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By NASA
An unexpectedly strong solar storm rocked our planet on April 23, 2023, sparking auroras as far south as southern Texas in the U.S. and taking the world by surprise.
Two days earlier, the Sun blasted a coronal mass ejection (CME) — a cloud of energetic particles, magnetic fields, and solar material — toward Earth. Space scientists took notice, expecting it could cause disruptions to Earth’s magnetic field, known as a geomagnetic storm. But the CME wasn’t especially fast or massive, and it was preceded by a relatively weak solar flare, suggesting the storm would be minor. But it became severe.
Using NASA heliophysics missions, new studies of this storm and others are helping scientists learn why some CMEs have more intense effects — and better predict the impacts of future solar eruptions on our lives.
During the night of April 23 to 24, 2023, a geomagnetic storm produced auroras that were witnessed as far south as Arizona, Arkansas, and Texas in the U.S. This photo shows green aurora shimmering over Larimore, North Dakota, in the early morning of April 24. Copyright Elan Azriel, used with permission Why Was This Storm So Intense?
A paper published in the Astrophysical Journal on March 31 suggests the CME’s orientation relative to Earth likely caused the April 2023 storm to become surprisingly strong.
The researchers gathered observations from five heliophysics spacecraft across the inner solar system to study the CME in detail as it emerged from the Sun and traveled to Earth.
They noticed a large coronal hole near the CME’s birthplace. Coronal holes are areas where the solar wind — a stream of particles flowing from the Sun — floods outward at higher than normal speeds.
“The fast solar wind coming from this coronal hole acted like an air current, nudging the CME away from its original straight-line path and pushing it closer to Earth’s orbital plane,” said the paper’s lead author, Evangelos Paouris of the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. “In addition to this deflection, the CME also rotated slightly.”
Paouris says this turned the CME’s magnetic fields opposite to Earth’s magnetic field and held them there — allowing more of the Sun’s energy to pour into Earth’s environment and intensifying the storm.
The strength of the April 2023 geomagnetic storm was a surprise in part because the coronal mass ejection (CME) that produced it followed a relatively weak solar flare, seen as the bright area to the lower right of center in this extreme ultraviolet image of the Sun from NASA’s Solar Dynamics Observatory. The CMEs that produce severe geomagnetic storms are typically preceded by stronger flares. However, a team of scientists think fast solar wind from a coronal hole (the dark area below the flare in this image) helped rotate the CME and made it more potent when it struck Earth. NASA/SDO Cool Thermosphere
Meanwhile, NASA’s GOLD (Global-scale Observations of Limb and Disk) mission revealed another unexpected consequence of the April 2023 storm at Earth.
Before, during, and after the storm, GOLD studied the temperature in the middle thermosphere, a part of Earth’s upper atmosphere about 85 to 120 miles overhead. During the storm, temperatures increased throughout GOLD’s wide field of view over the Americas. But surprisingly, after the storm, temperatures dropped about 90 to 198 degrees Fahrenheit lower than they were before the storm (from about 980 to 1,070 degrees Fahrenheit before the storm to 870 to 980 degrees Fahrenheit afterward).
“Our measurement is the first to show widespread cooling in the middle thermosphere after a strong storm,” said Xuguang Cai of the University of Colorado, Boulder, lead author of a paper about GOLD’s observations published in the journal JGR Space Physics on April 15, 2025.
The thermosphere’s temperature is important, because it affects how much drag Earth-orbiting satellites and space debris experience.
“When the thermosphere cools, it contracts and becomes less dense at satellite altitudes, reducing drag,” Cai said. “This can cause satellites and space debris to stay in orbit longer than expected, increasing the risk of collisions. Understanding how geomagnetic storms and solar activity affect Earth’s upper atmosphere helps protect technologies we all rely on — like GPS, satellites, and radio communications.”
