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ARCTIC AURORA SEASON HAS BEGUN: As summer comes to an end, skies are darkening around the Arctic Circle--and aurora season has begun. A solar wind stream on Aug. 19-20 sparked the first easily visible Northern Lights in months. It looked a lot like autumn. Aurora alerts: SMS Text
THE BACKWARD TAIL OF COMET 3I/ATLAS: Last month, when astronomers used the Hubble Space Telescope to photograph 3I/ATLAS, they had a "Eureka!" moment. The mysterious interstellar visitor had a fuzzy atmosphere and a growing tail. Clearly, it was a comet.
However, something was not quite right. Take a look, and see if you can spot the problem:
The tail of 3I/ATLAS points almost straight toward the sun. Normally, comet dust tails are pushed away from the sun by radiation pressure. 3I/ATLAS is doing the opposite—it's backwards.
Why? Researchers led by David Jewitt of UCLA believe they have an explanation: "It is due to the preferential sublimation of ice on the hot day side of the nucleus and the near absence of sublimation on the night side," they wrote in a paper reporting the observations.
In other words, 3I/ATLAS *is* a comet, but only the sun-heated side is producing lots of dust. The emerging dust particles are too big for radiation pressure to bend them back into an ordinary tail.
This is unusual, but not unheard of. Solar system comets have been known to produce sunward fans or jets, typically from localized "hot spots" on their rotating nuclei. What makes 3I/ATLAS different is the dominance of its sunward plume, dwarfing a barely visible anti-solar tail behind it.
If 3I/ATLAS is indeed a comet, it may have been wandering through the galaxy for longer than our Solar System has existed. Billions of years of cosmic ray bombardment will have altered its surface--knocking hydrogen atoms out while heavier molecules remained behind. This process could create a hardened crust that might not sputter dust and gas like fresher comets from the Solar System.
Researchers will be very interested to see how the tail of 3I/ATLAS evolves as it approaches the sun for a close encounter in October 2025. Will it remain backward? Or will the crust crumble and allow smaller particles to escape, forming a more normal anti-solar tail?
Of course, if it is a spaceship as Harvard professor Avi Loeb suggests, something completely different may occur. Either way, stay tuned.
Realtime 3I/ATLAS Photo Gallery
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"ALWAYS AND FOREVER" METEOR CRATER PENDANT: Have you heard of Moissanite? It's a mineral discovered by 19th-century chemist Henri Moissan in Arizona's Meteor Crater. At first, he thought it was diamond, but later realized it was even more rare. It's a diamond lookalike that, until the 1950s, was found naturally only in meteorites.
On Aug. 2nd, the students of Earth to Sky Calculus launched this Moissanite pendant to the stratosphere onboard a cosmic ray research balloon:
You can have it for $129.95. Engraved with the words "I love you always and forever," the sterling silver frame bends around the Moissanite in a heart-shaped curve--all highlighted by glittering 5A cubic zirconia nuggets.
The students are selling space pendants to pay the helium bill for their cosmic ray ballooning program. Each one comes with a greeting card showing the jewelry in flight and telling the story of its trip to the stratosphere and back again.
Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education
AURORA SEASON BEGINS: Around the Arctic Circle, it's been a long summer of bright nights and no auroras. Now the seasons are changing. Jónína Óskarsdóttir sends this picture from Fáskrúðsfjörður, Iceland:
"Just after 1 am on Aug. 20th, the sky filled with enormous green auroras," says Óskarsdóttir. "What a wonderful start of the new season!"
The auroras she photographed were sparked by a stream of solar wind blowing faster than 600 km/s. Earth is still inside the stream today, and the darkness will be a little deeper. As a result, the second day of the new season could be even better than the first. Submit your photos here.
more images: from John David McKinnon of Fort Smith/Tthebacha, Northwest Territories, Canada; from Todd Salat of Mat-Su Valley, Alaska
Realtime Aurora Photo Gallery
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Realtime Space Weather Photo Gallery
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Realtime Noctilucent Cloud Photo Gallery
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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 Aug 20, 2025, the network reported 10 fireballs.
