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CHANCE OF FLARES: Solar activity is low, but the quiet could soon be interrupted by an M-class solar flare. Fast-growing sunspot AR2390 has an unstable 'beta-gamma' magnetic field that harbors energy for moderately strong explosions. Any such flare on July 27th will likely be geoeffective because the sunspot is directly facing Earth. Solar flare alerts: text or voice.
WILL THE MOON REALLY TURN BLUE? When someone says "Once in a Blue Moon," you know what they mean: rare, seldom, even absurd. This year it means "the end of July." For the second time this month, the Moon is about to become full. There was one full Moon on July 2nd, and now another is coming on July 31st. According to modern folklore, the second full Moon in a calendar month is "blue." Strange but true: Sometimes the Moon really turns blue. Scroll past the waxing full Moon, photographed on July 25th by Giuseppe Petricca of Pisa, Italy, for more information:
The blue areas in the color-enhanced image (right) are caused by Titanium in lunar soil. [more]
A truly-blue Moon usually requires a volcanic eruption. Back in 1883, for example, people saw blue moons almost every night after the Indonesian volcano Krakatoa exploded with the force of a 100-megaton nuclear bomb. Plumes of ash rose to the very top of Earth's atmosphere, and the Moon became an azure-colored disk.
Krakatoa's ash was the reason. Some of the plumes were filled with particles 1 micron wide, about the same as the wavelength of red light. Particles of this special size strongly scatter red light, while allowing blue light to pass through. Krakatoa's clouds thus acted like a blue filter. People also saw blue-colored Moons in 1983 after the eruption of the El Chichon volcano in Mexico. And there are reports of blue Moons caused by Mt. St. Helens in 1980 and Mount Pinatubo in 1991.
Forest fires can do the same trick. A famous example is the giant muskeg fire of Sept. 1953 in Alberta, Canada. Clouds of smoke containing micron-sized oil droplets produced lavender suns and blue Moons all the way from North America to England. At this time of year, summer wildfires often produce smoke with an abundance of micron-sized particles–just the right size to turn the Moon truly blue. Sky watchers in western parts of the USA and Canada, where wildfires are in progress, could experience this phenomenon.
Realtime Space Weather Photo Gallery
RADS ON A PLANE: Many people think that only astronauts have to worry about cosmic radiation. Not so. Regular air travelers are exposed to cosmic rays, too. This week, Spaceweather.com's Dr. Tony Phillips and the students of Earth to Sky Calculus flew across the United States to conduct a transcontinental launch of space weather balloons. They took radiation sensors on board the plane to find out how many cosmic rays they would absorb during the flight. Here are the data they collected:
Radiation levels in the cabin of the Airbus 319 (Spirit Airlines FL640) tripled within ten minutes after takeoff, and were nearly 30 times ground level by the time the plane reached cruising altitude at 39,000 feet. Summing over the entire flight, the sensors measured about 1 mrem of radiation--similar to a dental x-ray.
There was no solar storm in progress. The extra radiation was just a regular drizzle of cosmic rays reaching down to aviation altitudes. This radiation is ever-present and comes from supernovas, black holes, and other sources across the galaxy. Solar activity modulates the intensity of cosmic rays. Gusts of solar wind and CMEs can actually cause radiation levels to drop by sweeping aside cosmic rays near Earth. Periods of low solar activity, on the other hand, allow radiation levels to rise.
Solar activity is not the only variable: Radiation levels vary within the plane itself. Different-colored lines in the data plot, above, represent different locations inside the cabin. On this particular flight, dose rates were highest in First Class and lowest near the toilets in the rear. This gradient is not understood; presumably, it has something to do with the way the fuselage and fuel tanks interact with energetic particles. The altitude of the plane matters as well. When the cruising altitude increased about two hours into the flight, dose rates increased accordingly. All of these factors make radiation levels onboard airplanes unpredictable.
The radiation sensors are the same ones that Earth to Sky Calculus routinely flies onboard helium balloons to measure cosmic rays in the stratosphere. They 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.
Stay tuned for updates from the return flight.
ALPHA CAPRICORNID METEOR SHOWER: Earth is passing through a stream of debris from Comet 169P/NEAT, source of the annual alpha Capricornid meteor shower. Over the weekend, NASA's network of all-sky meteor cameras recorded more than a dozen alpha Capricornid fireballs over the USA, including this one above Mount Hopkins, Arizona:
This is an annual shower, which peaks every year between the 25th and 30th of July. Peak rates are typically no higher than 5 to 10 meteors per hour.
Every year, however, the alpha Capricornids are improving. According to the research of meteor experts Peter Jenniskens and Jeremie Vaubaillon, the debris stream is slowly drifting across Earth's orbit, so that each year our planet passes a little closer to its heart. The bulk of the dust will not be in Earth's path until the 24th century. If their predictions are correct, the Alpha Capricornids will become a major annual storm in 2200 - 2400 A.D., one that will be "stronger than any current annual shower."
Until then, sky watchers should remain alert for a relatively small number of alpha Capricornid fireballs in the nights ahead. Observers in both hemispheres can see this minor but beautiful shower. The best time to look is during the hours around local midnight when the constellation Capricorn reaches its highest point in the southern sky.
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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 Jul. 27, 2015, the network reported 10 fireballs.
(4 sporadics, 3 Southern delta Aquariids, 2 alpha Capricornids, 1 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 July 27, 2015 there were 1602 potentially hazardous asteroids. 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.
| ||The official U.S. government space weather bureau |
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| ||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 |
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