENCE CREDIT: NASA, ESA, CSA, STScI, and Kristen McQuinn (Rutgers University). IMAGE PROCESSING: Alyssa Pagan (STScI).
So, tell us a bit about this galaxy, WLM. What’s interesting about it?
WLM is a dwarf galaxy in our galactic neighborhood. It’s fairly close to the Milky Way (only about 3 million light-years from Earth), but it’s also relatively isolated. We think WLM hasn’t interacted with other systems, which makes it really nice for testing our theories of galaxy formation and evolution. Many of the other nearby galaxies are intertwined and entangled with the Milky Way, which makes them harder to study.
Another interesting and important thing about WLM is that its gas is similar to the gas that made up galaxies in the early universe. It’s fairly unenriched, chemically speaking. (That is, it’s poor in elements heavier than hydrogen and helium.)
This is because the galaxy has lost many of these elements through something we call galactic winds. Although WLM has been forming stars recently – throughout cosmic time, really – and those stars have been synthesizing new elements, some of the material gets expelled from the galaxy when the massive stars explode. Supernovae can be powerful and energetic enough to push material out of small, low-mass galaxies like WLM.
This makes WLM super interesting in that you can use it to study how stars form and evolve in small galaxies like those in the ancient universe.
You arranged to show this image at a planetarium. How did you feel when you saw the image projected on the dome?
It was just inspiring. It really was incredible. I will never look at these images the same again. Seeing this on the dome, it was like looking up at our own night sky – at the Milky Way – from a dark site. I could imagine that we were standing on a planet in the WLM galaxy and looking up at its night sky.
We can see a myriad of individual stars of different colors, sizes, temperatures, ages, and stages of evolution; interesting clouds of nebular gas within the galaxy; foreground stars with Webb’s diffraction spikes; and background galaxies with neat features like tidal tails. It’s really a gorgeous image.
And, of course, the view is far deeper and better than our eyes could possibly see. Even if you were looking out from a planet in the middle of this galaxy, and even if you could see infrared light, you would need bionic eyes to be able to see what Webb sees.
What are you trying to find out by studying WLM?
The main science focus is to reconstruct the star formation history of this galaxy. Low-mass stars can live for billions of years, which means that some of the stars that we see in WLM today formed in the early universe. By determining the properties of these low-mass stars (like their ages), we can gain insight into what was happening in the very distant past. It’s very complementary to what we learn about the early formation of galaxies by looking at high-redshift systems, where we see the galaxies as they existed when they first formed.
The Early Release Science programs were designed to highlight Webb’s capabilities and help astronomers prepare for future observations. How are you supporting other astronomers with this work?
In a few ways. We’re checking the calibration of the NIRCam instrument itself. We’re checking our stellar evolution models. And we’re developing software to measure star brightnesses.
We already studied this exact same field very carefully with Hubble. Now we’re looking at the near-infrared light with Webb, and we’re using WLM as a sort of standard for comparison (like you would use in a lab) to help us make sure we understand the Webb observations. We want to make sure we’re measuring the stars’ brightnesses really, really accurately and precisely. We also want to make sure that we understand our stellar evolution models in the near-infrared.
Our team is also charged with developing a public software tool to measure the brightness of all the resolved stars in the NIRCam images. This is a non-proprietary tool that everyone will be able to use. We are developing and testing the software, and optimizing the parameters used for measurements. This is a bedrock tool for astronomers around the world. If you want to do anything with resolved stars that are crowded together on the sky, you need a tool like this.
About the Author
Kristen McQuinn is an assistant professor in the Department of Physics and Astronomy at Rutgers University, and co-investigator on Director’s Discretionary Early Release Science program 1334.
The James Webb Space Telescope’s Mid-Infrared Instrument (MIRI) has four observing modes. On Aug. 24, after measuring increased friction in one of the grating wheels used in MIRI’s medium resolution spectrometry (MRS) mode, the Webb team paused science observations using this specific mode. Since then, a team of experts has carried out an in-depth investigation that has reviewed instrument design as well as historical and postlaunch data.
The team concluded the issue is likely caused by increased contact forces between sub-components of the wheel central bearing assembly under certain conditions. Based on this, the team developed and vetted a plan for how to use the affected mechanism during science operations.
An engineering test was executed Wednesday, Nov. 2, that successfully demonstrated predictions for wheel friction. Webb will resume MIRI MRS science observations by Saturday, Nov. 12, starting with a unique opportunity to observe Saturn’s polar regions, just before they become unobservable by Webb for the next 20 years. The team will schedule additional MRS science observations, initially at a limited cadence, following a plan to keep the affected wheel in balance, monitor wheel health, and prepare MIRI MRS for a return to full science operations.
