This is an AI Free Zone: Text created by Large Language Models is spreading across the Internet. It's well-written, but frequently inaccurate. If you find a mistake on Spaceweather.com, rest assured it was made by a real human being.
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A HOLE IN THE SUN'S ATMOSPHERE: A canyon-shaped hole in the sun's atmosphere is facing Earth and spewing a stream of solar wind in our direction. G1-class geomagnetic storms are possible on Dec. 18th when it arrives. Aurora alerts: SMS Text.
THE NON-GRAVITATIONAL ACCELERATION OF 3I/ATLAS: When non-experts hear that "Comet 3I/ATLAS has non-gravitational acceleration," some think it means the interstellar object must be a spaceship. Not so. All comets have non-gravitational acceleration.
A new paper published in Research Notes of the AAS explains why--and shows how 3I/ATLAS behaves very much like the comets we know from our own Solar System.
Comet 3I/ATLAS photographed Dec.2, 2025, by Gerald Rhemann and Michael Jäger
“We measured the non-gravitational acceleration of 3I/ATLAS using long-baseline astrometry from NASA’s Psyche spacecraft and ESA’s Mars Trace Gas Orbiter,” explains lead author Marshall Eubanks. “The results are pretty typical of ordinary comets, and certainly not record-breaking.”
Non-gravitational acceleration comes from the gentle push comets experience from their own outgassing. Jets of icy material sublimating from the nucleus recoil like tiny rocket engines, nudging the comet off the path it would follow under gravity alone.
"Until recently, finding non-gravitational accelerations in comets required observations over multiple orbits--which we will never have for interstellar objects," says Eubanks. "Now, using interplanetary spacecraft, we can measure these small accelerations--just a few hundred millionths of Earth’s gravity--during a single flythrough of the solar system."
For 3I/ATLAS, the acceleration caused by outgassing is about 5 × 10⁻⁷ m s⁻², comparable to that of many small Solar System comets. Using this value, along with measurements of carbon dioxide production, the team estimated the comet’s mass at about 44 million metric tons and its radius between 260 and 370 meters--again, entirely typical.
The comparison between 3I/ATLAS and the original interstellar object 1I/‘Oumuamua is striking. In 2017 when 1I/‘Oumuamua was passing through the Solar System, its non-gravitational acceleration (~10⁻⁶ m s⁻²) attracted attention. Why? Because ‘Oumuamua didn't have any obvious outgassing. This laid the foundation for Avi Loeb's claims that 1I/'Oumuamua might be a light sail or some other kind of tech.
3I/ATLAS, on the other hand, seems normal. It has obvious cometary outgassing with a non-gravitational acceleration to match. Claiming that it, too, is a spacecraft does not fit the data.
Conclusion: 3I/ATLAS is exotic and wonderful. It is also a comet.
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10% OFF CHRISTMAS GIFTS FROM SPACE: Christmas is coming. Are you looking for a far-out gift? Check out the Earth to Sky Store. It's filled with items that have visited the edge of space onboard cosmic ray research balloons:
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Every night, a network
of
NASA
all-sky cameras scans the skies above the United
States for meteoritic fireballs. Automated software
maintained by NASA's Meteoroid Environment Office
calculates their orbits, velocity, penetration depth
in Earth's atmosphere and many other characteristics.
Daily results are presented here on Spaceweather.com.
On Dec. 15 2025, the network reported 27 fireballs.
(13 Geminids, 10 sporadics, 2 Hydrids, 1 Dec. Monocerotid, 1 Dec. Leonis Minorid)
In this diagram of the inner solar system, all of the fireball orbits intersect at a single point--Earth. The orbits are color-coded by velocity, from slow (red) to fast (blue).
[Larger image] [movies]
Potentially Hazardous Asteroids (
PHAs)
are space rocks larger than approximately 100m that
can come closer to Earth than 0.05 AU. None of the
known PHAs is on a collision course with our planet,
although astronomers are finding
new
ones all the time.
On December 16, 2025 there were 2349 potentially hazardous asteroids.
