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SOLAR WIND STORM: Earth is inside a stream of solar wind blowing faster than 550 km/s. As a result, NOAA forecasters say there is a 40% chance of G1-class geomagnetic storms on Sept. 18th. High-latitude sky watchers should be alert for auroras. Free: Aurora Alerts
PLANETS FOR BREAKFAST: Are you awake before sunrise? Look east! Three planets have lined up in the pre-dawn sky--and the crescent Moon is gliding among them. This morning in Malaysia, Shahrin Ahmad photographed Venus just a fraction of a degree from the lunar disk:
About 20 minutes later, the Moon completely covered Venus. "I almost saw it," says Ahmad, "but the clouds came in just as the occultation began." Later today, the Moon will pass Mars and Mercury as well, producing three lunar occultations in a single day.
Tomorrow offers something new: Venus approaches Regulus, a bright blue star in the constellation Leo. The two will pass less than 1 degree apart on Sept. 19th and 20th forming a bright "double star" in the morning sky. Set your alarm for dawn and enjoy the show! Sky maps: Sept.18, 19, 20.
Realtime Space Weather Photo Gallery
PHYSICS OF AN EXPLODING SPACE WEATHER BALLOON: This month, the students of Earth to Sky Calculus have been launching space weather balloons at a frenetic pace, more than half a dozen so far. Their goal: To monitor the effect of September's surprising solar flares on Earth's upper atmosphere. At the apex of every flight, the balloon explodes and the payload parachutes back to Earth. On Sept. 13th, a new upward-facing camera photographed the pop:
This image illustrates recent findings about the physics of exploding balloons. In Oct. 2015, researchers Sébastien Moulinet and Mokhtar Adda-Bedia of the Ecole Normale Supérieure published a Physical Review Letter entitled "Popping Balloons: A Case Study of Dynamical Fragmentation." In it, they reported the results of a series of fun yet informative laboratory experiments in which one balloon after another was popped and analyzed.
Basically, there are two ways a balloon can pop: along a single seam (the "opening regime") or along many tears (the "fragmentation regime"). This video shows the two regimes in action. Which way the balloon decided to pop depends on the stress in the rubber membrane. When the stress is low, it can be relieved with a single tear, but when the stress is high, many tears are required to do the job.
Clearly, space weather balloons explode in the fragmentation regime. This is hardly a surprise. When space weather balloons are launched, they measure no more than 6 to 8 feet in diameter. By the time they reach the stratosphere, they have stretched into a sphere as wide as a house. That's a lot of tension to release! More information about this research is available from the American Physical Society.
Realtime Space Weather Photo Gallery
ROSE QUARTZ CRYSTAL ECLIPSE PENDANTS: On Aug. 21st during the Great American Solar Eclipse, the students of Earth to Sky Calculus launched 11 space weather balloons from the path of totality. They aimed to photograph the Moon's shadow from the stratosphere--and they succeeded. As a fundraiser, some of the balloons carried jewelry. Here is a rose quartz crystal pendant entering the Moon's shadow more than 90,000 feet above the Malheur National Forest in eastern Oregon:
During the 2.5 hour flight, the pendants were wrapped in the Moon's shadow for more than two minutes, experiencing a spooky darkness colder than -50 C.
You can have one for $149.95. Each crystal pendant comes with a unique gift card showing the jewelry passing through the Moon's shadow and floating at the top of Earth's atmosphere. The interior of the card tells the story of the flight and confirms that this gift has been to the edge of space and back again.
Far Out Gifts: Earth to Sky Store
All proceeds support hands-on STEM education
Realtime Aurora Photo Gallery
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 Sep. 18, 2017, the network reported 14 fireballs.
