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, 10:39 PM GMT on October 28, 2009
INDONESIAN ASTEROID: Earlier this month, with no warning, a ~10-meter wide asteroid hit Earth's atmosphere above Indonesia and exploded. The break-up was so powerful, it triggered nuclear test ban sensors thousands of kilometers away. A just-released analysis of infrasound data shows that the asteroid detonated with an energy equivalent of about 50 kton of TNT, similar to a small atomic bomb. This significant impact has received relatively little attention in Western press. Details are available today on http://spaceweather.com.
By: Susie77, 11:34 PM GMT on October 27, 2009
[ I know it's sure been hiding out around HERE lately....]
The Sun's Sneaky Variability
October 27, 2009: Every 11 years, the sun undergoes a furious upheaval. Dark sunspots burst forth from beneath the sun's surface. Explosions as powerful as a billion atomic bombs spark intense flares of high-energy radiation. Clouds of gas big enough to swallow planets break away from the sun and billow into space. It's a flamboyant display of stellar power.
So why can't we see any of it?
None of the drama of Solar Maximum is visible to the human eye. Look at the sun in the noontime sky and—ho-hum—it's the same old bland ball of bright light.
"The problem is, human eyes are tuned to the wrong wavelength," explains Tom Woods, a solar physicist at the University of Colorado in Boulder. "If you want to get a good look at solar activity, you need to look in the EUV."
EUV is short for "extreme ultraviolet," a high-energy form of ultraviolet radiation with wavelengths between 1 and 120 nanometers. EUV photons are much more energetic and dangerous than the ordinary UV rays that cause sunburns. Fortunately for humans, Earth's atmosphere blocks solar EUV; otherwise a day at the beach could be fatal.
When the sun is active, intense solar EUV emissions can rise and fall by factors of thousands in just a matter of minutes. These surges heat Earth's upper atmosphere, puffing it up and increasing the drag on satellites. EUV photons also break apart atoms and molecules, creating a layer of ions in the upper atmosphere that can severely disturb radio signals.
To monitor these energetic photons, NASA is going to launch a sensor named "EVE," short for EUV Variability Experiment, onboard the Solar Dynamics Observatory as early as this winter.
"EVE gives us the highest time resolution (10 sec) and the highest spectral resolution (< 0.1 nm) that we've ever had for measuring the sun, and we'll have it 24/7," says Woods, the lead scientist for EVE. "This is a huge improvement over past missions."
Although EVE is designed to study solar activity, its first order of business is to study solar inactivity. SDO is going to launch during the deepest solar minimum in almost 100 years. Sunspots, flares and CMEs are at low ebb. That's okay with Woods. He considers solar minimum just as interesting as solar maximum.
"Solar minimum is a quiet time when we can establish a baseline for evaluating long-term trends," he explains. "All stars are variable at some level, and the sun is no exception. We want to compare the sun's brightness now to its brightness during previous minima and ask ourselves, is the sun getting brighter or dimmer?"
Lately, the answer seems to be dimmer. Measurements by a variety of spacecraft indicate a 12-year lessening of the sun's "irradiance" by about 0.02% at visible wavelengths and 6% at EUV wavelengths. These results, which compare the solar minimum of 2008-09 to the previous minimum of 1996, are still very preliminary. EVE will improve confidence in the trend by pinning down the EUV spectrum with unprecedented accuracy.
The sun's intrinsic variability and its potential for future changes are not fully understood — hence the need for EVE. "The EUV portion of the sun's spectrum is what changes most during a solar cycle," says Woods, "and that is the part of the spectrum we will be observing."
Woods gazes out his office window at the Colorado sun. It looks the same as usual. EVE, he knows, will have a different story to tell.
By: Susie77, 9:16 PM GMT on October 25, 2009
From Space Weather [dot] com
BIG SUNSPOT: The sun is showing signs of life. Sunspot 1029 emerged over the weekend, and it is crackling with B- and C-class solar flares. The active region's magnetic polarity identifies it as a member of new Solar Cycle 24. If its growth continues apace, sunspot 1029 could soon become the biggest sunspot of 2009. Check http://spaceweather.com for animations and updates.
MONDAY NIGHT SKY SHOW: When the sun sets on Monday, Oct. 26th, go outside and look south. Jupiter and the Moon are converging for a beautiful conjunction. The bright pair can been seen even through thinly-clouded skies and city lights. Don't miss it!
By: Susie77, 11:49 PM GMT on October 19, 2009
The 2009 Orionid Meteor Shower
October 19, 2009: The Orionid meteor shower peaks this week and it could be a very good show.
"Earth is passing through a stream of debris from Halley's Comet, the source of the Orionids," says Bill Cooke of NASA's Meteoroid Environment Office. "Flakes of comet dust hitting the atmosphere should give us dozens of meteors per hour."