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Recent
& Upcoming Earth-asteroid encounters:
| Asteroid |
Date(UT) |
Miss Distance |
Velocity (km/s) |
Diameter (m) |
| 2025 WK4 |
2025-Dec-10 |
8.9 LD |
5.5 |
32 |
| 2025 XP2 |
2025-Dec-10 |
7.5 LD |
4.6 |
10 |
| 2025 XH2 |
2025-Dec-10 |
9.3 LD |
8.3 |
23 |
| 2025 XL4 |
2025-Dec-10 |
0.8 LD |
9.8 |
3 |
| 2025 XL |
2025-Dec-10 |
6.1 LD |
14.4 |
30 |
| 2025 XB1 |
2025-Dec-10 |
0.3 LD |
8.6 |
6 |
| 2025 XR1 |
2025-Dec-10 |
3.9 LD |
5.6 |
5 |
| 1999 SF10 |
2025-Dec-10 |
8.2 LD |
4.4 |
46 |
| 2025 XC2 |
2025-Dec-11 |
13.6 LD |
8.9 |
53 |
| 2025 XN3 |
2025-Dec-11 |
8.6 LD |
12.7 |
10 |
| 2019 XN3 |
2025-Dec-11 |
4.9 LD |
3.7 |
15 |
| 2025 XO4 |
2025-Dec-11 |
13.3 LD |
13.4 |
23 |
| 2025 XX3 |
2025-Dec-11 |
3.7 LD |
6.6 |
7 |
| 2025 XK1 |
2025-Dec-12 |
2.6 LD |
4.3 |
12 |
| 2025 XK4 |
2025-Dec-12 |
5.6 LD |
9.9 |
11 |
| 2025 XA3 |
2025-Dec-12 |
3.6 LD |
6 |
11 |
| 2025 XZ3 |
2025-Dec-12 |
0.4 LD |
9.2 |
6 |
| 2025 WH20 |
2025-Dec-12 |
10.9 LD |
8.9 |
27 |
| 2025 XG2 |
2025-Dec-12 |
3.9 LD |
8.3 |
16 |
| 2025 XF2 |
2025-Dec-12 |
1.3 LD |
6.9 |
6 |
| 2025 XF1 |
2025-Dec-13 |
0.8 LD |
3.6 |
9 |
| 2025 WY9 |
2025-Dec-13 |
14.5 LD |
5.3 |
17 |
| 2025 XZ4 |
2025-Dec-13 |
0.9 LD |
20.2 |
11 |
| 2025 XS3 |
2025-Dec-14 |
1.5 LD |
9.2 |
3 |
| 2025 XW3 |
2025-Dec-14 |
0.5 LD |
9 |
5 |
| 2025 XW2 |
2025-Dec-14 |
5.8 LD |
17.6 |
28 |
| 2025 TZ |
2025-Dec-15 |
17.8 LD |
6.2 |
53 |
| 2025 WA14 |
2025-Dec-15 |
20 LD |
9.3 |
34 |
| 2025 XX2 |
2025-Dec-15 |
2.4 LD |
8.2 |
11 |
| 2016 YH |
2025-Dec-15 |
7.6 LD |
8.8 |
28 |
| 2025 WA3 |
2025-Dec-15 |
8.9 LD |
19.4 |
259 |
| 2025 XN4 |
2025-Dec-16 |
0.5 LD |
14.8 |
12 |
| 2025 XP4 |
2025-Dec-17 |
14 LD |
8 |
31 |
| 2025 XJ2 |
2025-Dec-17 |
5.7 LD |
11.9 |
20 |
| 2025 WD4 |
2025-Dec-17 |
19.9 LD |
12.7 |
45 |
| 2025 WN6 |
2025-Dec-17 |
15.9 LD |
2.9 |
37 |
| 2025 XV |
2025-Dec-18 |
6.8 LD |
9.5 |
97 |
| 2015 XX168 |
2025-Dec-18 |
6 LD |
11.4 |
27 |
| 2025 XV3 |
2025-Dec-19 |
14.7 LD |
15 |
54 |
| 2025 XQ3 |
2025-Dec-19 |
9 LD |
15.1 |
33 |
| 2025 XV1 |
2025-Dec-20 |
16.9 LD |
7.8 |
23 |
| 2010 WR7 |
2025-Dec-20 |
19.4 LD |
8.3 |
71 |
| 2025 XT4 |
2025-Dec-20 |
6.6 LD |
6 |
9 |
| 2025 XC4 |
2025-Dec-20 |
14.5 LD |
9.6 |
22 |
| 2025 XX4 |
2025-Dec-20 |
16.7 LD |
5.9 |
25 |
| 2025 WT3 |
2025-Dec-22 |
16 LD |
4.5 |
25 |
| 2025 XP3 |
2025-Dec-26 |
13.4 LD |
13.5 |
56 |
| 2025 XJ4 |
2025-Dec-27 |
14.4 LD |
6.7 |
36 |
| 2021 AB1 |
2025-Dec-28 |
10.2 LD |
12.3 |
16 |
| 2019 AU |
2025-Dec-30 |
19.3 LD |
2.8 |
16 |
| 2024 AV2 |
2025-Dec-30 |
17.9 LD |
7 |
17 |
| 2014 AF16 |
2026-Jan-04 |
9 LD |
9.6 |
34 |
| 2025 XS4 |
2026-Jan-06 |
8 LD |
6.5 |
24 |
| 2023 XM15 |
2026-Jan-07 |
15.2 LD |
6.9 |
51 |
| 2022 GR3 |
2026-Jan-12 |
14.5 LD |
12.9 |
9 |
| 2025 XN1 |
2026-Jan-14 |
9.2 LD |
4.7 |
35 |
| 2022 OB5 |
2026-Jan-14 |
1.7 LD |
2.2 |
6 |
| 2025 BL |
2026-Jan-17 |
4.7 LD |
6.9 |
28 |
| 2004 MO3 |
2026-Jan-17 |
17 LD |
10.2 |
129 |
| 2011 AM37 |
2026-Jan-17 |
19.8 LD |
5.1 |
4 |
| 2019 LZ4 |
2026-Jan-23 |
14.2 LD |
11.6 |
45 |
| 2022 AG |
2026-Jan-29 |
13.7 LD |
5.3 |
34 |
| 2020 GE |
2026-Jan-29 |
16.2 LD |
1.2 |
8 |
| 2023 RX1 |
2026-Jan-31 |
8.8 LD |
1.2 |
3 |
| 2022 OC3 |
2026-Jan-31 |
1.3 LD |
3.8 |
8 |
| 2021 CZ5 |
2026-Feb-09 |
18.3 LD |
9.3 |
23 |
| 2025 CC |
2026-Feb-09 |
17.6 LD |
5.1 |
11 |
| 2019 CN2 |
2026-Feb-11 |
20 LD |
9.2 |
7 |
| 2022 DV |
2026-Feb-12 |
15.4 LD |
5 |
18 |
Notes: LD means
"Lunar Distance." 1 LD = 384,401 km, the distance
between Earth and the Moon. 1 LD also equals 0.00256
AU.
| |
Cosmic Rays in the Atmosphere |