Predicting When Storms Strike
To predict when a CME will trigger a geomagnetic storm, or be “geoeffective,” some scientists are combining observations with machine learning. A paper published last November in the journal Solar Physics describes one such approach called GeoCME.
Machine learning is a type of artificial intelligence in which a computer algorithm learns from data to identify patterns, then uses those patterns to make decisions or predictions.
Scientists trained GeoCME by giving it images from the NASA/ESA (European Space Agency) SOHO (Solar and Heliospheric Observatory) spacecraft of different CMEs that reached Earth along with SOHO images of the Sun before, during, and after each CME. They then told the model whether each CME produced a geomagnetic storm.
Then, when it was given images from three different science instruments on SOHO, the model’s predictions were highly accurate. Out of 21 geoeffective CMEs, the model correctly predicted all 21 of them; of 7 non-geoeffective ones, it correctly predicted 5 of them.
“The algorithm shows promise,” said heliophysicist Jack Ireland of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who was not involved in the study. “Understanding if a CME will be geoeffective or not can help us protect infrastructure in space and technological systems on Earth. This paper shows machine learning approaches to predicting geoeffective CMEs are feasible.”
The white cloud expanding outward in this image sequence is a coronal mass ejection (CME) that erupted from the Sun on April 21, 2023. Two days later, the CME struck Earth and produced a surprisingly strong geomagnetic storm. The images in this sequence are from a coronagraph on the NASA/ESA (European Space Agency) SOHO (Solar and Heliospheric Observatory) spacecraft. The coronagraph uses a disk to cover the Sun and reveal fainter details around it. The Sun’s location and size are indicated by a small white circle. The planet Jupiter appears as a bright dot on the far right. NASA/ESA/SOHO Earlier Warnings
During a severe geomagnetic storm in May 2024 — the strongest to rattle Earth in over 20 years — NASA’s STEREO (Solar Terrestrial Relations Observatory) measured the magnetic field structure of CMEs as they passed by.
When a CME headed for Earth hits a spacecraft first, that spacecraft can often measure the CME and its magnetic field directly, helping scientists determine how strong the geomagnetic storm will be at Earth. Typically, the first spacecraft to get hit are one million miles from Earth toward the Sun at a place called Lagrange Point 1 (L1), giving us only 10 to 60 minutes advanced warning.
By chance, during the May 2024 storm, when several CMEs erupted from the Sun and merged on their way to Earth, NASA’s STEREO-A spacecraft happened to be between us and the Sun, about 4 million miles closer to the Sun than L1.
A paper published March 17, 2025, in the journal Space Weather reports that if STEREO-A had served as a CME sentinel, it could have provided an accurate prediction of the resulting storm’s strength 2 hours and 34 minutes earlier than a spacecraft could at L1.
According to the paper’s lead author, Eva Weiler of the Austrian Space Weather Office in Graz, “No other Earth-directed superstorm has ever been observed by a spacecraft positioned closer to the Sun than L1.”
Earth’s Lagrange points are places in space where the gravitational pull between the Sun and Earth balance, making them relatively stable locations to put spacecraft. NASA By Vanessa Thomas
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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By European Space Agency
Asteroid 2024 YR4 made headlines earlier this year when its probability of impacting Earth in 2032 rose as high as 3%. While an Earth impact has now been ruled out, the asteroid’s story continues.
The final glimpse of the asteroid as it faded out of view of humankind’s most powerful telescopes left it with a 4% chance of colliding with the Moon on 22 December 2032.
The likelihood of a lunar impact will now remain stable until the asteroid returns to view in mid-2028. In this FAQ, find out why we are left with this lingering uncertainty and how ESA's planned NEOMIR space telescope will help us avoid similar situations in the future.
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By Space Force
Lt. Gen. Thomas James, U.S. Space Command deputy commander, attended the Prague Security Studies Institute’s 8th Prague Space Security Conference in the Czech Republic, June 15-17.