(8 sporadics, 1 Perseids, 1 Northern iota Aquariid)
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 August 21, 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 PF2 |
2025-Aug-15 |
0.1 LD |
13.1 |
3 |
| 2021 PJ1 |
2025-Aug-15 |
4.3 LD |
9.3 |
24 |
| 2025 PT1 |
2025-Aug-15 |
4.8 LD |
12.5 |
18 |
| 2025 QJ1 |
2025-Aug-15 |
9.2 LD |
13.6 |
25 |
| 2025 PW1 |
2025-Aug-15 |
0.7 LD |
8.5 |
10 |
| 2025 QA |
2025-Aug-16 |
5.9 LD |
7.4 |
18 |
| 2025 QQ |
2025-Aug-16 |
2.7 LD |
11.1 |
19 |
| 2025 QO |
2025-Aug-16 |
3.1 LD |
7.1 |
8 |
| 2025 QU |
2025-Aug-16 |
4.5 LD |
9.8 |
12 |
| 2025 CO3 |
2025-Aug-16 |
19.8 LD |
8.4 |
90 |
| 2025 PR1 |
2025-Aug-16 |
2.6 LD |
7.9 |
13 |
| 2025 QR |
2025-Aug-17 |
7 LD |
12.2 |
25 |
| 2025 PH3 |
2025-Aug-17 |
14.1 LD |
7.2 |
30 |
| 2025 PM |
2025-Aug-17 |
2.7 LD |
13.5 |
54 |
| 2025 PL2 |
2025-Aug-18 |
4.5 LD |
25.2 |
21 |
| 2025 PB2 |
2025-Aug-18 |
5.6 LD |
17.3 |
32 |
| 2025 QC |
2025-Aug-18 |
14.6 LD |
7.6 |
19 |
| 2025 PY1 |
2025-Aug-18 |
0.8 LD |
6.8 |
10 |
| 2025 QA1 |
2025-Aug-18 |
16.2 LD |
12.2 |
30 |
| 2025 PM1 |
2025-Aug-20 |
9.7 LD |
4.9 |
24 |
| 2025 OV4 |
2025-Aug-20 |
7.6 LD |
10.8 |
52 |
| 1997 QK1 |
2025-Aug-20 |
7.9 LD |
9.8 |
315 |
| 2025 PW2 |
2025-Aug-20 |
3.9 LD |
11.4 |
13 |
| 2025 OB3 |
2025-Aug-21 |
8.8 LD |
7 |
50 |
| 2022 QD3 |
2025-Aug-21 |
15 LD |
6.9 |
35 |
| 2025 PN2 |
2025-Aug-21 |
9.9 LD |
16.6 |
32 |
| 2025 QY |
2025-Aug-22 |
7.5 LD |
7.8 |
16 |
| 2023 PX |
2025-Aug-22 |
2.4 LD |
8.3 |
23 |
| 2025 PR |
2025-Aug-23 |
17.6 LD |
3.4 |
24 |
| 2019 QQ6 |
2025-Aug-24 |
9.4 LD |
17.2 |
31 |
| 2025 QC1 |
2025-Aug-27 |
4.2 LD |
9.4 |
22 |
| 2025 PM2 |
2025-Aug-27 |
9.7 LD |
18.5 |
62 |
| 2025 PX |
2025-Aug-29 |
16.5 LD |
7 |
52 |
| 2017 RK15 |
2025-Aug-29 |
15.8 LD |
13.2 |
26 |
| 2020 TS1 |
2025-Aug-29 |
17.8 LD |
3.3 |
5 |
| 1998 SH2 |
2025-Aug-30 |
8.1 LD |
17.3 |
246 |
| 2025 PJ3 |
2025-Sep-01 |
7.9 LD |
11.7 |
30 |
| 2025 PF3 |
2025-Sep-03 |
16.4 LD |
6.9 |
21 |
| 2025 OG1 |
2025-Sep-05 |
14.5 LD |
4.2 |
35 |
| 2019 JG1 |
2025-Sep-09 |
18.8 LD |
7.9 |
17 |
| 2009 FF |
2025-Sep-11 |
6.8 LD |
12.9 |
155 |
| 2015 SA |
2025-Sep-13 |
10.3 LD |
9.1 |
31 |
| 2022 SS2 |
2025-Sep-13 |
2.4 LD |
7.2 |
13 |
| 2025 FA22 |
2025-Sep-18 |
2.2 LD |
10.8 |
166 |
| 2025 PJ1 |
2025-Sep-21 |
11.6 LD |
11.9 |
134 |
| 2022 SW12 |
2025-Sep-23 |
15 LD |
17.6 |
210 |
| 2021 RN16 |
2025-Sep-23 |
10.1 LD |
8.8 |
7 |
| 2018 QT1 |
2025-Sep-23 |
13 LD |
12.7 |
138 |
| 2019 SF6 |
2025-Sep-28 |
20 LD |
8.4 |
20 |
| 152664 |
2025-Sep-29 |
10.1 LD |
18.6 |
412 |
| 2020 GE1 |
2025-Oct-02 |
13.7 LD |
4.7 |
14 |
| 2022 TU1 |
2025-Oct-08 |
16.9 LD |
12.9 |
10 |
| 2020 QU5 |
2025-Oct-09 |
7.1 LD |
13.6 |
26 |
| 2022 AY5 |
2025-Oct-14 |
7.4 LD |
8.4 |
5 |
| 2022 UY3 |
2025-Oct-15 |
10.2 LD |
7.4 |
15 |
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. |
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Researchers
call it a "Hubble for the sun." SDO
is the most advanced solar observatory ever. |
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3D
views of the sun from NASA's Solar and Terrestrial
Relations Observatory |
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Realtime
and archival images of the Sun from SOHO. |
| |
information about sunspots based on the latest NOAA/USAF Active Region Summary |
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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 |
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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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