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HAPPY SOLSTICE! Today is the shortest day of the year in the northern hemisphere, and the longest day in the south--that is, it's the "December solstice." The exact moment of the solstice is Thursday, Dec. 21st, at 10:27 p.m. EST, when the sun stops moving south and starts moving north again. This event marks the beginning of winter in the north and summer in the south.
PSCs SPILL OUT OF THE ARCTIC: Normally, polar stratospheric clouds (PSCs) are confined inside the Arctic Circle. Only above the poles can the stratosphere become cold enough to create these rare clouds. However, during this week's outbreak of PSCs, the clouds have spilled out of the Arctic to places they are seldom seen. This morning, Ian Carstairs photographed them over Harleston, Norfolk, UK:
"The display has spread south all the way to +52N," says Nock. That's more than 14 degrees below the Arctic Circle.
Widely considered to be the most beautiful clouds on Earth, polar stratospheric clouds are a sign of extreme cold. PSCs form when the temperature in the Arctic stratosphere drops to a staggeringly-low -85 C. Then, and only then, can widely-spaced water molecules in the dry stratosphere coalesce into tiny ice crystals. High-altitude sunlight shining through the crystals creates intense iridescent colors that rival auroras.
Something new: For the rest of this northern winter season, we will publish daily predictions of temperatures in the Arctic stratosphere. This will help sky watchers know when to look for these rare clouds. The predictions are right here.
more images: from Shaun Greenwell of Newcastle upon Tyne, UK; from Alan C Tough of Elgin, Moray, Scotland; from Lesley Robertson of Black Isle, Scotland; from Sheri Karl of Aberdeen, Scotland; from Jamie McBean of Herne Bay, Kent, UK; from Tomas of Perthshire, Scotland; from Gordon Ward of Hightown Castleford UK; from Les Brooks of East Shore Village, County Durham, UK; from Michael Horne of Luncarty, Scotland; from Steve Brown of North Yorkshire, UK; from Stu Nock of Manchester, UK
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BIG SUNSPOT ALERT: Sunspot AR3529 is still growing, quadrupling in size since Tuesday. This 48-hour movie from NASA's Solar Dynamics Observatory shows its rapid development:
With two primary dark cores twice the size of Earth, AR3529 is an easy target for solar filtered telescopes. You can even see it through eclipse glasses--no magnification required.
Of greater interest is the sunspot's 'delta-class' magnetic field. Within the sunspot + and - magnetic polarities are pressing together. Magnetic reconnection could produce an X-class solar flare. Any eruptions today will be Earth-directed, as the sunspot is almost directly facing Earth. Solar flare alerts: SMS Text
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CHRISTMAS GIFTS FROM THE EDGE OF SPACE: Are you looking for a far-out Christmas gift? Check out the Earth to Sky Store. It's filled with unique items that have flown to the edge of space onboard cosmic ray research balloons.
Carried aloft by giant helium balloons, these unique gifts have flown above 99.7% of Earth's atmosphere, experiencing space-like blasts of cosmic rays, extreme cold, and a wild ride parachuting back to Earth after the balloon explodes. Even Amazon doesn't carry items this far out.
Don't forget to enter coupon code "BUZZALDRIN" at checkout for a 10% holiday discount.
Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education
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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 21, 2023, the network reported 6 fireballs.
(4 sporadics, 2 December Leonis Minorids)
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 21, 2023 there were 2349 potentially hazardous asteroids.