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By NASA
7 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
In the summer 2025 issue of the NASA History Office’s News & Notes newsletter, examples of leadership and critical decision-making in NASA’s history form the unifying theme. Among the topics discussed are NASA’s Shuttle-Centaur program, assessing donations to the NASA Archives, how the discovery of the first exoplanet orbiting a sun-like star catalyzed NASA’s exoplanet program, and Chief of the Medical Operations Office Charles A. Berry’s decisions surrounding crew health when planning the Project Gemini missions.
Volume 42, Number 2
Summer 2025
Featured Articles
From the Chief Historian
By Brian Odom
NASA’s is a history marked by critical decisions. From George Mueller’s 1963 decision for “all up” testing of the Saturn V rocket to Michael Griffin’s 2006 decision to launch a final servicing mission to the Hubble Space Telescope, the agency has continually met key inflection points with bold decisions. These choices, such as the decision to send a crewed Apollo 8 mission around the Moon in December 1968, stand at the center of the agency’s national legacy and promote confidence in times of crisis. Continue Reading
Shuttle-Centaur: Loss of Launch Vehicle Redundancy Leads to Discord
By Robert Arrighi
“Although the Shuttle/Centaur decision was very difficult to make, it is the proper thing to do, and this is the time to do it.” With those words on June 19, 1986, NASA Administrator James Fletcher canceled the intensive effort to integrate the Centaur upper stage with the Space Shuttle to launch the Galileo and Ulysses spacecraft. The decision, which was tied to increased safety measures following the loss of Challenger several months earlier, brought to the forefront the 1970s decision to launch all U.S. payloads with the Space Shuttle. Continue Reading
Lewis Director Andy Stofan speaks at the Shuttle-Centaur rollout ceremony on August 23, 1985 at General Dynamics’s San Diego headquarters. Galileo mission crew members Dave Walker, Rick Hauck, and John Fabian were among those on stage. NASA A View into NASA’s Response to the Apollo 1 Tragedy
By Kate Mankowski
On January 27, 1967, Mission AS-204 (later known as Apollo 1) was conducting a simulated countdown when a fire suddenly broke out in the spacecraft, claiming the lives of astronauts Virgil I. “Gus” Grissom, Edward H. White, and Roger B. Chaffee. The disaster highlighted the risks that come with spaceflight and the work that still needed to be accomplished to meet President Kennedy’s challenge of going to the Moon before the end of the decade. With the complexity of the Apollo spacecraft, discerning the cause of the fire proved to be incredibly difficult. Continue Reading
The Fight to Fund AgRISTARS
By Brad Massey
Robert MacDonald, the manager of NASA’s Large Area Crop Inventory Experiment (LACIE), was not pleased in January 1978 after he read a draft copy of the U.S. General Accounting Office’s (GAO’s) “Crop Forecasting by Satellite: Progress and Problems” report. The draft’s authors argued that LACIE had not achieved its goals of accurately predicting harvest yields in the mid-1970s. Therefore, congressional leaders should “be aware of the disappointing performance of LACIE to date when considering the future direction of NASA’s Landsat program and the plans of the Department of Agriculture.” Continue Reading
The Hubble Space Telescope: The Right Project at the Right Time
By Jillian Rael
This year, NASA commemorates 35 years of the Hubble Space Telescope’s study of the cosmos. From observations of never-before-seen phenomena within our solar system, to the discovery of distant galaxies, the confirmation of the existence of supermassive black holes, and precision measurements of the universe’s expansion, Hubble has made incredible contributions to science, technology, and even art. Yet, for all its contemporary popularity, the Hubble program initially struggled for congressional approval and consequential funding. For its part, NASA found new ways to compromise and cut costs, while Congress evaluated national priorities and NASA’s other space exploration endeavors against the long-range value of Hubble. Continue Reading
Within the tempestuous Carina Nebula lies “Mystic Mountain.”NASA/ESA/M. Livio/Hubble 20th Anniversary Team Appraisal: The Science and Art of Assessing Donations to the NASA Archives
