The University of Western Australia's new Zadko telescope has discovered a new asteroid - a 4 kilometer (2.5 mile) wide rock orbiting in the outer reaches of our solar system. Curtin University Honors student, Mick Todd, used the UWA facility to make the unexpected discovery while searching the sky for potentially hazardous asteroids.

After checking the major astronoimcal databases, it became clear that the Zadko Telescope had imaged a new asteroid. Unlike comets, asteroids are numbered not named. So instead of a Mick Todd asteroid, it will be known as asteroid 2009 FH19.

In recent years, there has been a dramatic increase in the number of rocks and asteroids being discovered because of sophisticated telescopes. This data is contributing to a better understanding of the solar system.

"In the next six months Mick plans to search for asteroids and rocks lurking closer to Earth. Some of these are so close that impacts can occur only hours after discovery," said Coward.

Such collaboration between UWA and Curtin has resulted in students like Mick Todd making world class discoveries, said Marjan Zadnik, a Curtin University professor.
 

"A huge amount of motion is visible over a very short interval of time," says Pete Lawrence who made the movie on April 22nd at his backyard observatory in Selsey, UK. "The prominence underwent many changes of form and at one point I could see real time movement as I watched the action on my computer screen."

Less than 24 hours later, Lawrence's prominence exploded and hurled a billion-ton cloud of gas away from the sun at nearly a million miles per hour: SOHO movie. That's moving. Readers, if you have a solar telescope and 17 minutes of spare time ... you know what to do.

New Gamma-Ray Burst Smashes Cosmic Distance Record 04.28.2009

  April 28, 2009: NASA's Swift satellite and an international team of astronomers have found a gamma-ray burst from a star that died when the universe was only 630 million years old--less than five percent of its present age. The event, dubbed GRB 090423, is the most distant cosmic explosion ever seen.

"The incredible distance to this burst exceeded our greatest expectations -- it was a true blast from the past," says Swift lead scientist Neil Gehrels at NASA's Goddard Space Flight Center.

Above: GRB 090423 as seen by NASA's Swift satellite. The image is a composite of data from Swift's UV/Optical and X-Ray telescopes. Credit: NASA/Swift/Stefan Immler [Larger image]

The burst occurred at 3:55 a.m. EDT on April 23rd. Swift quickly pinpointed the explosion, allowing telescopes on Earth to target the burst before its afterglow faded away. Astronomers working in Chile and the Canary Islands independently measured the explosion's redshift. It was 8.2, smashing the previous record of 6.7 set by an explosion in September 2008. A redshift of 8.2 corresponds to a distance of 13.035 billion light years.

Gamma-ray bursts are the most luminous explosions in the Universe. Most occur when massive stars run out of nuclear fuel. As their cores collapse into a black hole or neutron star, jets of matter punch through the star and blast into space. There, they strike gas previously shed by the star and heat it, which generates short-lived afterglows in many wavelengths.

For years, astronomers have been hunting for gamma-ray bursts from the earliest generations of stars--and mysteriously failing to find them. The detection of GRB 090423 is an important milestone in the quest to locate bursts in the redshift range 10 to 20. More information: "The Case of the Missing Gamma-ray Bursts."

At the same time, Fox led an effort to obtain infrared images of the afterglow using the Gemini North Telescope on Mauna Kea. The source appeared in longer-wavelength images but was absent in an image taken at the shortest wavelength of 1 micron. This "drop out" corresponded to a distance of about 13 billion light-years.

An artist's concept of a gamma-ray burst in action.
Credit: NASA/Swift/Cruz deWilde.

As Fox spread the word about the record distance, telescopes around the world turned to observe the afterglow before it faded away.

At the Galileo National Telescope on La Palma in the Canary Islands, a team including Guido Chincarini at the University of Milan-Bicocca, Italy, determined that the afterglow's redshift was 8.2. Tanvir's team, gathering nearly simultaneous observations using one of the European Southern Observatory's Very Large Telescopes on Cerro Paranal, Chile, arrived at the same number.

"It's an incredible find," Chincarini says. "What makes it even better is that a telescope named for Galileo made this measurement during the year in which we celebrate the 400th anniversary of Galileo's first astronomical use of the telescope."

