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NASA's Great Observatories Begin Deepest Ever Probe of the Universe
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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.
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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
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By USH
3I/ATLAS as an interstellar visitor, discovered on July 1. Estimated to be up to 15 miles (24 kilometers) wide, it’s barreling toward the Sun at over 130,000 mph. Fortunately, it won’t come closer to Earth than 1.6 astronomical units — about 150 million miles (240 million kilometers) according to NASA.
NASA insists there's no reason for concern — it’s just a comet, end of story. But here's where things get interesting: 3I/ATLAS is the third known interstellar object to enter our solar system, following the enigmatic ‘Oumuamua in 2017 and comet Borisov in 2019. And like those two, it behaves in ways that deviate from what we expect of natural comets.
A newly published paper on the preprint server arXiv (July 16) challenges NASA’s official explanation. The study, co-authored by three scientists, including Harvard astrophysicist Avi Loeb, suggests that 3I/ATLAS might not be a comet at all. Instead, the team proposes it could be an artificial object: a surveillance probe sent by an unknown extraterrestrial intelligence, possibly even one with hostile intent.
Loeb, warns that if this hypothesis turns out to be accurate, the consequences for humanity could be profound. He suggests that preparing defensive countermeasures might be necessary if this object poses a real threat.
What makes 3I/ATLAS so unusual?
According to Loeb, the object’s trajectory is so rare that the odds of a natural comet following the same path are less than 0.005%.
It will pass unusually close to three planets — Venus, Mars, and Jupiter — raising further suspicion.
Most telling of all: 3I/ATLAS lacks a coma, the cloud of gas and dust that typically surrounds comets.
"When analyzed with an open mind, the data offers compelling evidence that 3I/ATLAS may be technological in nature," Loeb explained.
In fact, Loeb outlines eight specific reasons why this object likely isn't a natural interstellar visitor — and why it may be of artificial origin. (You can read his full breakdown (here).
The idea that this mysterious object might be an alien craft, possibly one preparing for closer contact with Earth, is unsettling to say the least. For now, we can only wait, watch... and wonder. View the full article
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By NASA
7 min read
NASA’s Parker Solar Probe Snaps Closest-Ever Images to Sun
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NASA’s Parker Solar Probe has taken the closest ever images to the Sun, captured just 3.8 million miles from the solar surface. The new close-up images show features in the solar wind, the constant stream of electrically charged subatomic particles released by the Sun that rage across the solar system at speeds exceeding 1 million miles an hour. These images, and other data, are helping scientists understand the mysteries of the solar wind, which is essential to understanding its effects at Earth. On its record-breaking pass by the Sun late last year, NASA’s Parker Solar Probe captured stunning new images from within the Sun’s atmosphere. These newly released images — taken closer to the Sun than we’ve ever been before — are helping scientists better understand the Sun’s influence across the solar system, including events that can affect Earth.
“Parker Solar Probe has once again transported us into the dynamic atmosphere of our closest star,” said Nicky Fox, associate administrator, Science Mission Directorate at NASA Headquarters in Washington. “We are witnessing where space weather threats to Earth begin, with our eyes, not just with models. This new data will help us vastly improve our space weather predictions to ensure the safety of our astronauts and the protection of our technology here on Earth and throughout the solar system.”
Parker Solar Probe started its closest approach to the Sun on Dec. 24, 2024, flying just 3.8 million miles from the solar surface. As it skimmed through the Sun’s outer atmosphere, called the corona, in the days around the perihelion, it collected data with an array of scientific instruments, including the Wide-Field Imager for Solar Probe, or WISPR.
Parker Solar Probe has revolutionized our understanding of the solar wind thanks to the spacecraft’s many passes through the Sun’s outer atmosphere.
Credit: NASA’s Goddard Space Flight Center/Joy Ng The new WISPR images reveal the corona and solar wind, a constant stream of electrically charged particles from the Sun that rage across the solar system. The solar wind expands throughout of the solar system with wide-ranging effects. Together with outbursts of material and magnetic currents from the Sun, it helps generate auroras, strip planetary atmospheres, and induce electric currents that can overwhelm power grids and affect communications at Earth. Understanding the impact of solar wind starts with understanding its origins at the Sun.
The WISPR images give scientists a closer look at what happens to the solar wind shortly after it is released from the corona. The images show the important boundary where the Sun’s magnetic field direction switches from northward to southward, called the heliospheric current sheet. It also captures the collision of multiple coronal mass ejections, or CMEs — large outbursts of charged particles that are a key driver of space weather — for the first time in high resolution.