(13 sporadics, 1 September epsilon Perseid)
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 September 18, 2017 there were 1803 potentially hazardous asteroids.
|
Recent & Upcoming Earth-asteroid encounters: Asteroid | Date(UT) | Miss Distance | Velocity (km/s) | Diameter (m) |
2017 RX1 | 2017-Sep-13 | 15.6 LD | 5.7 | 59 |
2017 RJ2 | 2017-Sep-15 | 1.4 LD | 15.9 | 11 |
2017 RK2 | 2017-Sep-17 | 2.5 LD | 7.7 | 9 |
2017 RX2 | 2017-Sep-18 | 6.2 LD | 12.6 | 18 |
2017 RU2 | 2017-Sep-18 | 6.8 LD | 8.9 | 23 |
2017 RG2 | 2017-Sep-19 | 7.9 LD | 8.4 | 46 |
2017 RQ15 | 2017-Sep-22 | 9.8 LD | 20.5 | 23 |
2017 RB15 | 2017-Sep-22 | 5.8 LD | 5 | 10 |
2017 PR25 | 2017-Sep-23 | 17.9 LD | 13.5 | 235 |
2017 RW2 | 2017-Sep-25 | 15.1 LD | 12.8 | 28 |
2017 RW1 | 2017-Sep-25 | 11 LD | 12.7 | 65 |
2017 RB16 | 2017-Sep-26 | 4.8 LD | 9.5 | 27 |
1989 VB | 2017-Sep-29 | 7.9 LD | 6.3 | 408 |
2017 RP15 | 2017-Sep-30 | 14.8 LD | 5.5 | 16 |
2017 OD69 | 2017-Oct-01 | 13.2 LD | 7.6 | 213 |
2004 RE84 | 2017-Oct-04 | 15.3 LD | 16.1 | 129 |
2017 RV1 | 2017-Oct-12 | 17.8 LD | 10.9 | 357 |
2012 TC4 | 2017-Oct-12 | 0.1 LD | 7.6 | 16 |
2005 TE49 | 2017-Oct-13 | 8.5 LD | 11.2 | 16 |
2013 UM9 | 2017-Oct-15 | 17 LD | 7.8 | 39 |
2006 TU7 | 2017-Oct-18 | 18.7 LD | 13.3 | 148 |
171576 | 2017-Oct-22 | 5.8 LD | 21.2 | 677 |
2003 UV11 | 2017-Oct-31 | 15 LD | 24.5 | 447 |
Notes: LD means "Lunar Distance." 1 LD = 384,401 km, the distance between Earth and the Moon. 1 LD also equals 0.00256 AU. MAG is the visual magnitude of the asteroid on the date of closest approach. | Cosmic Rays in the Atmosphere |
Readers, thank you for your patience while we continue to develop this new section of Spaceweather.com. We've been working to streamline our data reduction, allowing us to post results from balloon flights much more rapidly, and we have developed a new data product, shown here:
This plot displays radiation measurements not only in the stratosphere, but also at aviation altitudes. Dose rates are expessed as multiples of sea level. For instance, we see that boarding a plane that flies at 25,000 feet exposes passengers to dose rates ~10x higher than sea level. At 40,000 feet, the multiplier is closer to 50x. These measurements are made by our usual cosmic ray payload as it passes through aviation altitudes en route to the stratosphere over California.
What is this all about? Approximately 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 radiation sensors that detect cosmic rays, a surprisingly "down to Earth" form of space weather. Cosmic rays can seed clouds, trigger lightning, and penetrate commercial airplanes. Furthermore, there are studies ( #1, #2, #3, #4) linking cosmic rays with cardiac arrhythmias and sudden cardiac death in the general population. Our latest measurements show that cosmic rays are intensifying, with an increase of more than 13% since 2015:
Why are cosmic rays intensifying? The main reason is the sun. Solar storm clouds such as coronal mass ejections (CMEs) sweep aside cosmic rays when they pass by Earth. During Solar Maximum, CMEs are abundant and cosmic rays are held at bay. Now, however, the solar cycle is swinging toward Solar Minimum, allowing cosmic rays to return. Another reason could be the weakening of Earth's magnetic field, which helps protect us from deep-space radiation.
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.
The data points in the graph above correspond to the peak of the Reneger-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 Reneger 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. |
| 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 |
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