By Alan Arellano
The major functions of an archivist center include appraising, arranging, describing, preserving, and providing access to historical records and documents. While together these are pillars of archival science, they are more of an art than a science in their application, fundamentally necessitating skilled decision making. Throughout the NASA archives, staff members make these decisions day in and day out. Continue Reading
Orbit Shift: How 50 Pegasi b Helped Pull NASA Toward the Stars in the 1990s
By Lois Rosson
On October 20, 1995, the New York Times reported the detection of a distant planet orbiting a Sun-like star. The star, catalogued as 51 Pegasi by John Flamsteed in the 18th century, was visible to the naked eye as part of the constellation Pegasus—and had wobbled on its axis just enough that two Swiss astronomers were able to deduce the presence of another object exerting its gravitational pull on the star’s rotation. The discovery was soon confirmed by other astronomers, and 51 Pegasi b was heralded as the first confirmed exoplanet orbiting a star similar to our own Sun. Continue Reading
Detail from an infographic about 51 Pegasi b and the significance of its discovery.NASA Four, Eight, Fourteen Days: Charles A. Berry, Gemini, and the Critical Steps to Living and Working in Space
By Jennifer Ross-Nazzal
In 1963, critical decisions had to be made about NASA’s upcoming Gemini missions if the nation were to achieve President John F. Kennedy’s lunar goals. Known as the bridge to Apollo, Project Gemini was critical to landing a man on the Moon by the end of the decade and returning him safely to Earth. The project would demonstrate that astronauts could rendezvous and dock their spacecraft to another space vehicle and give flight crews the opportunity to test the planned extravehicular capabilities in preparation for walking on the lunar surface on future Apollo flights. Perhaps most importantly, Gemini had to show that humans could live and work in space for long periods of time, a fiercely debated topic within and outside of the agency. Continue Reading
Dr. Charles Berry prepares to check the blood pressure of James A. McDivitt, Command Pilot for the Gemini IV mission. McDivitt is on the tilt table at the Aero Medical Area, Merritt Island, FL, where he and Gemini IV pilot Edward H. White II underwent preflight physicals in preparation for their four-day spaceflight.NASA Imagining Space: The Life and Art of Robert McCall
By Sandra Johnson
As we walked into Bob McCall’s Arizona home, it quickly became obvious that two talented and creative people lived there. Tasked with interviewing one of the first artists to be invited to join the NASA Art Program, our oral history team quickly realized the session with McCall would include a unique perspective on NASA’s history. We traveled to Arizona in the spring of 2000 to capture interviews with some of the pioneers of spaceflight and had already talked to an eclectic group of subjects in their homes, including a flight controller for both Gemini and Apollo, an astronaut who had flown on both Skylab and Space Shuttle missions, a former NASA center director, and two former Women’s Airforce Service Pilots (WASPs) who ferried airplanes during WWII. However, unlike most interviews, the setting itself provided a rare glimpse into the man and his inspiration. Continue Reading
Inside the Archives: Biomedical Branch Files
By Alejandra Lopez
The Biomedical Branch Files (1966–2008) in the Johnson Space Center archives showcase the inner workings of a NASA office established to perform testing to provide a better understanding of the impacts of spaceflight on the human body. Ranging from memos and notes to documents and reports, this collection is an invaluable resource on the biomedical research done with NASA’s Apollo, Skylab, Space Shuttle, and Space Station projects. Files in the collection cover work done by groups within the branch such as the Toxicology, Microbiology, Clinical, and Biochemistry Laboratories. It also reveals the branch’s evolution and changes in its decision-making process over the years. Continue Reading
Dr. Carolyn S. Huntoon, shown here in 1972, became the Biomedical Branch’s first chief in 1977.NASA Download the Summer 2025 Edition More Issues of NASA History News and Notes Share
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