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Solar wind
speed: 524.9 km/sec
density: 3.7 protons/cm3
explanation | more data
Updated: Today at 2347 UT
X-ray Solar Flares
6-hr max: C5
1940 UT Apr25
24-hr: C5
1940 UT Apr25
explanation | more data
Updated: Today at: 2300 UT
Daily Sun: 25 Apr 13
Sunspot AR1726 has a delta-class magnetic field that poses a continued threat for X-class flares. Credit: SDO/HMI
Sunspot number: 92
What is the sunspot number?
Updated 25 Apr 2013

Spotless Days
Current Stretch: 0 days
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%)
Since 2004: 821 days
Typical Solar Min: 486 days

25 Apr 2013

The Radio Sun
10.7 cm flux: 118 sfu
explanation | more data
Updated 25 Apr 2013

Current Auroral Oval:
Switch to: Europe, USA, New Zealand, Antarctica
Planetary K-index
Now: Kp= 3 quiet
24-hr max: Kp= 3
explanation | more data
Interplanetary Mag. Field
Btotal: 8.0 nT
Bz: 0.8 nT north
explanation | more data
Updated: Today at 2347 UT
Coronal Holes: 25 Apr 13
Solar wind flowing from this major coronal hole could reach Earth on April 26-28. Credit: SDO/AIA.
NOAA Forecasts
Updated at: 2013 Apr 25 2200 UTC
0-24 hr
24-48 hr
40 %
40 %
15 %
15 %
Geomagnetic Storms:
Probabilities for significant disturbances in Earth's magnetic field are given for three activity levels: active, minor storm, severe storm
Updated at: 2013 Apr 25 2200 UTC
0-24 hr
24-48 hr
15 %
10 %
05 %
01 %
01 %
01 %
High latitudes
0-24 hr
24-48 hr
15 %
15 %
25 %
15 %
25 %
10 %
Thursday, Apr. 25, 2013
What's up in space

When is the best time to see auroras? Where is the best place to go? And how do you photograph them? These questions and more are answered in a new book, Northern Lights - a Guide, by Pal Brekke & Fredrik Broms.

Northern Lights - a Guide

THE FULL MOON AND SATURN: When the sun goes down tonight, step outside and face east. The golden "star" next to the rising full Moon is Saturn. Saturn and the Moon will be up, together, all night long. Saturn's rings and lunar mountains are easy targets for small telescopes. Take a look!

BIG SUNSPOT, CHANCE OF FLARES: Sunspot AR1726 is turning away from Earth, but the threat of flares is not subsiding. The sunspot has a delta-class magnetic field that harbors energy for powerful eruptions. NOAA forecasters estimate a 40% chance of M-class flares and a 15% chance of X-flares on April 25th. Solar flare alerts: text, voice.

Amateur astronomer Alan Friedman photographed the sunspot on April 23rd. His H-alpha telescope, tuned to the red glow of solar hydrogen, revealed a seething active region spanning more than 125,000 km (10 Earth diameters) wide:

"The full-sized image reminds me of a Clementine orange," notes Friedman. "I captured the fruity shot through a turbulent jet stream on a beautiful spring day in Buffalo, NY."

The sheer size of the sunspot makes it an easy target for backyard solar telescopes. Browse the gallery for views from around the world.

Realtime Space Weather Photo Gallery

ELLIPTICAL MOON HALOS: The moon is waxing full, which means now is the time to be alert for icy moon halos. On April 22nd, Darryl Luscombe of Sointula, British Columbia, saw an unusual specimen. Instead of being circular, as usual, this halo was elliptical:

"I dont think I have ever seen an elliptical halo around the moon before," says Luscombe. "I looked up and just stared for about a minute. Then I raced inside to get my camera. I just managed to photograph it before it disappeared."

Atmospheric optics expert Les Cowley comments on the apparition: "There have been quite a few ellipticals seen in the last few weeks both in Europe and the US. Something strange [is happening] in all our skies!"

"These unusual ice halos are much smaller than the ordinary 22 degree halo encircling the sun or moon," Cowley continues. "In the 22 degree halo the ring is effectively made by light refracting through a 60 degree ice prism. The smaller elliptical halos need much narrower prisms and we think that six sided plate shaped crystals with very shallow pyramidal ends might do the work. The problem is that such crystals are unphysical and computer simulations using them do not predict the halo very well. An alternative is the wedge shaped sections of small snowflake-like crystals. Whatever their cause, they are rare and mysterious!"

Realtime Space Weather Photo Gallery

LYRID FIREBALLS: For the past few days, Earth has been passing through a stream of debris from ancient Comet Thatcher, source of the annual Lyrid meteor shower. According to international observers, the encounter produced as many as 25 meteors per hour. Some of these were fireballs. NASA's All Sky Fireball Network detected more than 30 Lyrids as bright as Venus on the nights around the shower's April 22nd peak. Here are their orbits:

In the diagram, the red splat marks the location of Earth; green elipses are the orbits of the meteoroids, triangulated by multiple cameras in the meteor network.

"The purple ellipse is the orbit of Comet Thatcher," adds Bill Cooke, lead scientist for NASA's Meteoroid Environment Office. "The orbits of the comet and the meteoroids match up nicely." According to Cooke, the Lyrid fireballs penetrated Earth's atmosphere as deeply as 44 miles above the planet's surface, traveling at an average speed of 105,000 mph.

The shower is subsiding now as Earth exits the debris stream.

Realtime Meteor Photo Gallery

Realtime Aurora Photo Gallery

Realtime Comet Photo Gallery

Realtime Noctilucent Cloud Photo Gallery
[previous years: 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2011]

  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 April 25, 2013 there were potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters:
Miss Distance
2005 NZ6
Apr 29
24.9 LD
1.3 km
2001 DQ8
Apr 30
74.3 LD
1.1 km
2004 BV102
May 25
69.9 LD
1.4 km
1998 QE2
May 31
15.2 LD
2.1 km
2000 FM10
Jun 5
50.3 LD
1.3 km
2002 KL3
Jun 6
66.4 LD
1.1 km
1999 WC2
Jun 12
39.2 LD
1.9 km
2006 RO36
Jun 18
70.9 LD
1.2 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.
  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.
  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
  the underlying science of space weather
Space Weather Alerts
  more links...
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