|
Recent & Upcoming Earth-asteroid encounters: Asteroid | Date(UT) | Miss Distance | Velocity (km/s) | Diameter (m) |
2023 XJ13 | 2023-Dec-16 | 9.7 LD | 9.2 | 14 |
2023 XJ10 | 2023-Dec-17 | 8.3 LD | 16.1 | 28 |
2023 XL14 | 2023-Dec-17 | 1.5 LD | 6.3 | 9 |
2023 XH1 | 2023-Dec-17 | 15.2 LD | 5.4 | 17 |
2023 YY | 2023-Dec-17 | 14.7 LD | 6.7 | 40 |
2023 XA14 | 2023-Dec-17 | 10.7 LD | 5.4 | 12 |
2023 XL11 | 2023-Dec-18 | 6.2 LD | 11.7 | 16 |
2023 YA1 | 2023-Dec-18 | 3.9 LD | 6.1 | 8 |
2023 YS | 2023-Dec-19 | 5.3 LD | 31.5 | 28 |
2023 XF2 | 2023-Dec-19 | 9.8 LD | 8 | 22 |
2016 XD2 | 2023-Dec-19 | 18.8 LD | 6.9 | 59 |
2023 YO | 2023-Dec-19 | 4.6 LD | 4.3 | 7 |
2023 XS | 2023-Dec-19 | 11.5 LD | 9.1 | 31 |
341843 | 2023-Dec-20 | 16.5 LD | 5.3 | 344 |
2023 YB | 2023-Dec-21 | 8.8 LD | 11.2 | 28 |
2018 YJ2 | 2023-Dec-21 | 18.4 LD | 13.1 | 154 |
2022 YG | 2023-Dec-22 | 11.2 LD | 5.1 | 17 |
2023 VD6 | 2023-Dec-23 | 10.6 LD | 15.5 | 159 |
2023 YP | 2023-Dec-23 | 0.9 LD | 7.7 | 9 |
2023 XN10 | 2023-Dec-23 | 18.4 LD | 9.9 | 65 |
2023 XD18 | 2023-Dec-23 | 3.9 LD | 11 | 17 |
2020 YO3 | 2023-Dec-23 | 3.6 LD | 16.6 | 42 |
2023 XN11 | 2023-Dec-24 | 9.3 LD | 10.4 | 42 |
2010 UE51 | 2023-Dec-24 | 9 LD | 1.3 | 7 |
2023 XP13 | 2023-Dec-24 | 11.9 LD | 18.7 | 28 |
2023 YT | 2023-Dec-25 | 6.1 LD | 4.4 | 21 |
2023 XK16 | 2023-Dec-25 | 8.7 LD | 7.4 | 38 |
2020 YR2 | 2023-Dec-25 | 13.8 LD | 8 | 8 |
2023 XJ3 | 2023-Dec-25 | 16.5 LD | 9.2 | 55 |
2020 KT4 | 2023-Dec-25 | 13.4 LD | 7.3 | 76 |
2023 XO7 | 2023-Dec-26 | 6.3 LD | 6.7 | 23 |
2023 YD | 2023-Dec-28 | 1.6 LD | 9.9 | 29 |
2023 YZ | 2023-Dec-29 | 10 LD | 5.6 | 29 |
2023 YM | 2023-Dec-30 | 10.1 LD | 12.4 | 37 |
2023 XE12 | 2023-Dec-31 | 14.7 LD | 11.8 | 42 |
2021 AM6 | 2023-Dec-31 | 18.3 LD | 6.6 | 17 |
2023 YR | 2024-Jan-02 | 4.5 LD | 12.2 | 39 |
2019 KK5 | 2024-Jan-03 | 10.6 LD | 20.9 | 98 |
2002 AY1 | 2024-Jan-08 | 15.2 LD | 17.3 | 230 |
2023 XN13 | 2024-Jan-09 | 15.8 LD | 1.4 | 8 |
2023 XT14 | 2024-Jan-10 | 12.2 LD | 6.4 | 27 |
2020 AC1 | 2024-Jan-11 | 19.3 LD | 5.3 | 7 |
2023 WZ3 | 2024-Jan-11 | 16.1 LD | 4 | 35 |
2021 CZ2 | 2024-Jan-16 | 8 LD | 14.3 | 113 |
2021 BL3 | 2024-Jan-23 | 17.2 LD | 23.4 | 41 |
2017 BG92 | 2024-Jan-25 | 11.8 LD | 6.3 | 6 |
2011 CQ1 | 2024-Jan-26 | 11.3 LD | 4.6 | 1 |
2007 EG | 2024-Jan-30 | 16 LD | 8.6 | 43 |
2008 OS7 | 2024-Feb-02 | 7.5 LD | 18.2 | 285 |
2019 CC5 | 2024-Feb-04 | 19.2 LD | 15 | 139 |
2023 SP1 | 2024-Feb-07 | 14.3 LD | 11.8 | 256 |
2020 DK | 2024-Feb-12 | 8.9 LD | 9.9 | 22 |
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 7 years, resulting in a unique dataset of in situ atmospheric measurements.
Latest results (July 2022): Atmospheric radiation is decreasing in 2022. Our latest measurements in July 2022 registered a 6-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.
| 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 |
| Authoritative predictions of space junk and satellite re-entries |
| 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. |
| from the NOAA Space Environment Center |
| the underlying science of space weather |
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