Friday, Aug. 6, 2021
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CO-ROTATING INTERACTION REGION: A co-rotating interaction region (CIR) might hit Earth’s magnetic field during the late hours of Aug. 6th. CIRs are transition zones between solar wind streams, fast vs. slow. They contain density gradients and compressed magnetic fields that can do a good job sparking high-latitude auroras. Aurora alerts: SMS Text.
THE PERSEID METEOR SHOWER IS UNDERWAY: Earth is entering a stream of debris from Comet 109P/Swift-Tuttle, source of the annual Perseid meteor shower. Although it won’t peak until mid-next week, the shower is already active. Last night alone NASA cameras detected more than a dozen Perseid fireballs over the USA, and Petr Horálek photographed this beauty burning up over the Czech Republic:
“I captured our first Perseid of the year over Proseč on Aug. 3rd,” reports Horálek. “Its rainbow hues were visible despite suburban light pollution.”
109P/Swift-Tuttle is a huge comet with a broad debris stream. It takes Earth weeks to cross it. The shower will probably be most intense on Aug. 11-12 (Wednesday night through Thursday morning) when our planet is closest to the stream’s dusty core. Adjacent nights could be almost equally good.
When should you look? Perseids may be seen any time after ~10 pm. Rates increase sharply after local midnight when the constellation Perseus is high in the sky (sky map). Observers in dark-sky sites can expect to count dozens of meteors during the moonless hours before sunrise.
Pro tip: Get away from city lights! Light pollution kills meteors, as shown this composite image of last year’s Perseid shower:
Tomáš Slovinský and Petr Horálek took the pictures last August from widely spaced locations in eastern Europe. “The left photograph comes from the darkest area of Slovakia – Dark Sky Park Poloniny with a Bortle 2 sky,” explains Horálek. “The right image is from Seč lake in the Czech Republic, where you can find a less-dark Bortle 4 sky. The difference between these two classes of sky is about a thousand naked-eye stars and innumerable faint meteors.”
“To enjoy the 2021 Perseids,” he urges, “find the darkest skies possible!”
THE MIDNIGHT SPACE PEARL: Space is black; so is this pearl. On July 22, 2021, the students of Earth to Sky Calculus launched the Midnight Pearl to the stratosphere onboard a cosmic ray research balloon. Here it is floating 96,785 feet above the Sierra Nevada mountains of central California:
You can have it for $179.95–earrings included! Matching pearl earrings flew inside the payload among the cosmic ray sensors.
The students are selling space pearls to support their cosmic ray ballooning program. Wrapped in a sterling silver infinity twist, each Midnight Pearl comes with a greeting card showing the pendant in flight and telling the story of its trip to the edge of space.
All Sky Fireball Network
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 06 2021, the network reported 52 fireballs.
(31 sporadics, 16 Perseids, 4 alpha Capricornids, 1 southern Delta Aquarid)
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]
|Near Earth Asteroids|
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 6, 2021 there were 2203 potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters:
|Asteroid||Date(UT)||Miss Distance||Velocity (km/s)||Diameter (m)|
|2021 OE1||2021-Aug-02||6.3 LD||9.8||19|
|2021 PC||2021-Aug-02||0.4 LD||11.8||15|
|2021 OZ||2021-Aug-02||14 LD||9||78|
|2020 PN1||2021-Aug-03||9.6 LD||4.6||30|
|2021 NL4||2021-Aug-03||12.8 LD||10.1||69|
|2020 PP1||2021-Aug-03||13 LD||3.6||16|
|2021 OB1||2021-Aug-04||10.2 LD||10.3||27|
|2021 OA1||2021-Aug-05||19.1 LD||6.5||45|
|2021 PJ||2021-Aug-06||8.2 LD||7.2||72|
|2021 PA1||2021-Aug-08||2.1 LD||16.7||14|
|2021 PP||2021-Aug-08||4.2 LD||8.8||53|
|2021 PN1||2021-Aug-09||2.4 LD||16.7||36|
|2021 PM1||2021-Aug-10||5.7 LD||10.5||32|
|2012 BA35||2021-Aug-11||6.9 LD||4.2||64|
|2021 OS1||2021-Aug-13||16.7 LD||7.9||41|
|2016 BQ||2021-Aug-14||4.4 LD||4.7||16|
|2021 PJ1||2021-Aug-15||4.3 LD||9.2||23|
|2021 PV||2021-Aug-20||18.6 LD||13.2||40|
|2016 AJ193||2021-Aug-21||8.9 LD||26.2||655|
|2019 UD4||2021-Aug-22||14.2 LD||5.5||86|
|2020 BC16||2021-Aug-24||15 LD||6.7||34|
|2011 UC292||2021-Aug-24||9 LD||8.5||98|
|2021 NS8||2021-Aug-25||18.4 LD||4.2||36|
|2021 PT||2021-Aug-29||12.9 LD||7.3||145|
|2017 RK15||2021-Aug-29||13.3 LD||11.6||26|
|2015 SW6||2021-Sep-05||15.9 LD||9.9||45|
|2010 RJ53||2021-Sep-09||9.6 LD||19.3||56|
|2020 KR2||2021-Sep-10||14.2 LD||5.1||17|
|2017 SL16||2021-Sep-20||12.8 LD||6.1||23|
|2021 NY1||2021-Sep-22||3.9 LD||9.4||174|
|2019 SF6||2021-Sep-26||16.4 LD||8.6||20|
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.
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 6 years, resulting in a unique dataset of in situ atmospheric measurements.
Latest results: Our most recent flight on June 25, 2021, confirms a trend of decreasing cosmic radiation:
Cosmic ray dose rates peaked in late 2019, and have been slowly declining ever since. This makes perfect sense. Solar Minimum was in late 2019. During Solar Minimum the sun’s magnetic field weakens, allowing more cosmic rays into the solar system. We expect dose rate to be highest at that time.
Now that Solar Minimum has passed, the sun is waking up again. Solar magnetic fields are strengthening, providing a stiffer barrier to cosmic rays trying to enter the solar system. The decline of cosmic radiation above California is a sign that new Solar Cycle 25 is gaining strength.
.Who cares? Cosmic rays are a surprisingly “down to Earth” form of space weather. They can seed clouds, 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. Somewhat more controversial studies (#1, #2, #3, #4) llink cosmic rays with cardiac arrhythmias and sudden cardiac death.
En route to the stratosphere, our sensors also pass through aviation altitudes:
In this plot, 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. The higher you fly, the more radiation you will absorb.
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 first graph (“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. (Click to Source)
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