Members Can Post Anonymously On This Site
Far-Flung Supernovae Shed Light on Dark Universe
-
Similar Topics
-
By NASA
Research Astrophysicist and Roman’s Deputy Wide Field Instrument Scientist – Goddard Space Flight Center
From a young age, Ami Choi — now a research astrophysicist at NASA — was drawn to the vast and mysterious. By the fifth grade, she had narrowed her sights to two career paths: marine biology or astrophysics.
“I’ve always been interested in exploring big unknown realms, and things that aren’t quite tangible,” Choi said. That curiosity has served her all throughout her career.
In addition to conducting research, Ami Choi shares science with the public at various outreach events, including tours at NASA’s Goddard Space Flight Center in Greenbelt, Md. This photo captures one tour stop, outside the largest clean room at Goddard.Credit: NASA/Travis Wohlrab As a student at University Laboratory High School in Urbana, Illinois, Choi gravitated toward astrophysics and was fascinated by things like black holes. She studied physics as an undergraduate at the University of Chicago, though she says math and physics didn’t necessarily come easily to her.
“I wasn’t very good at it initially, but I really liked the challenge so I stuck with it,” Choi said.
Early opportunities to do research played a pivotal role in guiding her career. As an undergraduate, Choi worked on everything from interacting galaxies to the stuff in between stars in our galaxy, called the interstellar medium. She learned how to code, interpret data, and do spectroscopy, which involves splitting light from cosmic objects into a rainbow of colors to learn about things like their composition.
After college, Choi read an article about physicist Janet Conrad’s neutrino work at Fermilab and was so inspired by Conrad’s enthusiasm and inclusivity that she cold-emailed her to see if there were any positions available in her group.
On October 14, 2023, Ami took a break from a thermal vacuum shift to snap a selfie with a partial eclipse. She was visiting BAE, Inc. in Boulder, Co., where the primary instrument for NASA’s Nancy Grace Roman Space Telescope was undergoing testing. Credit: Courtesy of Ami Choi “That one email led to a year at Fermilab working on neutrino physics,” Choi said.
She went on to earn a doctorate at the University of California, Davis, where she studied weak gravitational lensing — the subtle warping of light by gravity — and used it to explore dark matter, dark energy, and the large-scale structure of the universe.
Her postdoctoral work took Choi first to the University of Edinburgh in Scotland, where she contributed to the Kilo-Degree Survey, and later to The Ohio State University, where she became deeply involved in DES (the Dark Energy Survey) and helped lay the groundwork for the Nancy Grace Roman Space Telescope — NASA’s next flagship astrophysics mission.
“One of my proudest moments came in 2021, when the DES released its third-year cosmology results,” Choi said. “It was a massive team effort conducted during a global pandemic, and I had helped lead as a co-convener of the weak lensing team.”
Choi regularly presents information about NASA’s Nancy Grace Roman Space Telescope to fellow scientists and the public. Here, she gives a Hyperwall talk at an AAS (American Astronomical Society) meeting.Credit: Courtesy of Ami Choi After a one-year stint at the California Institute of Technology in Pasadena, where Choi worked on SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer)—an observatory that’s surveying stars and galaxies—she became a research astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. She also serves as the deputy Wide Field Instrument scientist for Roman. Choi operates at the intersection of engineering, calibration, and cosmology, helping translate ground-based testing into flight-ready components that will help Roman reveal large swaths of the universe in high resolution.
“I’m very excited for Roman’s commissioning phase — the first 90 days when the spacecraft will begin transmitting data from orbit,” Choi said.
Choi, photographed here in Death Valley, finds joy in the natural world outside of work. She cycles, hikes, and tends a small vegetable garden with a friend from grad school. Credit: Insook Choi (used with permission) She’s especially drawn to so-called systematics, which are effects that can alter the signals scientists are trying to measure. “People sometimes think of systematics as nuisances, but they’re often telling us something deeply interesting about either the physics of something like a detector or the universe itself,” Choi said. “There’s always something more going on under the surface.”