ARIZONA FIREBALL: Over the weekend, midnight sky watchers in Arizona and New Mexico witnessed a "spectacular fireball" that exploded in "a flash like lightning." The brightness may have exceeded that of a full Moon. The approximate time was 0604 UT, a few minutes past midnight MDT on April 26th. A fireball camera operated by Thomas Ashcraft near Santa Fe, NM, captured the event, which was brilliant despite its low elevation:

Sonic Movie 1 : ELF/VLF reception, 11 seconds. 500 KB FBvlf20090426_0604UT_Ashcraft2.mp4

NOTE: the crackling sound and tweeks are natural lightning emissions called sferics. If you listen acutely there is a possible enhancement of noise in sync with the flareup of the meteor at 3 seconds into the movie. This enhancement may be meteor related but it is difficult to say conclusively.

Sonic Movie 2 : Forward scatter reception only at 61.250 MHz. 30 seconds, 1.1 MB FBs61_20090426_0604ut_Ashcraft.mp4

Sonic Movie 3: 61.250 MHz and ELF/VLF reception stereo, 30 seconds. 1.1 MB FBvs61_20090426_0604UT_Ashcraft.mp435.50

The complex explosion produced not one but two billion-ton coronal mass ejections (CMEs): movie. An impact from such a double-CME would almost surely spark magnetic storms around the poles of Earth, but it is not heading in our direction. The chance of auroras remains low.

Minutes later, the Moon passed directly in front of Venus, producing a crescent vs. crescent eclipse. Browse the links below for some of the best shots.

more images: from Adrian New of Fort Davis, Texas; from Greg Stablein of Memphis, Tennessee; from Val Ricks of The Woodlands, Texas; from Paul Kinzer of Galesville, Wisconsin; from Tom Polakis of Tempe, Arizona; from Peggy Collins of Pacoima, California; from Bill Meyers of Omaha, Nebraska; from Bret Dahl of Plano, Texas; from Antonio Estrada of Toluca, México; a movie from John McNair of Monument, Colorado; from Mark Seibold of Portland Oregon;

SURGING PROMINENCE: Every clear day, astrophotographer Pete Lawrence of Selsey, UK, scans the limb of the sun for photogenic prominences. "This morning I spotted a rather odd looking one," he says. "I've never seen anything quite like it before." This photo shows the view through his SolarScope SF-70:

The twisting, swirling maelstrom underwent many changes in the hours that followed Lawrence's first sighting. "At one point I could see real time movement on my computer screen," he says. "It was amazing!"

Apparently, even the quiet sun has something to offer. If you have a solar telescope, take a look.

images: from Pete Lawrence of Selsey, West Sussex, UK;

from Jan Timmermans of Valkenswaard, The Netherlands Current conditions Solar wind
speed: 415.8 km/sec
density: 0.7 protons/cm³
explanation | more data
Updated: Today at 2346 UT

Got clouds? No problem. If you can't see the shower, you can listen to it on Space Weather Radio. We are streaming live signals from the Air Force Space Surveillance Radar in Texas. Whenever a meteor passes overhead--ping!--there is an echo. The Lyrids should produce a surge of activity on April 22nd.

On April 2nd, ham radio operator Stan Nelson of Roswell, New Mexico, was listening to the radar's signals when the International Space Station and a meteor passed through the beam in quick succession. Click on the dynamic spectrum to listen:

audio: with noise reduction | w/o noise reduction

The slowly descending tone at the beginning of the soundtrack is the radar's doppler-shifted reflection from the ISS. It sounds like the whistle of a train racing past a stationary bystander. Indeed, the basic physics of the doppler shift is the same in both cases.

The rapidly descending tone near the end of the soundtrack is the radar's doppler-shifted reflection from a meteor. Because meteors travel through space some two to ten times faster than Earth-orbiting spacecraft, their radar reflections are much more sharply doppler shifted.

On April 22nd you might hear both kinds of reflections as Lyrid meteors and various Earth-orbiting satellites pass over the radar facility. Tune in!
 

THIS IS WHAT WE WORRY ABOUT FOR THE FUTURE WHEN IT'S DIRECTED AT EARTH: A billion-ton cloud of hot magnetized gas has just left the sun. The Solar and Heliospheric Observatory (SOHO) recorded the explosion at the end of the day on April 17th:

The bright coronal mass ejection (CME) is not heading for Earth, so there will be no geomagnetic effects from the explosion. But it does remind us that sunspots are not required for solar activity. The source of the blast appears to be an erupting prominence high above the sun's northeastern limb.

