sábado, 14 de septiembre de 2013

What's up in space

Listen to radar echoes from satellites and meteors, live on listener-supported Space Weather Radio. 
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VOYAGER 1 HAS LEFT THE SOLAR SYSTEM: Researchers have long waited for one of the Voyager probes
to leave the solar system. In a surprising turn of events, NASA announced on Thursday that Voyager 1 entered 
interstellar space a whole year ago. This event sets in motion a new era of exploration of the realm between the
 stars. Congratulations to the Voyager team! [full story]

ALL QUIET ALERT: With the Sun's disk almost completely devoid of sunspots, solar flare activity has come to
a halt. Measurements by NOAA's GOES 15 satellite show that the sun's global x-ray emission, a key metric of 
solar activity, has flatlined:
The quiet is unlikely to break this weekend. NOAA forecasters estimate a scant 1% chance of 
M- or X-class solar flares during the next 24-48 hours.
The quiet spell is a bit strange because 2013 is supposed to be a year of solar maximum, with lots 
of flares and sunspots. Supporting this view are data from NASA-supported observatories which 
show that the sun's magnetic field is poised to flip--a long-held sign that Solar Max has arrived. 
Nevertheless, solar activity is low.
One possible explanation is that Solar Max is double-peaked and we are in the valley between peaks. If so, solar activity could surge again in late 2013-2014. No one can say for sure, though. Researchers have 
been studying sunspots for more than 400 years, and we still cannot predict the behavior of the 
solar cycle. Continued quiet or stormy space weather? Both are possible in the weeks and months 
ahead. Solar flare alerts: textvoice.

RUSSIAN AURORAS: Earth is inside a stream of medium-speed (500 km/s) solar wind. While this 
is not yet causing a geomagnetic storm, the action of the wind is sufficient to ignite bright auroras 
around the Arctic Circle. Valentin Jiganov sends this picture taken on Sept. 13th from Khibiny in the 
Murmansk region of Russia:
Such displays could spread around the Arctic Circle tonight. NOAA forecasters estimate a 45% 
chance of polar geomagnetic storms on Sept. 13th as the solar wind continues to blow. Aurora alerts: textvoice.

METEOR OUTBURST? European sky watchers have witnessed an outburst of September epsilon Perseid meteors. "The outburst occurred around UT midnight on Sept. 9-10," says Bill Cooke, head of
 NASA's Meteoroid Environment Office. "During a two hour period, meteors appeared at a rate 
equivalent to ~50 per hour (ZHR). We did not see the outburst in North America because it was 
still daylight at the time."
NASA all-sky cameras have been recording epsilon Perseid fireballs for days, albeit at a much
 lower rate than what the Europeans saw. The shower has been active since early September,
 allowing Cooke's team to calculate orbits for more than a dozen meteoroids:
In the diagram, orbits are color-coded by velocity. Epsilon Perseid meteoroids hit Earth's 
atmosphere at a "blue-green" speed of about 62 km/s (139,000 mph). According to NASA data, 
the debris stream appears to be rich in fireball-producing meteoroids.
The epsilon Perseid shower peaks every year around this time, but the shower is not well known
 because it is usually weak, producing no more than 5 meteors per hour. In 2008 the shower 
surprised observers with an outburst five times as active, and this year the shower may have 
doubled even that. Clearly, the epsilon Perseid debris stream contains some dense filaments of 
material that Earth usually misses but sometimes hits.
No one knows the source of the September epsilon Perseid meteor shower. Whatever the parent 
is, probably a comet, its orbit must be similar to the green ellipses shown in the orbit-map above. 
As NASA cameras continue to gather data on this shower, orbital parameters will become more 
accurately known, possibly leading to a match.
Meanwhile, sky watchers should be alert for more epsilon Perseids in the nights ahead. The 
shower is waning but still active and more outbursts are possible.


 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 September 14, 2013 there were 1426 potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters:
Asteroid
Date(UT)
Miss Distance
Size
2013 RR43
Sep 7
1.5 LD
36 m
2013 RS43
Sep 13
2.9 LD
18 m
2000 DK79
Nov 10
49.1 LD
3.2 km
2011 JY1
Nov 13
8.2 LD
57 m
2001 AV43
Nov 18
3 LD
57 m
2010 CL19
Nov 25
37.6 LD
1.3 km
2013 NJ
Nov 26
2.5 LD
180 m
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.
 Essential web links
NOAA Space Weather Prediction Center
 The official U.S. government space weather bureau
Atmospheric Optics
 The first place to look for information about sundogs, pillars, rainbows and related phenomena.
Solar Dynamics Observatory
 Researchers call it a "Hubble for the sun." SDO is the most advanced solar observatory ever.
STEREO
 3D views of the sun from NASA's Solar and Terrestrial Relations Observatory
Solar and Heliospheric Observatory
 Realtime and archival images of the Sun from SOHO.
Daily Sunspot Summaries
 from the NOAA Space Environment Center
Heliophysics
 the underlying science of space weather
Space Weather Alerts
  
 more links...