While she’s eager to learn more about things like dark energy, Choi is also looking forward to seeing all the other ways our understanding of the universe grows. “It’s more than just an end goal,” she said. “It’s about everything we learn along the way. Every challenge we overcome, every detail we uncover, is an important discovery too.”
For those who hope to follow a similar path, Choi encourages staying curious, being persistent, and taking opportunities to get involved in research. And don’t let the tricky subjects scare you away! “You don’t have to be perfect at math or physics right away,” she said. “What matters most is a deep curiosity and the tenacity to keep pushing through.”
By Ashley Balzer
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Share
Details
Last Updated Sep 09, 2025 EditorAshley BalzerLocationGoddard Space Flight Center Related Terms
Goddard Space Flight Center Nancy Grace Roman Space Telescope People of Goddard View the full article
-
By NASA
6 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
This artist’s concept shows a brown dwarf — an object larger than a planet but not massive enough to kickstart fusion in its core like a star. Brown dwarfs are hot when they form and may glow like this one, but over time they get closer in temperature to gas giant planets like Jupiter. NOIRLab/NSF/AURA/R. Proctor An unusual cosmic object is helping scientists better understand the chemistry hidden deep in Jupiter and Saturn’s atmospheres — and potentially those of exoplanets.
Why has silicon, one of the most common elements in the universe, gone largely undetected in the atmospheres of Jupiter, Saturn, and gas planets like them orbiting other stars? A new study using observations from NASA’s James Webb Space Telescope sheds light on this question by focusing on a peculiar object that astronomers discovered by chance in 2020 and called “The Accident.”
The results were published on Sept. 4 in the journal Nature.
As shown in this graphic, brown dwarfs can be far more massive than even large gas planets like Jupiter and Saturn. However, they tend to lack the mass that kickstarts nuclear fusion in the cores of stars, causing them to shine. NASA/JPL-Caltech The Accident is a brown dwarf, a ball of gas that’s not quite a planet and not quite a star. Even among its already hard-to-classify peers, The Accident has a perplexing mix of physical features, some of which have been previously seen in only young brown dwarfs and others seen only in ancient ones. Because of those features, it slipped past typical detection methods before being discovered five years ago by a citizen scientist participating in Backyard Worlds: Planet 9. The program lets people around the globe look for new discoveries in data from NASA’s now-retired NEOWISE (Near-Earth Object Wide-field Infrared Survey Explorer), which was managed by NASA’s Jet Propulsion Laboratory in Southern California.
The brown dwarf nicknamed “The Accident” can be seen moving in the bottom left corner of this video, which shows data from NASA’s now-retired NEOWISE (Near-Earth Object Wide-Field Infrared Survey Explorer), launched in 2009 with the moniker WISE. NASA/JPL-Caltech/Dan Caselden The Accident is so faint and odd that researchers needed NASA’s most powerful space observatory, Webb, to study its atmosphere. Among several surprises, they found evidence of a molecule they couldn’t initially identify. It turned out to be a simple silicon molecule called silane (SiH4). Researchers have long expected — but been unable — to find silane not only in our solar system’s gas giants, but also in the thousands of atmospheres belonging to brown dwarfs and to the gas giants orbiting other stars. The Accident is the first such object where this molecule has been identified.
Scientists are fairly confident that silicon exists in Jupiter and Saturn’s atmospheres but that it is hidden. Bound to oxygen, silicon forms oxides such as quartz that can seed clouds on hot gas giants, bearing a resemblance to dust storms on Earth. On cooler gas giants like Jupiter and Saturn, these types of clouds would sink far beneath lighter layers of water vapor and ammonia clouds, until any silicon-containing molecules are deep in the atmosphere, invisible even to the spacecraft that have studied those two planets up close.
Some researchers have also posited that lighter molecules of silicon, like silane, should be found higher up in these atmospheric layers, left behind like traces of flour on a baker’s table. That such molecules haven’t appeared anywhere except in a single, peculiar brown dwarf suggests something about the chemistry occurring in these environments.
