Sometimes I complain about the earthly weather, but mostly I like to post about astronomy and space events. Hope you enjoy the articles.
By: Susie77, 10:12 PM GMT on July 27, 2010
Well, that's what the sci guys call 'em.
From NASA Science
Spacequakes Rumble Near Earth
Rumbles without sound
Auroras rain down
Magnetic fields shake
Beware the spacequake
July 27, 2010: Researchers using NASA's fleet of five THEMIS spacecraft have discovered a form of space weather that packs the punch of an earthquake and plays a key role in sparking bright Northern Lights. They call it "the spacequake."
A spacequake is a temblor in Earth's magnetic field. It is felt most strongly in Earth orbit, but is not exclusive to space. The effects can reach all the way down to the surface of Earth itself.
"Magnetic reverberations have been detected at ground stations all around the globe, much like seismic detectors measure a large earthquake," says THEMIS principal investigator Vassilis Angelopoulos of UCLA.
It's an apt analogy because "the total energy in a spacequake can rival that of a magnitude 5 or 6 earthquake," according to Evgeny Panov of the Space Research Institute in Austria. Panov is first author of a paper reporting the results in the April 2010 issue of Geophysical Research Letters (GRL).
In 2007, THEMIS discovered the precursors of spacequakes. The action begins in Earth's magnetic tail, which is stretched out like a windsock by the million mph solar wind. Sometimes the tail can become so stretched and tension-filled, it snaps back like an over-torqued rubber band. Solar wind plasma trapped in the tail hurtles toward Earth. On more than one occasion, the five THEMIS spacecraft were in the line of fire when these "plasma jets" swept by. Clearly, the jets were going to hit Earth. But what would happen then? The fleet moved closer to the planet to find out.
"Now we know," says THEMIS project scientist David Sibeck of the Goddard Space Flight Center. "Plasma jets trigger spacequakes."
According to THEMIS, the jets crash into the geomagnetic field some 30,000 km above Earth's equator. The impact sets off a rebounding process, in which the incoming plasma actually bounces up and down on the reverberating magnetic field. Researchers call it "repetitive flow rebuffing." It's akin to a tennis ball bouncing up and down on a carpeted floor. The first bounce is a big one, followed by bounces of decreasing amplitude as energy is dissipated in the carpet.
"We've long suspected that something like this was happening," says Sibeck. "By observing the process in situ, however, THEMIS has discovered something new and surprising."
The surprise is plasma vortices, huge whirls of magnetized gas as wide as Earth itself, spinning on the verge of the quaking magnetic field.
"When plasma jets hit the inner magnetosphere, vortices with opposite sense of rotation appear and reappear on either side of the plasma jet," explains Rumi Nakamura of the Space Research Institute in Austria, a co-author of the study. "We believe the vortices can generate substantial electrical currents in the near-Earth environment."
Acting together, vortices and spacequakes could have a noticeable effect on Earth. The tails of vortices may funnel particles into Earth's atmosphere, sparking auroras and making waves of ionization that disturb radio communications and GPS. By tugging on surface magnetic fields, spacequakes generate currents in the very ground we walk on. Ground current surges can have profound consequences, in extreme cases bringing down power grids over a wide area.
After THEMIS discovered the jets and quakes, Joachim Birn of the Los Alamos National Lab in New Mexico conducted a computer simulation of the rebounding process. Lo and behold, vortices appeared in good accord with THEMIS measurements. Moreover, the simulations suggest that the rebounding process can be seen from Earth's surface in the form of ripples and whirls in auroral displays. Ground stations report just such a phenomenon.
"It's a complicated process, but it all fits together," says Sibeck.
The work isn't finished. "We still have a lot to learn," he adds. "How big can spacequakes become? How many vortices can swirl around Earth at once--and how do they interact with one another?"
Stay tuned for answers from THEMIS.
a magnitude six
By: Susie77, 10:30 PM GMT on July 20, 2010
By: Susie77, 9:50 PM GMT on July 15, 2010
From NASA Science
Rosetta Discovers Haunting Beauty in Deep Space
July 14, 2010: The European Space Agency's Rosetta spacecraft has beamed back close-up photographs of asteroid Lutetia, an ancient, cratered relic from the dawn of the solar system. Scientists are abuzz about the stunning images, which reveal a worldlet of haunting, alien beauty.
"I've never seen anything like it," says Claudia Alexander, project scientist for the U.S. Rosetta Project. "It looked as though it could have been fractured off of a mother asteroid – it was all angles and flat planes, ancient impacts overlaid by newer ones, covered by dust of some kind."
Asteroid Lutetia (Alfred Hitchcock, 550px)
Some observers are calling this the "Alfred Hitchcock" shot. Rosetta took the picture as it was receding from Lutetia on July 10th. Credit: ESA
She is particularly intrigued by a giant dent in the asteroid's side.
