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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
COMET TAIL: Receding Comet Lovejoy (C/2014 Q2) has faded a bit from its peak brightness earlier this month, but it is still a spectacular comet. Trace the tormented streamers of gas flowing from the comet's icy nucleus in this deep-sky exposure from astrophotographer Gerald Rhemann of Puchenstuben, Austria:
Actually, that was only half of Lovejoy's tail. Click here to see the rest.
The many kinks, eddies and whorls propagating down the tail are caused by an unknown combination of (1) variable activity in the comet's nucleus and (2) gusts of solar wind buffeting the streamers of emerging gas. Every time astronomers photograph the structure, it looks different. Indeed, this is one of the most dynamic comets in years.
Shining like a star of magnitude 4.4, Comet Lovejoy is a difficult target for the naked eye, but as Rhemann's photo shows, it is a wonderful subject for deep-sky photography. The comet is currently passing through the constellation Aries high in the evening sky. The Minor Planet Center has published an ephemeris for accurate pointing of telescopes.
Realtime Comet Photo Gallery
A GREEN FLASH FROM VENUS: You've probably heard of the green flash--an emerald ray that briefly caps the sun as the solar disk sinks into the waves of a clear ocean horizon. Green flashes from the sun are so rare, they were once thought to be mythological. Now consider the following: a green flash from Venus. "I saw one," says photographer Kouji Ohnishi who sends this picture from Nagano, Japan:
"Venus was setting behind Mt.Hodaka (3190m) on Jan. 13th when the green flash appeared," he says.
Can it be real? "Yes, indeed," says atmospheric optics expert Les Cowley, who explains the phenomenon: "Venus flashes green as it touches the mountain -- but surely the mountain is above the normal horizon where flashes occur? We see these mountainside green flashes because the normal temperature gradients in the air are compressed and strengthened when wind blows across the mountain ridges. The strengthening can mimic conditions over the sea surface and sometimes be enough to produce mirages - the stuff of green flashes."
Astonishingly, Ohnishi also recorded a green flash from Mercury. "What a way to end the day!"
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
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. 24, 2015, the network reported 9 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 24, 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 |