“Sometimes it’s the extreme objects that help us understand what’s happening in the average ones,” said Faherty, a researcher at the American Museum of Natural History in New York City, and lead author on the new study.
Happy accident
Located about 50 light-years from Earth, The Accident likely formed 10 billion to 12 billion years ago, making it one of the oldest brown dwarfs ever discovered. The universe is about 14 billion years old, and at the time that The Accident developed, the cosmos contained mostly hydrogen and helium, with trace amounts of other elements, including silicon. Over eons, elements like carbon, nitrogen, and oxygen forged in the cores of stars, so planets and stars that formed more recently possess more of those elements.
Webb’s observations of The Accident confirm that silane can form in brown dwarf and planetary atmospheres. The fact that silane seems to be missing in other brown dwarfs and gas giant planets suggests that when oxygen is available, it bonds with silicon at such a high rate and so easily, virtually no silicon is left over to bond with hydrogen and form silane.
So why is silane in The Accident? The study authors surmise it is because far less oxygen was present in the universe when the ancient brown dwarf formed, resulting in less oxygen in its atmosphere to gobble up all the silicon. The available silicon would have bonded with hydrogen instead, resulting in silane.
“We weren’t looking to solve a mystery about Jupiter and Saturn with these observations,” said JPL’s Peter Eisenhardt, project scientist for the WISE (Wide-field Infrared Survey Explorer) mission, which was later repurposed as NEOWISE. “A brown dwarf is a ball of gas like a star, but without an internal fusion reactor, it gets cooler and cooler, with an atmosphere like that of gas giant planets. We wanted to see why this brown dwarf is so odd, but we weren’t expecting silane. The universe continues to surprise us.”
Brown dwarfs are often easier to study than gas giant exoplanets because the light from a faraway planet is typically drowned out by the star it orbits, while brown dwarfs generally fly solo. And the lessons learned from these objects extend to all kinds of planets, including ones outside our solar system that might feature potential signs of habitability.
“To be clear, we’re not finding life on brown dwarfs,” said Faherty. “But at a high level, by studying all of this variety and complexity in planetary atmospheres, we’re setting up the scientists who are one day going to have to do this kind of chemical analysis for rocky, potentially Earth-like planets. It might not specifically involve silicon, but they’re going to get data that is complicated and confusing and doesn’t fit their models, just like we are. They’ll have to parse all those complexities if they want to answer those big questions.”
More about WISE, Webb
A division of Caltech, JPL managed and operated WISE for NASA’s Science Mission Directorate. The mission was selected competitively under NASA’s Explorers Program managed by the agency’s Goddard Space Flight Center in Greenbelt, Maryland. The NEOWISE mission was a project of JPL and the University of Arizona in Tucson, supported by NASA’s Planetary Defense Coordination Office.
For more information about WISE, go to:
https://www.nasa.gov/mission_pages/WISE/main/index.html
The James Webb Space Telescope is the world’s premier space science observatory, and an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
To learn more about Webb, visit:
https://science.nasa.gov/webb
News Media Contacts
Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov
Christine Pulliam
Space Telescope Science Institute, Baltimore, Md.
cpulliam@stsci.edi
2025-113
Share
Details
Last Updated Sep 09, 2025 Related Terms
James Webb Space Telescope (JWST) Brown Dwarfs Exoplanets The Search for Life Explore More
6 min read NASA Webb Looks at Earth-Sized, Habitable-Zone Exoplanet TRAPPIST-1 e
Scientists are in the midst of observing the exoplanet TRAPPIST-1 e with NASA’s James Webb…
Article 1 day ago 5 min read Glittering Glimpse of Star Birth From NASA’s Webb Telescope
This is a sparkling scene of star birth captured by NASA’s James Webb Space Telescope.…
Article 5 days ago 5 min read Astronomers Map Stellar ‘Polka Dots’ Using NASA’s TESS, Kepler
Scientists have devised a new method for mapping the spottiness of distant stars by using…
Article 2 weeks ago Keep Exploring Discover Related Topics
Missions
Humans in Space
Climate Change
Solar System
View the full article
-
By NASA
Explore This Section Science Uncategorized NASA eClips STEM Student… Overview Learning Resources Science Activation Teams SME Map Opportunities More Science Activation Stories Citizen Science 3 min read
NASA eClips STEM Student Ambassadors Light Up CNU’s 2025 STEM Community Day
More than 2,000 curious visitors from Newport News and the surrounding Hampton Roads region of Virginia flocked to Christopher Newport University (CNU) on May 31, 2025 for their annual STEM (Science, Technology, Engineering, & Mathematics) Community Day, and the NASA eClips team from the National Institute of Aerospace’s Center for Integrative STEM Education (NIA-CISE) made sure every one of them left with their eyes—and imaginations—fixed on the Sun.
