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Solar System fingerprints found in memories of ESA flotilla
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By European Space Agency
Astronomers have confirmed the discovery of a rare celestial visitor: a comet from beyond our Solar System.
Officially named 3I/ATLAS, this newly identified interstellar object is only the third of its kind ever observed, following the famous 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019.
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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
At the Living Planet Symposium, attendees have been hearing how ESA’s Next Generation Gravity Mission could provide the first opportunity to directly track a vital ocean circulation system that warms our planet – but is now weakening, risking a possible collapse with far-reaching consequences.
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By European Space Agency
Video: 00:06:07 Space is huge and essential to humankind, fuelling knowledge, supporting our economies and driving global prosperity. None of this would be possible without reliable access to space.
Since 1979, Europe has relied on the Ariane rockets and Vega series to launch its missions. Today, with Ariane 6 and Vega-C, ESA ensures Europe's autonomous and independent access to space. But we are also looking ahead. With the Ariane Smart Transfer and Release In-orbit Ship (ASTRIS), Phoebus, P160C boosters, the MR-10 engine and more, ESA is enhancing its rockets with new innovations that improve cost, performance, capability and sustainability.
ESA is also leading the way in developing new propulsion systems to power the European launchers of the future. In collaboration with industry, ESA is supporting the development of new technologies to be used on rocket, boosters, upper stages, landers and spacecraft.
Initiaves like Boosters for European Space Transportation (BEST!), Technologies for High-thrust Re-Usable Space Transportation (THRUST!) and Future Innovation and Research in Space Transporation programme (FIRST!), are advancing key technologies for reusable boosters, engines and other innovations crucial for the future of space exploration. ESA's Space Rider is a reusable spacecraft and robotic laboratory, designed to stay in low Earth-orbit for two months and return payloads to Earth. Themis is a prototype for testing reusable rocket technologies, including vertical takeoff, landing and reuse, powered by the Prometheus engine.
The future of space transport extends beyond Earth launches, with in-orbit operations, transportation systems to support satellite servicing, orbital refuelling, and payload transfers between orbits.
To support all of this, ESA is upgrading its ground support and Europe's Spaceport in French Guiana, to accommodate more launches.
Through programmes like ‘Boost!’ ESA is empowering the European Space Industry, supporting innovative companies which are creating new launch services. The European Launcher Challenge is shaping a competitive European launch sector for the future, strengthening Europe's autonomous access to space.
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