The sun may be blank, but it is not quiet. Monitoring is encouraged.

more images: from Alan Friedman of Buffalo, New York; from Leslie Marczi of Welland, Ontario, Canada; from James Kevin Ty of Manila, the Philippines; from Fabio Acquarone of Caramagna, Liguria, Italy; from Michael Buxton of Ocean Beach, California;

Each second in the SOHO animation corresponds to an hour or more of real time. "The speed of the CME was only 240 km/s," says Vourlidas. "The solar wind speed is about 300 km/s, so the CME is actually being dragged."

Vourlidas has examined thousands of CMEs recorded by SOHO over the past 13 years, and he's rarely seen such plodding explosions. In active times, CMEs can blast away from the sun faster than 1000 km/s. Even during the solar minimum of 1996, CMEs often revved up to 500 or 600 km/s. "Almost all the CMEs we've seen since the end of April 2008, however, are very slow, less than 300 km/s."

Is this just another way of saying "the sun is very quiet?" Or do slow-motion CMEs represent a new and interesting phenomena? The jury is still out. One thing is clear: solar minimum is more interesting than we thought.

 Spotless Days
Current Stretch: 19 days
2009 total: 91 days (88%)
Since 2004: 602 days
Typical Solar Min: 485 days
explanation | more info
Updated 14 Apr 2009
 

April 14, 2009: This just in: The Sun is blasting the solar system with croissants.

Researchers studying data from NASA's twin STEREO probes have found that ferocious solar storms called CMEs (coronal mass ejections) are shaped like a French pastry. The elegance and simplicity of the new "croissant model" is expected to dramatically improve forecasts of severe space weather.

"We believe we can now predict when a CME will hit Earth with only 3-hours of uncertainty," says Angelos Vourlidas of the Naval Research Lab, who helped develop the model. "That's a four-fold improvement over older methods."

Above: An artist's concept of a croissant-shaped CME. Click on the image to launch a movie of the explosion. Credit: NASA

Coronal mass ejections are billion-ton clouds of hot magnetized gas that explode away from the sun at speeds topping a million mph. Sometimes the clouds make a beeline for Earth and when they hit they can cause geomagnetic storms, satellite outages, auroras, and power blackouts. The ability to predict the speed and trajectory of a CME is key to space weather forecasting.

"This is an important advance," says Lika Guhathakurta, STEREO program scientist at NASA headquarters in Washington DC. "From a distance, CMEs appear to be a complicated and varied population. What we have discovered is that they are not so varied after all. Almost all of the 40-plus CMEs we have studied so far with STEREO have a common shape--akin to a croissant."

"STEREO has done what no previous mission could," notes Guhathakurta.

Vourlidas says he is not surprised that CMEs resemble French pastries. "I have suspected this all along. The croissant shape is a natural result of twisted magnetic fields on the sun and is predicted by a majority of theoretical models."

He offers the following analogy: Take a length of rope and hold one end in each hand. Start twisting the ends in opposite directions. Twist, twist and continue twisting until the middle of the rope is a fat knotted mess.

"That's how CMEs get started—as twisted ropes of solar magnetism. When the energy in the twist reaches some threshold, there is an explosion which expels the CME away from the sun. It looks like a croissant because the twisted ropes are fat in the middle and thin on the ends."

Right: A computer model of a croissant-shaped CME. Models like this can be rapidly fit to real CMEs as soon as they are observed, allowing forecasters to accurately estimate the speed and trajectory of the storms: movie. Credit: NASA.

The shape alone, however, does not tell the full story of a CME. The contents of the CME must be considered, too. How much plasma does it contain? What is the orientation and strength of its internal magnetic field? When a CME strikes, the havoc it causes will depend on the answers—answers the croissant model does not yet provide.

"There is more work to do. We must learn to look at a CME and not only trace its shape, but also inventory in contents," says Guhathakurta. "We are halfway there."

Eventually, the quest to learn what lies inside the croissant will be taken up by other spacecraft such as the Solar Dynamics Observatory, slated to launch in August 2009, and Solar Probe+, a daring mission (still on the drawing board) to fly close to the sun and actually enter these storms near their source.

STEREO isn't finished, though. The two probes are continuing their journeys to opposite sides of the sun for a 24/7, 360-degree view of the star. Along the way, they'll actually run into a few CMEs and have the chance to sample the 'croissants' in situ.