At the heart of the NASA eClips exhibit were NIA’s STEM Student Ambassadors—a team of carefully selected high school students from the Tidewater region of Virginia who underwent extensive training with NASA eClips educators during the summer of 2024. These bright, enthusiastic young leaders are passionate about communicating about and advocating for STEM. The STEM Student Ambassador program is made possible through a Coastal Virginia STEM Hub grant from the Virginia General Assembly and is already having an impact.
Throughout the day, the Ambassadors engaged learners of all ages with two creative, hands-on experiences that connected STEM and the arts:
Chalk Corona – Using black construction paper and vibrant chalk, participants recreated the Sun’s corona—the super-hot, gaseous “crown” that’s visible during a total solar eclipse. While they shaded and smudged, the Ambassadors explained why the corona is so important to solar research and handed out certified solar viewers for safe Sun-watching back home. Pastel Auroras – Visitors also discovered how solar wind, storms, and coronal mass ejections (aka Sun “sneezes”) spark Earth’s dazzling auroras. Guided by the Ambassadors, budding artists layered pastels to capture swirling curtains of light, tying recent mid-Atlantic aurora sightings to real-time space weather. Throughout the day, the Ambassadors’ energy was contagious, turning complex heliophysics into hands-on fun and opening eyes to the opportunities and careers that await in STEM. Judging by the smiles—and the dusting of chalk and pastels—NASA eClips’ presence was, quite literally, the “crowning” touch on an unforgettable community celebration of STEM.
The NASA eClips project provides educators with standards-based videos, activities, and lessons to increase STEM literacy through the lens of NASA. It is supported by NASA under cooperative agreement award number NNX16AB91A and is part of NASA’s Science Activation Portfolio. Learn more about how Science Activation connects NASA science experts, real content, and experiences with community leaders to do science in ways that activate minds and promote deeper understanding of our world and beyond: https://science.nasa.gov/learn
Two STEM Student Ambassadors engage a young girl while she creates her own Pastel Aurora artwork. Share
Details
Last Updated Jul 22, 2025 Editor NASA Science Editorial Team Related Terms
Opportunities For Students to Get Involved Science Activation The Sun Explore More
2 min read GLOBE-Trotting Science Lands in Chesapeake with NASA eClips
Article
1 day ago
6 min read NASA’s TRACERS Studies Explosive Process in Earth’s Magnetic Shield
Article
6 days ago
3 min read NASA Citizen Science and Your Career: Stories of Exoplanet Watch Volunteers
Doing NASA Science brings many rewards. But can taking part in NASA citizen science help…
Article
6 days ago
Keep Exploring Discover More Topics From NASA
James Webb Space Telescope
Webb is the premier observatory of the next decade, serving thousands of astronomers worldwide. It studies every phase in the…
Perseverance Rover
This rover and its aerial sidekick were assigned to study the geology of Mars and seek signs of ancient microbial…
Parker Solar Probe
On a mission to “touch the Sun,” NASA’s Parker Solar Probe became the first spacecraft to fly through the corona…
Juno
NASA’s Juno spacecraft entered orbit around Jupiter in 2016, the first explorer to peer below the planet’s dense clouds to…
View the full article
-
By NASA
A funky effect Einstein predicted, known as gravitational lensing — when a foreground galaxy magnifies more distant galaxies behind it — will soon become common when NASA’s Nancy Grace Roman Space Telescope begins science operations in 2027 and produces vast surveys of the cosmos.
