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CHANCE OF STORMS: NOAA forecasters estimate a 60% chance of polar geomagnetic storms on Jan. 25-26. That's when a solar wind stream flowing from a southern hole in the sun's atmosphere is expected to reach Earth. Arctic sky watchers should be alert for auroras later this weekend. Aurora alerts: text, voice
SKI HALOES: For people in the northern hemisphere, now is the time to go skiing. Little known fact: Ski lifts are great places to see ice halos. Olivier Staiger photographed this specimen on Jan. 23rd while he was riding in a cable car in the Les Violettes ski region of Switzerland:
"All morning the area was blanketed in stratus clouds and fog," says Staiger. "Shortly before arriving at Les Violettes, the cable-car emerged from the fog and I saw this very nice display of ice halos, sundogs and more."
Snow-making machines at the ski resort played a key role in creating this display. Atmospheric optics expert Les Cowley explains: "Diamond dust ice crystals growing slowly downwind of ski-slope snow blowers filled the air. Sunlight shining through the crystals produced the display. These man-made crystals tend to be more optically perfect than the ones in clouds and so we get bright, sharp and often very rare halos. Outstanding in this display is a lower tangent arc shining just below the horizon. More halos are labeled here."
Going skiing? Be alert for halos. More examples may be found in the realtime photo gallery.
RARE SHADOWS ON JUPITER: Anyone who looks at Jupiter through a telescope is almost guaranteed to see the Galilean satellites (Io, Europa, Ganymede and Callisto) circling the giant planet. On rare occasions, observers catch one of those moons casting its shadow on Jupiter's cloudtops. On Jan 24th, observers in North America and the Carribean saw not one, but three shadows. Efrain Morales Rivera sends this picture from Aquadilla, Puerto Rico:
"I was happy to be able to observe this rare event," says Rivera. A full-sized version of his image matches each shadow to a moon. One belongs to Io, one to Europa, and one to Callisto. If you think you count four shadows, that's because the solid body of Callisto is passing in front of Jupiter and its dark silhouette looks like a shadow, too.
The reason for this "triple shadow transit" has to do with Jupiter's seasons. Jupiter is about to have an equinox--that is, the sun is about to cross Jupiter's equatorial plane. This edge-on alignment with the sun encourages Jupiter's moons to cast their shadows on the planet below. For the record, Jupiter's equinox is on Feb. 5th. Observers of the giant planet should remain alert for shadows.
Realtime Space Weather Photo Gallery
BRIGHT ASTEROID FLYBY: A large asteroid is about to fly past Earth. On the night of Jan. 26-27, mountain-sized space rock 2004 BL86 will be only 3 times farther from us than the Moon. There's no danger of a collision, but the flyby will be easy to observe. Sunlight reflected from the surface of 2004 BL86 will make it glow like a 9th magnitude star. Amateur astronomers with even small backyard telescopes will be able to see it zipping among the stars of the constellation Cancer. Check out this video, prepared by the Sociedad de Astronomia del Caribe, for detailed observing tips:
NASA radars will be observing, too. As the asteroid passes by, astronomers will use the Deep Space Network antenna at Goldstone, California, and the giant Arecibo radar in Puerto Rico to "ping" 2004 BL86, pinpointing the asteroid's location and tracing its shape.
"When we get our radar data back the day after the flyby, we will have the first detailed images," said radar astronomer Lance Benner of JPL, the principal investigator for the Goldstone radar observations of the asteroid. "At present, we know almost nothing about this asteroid, so there are bound to be surprises."
At the moment, astronomers think the asteroid is about a third of a mile (0.5 kilometers) in diameter. The flyby of 2004 BL86 will be the closest by any known space rock this large until asteroid 1999 AN10 flies past Earth in 2027.
Realtime Aurora Photo Gallery
Realtime Comet Photo Gallery
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 Jan. 25, 2015, the network reported 13 fireballs.
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]
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 January 25, 2015 there were 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 |