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WEEKEND FORECAST: Geomagnetic activity is subsiding on Aug. 8th as Earth exits one solar wind stream--but it could flare up again before the weekend is over as our planet enters a second stream. NOAA forecasters estimate a 55% chance of geomagnetic storms on Aug. 9th-10th as the solar wind speed rebounds. High-latitude sky watchers should remain alert for auroras. Aurora alerts: text or voice.
BIG SUNSPOT FACES EARTH: The rapid growth of sunspot AR2396 is continuing. Yesterday it was huge. Today it is 50% larger. Astrophotographer "Yvan" sends this picture from Berlare, Belgium:
The growing sunspot group stretches more than 150,000 km from end to end. All by itself, the primary dark core is more than three times the size of Earth. These dimensions make AR2390 an easy target for backyard solar telescopes.
As a matter of fact, it can even be seen with the unaided eye. "Desert haze covering the sky of southern Spain is allowing us to see the sun's disk without a filter," reports Leonor Ana. This is what she saw looking out her kitchen window on August 7th:
"I took the picture just as some birds were passing by," she says. "Perfect timing!"
Of even greater interest is the sunspot's 'beta-gamma' magnetic field, which is invisible to the human eye but nevertheless harbors energy for powerful explosions. NOAA forecasters estimate a 40% to 55% chance of M-class flares this weekend. Any such explosion will surely be geoeffective as the sunspot is directly facing Earth. Solar flare alerts: text or voice.
Warning: Even when the sun is dimmed by low-hanging clouds or haze, it can still damage your eyes. Sunlight magnified by unfiltered optics is dangerously bright. If you chose to photograph the sun, as Leonor Ana did, use the camera's LCD screen for safe viewfinding. Never look into the eyepiece of an unfiltered camera or telescope when the sun is in the field of view.
Realtime Space Weather Photo Gallery
A SLIVER OF VENUS: On August 15th, Venus will pass almost directly between Earth and the sun--an event astronomers call "inferior solar conjunction." As Venus approaches the sun, the planet is turning its night side toward Earth, reducing its luminous glow to a thin sliver. Giorgio Rizzarelli sends these images of the narrowing crescent from Trieste, Italy:
In the days ahead, the crescent of Venus will become increasingly thin and circular. The horns of the crescent might actually touch when the Venus-sun angle is least on August 15th (7.9o). This is arguably the most beautiful time to observe Venus--but also the most perilous. The glare of the nearby sun magnified by a telescope can damage the eyes of anyone looking through the eyepiece.
Anthony J. Cook of the Griffith Observatory has some advice for observers: "I have observed Venus at conjunction, but only from within the shadow of a building, or by adding a mask to the front end of the telescope to fully shadow the optics from direct sunlight. This is tricky with a refractor or a catadioptric, because the optics start at the front end of the tube. Here at Griffith Observatory, I rotate the telescope dome to make sure the lens of the telescope is shaded from direct sunlight, even through it means that the lens will be partially blocked when aimed at Venus. With our Newtonian telescope, I add a curved cardboard mask at the front end of the tube to shadow the primary mirror."
Potential observers should take precautions as outlined above. That said, if you have a GOTO telescope, command it to slew to Venus this evening. The slender cresent is only 12o from the sun on Aug. 8th, and it's a beauty!
Realtime Venus Photo Gallery
Realtime Aurora Photo Gallery
Realtime Sprite Photo Gallery
Realtime NLC 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 Aug. 8, 2015, the network reported 65 fireballs.
(50 sporadics, 13 Perseids, 1 Southern iota Aquariid, 1 Southern delta 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 8, 2015 there were 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 |
| 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 |
| the underlying science of space weather |
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