"My first guess would be that it's the remnant of a giant collision that occurred sometime in the distant past," says Alexander. "The edges look shallow rather than sharp and deep as might be the case with a fresh crater. I'm sure there will be much more analysis of that feature in the weeks to come."
And then there's the perplexing appearance that boulders rolled down Lutetian slopes at some point.
"If that is indeed what we're seeing, the question becomes 'what could have caused the rolling? Perhaps the asteroid spun-up, spun-down, or experienced some orbital irregularity. It's not clear right now that the asteroid is subject to the forces that could cause these things. This is another issue for further study."
"Right now we have more questions than answers," Alexander continues. "We can only speculate at this point about what we're seeing in the pictures."
Asteroid Lutetia has been a target of interest among astronomers for many years. It is one of the largest asteroids in the solar system and has a strange spectrum of reflected light that doesn't look quite like any other asteroid. When the opportunity presented itself for Rosetta to pay a visit en route to its prime target, comet 67P/Churyumov-Gerasimenko in 2014, mission planners couldn't pass it up.
Now that Alexander has seen the images, she can't help but wonder what it would be like to have a walk around.
"Astronauts would have a hard time walking on Lutetia -- the gravity is likely to be much less than that of the moon," she says. "Also, the surface regolith looks very powdery, so astronauts might find themselves sinking in maybe a half-inch or so as they walked."
NASA's MIRO (Microwave Instrument for the Rosetta Orbiter) instrument will help determine whether the surface layers are powdery or rocky. As scientists analyze data from Rosetta's other instruments, they'll be able to determine Lutetia's mass and density, thus revealing more about the asteroid's composition and helping solve the riddle of its origin.
Is Lutetia a 130-km fragment from a planet that broke apart billions of years ago? Or is it one of the original planetary building blocks astronomers call "planetesimals" that has remained the same because no planet sucked it in during the solar system's formative years?
As scientists begin to answer these questions with the Rosetta data, they'll gain new insights into the origin and history of asteroids, and also learn more about the evolution of the solar system itself. An asteroid's contents can reveal something about the conditions and makeup of the solar nebula where the asteroid formed.
"Rosetta took measurements with 17 different instruments," says Rita Schulz, ESA Project Scientist for the Rosetta Mission. "When all the data are analyzed, Lutetia will be one of the best known asteroids out there."
"These spectacular images," she says, "are just the beginning."
By: Susie77, 10:09 PM GMT on July 10, 2010
From Space Weather [dot] com
SUNSET CONJUNCTION: Look west at sunset. Venus is passing by 1st magnitude star Regulus. They're only a little more than a degree apart. Bright Venus catches the eye first. As the glow of sunset fades, Regulus pops out of the twilight a little below Venus. The view through binoculars is superb.
By: Susie77, 11:28 PM GMT on July 06, 2010
Today is the last day for KFUO, Classic 99, broadcasting from St. Louis, Missouri. At 10pm tonight they will
turn over the reins to JOY, a contemporary Christian music format.
KFUO has broadcast classical music for 62 years. I have listened to
them, and become friends with the musical presenters, for over 40 yrs.
now. (One of them was my 10th grade algebra teacher, Mr. Elliott.)
They have been part of my life, and part of my childrens' lives. They
grew up hearing classical music on the radio. I asked the mid-shift
guy, John Roberts, to play Pachelbel's Canon in D for Rachel as she
was on her way to her wedding, and they did so. The night that Rich
died, they played Beethoven's Ninth at 2am, as I drove to the hospital
where he was airlifted. Through this symphony of joy I knew that Rich
still lived. When I was recovering from my brain aneurysm, I asked
Rich to bring my little radio which he tuned to 99.1 for me. I also
listened to classical music in my headphones while in the ICU. I
credit that in part to my wonderful recovery, against the odds.
This station brought us news of all the arts in St. Louis. Even
though it was over a hour's drive, I took the kids to see the
Nutcracker Ballet a few yrs ago, because we heard about it on KFUO.
Last year I got to experience my favorite piece of music of all time
-- Beethoven's Ninth -- because they gave us the heads up. We went to
see various Art Museum exhibits because we heard about them on KFUO.
That's the minimum of my list of remembering.
I will miss you, John and Tom and Dick and Charlie and Jim and the
other Jim. I will miss the music too. But mostly I will miss your
presence as part of my life and part of the life of my family. Thanks
for closing your last day with our words to you and with the music we
love so much. I am sorry that once again, the Dark Ages have descended.
By: Susie77, 10:12 PM GMT on July 06, 2010
We went to see the new Hubble Imax movie yesterday at the St. Louis Science Center. If you get a chance to see this movie, well worth it!
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.