“In these images, we’re seeing the CMEs basically piling up on top of one another,” said Angelos Vourlidas, the WISPR instrument scientist at the Johns Hopkins Applied Physics Laboratory, which designed, built, and operates the spacecraft in Laurel, Maryland. “We’re using this to figure out how the CMEs merge together, which can be important for space weather.”
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This video, made from images taken by Parker Solar Probe’s WISPR instrument during its record-breaking flyby of the Sun on Dec. 25, 2024, shows the solar wind racing out from the Sun’s outer atmosphere, the corona. NASA/Johns Hopkins APL/Naval Research Lab When CMEs collide, their trajectory can change, making it harder to predict where they’ll end up. Their merger can also accelerate charged particles and mix magnetic fields, which makes the CMEs’ effects potentially more dangerous to astronauts and satellites in space and technology on the ground. Parker Solar Probe’s close-up view helps scientists better prepare for such space weather effects at Earth and beyond.
Zooming in on Solar Wind’s Origins
The solar wind was first theorized by preeminent heliophysicist Eugene Parker in 1958. His theories about the solar wind, which were met with criticism at the time, revolutionized how we see our solar system. Prior to Parker Solar Probe’s launch in 2018, NASA and its international partners led missions like Mariner 2, Helios, Ulysses, Wind, and ACE that helped scientists understand the origins of the solar wind — but from a distance. Parker Solar Probe, named in honor of the late scientist, is filling in the gaps of our understanding much closer to the Sun.
At Earth, the solar wind is mostly a consistent breeze, but Parker Solar Probe found it’s anything but at the Sun. When the spacecraft reached within 14.7 million miles from the Sun, it encountered zig-zagging magnetic fields — a feature known as switchbacks. Using Parker Solar Probe’s data, scientists discovered that these switchbacks, which came in clumps, were more common than expected.
When Parker Solar Probe first crossed into the corona about 8 million miles from the Sun’s surface in 2021, it noticed the boundary of the corona was uneven and more complex than previously thought.
As it got even closer, Parker Solar Probe helped scientists pinpoint the origin of switchbacks at patches on the visible surface of the Sun where magnetic funnels form. In 2024 scientists announced that the fast solar wind — one of two main classes of the solar wind — is in part powered by these switchbacks, adding to a 50-year-old mystery.
However, it would take a closer view to understand the slow solar wind, which travels at just 220 miles per second, half the speed of the fast solar wind.
“The big unknown has been: how is the solar wind generated, and how does it manage to escape the Sun’s immense gravitational pull?” said Nour Rawafi, the project scientist for Parker Solar Probe at the Johns Hopkins Applied Physics Laboratory. “Understanding this continuous flow of particles, particularly the slow solar wind, is a major challenge, especially given the diversity in the properties of these streams — but with Parker Solar Probe, we’re closer than ever to uncovering their origins and how they evolve.”
Understanding Slow Solar Wind
The slow solar wind, which is twice as dense and more variable than fast solar wind, is important to study because its interplay with the fast solar wind can create moderately strong solar storm conditions at Earth sometimes rivaling those from CMEs.
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This artist’s concept shows a representative state of Earth’s magnetic bubble immersed in the slow solar wind, which averages some 180 to 300 miles per second. NASA’s Goddard Space Flight Center Conceptual Image Lab Prior to Parker Solar Probe, distant observations suggested there are actually two varieties of slow solar wind, distinguished by the orientation or variability of their magnetic fields. One type of slow solar wind, called Alfvénic, has small-scale switchbacks. The second type, called non-Alfvénic, doesn’t show these variations in its magnetic field.
As it spiraled closer to the Sun, Parker Solar Probe confirmed there are indeed two types. Its close-up views are also helping scientists differentiate the origins of the two types, which scientists believe are unique. The non-Alfvénic wind may come off features called helmet streamers — large loops connecting active regions where some particles can heat up enough to escape — whereas Alfvénic wind might originate near coronal holes, or dark, cool regions in the corona.
In its current orbit, bringing the spacecraft just 3.8 million miles from the Sun, Parker Solar Probe will continue to gather additional data during its upcoming passes through the corona to help scientists confirm the slow solar wind’s origins. The next pass comes Sept. 15, 2025.
“We don’t have a final consensus yet, but we have a whole lot of new intriguing data,” said Adam Szabo, Parker Solar Probe mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
By Mara Johnson-Groh
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Last Updated Jul 10, 2025 Related Terms
Heliophysics Goddard Space Flight Center Heliophysics Division Missions NASA Centers & Facilities NASA Directorates Parker Solar Probe (PSP) Science & Research Science Mission Directorate Solar Wind Space Weather Explore More
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