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SUNSET
CONJUNCTION: When the sun goes down
tonight, step outside and look west. Venus and the
crescent Moon are shining side-by-side through the
twilight. It's a beautiful way to end the day.
GEOMAGNETIC
STORM: Earth is passing through
the wake of a CME, and this is causing geomagnetic
storms at high latitudes. Last night, auroras were
spotted in more than a dozen US states including
Michigan,
Nebraska,
Kansas,
Wisconsin,
North
Dakota, South
Dakota, Iowa,
Illinois,
and Colorado.
Here is what the sky looked like over Grand Portage,
Minnesota:
"The auroras were incredible!"
says photographer Travis Novitsky.
Europeans witnessed a good show, too:
"My girlfriend and I were on the Co. Antrim
coast of Northern Ireland, and the
auroras we saw were sublime!" reports Martin
McKenna. "It's the best I've seen here since
2005, with vertical green pillars of light some
60 degrees high accompanied by amazing pulsating
motions like the beating of a heart. We could even
see the beams reflecting on the ocean forming their
own glitter paths - what a night!"
The storm is subsiding
now. Nevertheless, high-latitude sky watchers
should remain alert for auroras as a fast solar
wind stream continues to buffet Earth's magnetic
field. Aurora alerts:
text,
phone.
more images: from
Steve Milner of Ft St John BC Canada; from
Paul Martin at the Beaghmore Stone Circles,
County Tyrone, N.Ireland; from
Yuichi Takasaka of Lumby, British Columbia,
Canada; from
Paul Kerr of Ballyliffin, Co. Donegal, Ireland;
from
Peter Gorman of Shroove, North Donegal, Ireland;
from
Jon Cooper of Hardendale, Cumbria, UK; from
Douglas Kiesling of Fergus Falls, MN
SIERRA
FIREBALL DECODED: On Sunday morning,
April 22nd, just as the Lyrid meteor shower was
dying down, a spectacular fireball exploded over
California's Sierra Nevada mountain range. The loud
explosion rattled homes from central California
to Reno, Nevada, and beyond. According to Bill Cooke,
head of NASA's Meteoroid Envronment Office, the
source of the blast was a meteoroid about the size
of a minivan.
"Elizabeth Silber at Western
University has searched for infrasound signals from
the explosion," says Cooke. "Infrasound
is very low frequency sound which can travel great
distances. There were strong signals at 2 stations,
enabling a triangulation of the energy source at
37.6N, 120.5W. This is marked by a yellow flag in
the map below."
"The energy is estimated at a whopping 3.8
kilotons of TNT, so this was a big event,"
he continues. "I am not saying there was a
3.8 kiloton explosion on the ground in California.
I am saying that the meteor possessed this amount
of energy before it broke apart in the atmosphere.
[The map] shows the location of the atmospheric
breakup, not impact with the ground."
"The fact that sonic booms were heard indicates
that this meteor penetrated very low in atmosphere,
which implies a speed less than 15 km/s (33,500
mph). Assuming this value for the speed, I get a
mass for the meteor of around 70 metric tons. Hazarding
a further guess at the density of 3 grams per cubic
centimeter (solid rock), I calculate a size of about
3-4 meters, or about the size of a minivan."
"This meteor was probably not a Lyrid; without
a trajectory, I cannot rule out a Lyrid origin,
but I think it likely that it was a background or
sporadic meteor."
News and eyewitness reports: #1,
#2,
#3,
#4.
CRESCENT
MOON ALERT: When the sun goes down
tonight, step outside and look west into the twilight.
You might see something like this:
Miguel Claro photographed the crescent
moon from Almada, Portugal. "Look just below
the bridge," he points out. "You can also
see Jupiter."
The slender crescent will be beaming
through the twilight for the next few evenings.
On Tuesday, April 24th, it will glide by Venus for
a spectacular sunset conjunction. Don't miss it!
more images: from
Stefano De Rosa of Turin, Italy; from
Robert Arn of Fort Collins, CO; from
Russell Vallelunga of Phoenix, Arizona; from
M. Raşid Tuğral of Ankara, Turkiye; from
Zain Ahmed of Karachi, Pakistan
