By Spaceweather.com, 08/10/2015
PERSEID METEOR SHOWER–THIS WEEK: Earth is entering a stream of debris from Comet Swift-Tuttle, source of the annual Perseid meteor shower. Forecasters expect meteor rates to peak at 100+ per hour on the night of Aug. 12-13 when our planet passes through the heart of the debris stream. Perseids produce more fireballs than any other meteor shower of the year, so stay tuned for a good show. [meteor radar] Solar flare alerts: text or voice.
THE SUNSPOT THAT WON’T EXPLODE: Measuring more than 150,000 km wide, sunspot AR2396 is one of the biggest sunspots of the current solar cycle. For the past week it has crossed the solar disk apparently poised to explode. Yet it has not. “It is a sleeping giant,” says Sergio Castillo, who photographed the behemoth from his backyard observatory in Corona, CA:
“AR2396 is huge, but dormant,” says Castillo. “There are very few flares erupting out of it.”
Castillo took the picture using a “Calcium K” filter tuned to the light of ionized calcium atoms in the sun’s lower atmosphere. Calcium K filters highlight the bright magnetic froth that sometimes forms around a sunspot’s dark core. AR2396 is very frothy, indeed.
Magnetic froth, however, does not herald an explosion. It merely means that the sunspot is photogenic. Observers with solar telescopes are encouraged to make their own contribution to the gallery:
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. Damian Peach sends this image of the narrowing crescent from his private observatory in Selsey, UK:
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!
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. 9, 2015, the network reported 42 fireballs.
(21 Perseids, 20 sporadics, 1 Northern 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]
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 10, 2015 there were 1603 potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters:
Asteroid
Date(UT)
Miss Distance
Size
2015 PK
Aug 6
0.2 LD
10 m
2005 NZ6
Aug 6
76.5 LD
1.4 km
2005 JF21
Aug 16
20.1 LD
1.6 km
2004 BO41
Aug 31
57.3 LD
1.2 km
1991 CS
Sep 4
62.1 LD
1.4 km
2014 KS76
Sep 14
8.7 LD
22 m
2004 TR12
Sep 15
58.8 LD
1.0 km
2000 FL10
Oct 10
65.7 LD
1.9 km
2011 QD48
Oct 17
67.5 LD
1.0 km
2014 UR
Oct 18
3.8 LD
21 m
2011 SE97
Oct 18
12 LD
50 m
2001 UY4
Oct 21
58.2 LD
1.0 km
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.
Current Conditions
Solar wind
speed: 493.6 km/sec
density: 3.9 protons/cm3
explanation | more data
Updated: Today at 1345 UT
X-ray Solar Flares
6-hr max: B7 0911 UT Aug10
24-hr: B8 0610 UT Aug10
explanation | more data
Updated: Today at: 1300 UT
Daily Sun: 10 Aug 15
Big sunspot AR2396 is quiet, but it poses a continued threat for M-classsolar flares.Credit: SDO/HMI
Sunspot number: 87
What is the sunspot number?
Updated 10 Aug 2015
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 10 Aug 2015
The Radio Sun
10.7 cm flux: 115 sfu
explanation | more data
Updated 10 Aug 2015
Current Auroral Oval:
Switch to: Europe, USA, New Zealand, Antarctica
Credit: NOAA/Ovation
Planetary K-index
Now: Kp= 2 quiet
24-hr max: Kp= 3 quiet
explanation | more data
Interplanetary Mag. Field
Btotal: 4.9 nT
Bz: 0.5 nT north
explanation | more data
Updated: Today at 1349 UT
Coronal Holes: 10 Aug 15
There are no large coronal holes on the Earthside of the sun. Credit: SDO/AIA.
Noctilucent Clouds
The northern season for NLCs is underway. NASA’s AIM spacecraft spotted the first noctilucent clouds over the Arctic Circle on May 19th
Switch view: Europe, USA, Asia, Polar
Updated at: 08-09-2015 16:55:02
NOAA Forecasts
Updated at: 2015 Aug 09 2200 UTC
FLARE
0-24 hr
24-48 hr
CLASS M
35 %
35 %
CLASS X
05 %
05 %
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 09 2200 UTC
Mid-latitudes
0-24 hr
24-48 hr
ACTIVE
35 %
30 %
MINOR
20 %
05 %
SEVERE
05 %
01 %
High latitudes
0-24 hr
24-48 hr
ACTIVE
15 %
20 %
MINOR
30 %
35 %
SEVERE
50 %
30 %
Space Weather Update: 08/10/2015
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