This image shows a simulated observation from NASA’s Nancy Grace Roman Space Telescope with an overlay of its Wide Field Instrument’s field of view. More than 20 gravitational lenses, with examples shown at left and right, are expected to pop out in every one of Roman’s vast observations. A journal paper led by Bryce Wedig, a graduate student at Washington University in St. Louis, Missouri, estimates that of those Roman detects, about 500 from the telescope’s High-Latitude Wide-Area Survey will be suitable for dark matter studies. By examining such a large population of gravitational lenses, the researchers hope to learn a lot more about the mysterious nature of dark matter.Credit: NASA, Bryce Wedig (Washington University), Tansu Daylan (Washington University), Joseph DePasquale (STScI) A particular subset of gravitational lenses, known as strong lenses, is the focus of a new paper published in the Astrophysical Journal led by Bryce Wedig, a graduate student at Washington University in St. Louis. The research team has calculated that over 160,000 gravitational lenses, including hundreds suitable for this study, are expected to pop up in Roman’s vast images. Each Roman image will be 200 times larger than infrared snapshots from NASA’s Hubble Space Telescope, and its upcoming “wealth” of lenses will vastly outpace the hundreds studied by Hubble to date.
Roman will conduct three core surveys, providing expansive views of the universe. This science team’s work is based on a previous version of Roman’s now fully defined High-Latitude Wide-Area Survey. The researchers are working on a follow-up paper that will align with the final survey’s specifications to fully support the research community.
“The current sample size of these objects from other telescopes is fairly small because we’re relying on two galaxies to be lined up nearly perfectly along our line of sight,” Wedig said. “Other telescopes are either limited to a smaller field of view or less precise observations, making gravitational lenses harder to detect.”
Gravitational lenses are made up of at least two cosmic objects. In some cases, a single foreground galaxy has enough mass to act like a lens, magnifying a galaxy that is almost perfectly behind it. Light from the background galaxy curves around the foreground galaxy along more than one path, appearing in observations as warped arcs and crescents. Of the 160,000 lensed galaxies Roman may identify, the team expects to narrow that down to about 500 that are suitable for studying the structure of dark matter at scales smaller than those galaxies.
“Roman will not only significantly increase our sample size — its sharp, high-resolution images will also allow us to discover gravitational lenses that appear smaller on the sky,” said Tansu Daylan, the principal investigator of the science team conducting this research program. Daylan is an assistant professor and a faculty fellow at the McDonnell Center for the Space Sciences at Washington University in St. Louis. “Ultimately, both the alignment and the brightness of the background galaxies need to meet a certain threshold so we can characterize the dark matter within the foreground galaxies.”
To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video
This video shows how a background galaxy’s light is lensed or magnified by a massive foreground galaxy, seen at center, before reaching NASA’s Roman Space Telescope. Light from the background galaxy is distorted, curving around the foreground galaxy and appearing more than once as warped arcs and crescents. Researchers studying these objects, known as gravitational lenses, can better characterize the mass of the foreground galaxy, which offers clues about the particle nature of dark matter.Credit: NASA, Joseph Olmsted (STScI) What Is Dark Matter?
Not all mass in galaxies is made up of objects we can see, like star clusters. A significant fraction of a galaxy’s mass is made up of dark matter, so called because it doesn’t emit, reflect, or absorb light. Dark matter does, however, possess mass, and like anything else with mass, it can cause gravitational lensing.
When the gravity of a foreground galaxy bends the path of a background galaxy’s light, its light is routed onto multiple paths. “This effect produces multiple images of the background galaxy that are magnified and distorted differently,” Daylan said. These “duplicates” are a huge advantage for researchers — they allow multiple measurements of the lensing galaxy’s mass distribution, ensuring that the resulting measurement is far more precise.