SPACE WEATHER BALLOON DATA: Almost once a week, Spaceweather.com and the students of Earth to Sky Calculus fly space weather balloons to the stratosphere over California. These balloons are equipped with sensors that detect secondary cosmic rays, a form of radiation from space that can penetrate all the way down to Earth's surface. Our monitoring program has been underway without interruption for 10 years, resulting in a unique dataset of in situ atmospheric measurements.
Latest results (Nov. 2024): Atmospheric radiation is sharply decreasing in 2024. Our latest measurements in November registered a 10-year low:
What's going on? Ironically, the radiation drop is caused by increasing solar activity. Solar Cycle 25 has roared to life faster than forecasters expected. The sun's strengthening and increasingly tangled magnetic field repels cosmic rays from deep space. In addition, solar coronal mass ejections (CMEs) sweep aside cosmic rays, causing sharp reductions called "Forbush Decreases." The two effects blend together to bring daily radiation levels down.
.Who cares? Cosmic rays are a surprisingly "down to Earth" form of space weather. They can alter the chemistry of the atmosphere, trigger lightning, and penetrate commercial airplanes. According to a study from the Harvard T.H. Chan school of public health, crews of aircraft have higher rates of cancer than the general population. The researchers listed cosmic rays, irregular sleep habits, and chemical contaminants as leading risk factors. A number of controversial studies (#1, #2, #3, #4) go even further, linking cosmic rays with cardiac arrhythmias and sudden cardiac death.
Technical notes: The radiation sensors onboard our helium balloons detect X-rays and gamma-rays in the energy range 10 keV to 20 MeV. These energies span the range of medical X-ray machines and airport security scanners.
Data points in the graph labeled "Stratospheric Radiation" correspond to the peak of the Regener-Pfotzer maximum, which lies about 67,000 feet above central California. When cosmic rays crash into Earth's atmosphere, they produce a spray of secondary particles that is most intense at the entrance to the stratosphere. Physicists Eric Regener and Georg Pfotzer discovered the maximum using balloons in the 1930s and it is what we are measuring today.
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The
official U.S. government space weather bureau |
| |
The
first place to look for information about sundogs,
pillars, rainbows and related phenomena. |
| |
Researchers
call it a "Hubble for the sun." SDO
is the most advanced solar observatory ever. |
| |
3D
views of the sun from NASA's Solar and Terrestrial
Relations Observatory |
| |
Realtime
and archival images of the Sun from SOHO. |
| |
information about sunspots based on the latest NOAA/USAF Active Region Summary |
| |
current counts of failed and deployed Starlink satellites from Jonathan's Space Page. See also, all satellite statistics. |
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Authoritative predictions of space junk and satellite re-entries |
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from
the NOAA Space Environment Center |
| |
fun to read, but should be taken with a grain of salt! Forecasts looking ahead more than a few days are often wrong. |
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from the NOAA Space Environment Center |
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the
underlying science of space weather |
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Got a chipped or cracked windshield that prevents you from seeing space weather events while driving? Get windshield replacement from SR Windows & Glass with free mobile auto glass service anywhere in the Phoenix area. |
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