NASA will share a new image or spectrum from the James Webb Space Telescope at least every other week on the mission’s blog. This week, check the blog on Wednesday, Nov. 9 at 11 a.m. EST for a new image highlighting a nearby dwarf galaxy.
In the meantime, learn more about what to expect as Webb observations make their way from raw data to published, peer-reviewed science.
Editor’s Note: This post highlights data from Webb science in progress, which has not yet been through the peer-review process.
NASA’s James Webb Space Telescope was specially designed to detect the faint infrared light from very distant galaxies and give astronomers a glimpse at the early universe. The nature of galaxies during this early period of our universe is not well known nor understood. But with the help of gravitational lensing by a cluster of galaxies in the foreground, faint background galaxies can be magnified and also appear multiple times in different parts of the image.
The massive gravity of galaxy cluster MACS0647 acts as a cosmic lens to bend and magnify light from the more distant MACS0647-JD system. It also triply lensed the JD system, causing its image to appear in three separate locations. These images, which are highlighted with white boxes, are marked JD1, JD2, and JD3; zoomed-in views are shown in the panels at right. In this image from Webb’s Near Infrared Camera (NIRCam) instrument, blue was assigned to wavelengths of 1.15 and 1.5 microns (F115W, F150W), green to wavelengths of 2.0 and 2.77 microns (F200W, F277W) and red to wavelengths of 3.65 and 4.44 microns (F365W, F444W). Download the full-resolution version from the Space Telescope Science Institute. Credits: SCIENCE: NASA, ESA, CSA, STScI, and Tiger Hsiao (Johns Hopkins University) IMAGE PROCESSING: Alyssa Pagan (STScI)
Today, we sit down with three astronomers working on Webb to talk about their latest findings. The team members are Dan Coe of AURA/STScI for the European Space Agency and the Johns Hopkins University; Tiger Hsiao of the Johns Hopkins University; and Rebecca Larson of the University of Texas at Austin. These scientists have been observing the distant galaxy MACS0647-JD with Webb, and they’ve found something interesting.
Dan Coe: I discovered this galaxy MACS0647-JD 10 years ago with the Hubble Space Telescope. At the time, I’d never worked on high redshift galaxies, and then I found this one that was potentially the most distant at redshift 11, about 97 percent of the way back to the big bang. With Hubble, it was just this pale, red dot. We could tell it was really small, just a tiny galaxy in the first 400 million years of the universe. Now we look with Webb, and we’re able to resolve TWO objects! We’re actively discussing whether these are two galaxies or two clumps of stars within a galaxy. We don’t know, but these are the questions that Webb is designed to help us answer.
Tiger Yu-Yang Hsiao: You can also see that the colors between the two objects are so different. One’s bluer; the other one is redder. The blue gas and the red gas have different characteristics. The blue one actually has very young star formation and almost no dust, but the small, red object has more dust inside, and is older. And their stellar masses are also probably different.
It’s really interesting that we see two structures in such a small system. We might be witnessing a galaxy merger in the very early universe. If this is the most distant merger, I will be really ecstatic!
Dan Coe: Due to the gravitational lensing of the massive galaxy cluster MACS0647, it’s lensed into three images: JD1, JD2, and JD3. They’re magnified by factors of eight, five, and two, respectively.
Rebecca Larson: Up to this point, we haven’t really been able to study galaxies in the early universe in great detail. We had only tens of them prior to Webb. Studying them can help us understand how they evolved into the ones like the galaxy we live in today. And also, how the universe evolved throughout time.
I think my favorite part is, for so many new Webb image we get, if you look in the background, there are all these little dots—and those are all galaxies! Every single one of them. It’s amazing the amount of information that we’re getting that we just weren’t able to see before. And this is not a deep field. This is not a long exposure. We haven’t even really tried to use this telescope to look at one spot for a long time. This is just the beginning!
This is a comparison between the Hubble Space Telescope images of MACS0647-JD from 2012 (filter information on Hubblesite.org) and the 2022 images from the James Webb Space Telescope (using the same color assignments as the image above). Note that MACS0647-JD appears as a faint, red dot in the Hubble image, but Webb reveals much more detail. Download the full-resolution version from the Space Telescope Science Institute. Credits: SCIENCE: NASA, ESA, CSA, STScI, and Tiger Hsiao (Johns Hopkins University) IMAGE PROCESSING: Alyssa Pagan (STScI)
About the authors: Dan Coe is an astronomer of AURA/STScI for the European Space Agency and the Johns Hopkins University. Tiger Hsiao is a Ph.D. graduate student at the Johns Hopkins University. Rebecca Larson is a National Science Foundation fellow and Ph.D. graduate student at the University of Texas at Austin. These NIRCam observations of MAC0647-JD are part of the team’s Cycle 1 program GO 1433 (PI Coe). The team is planning more a detailed study of the physical properties of MACS0647-JD with Webb spectroscopy in January 2023. Read the team’s science paper here.
