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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
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
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: text,
voice.
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.
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.
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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