The best time to look is before sunrise on Wednesday, Oct. 21st. That's when Earth encounters the densest part of Halley's debris stream. Observing is easy: Wake up a few hours before dawn, brew some hot chocolate, go outside and look up. No telescope is required to see Orionids shooting across the sky.
Orionids appear every year around this time when Earth orbits through an area of space littered with debris from the ancient comet. Normally, the shower produces 10 to 20 meteors per hour, a modest display. The past few years, however, have been much better than usual.
"Since 2006, the Orionids have been one of the best showers of the year, with counts of 60 or more meteors per hour," says Cooke.
According to Japanese meteor scientists Mikiya Sato and Jun-ichi Watanabe, 2006 marked Earth's first encounter with some very old debris. "We have found that the [elevated activity of 2006] was caused by dust trails ejected from 1P/Halley in 1266 BC, 1198 BC, and 911 BC," they wrote in the August 2007 edition of Publications of the Astronomical Society of Japan. In their paper "Origin of the 2006 Orionid Outburst," Sato and Watanabe used a computer to model the structure and evolution of Halley's many debris streams stretching back in time as far as 3400 years. The debris that hit Earth in 2006 was among the oldest they studied and was rich in large fireball-producing meteoroids.
Repeat encounters produced good displays in 2007 and 2008—and "the meteoroids are expected to approach Earth [again] in 2009," say Sato and Watanabe. They note that these old broad streams tend to produce equally broad showers, lasting several nights around the peak. So, if clouds interfere on the 21st, try again on the 22nd or 23rd.
The phase of the Moon favors a good show. The Moon is almost new and completely absent from the pre-dawn sky at the time of the shower's peak. Bright moonlight will not be a problem.
Last but not least, the display will be framed by some of the prettiest stars and planets in the night sky. In addition to Orionids, you'll see brilliant Venus, red Mars, the dog star Sirius, and bright winter constellations such as Orion, Gemini and Taurus. Even if the shower is a dud, the rest of the sky is dynamite.
Set your alarm and enjoy the show.
By: Susie77, 12:27 PM GMT on October 11, 2009
So I bought these garlic bulbs to plant this fall. (Not the eatin' kind from the grocery store, but the plantin' kind.) The directions say to plant after we've had a couple of good frosts/freezes. And mulch well. This is climate Zone 6 here. Any advice? I haven't had much luck with growing garlic.
By: Susie77, 11:44 PM GMT on October 08, 2009
Space dot Com
Slam-Bang Coverage! Get Ready for the LCROSS Moon Crash
By SPACE.com Staff
posted: 01 October 2009
04:00 pm ET
NASA's LCROSS probe and its spent Centaur rocket stage will be purposely crashed into the large crater Cabeus Friday, Oct. 9, at 7:30 a.m. EDT (1130 GMT) in an effort to kick up lunar dirt to see what's in it. Scientists are hoping to see signs of water.
SPACE.com is providing complete coverage of the mission and related lunar science news, features and video - all on the heels of the exciting recent announcements that there is water in scant quantities across the lunar surface and tentative new evidence of water ice in shaded lunar craters.
By: Susie77, 11:40 AM GMT on October 07, 2009
From a slightly different source this time.... CNN:
Scientists discover massive ring around Saturn
* Story Highlights
* Newly discovered ring is so large it would take 1 billion Earths to fill it
* Ring is made up of ice and dust particles that are so far apart it's hard to see
* Ring material may come from comet, meteor collisions with moon Phoebe
updated 4 hours, 34 minutes ago
(CNN) -- Scientists at NASA have discovered a nearly invisible ring around Saturn -- one so large that it would take 1 billion Earths to fill it.
NASA's Spitzer Space Telescope has spotted a massive, nearly invisible ring around Saturn.
NASA's Spitzer Space Telescope has spotted a massive, nearly invisible ring around Saturn.
The ring's orbit is tilted 27 degrees from the planet's main ring plane. The bulk of it starts about 3.7 million miles (6 million km) away from the planet and extends outward another 7.4 million miles (12 million km).
Its diameter is equivalent to 300 Saturns lined up side to side. And its entire volume can hold one billion Earths, NASA Jet Propulsion Laboratory said late Tuesday.
"This is one supersized ring," said Anne Verbiscer, an astronomer at the University of Virginia in Charlottesville.
Verbiscer and two others are authors of a paper about the discovery published Wednesday in the journal Nature.
The obvious question: Why did it take scientists so long to discover something so massive?
The ring is made up of ice and dust particles that are so far apart that "if you were to stand in the ring, you wouldn't even know it," Verbiscer said in a statement.
Also, Saturn doesn't receive a lot of sunlight, and the rings don't reflect much visible light.
But the cool dust -- about 80 Kelvin (minus 316 degrees Fahrenheit) -- glows with thermal radiation. NASA's Spitzer Space Telescope, used to spot the ring, picked up on the heat.