Roman’s 300-megapixel camera, known as its Wide Field Instrument, will allow researchers to accurately determine the bending of the background galaxies’ light by as little as 50 milliarcseconds, which is like measuring the diameter of a human hair from the distance of more than two and a half American football fields or soccer pitches.
The amount of gravitational lensing that the background light experiences depends on the intervening mass. Less massive clumps of dark matter cause smaller distortions. As a result, if researchers are able to measure tinier amounts of bending, they can detect and characterize smaller, less massive dark matter structures — the types of structures that gradually merged over time to build up the galaxies we see today.
With Roman, the team will accumulate overwhelming statistics about the size and structures of early galaxies. “Finding gravitational lenses and being able to detect clumps of dark matter in them is a game of tiny odds. With Roman, we can cast a wide net and expect to get lucky often,” Wedig said. “We won’t see dark matter in the images — it’s invisible — but we can measure its effects.”
“Ultimately, the question we’re trying to address is: What particle or particles constitute dark matter?” Daylan added. “While some properties of dark matter are known, we essentially have no idea what makes up dark matter. Roman will help us to distinguish how dark matter is distributed on small scales and, hence, its particle nature.”
Preparations Continue
Before Roman launches, the team will also search for more candidates in observations from ESA’s (the European Space Agency’s) Euclid mission and the upcoming ground-based Vera C. Rubin Observatory in Chile, which will begin its full-scale operations in a few weeks. Once Roman’s infrared images are in hand, the researchers will combine them with complementary visible light images from Euclid, Rubin, and Hubble to maximize what’s known about these galaxies.
“We will push the limits of what we can observe, and use every gravitational lens we detect with Roman to pin down the particle nature of dark matter,” Daylan said.
The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by NASA’s Jet Propulsion Laboratory in Southern California; Caltech/IPAC in Pasadena, California; the Space Telescope Science Institute in Baltimore; and a science team comprising scientists from various research institutions. The primary industrial partners are BAE Systems, Inc. in Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.
By Claire Blome
Space Telescope Science Institute, Baltimore, Md.
Share
Details
Last Updated Jun 12, 2025 EditorAshley BalzerContactAshley Balzerashley.m.balzer@nasa.govLocationNASA Goddard Space Flight Center Related Terms
Nancy Grace Roman Space Telescope Astrophysics Dark Matter Galaxies Galaxies, Stars, & Black Holes Galaxies, Stars, & Black Holes Research The Universe Explore More
6 min read NASA’s Roman Mission Shares Detailed Plans to Scour Skies
Article 2 months ago 5 min read Millions of Galaxies Emerge in New Simulated Images From NASA’s Roman
Article 2 years ago 6 min read Team Preps to Study Dark Energy via Exploding Stars With NASA’s Roman
Article 3 months ago View the full article
-
By USH
On the night of Friday, May 16, something extraordinary lit up the skies over the American Southwest. A brilliant, fast-moving streak of light that captivated onlookers from Arizona to Colorado.
Witnesses in towns such as Safford, Fountain Hills, and Payson, as well as regions of New Mexico and Colorado, were left asking the same question: What exactly did we just see?
Speculation spread rapidly. Some suggested a Chinese rocket launch earlier that day could be responsible, possibly placing satellites into orbit. Others floated more exotic theories: perhaps STEVE, a rare atmospheric light phenomenon similar to the aurora borealis, or even a “light pillar,” formed when light reflects off high-altitude ice crystals.
Attempts to reach officials at Luke Air Force Base near Phoenix, Davis-Monthan Air Force Base in southern Arizona, and Kirtland Air Force Base in Albuquerque have so far yielded no response.
What if it wasn’t a rocket plume from a Chinese launch at all? What if something entirely different passed near our planet, like a comet or UFO, or perhaps it was a test of a space-based weapon or a directed-energy system?
Whatever it may have been, it remains a strange phenomenon, leaving many to wonder what truly streaked across the sky.
View the full article
-
-
Check out these Videos
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.