– Ann Jenkins, Principal Science Writer, Office of Public Outreach, Space Telescope Science Institute
NASA will share a new image or spectrum from the James Webb Space Telescope at least every other week on the mission’s blog. This week, check the blog on Wednesday, Oct. 26 at 11 a.m. EDT for a new image highlighting a distant, lensed galaxy and intervening galaxy cluster.
In the meantime, learn more about what to expect as Webb observations make their way from raw data to published, peer-reviewed science.
The latest image from NASA‘s James Webb Space Telescope is a new perspective on the binary star Wolf-Rayet 140, revealing details and structure in a new light. Astronomer Ryan Lau of NSF’s NOIRLab, principal investigator of the Webb Early Release Science program that observed the star, shares his thoughts on the observations.
“On the night that my team’s Early Release Science observations of the dust-forming massive binary star Wolf-Rayet (WR) 140 were taken, I was puzzled by what I saw in the preview images from the Mid-Infrared Instrument (MIRI). There seemed to be a strange-looking diffraction pattern, and I worried that it was a visual effect created by the stars’ extreme brightness. However, as soon as I downloaded the final data I realized that I was not looking at a diffraction pattern, but instead rings of dust surrounding WR 140 – at least 17 of them.
Shells of cosmic dust created by the interaction of binary stars appear like tree rings around Wolf-Rayet 140. The remarkable regularity of the shells’ spacing indicates that they form like clockwork during the stars’ eight-year orbit cycle, when the two members of the binary make their closest approach to one another. In this image, blue, green, and red were assigned to Webb’s Mid-Infrared Instrument (MIRI) data at 7.7, 15, and 21 microns (F770W, F1500W, and F2100W filters, respectively). Credit: NASA, ESA, CSA, STScI, JPL-Caltech. Download/View the full-resolution version and supporting visuals from the Space Telescope Science Institute.
“I was amazed. Although they resemble rings in the image, the true 3D geometry of those semi-circular features is better described as a shell. The shells of dust are formed each time the stars reach a point in their orbit where they are closest to each other and their stellar winds interact. The even spacing between the shells indicates that dust formation events are occurring like clockwork, once in each eight-year orbit. In this case, the 17 shells can be counted like tree rings, showing more than 130 years of dust formation. Our confidence in this interpretation of the image was strengthened by comparing our findings to the geometric dust models by Yinuo Han, a doctoral student at the University of Cambridge, which showed a near-perfect match to our observations.
“One of the biggest surprises was how many shells the telescope was able to detect. The shells furthest from the binary star have traversed over 70,000 times the distance from Earth to the Sun, at speeds of around 6 million miles per hour, through the harsh environment around a WR star—some of the hottest and most luminous stars known. The survival of these distant shells shows that the dust formed by WR binaries like WR 140 will likely survive to enrich the surrounding interstellar environment. However, it wasn’t enough for us to see these dusty shells. We wanted to know their spectroscopic signature and chemical composition. What will they add to the interstellar medium?
“With the Medium-Resolution Spectroscopy (MRS) mode on MIRI, we obtained the first spatially resolved mid-infrared spectra of a dust-forming WR binary in our observation of WR 140, and were able to directly probe the chemical signatures of its dust shells. Broad and prominent features in the spectral lines at 6.4 and 7.7 microns told us that the dust was composed of compounds consistent with Polycyclic Aromatic Hydrocarbons (PAHs). This carbonaceous material plays an important role in the interstellar medium and the formation of stars and planets, but its origin is a long-standing mystery. With the combined results of JWST’s MRS spectra and MIRI imaging, we now have evidence that WR binaries can be an important source of carbon-rich compounds that enrich the interstellar environment of our galaxy, and likely galaxies beyond our own.”
About the author:
Ryan Lau is an Assistant Astronomer at the National Science Foundation’s NOIRLab. His team’s observations of WR 140 are the results of the Director’s Discretionary-Early Release Science program 1349. Learn more about the findings here.
Editor’s Note: This post highlights data from a paper appearing today inNature Astronomy.
NASA will share a new image or spectrum from the James Webb Space Telescope at least every other week on the mission’s blog. This week, check the blog on Wednesday, Oct. 12 at 11 a.m. EDT for a new image highlighting a nebula surrounding a pair of stars.
In the meantime, learn more about what to expect as Webb observations make their way from raw data to published, peer-reviewed science.
Editor’s Note: This post highlights data from Webb science in progress, which has not yet been through the peer-review process. Here, Webb interdisciplinary scientist Rogier Windhorst and his teamdiscuss their observations.
