Spotless Days Current Stretch: 0 days 2015 total: 0 days (0%) 2014 total: 1 day (<1%) 2013 total: 0 days (0%) 2012 total: 0 days (0%) 2011 total: 2 days (<1%) 2010 total: 51 days (14%) 2009 total: 260 days (71%) Updated 06 Aug 2015
Planetary K-index Now: Kp= 2 quiet 24-hr max: Kp= 4 unsettled explanation | more data
Interplanetary Mag. Field Btotal: 7.8 nT Bz: 0.5 nT north explanation | more data Updated: Today at 2348 UT
Coronal Holes: 06 Aug 15
There are no large coronal holes on the Earthside of the sun. Credit: SDO/AIA.
Noctilucent CloudsThe northern season for NLCs is underway. NASA's AIM spacecraft spotted the first noctilucent clouds over the Arctic Circle on May 19th.
Geomagnetic Storms: Probabilities for significant disturbances in Earth's magnetic field are given for three activity levels: active, minor storm, severe storm
Updated at: 2015 Aug 06 2200 UTC
Mid-latitudes
0-24 hr
24-48 hr
ACTIVE
50 %
35 %
MINOR
25 %
15 %
SEVERE
05 %
01 %
High latitudes
0-24 hr
24-48 hr
ACTIVE
05 %
15 %
MINOR
25 %
30 %
SEVERE
70 %
50 %
Thursday, Aug. 6, 2015
What's up in space
Learn to photograph Northern Lights like a pro. Sign up for Peter Rosen's Aurora Photo Courses in Abisko National Park, winner of the TripAdvisor Certificate of Excellence Award 2015.
CHANCE OF STORMS: A stream of high speed solar wind is buffeting Earth's magnetic field on Aug.6th. As a result, the chance of polar geomagnetic storms during the next 48 hours is as high as 70%. High-latitude sky watchers should be alert for auroras, especially during the hours around local midnight. Aurora alerts: text or voice.
YES, THIS IS REAL: NOAA's Deep Space Climate Observatory (DSCOVR), on a mission to monitor the solar wind a million miles from Earth, has taken a unique picture of the Earth-Moon system. It shows the farside of the Moon crossing the iconic "blue marble" on July 16th. Click to witness the transit:
DSCOVR is a partnership between NOAA, NASA, and the U.S. Air Force. The July 16th images were captured by NASA's Earth Polychromatic Imaging Camera (EPIC), a four megapixel CCD camera and telescope onboard the distant observatory.
Because the Moon is tidally locked to Earth, only one side is visible from our planet. The unseen farside of the Moon was shrouded in mystery until 1959 when the Soviet Luna 3 spacecraft swung around the Moon and photographed it for the first time. DSCOVR will repeat the trick about twice a year as observatory periodically crosses the orbital plane of the Moon.
Once EPIC begins regular observations next month, NASA will post daily color images of Earth to a dedicated public website. These images, showing different views of the planet as it rotates through the day, will be available 12 to 36 hours after they are acquired. Read the NASA press release for more information.
PERSEID FIREBALLS: Earth is entering a stream of debris from Comet Swift-Tuttle, source of the annual Perseid meteor shower. Peak rates of 100+ meteors per hour are expected next week when Earth approaches the heart of the debris stream. The display, however, is already underway. "Our network of meteor cameras has picked up more than 78 Perseid fireballs since July 27th," reports Bill Cooke of NASA's Meteoroid Environment Office. He prepared this solar system diagram showing the orbits of all the fireballs so far:
The green ellipses trace the orbits of Perseid meteoroids. They are a good match to the orbit of the parent comet, shown in purple.
"Comet debris particles a few cm wide are hitting the atmosphere with an average speed of 59.6 km/s (133,350 mph)," continues Cooke. "The average magnitude of the resulting fireballs is -3.7, about as bright as Venus."
Cooke and colleagues have been monitoring fireball activity for years, and they have found that the Perseids produce more fireballs than any other annual shower. Check out their data.
"Comet Swift-Tuttle has a huge nucleus--about 26 km in diameter," notes Cooke. "Most other comets are much smaller, with nuclei only a few kilometers across. As a result, Comet Swift-Tuttle produces a large number of meteoroids, many of which are hefty enough to produce fireballs."
More fireballs are in the offing as Earth moves deeper into the debris stream of Comet Swift-Tuttle. Stay tuned!
INFERIOR CONJUNCTION 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. Astrophotographer Pete Lawrence of Selsey, UK, has been monitoring the transformation:
"A reasonably run of clear days in the UK has given me the opportunity to capture the Venusian crescent from 25 July to August 3rd, with July 26, 27 and 28 missing due to poor weather," explains Lawrence. "The progression of the crescent as Venus approaches inferior conjunction is clear."
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. 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."
For the rest of this week Venus can still be observed without elaborate precautions in deep twilight after sunset. Every evening the crescent grows and narrows. Scan the realtime photo gallery for updates.
NEUTRONS ON A PLANE: Want to experience space weather? It's easy. Just step onboard an airplane. Recently, Spaceweather.com and the students of Earth to Sky Calculus have been monitoring cosmic radiation levels in the cabins of commercial jets. Measurements of X-rays and gamma-rays show that travelers absorb the equivalent of one or more dental X-rays on a typical flight across the USA. But X-rays and gamma-rays represent only a fraction of the total radiation evnvironment. On July 23, 2015, for the first time, they carried a neutron bubble chamber onboard. Here is what the chamber looked like at the end of a 5 hour flight from Boston to Las Vegas:
Each of the bubbles is formed by an energetic neutron passing through the chamber. By counting the bubbles, it is possible to estimate the total dose of neutron radiation. The answer, for this particular flight, was 1240 microRads (energy range 200 keV - 15 MeV). How does this compare to ionizing radiation? X-ray and gamma-ray sensors carried onboard the same plane accumulated a lesser dose of 860 microRads (energy range 10 keV to 20 MeV).
Lesson: When characterizing the radiation environment inside an airplane, neutrons are at least as important as X-rays and gamma-rays.
Among researchers it is well known that neutrons are an important form of cosmic rays, providing much of the biologically effective radiation dose at altitudes of interest to aviation and space tourism. Low-energy neutrons also cause single-event upsets in aircraft avionics, especially devices that contain Boron 10.
During the five hours of the July 23rd flight, the radiation sensors accumulated a total dose of 2100 microRads (neutrons + X-rays + gamma-rays). This is ~140 times the dose of cosmic rays at sea level during the same 5 hours.
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. 6, 2015, the network reported 86 fireballs. (73 sporadics, 8 Perseids, 2 Southern delta Aquariids, 1 Northern delta Aquariid, 1 , 1 alpha Capricornid)
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, 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.