One of Saturn's moons, Phoebe, orbits within the ring. As Phoebe collides with comets, it kicks up planetary dust. Scientists believe the ice and dust particles that make up the ring stems from those collisions.
The ring may also help explain an age-old mystery surrounding another of Saturn's moons: Iapetus.
Astronomer Giovanni Cassini, who first spotted Iapetus in 1671, deduced the moon has a white and dark side -- akin to a yin-yang symbol. But scientists did not know why.
The new ring orbits in the opposite direction to Iapetus. And, say researchers, it's possible that the moon's dark coloring is a result of the ring's dust particles splattering against Iapetus like bugs on a windshield.
"Astronomers have long suspected that there is a connection between Saturn's outer moon Phoebe and the dark material on Iapetus," said Douglas Hamilton of the University of Maryland in College Park -- one of the three authors reporting on the findings in the journal Nature.
"This new ring provided convincing evidence of that relationship."
By: Susie77, 11:50 PM GMT on October 06, 2009
The Fall of the Maya: "They Did it to Themselves"
October 6, 2009: For 1200 years, the Maya dominated Central America. At their peak around 900 A.D., Maya cities teemed with more than 2,000 people per square mile -- comparable to modern Los Angeles County. Even in rural areas the Maya numbered 200 to 400 people per square mile. But suddenly, all was quiet. And the profound silence testified to one of the greatest demographic disasters in human prehistory -- the demise of the once vibrant Maya society.
"They did it to themselves," says veteran archeologist Tom Sever.
"The Maya are often depicted as people who lived in complete harmony with their environment,' says PhD student Robert Griffin. "But like many other cultures before and after them, they ended up deforesting and destroying their landscape in efforts to eke out a living in hard times."
A major drought occurred about the time the Maya began to disappear. And at the time of their collapse, the Maya had cut down most of the trees across large swaths of the land to clear fields for growing corn to feed their burgeoning population. They also cut trees for firewood and for making building materials.
"They had to burn 20 trees to heat the limestone for making just 1 square meter of the lime plaster they used to build their tremendous temples, reservoirs, and monuments," explains Sever.
He and his team used computer simulations to reconstruct how the deforestation could have played a role in worsening the drought. They isolated the effects of deforestation using a pair of proven computer climate models: the PSU/NCAR mesoscale atmospheric circulation model, known as MM5, and the Community Climate System Model, or CCSM.
"We modeled the worst and best case scenarios: 100 percent deforestation in the Maya area and no deforestation," says Sever. "The results were eye opening. Loss of all the trees caused a 3-5 degree rise in temperature and a 20-30 percent decrease in rainfall."
The results are telling, but more research is needed to completely explain the mechanisms of Mayan decline. Archeological records reveal that while some Maya city-states did fall during drought periods, some survived and even thrived.
"We believe that drought was realized differently in different areas," explains Griffin. "We propose that increases in temperature and decreases in rainfall brought on by localized deforestation caused serious enough problems to push some but not all city-states over the edge."
The Maya deforested through the use of slash-and-burn agriculture – a method still used in their old stomping grounds today, so the researchers understand how it works.
"We know that for every 1 to 3 years you farm a piece of land, you need to let it lay fallow for 15 years to recover. In that time, trees and vegetation can grow back there while you slash and burn another area to plant in."
But what if you don't let the land lay fallow long enough to replenish itself? And what if you clear more and more fields to meet growing demands for food?
"We believe that's what happened," says Griffin. "The Maya stripped large areas of their landscape bare by over-farming."
Not only did drought make it difficult to grow enough food, it also would have been harder for the Maya to store enough water to survive the dry season.
"The cities tried to keep an 18-month supply of water in their reservoirs," says Sever. "For example, in Tikal there was a system of reservoirs that held millions of gallons of water. Without sufficient rain, the reservoirs ran dry." Thirst and famine don't do much for keeping a populace happy. The rest, as the saying goes, is history.
"In some of the Maya city-states, mass graves have been found containing groups of skeletons with jade inlays in their teeth – something they reserved for Maya elites – perhaps in this case murdered aristocracy," he speculates.
No single factor brings a civilization to its knees, but the deforestation that helped bring on drought could easily have exacerbated other problems such as civil unrest, war, starvation and disease.
Many of these insights are a result of space-based imaging, notes Sever. "By interpreting infrared satellite data, we've located hundreds of old and abandoned cities not previously known to exist. The Maya used lime plaster as foundations to build their great cities filled with ornate temples, observatories, and pyramids. Over hundreds of years, the lime seeped into the soil. As a result, the vegetation around the ruins looks distinctive in infrared to this day."
"Space technology is revolutionizing archeology," he concludes. "We're using it to learn about the plight of ancients in order to avoid a similar fate today."
Light Ice Pellets Rain Mist