“We got more than we bargained for by combining data from NASA’s James Webb Space Telescope and NASA’s Hubble Space Telescope! Webb’s new data allowed us to trace the light that was emitted by the bright white elliptical galaxy, at left, through the winding spiral galaxy at right – and identify the effects of interstellar dust in the spiral galaxy. This image of galaxy pair VV 191 includes near-infrared light from Webb, and ultraviolet and visible light from Hubble.
Researchers traced light that was emitted by the bright white elliptical galaxy on the left through the spiral galaxy at right. As a result, they were able to identify the effects of interstellar dust in the spiral galaxy. Webb’s near-infrared data also shows us the galaxy’s longer, extremely dusty spiral arms in far more detail, giving them an appearance of overlapping with the central bulge of the bright white elliptical galaxy on the left, though the pair are not interacting. In this image, green, yellow, and red were assigned to Webb’s near-infrared data taken in 0.9, 1.5, and 3.56 microns (F090W, F150W, and F356W respectively). Blue was assigned to two Hubble filters, ultraviolet data taken in 0.34 microns (F336W) and visible light in 0.61 microns (F606W). Read the full description and download the image files by clicking or tapping the image above. Credit: NASA, ESA, CSA, Rogier Windhorst (ASU), William Keel (University of Alabama), Stuart Wyithe (University of Melbourne), JWST PEARLS Team
“Webb’s near-infrared data also show us the galaxy’s longer, extremely dusty spiral arms in far more detail, giving the arms an appearance of overlapping with the central bulge of the bright white elliptical galaxy on the left. Although the two foreground galaxies are relatively close astronomically speaking, they are not actively interacting.
“VV 191 is the latest addition to a small number of galaxies that helps researchers like us directly compare the properties of galactic dust. This target was selected from nearly 2,000 superimposed galaxy pairs identified by Galaxy Zoo citizen science volunteers.
“Understanding where dust is present in galaxies is important, because dust changes the brightness and colors that appear in images of the galaxies. Dust grains are partially responsible for the formation of new stars and planets, so we are always seeking to identify their presence for further studies.
Above the white elliptical galaxy at left, a faint red arc appears in the inset at 10 o’clock. This is a very distant galaxy whose appearance is warped. Its light is bent by the gravity of the elliptical foreground galaxy. Plus, its appearance is duplicated. The stretched red arc is warped where it reappears – as a dot – at 4 o’clock. In this image, green, yellow, and red were assigned to Webb’s near-infrared data taken in 0.9, 1.5, and 3.56 microns (F090W, F150W, and F356W respectively). Blue was assigned to two Hubble filters, ultraviolet data taken in 0.34 microns (F336W) and visible light in 0.61 microns (F606W). Read the full description and download the image files by clicking or tapping the image above. Credit: NASA, ESA, CSA, Rogier Windhorst (ASU), William Keel (University of Alabama), Stuart Wyithe (University of Melbourne), JWST PEARLS Team
“The image holds a second discovery that’s easier to overlook. Examine the white elliptical galaxy at left. A faint red arc appears in the inset at 10 o’clock. This is a very distant galaxy whose light is bent by the gravity of the elliptical foreground galaxy – and its appearance is duplicated. The stretched red arc is warped where it reappears – as a dot – at 4 o’clock. These images of the lensed galaxy are so faint and so red that they went unrecognized in Hubble data, but are unmistakable in Webb’s near-infrared image. Simulations of gravitationally lensed galaxies like this help us reconstruct how much mass is in individual stars, along with how much dark matter is in the core of this galaxy.
“Like many Webb images, this image of VV 191 shows additional galaxies deeper and deeper in the background. Two patchy spirals to the upper left of the elliptical galaxy have similar apparent sizes, but show up in very different colors. One is likely very dusty and the other very far away, but we – or other astronomers – need to obtain data known as spectra to determine which is which.”
About the authors:
Webb interdisciplinary scientist Rogier Windhorst of Arizona State University and his team obtained the data used in this image from early results of the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) JWST Guaranteed Time Observation (GTO) programs, GTO 1176 and 2738. Additional data from Hubble’s STARSMOG snapshot program (SNAP 13695) and GO 15106, were added. Jake Summers, also of Arizona State, performed the pipeline data reduction. The dust analysis was led by William Keel of the University of Alabama, while the Hubble data acquisition was led by Benne Holwerda of the University of Louisville in Kentucky. The detailed gravitational-lensing analysis was conducted by Giovanni Ferrami and Stuart Wyithe, both of the University of Melbourne, Australia and ASTRO 3D, Australia.
NASA will share a new image or spectrum from the James Webb Space Telescope at least every other week on the mission’s blog. This week, check the blog on Wednesday, Oct. 5 at 10 a.m. EDT for a new image highlighting a galaxy pair.
In the meantime, learn more about what to expect as Webb observations make their way from raw data to published, peer-reviewed science.
