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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
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.
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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.
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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.
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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.
(9 sporadics)
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 1542
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.
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The
official U.S. government space weather bureau |
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The
first place to look for information about sundogs,
pillars, rainbows and related phenomena. |
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Researchers
call it a "Hubble for the sun." SDO
is the most advanced solar observatory ever. |
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3D
views of the sun from NASA's Solar and Terrestrial
Relations Observatory |
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Realtime
and archival images of the Sun from SOHO. |
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from
the NOAA Space Environment Center |
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the
underlying science of space weather |