Author: Dr. Tony Phillips | Credit: Science@NASA

RADIO STORMS ON JUPITER: On April 11th, the loudspeaker of Thomas Ashcraft's 21 MHz radio telescope in New Mexico suddenly began to hiss and crackle. The sounds grew louder as Jupiter rose in the blue morning sky. "I am pleased to report," says Ashcraft, "a successful recording of Jovian S-bursts--the first of 2009." Click on the image to listen:

> by ham radio antennas on Earth. Jovian S-bursts and L-bursts can mimic the sounds of woodpeckers, whales, and waves crashing on the beach. Here are a few audio samples: S-bursts, S-bursts (slowed down 128:1), L-Bursts

"I recorded the storm in broad daylight," notes Ashcraft. "One of the advantages of this long solar minimum is that the daytime ionosphere is quieter and more transparent to decametric radio waves. There will definitely be more good Jupiter storms in the months to come." Stay tuned!

Earth is inside a solar wind stream flowing from the indicated coronal hole. Credit: SOHO Extreme UV Telescope

April 9, 2009: NASA's twin STEREO probes are entering a mysterious region of space to look for remains of an ancient planet which once orbited the Sun not far from Earth. If they find anything, it could solve a major puzzle--the origin of the Moon.

"The name of the planet is Theia," says Mike Kaiser, STEREO project scientist at the Goddard Space Flight Center. "It's a hypothetical world. We've never actually seen it, but some researchers believe it existed 4.5 billion years ago—and that it collided with Earth to form the Moon."

Right: An artist's concept of one of the STEREO spacecraft. [Larger image]

The "Theia hypothesis" is a brainchild of Princeton theorists Edward Belbruno and Richard Gott. It starts with the popular Great Impact theory of the Moon's origin. Many astronomers hold that in the formative years of the solar system, a Mars-sized protoplanet crashed into Earth. Debris from the collision, a mixture of material from both bodies, spun out into Earth orbit and coalesced into the Moon. This scenario explains many aspects of lunar geology including the size of the Moon's core and the density and isotopic composition of moon rocks.

Belbruno and Gott believe it came from a Sun-Earth Lagrange point.

Sun-Earth Lagrange points are regions of space where the pull of the Sun and Earth combine to form a "gravitational well." The flotsam of space tends to gather there much as water gathers at the bottom of a well on Earth. 18th-century mathematician Josef Lagrange proved that there are five such wells in the Sun-Earth system: L1, L2, L3, L4 and L5 located as shown in the diagram below.

When the solar system was young, Lagrange points were populated mainly by planetesimals, the asteroid-sized building blocks of planets. Belbruno and Gott suggest that in one of the Lagrange points, L4 or L5, the planetesimals assembled themselves into Theia, nicknamed after the mythological Greek Titan who gave birth to the Moon goddess Selene.

Above: Sun-Earth Lagrange points. The STEREO probes are about to pass through L4 and L5. Solar observatories often park themselves at L1 while deep space observatories prefer L2. [more]

"Their computer models show that Theia could have grown large enough to produce the Moon if it formed in the L4 or L5 regions, where the balance of forces allowed enough material to accumulate," says Kaiser. "Later, Theia would have been nudged out of L4 or L5 by the increasing gravity of other developing planets like Venus and sent on a collision course with Earth."

If this idea is correct, Theia itself is long gone, but some of the ancient planetesimals that failed to join Theia may still be lingering at L4 or L5.

"The STEREO probes are entering these regions of space now," says Kaiser. "This puts us in a good position to search for Theia's asteroid-sized leftovers."

Just call them "Theiasteroids."

Astronomers have looked for Theiasteroids before using telescopes on Earth, and found nothing, but their results only rule out kilometer-sized objects. By actually entering L4 and L5, STEREO will be able to hunt for much smaller bodies at relatively close range.

Right: This dynamical simulation shows how asteroids linger in the gravitational well of a Lagrange point of the Sun-Jupiter system. The principle of Sun-Earth Lagrange points is the same. Credit: Prof. Aldo Vitagliano/SOLEX.

"The search actually began last month when both spacecraft rolled 180 degrees so that they could take a series of 2-hour exposures of the general L4/L5 areas. In the first sets of images, amateur astronomers found some known asteroids and new comet Itagaki was imaged just a couple of days after the announcement of its discovery. No Theiasteroids however."

Hunting for Theiasteroids is not STEREO's primary mission, he points out. "STEREO is a solar observatory. The two probes are flanking the sun on opposite sides to gain a 3D view of solar activity. We just happen to be passing through the L4 and L5 Lagrange points en route. This is purely bonus science."

"We might not see anything," he continues, "but if we discover lots of asteroids around L4 or L5, it could lead to a mission to analyze the composition of these asteroids in detail. If that mission discovers the asteroids have the same composition as the Earth and Moon, it will support Belbruno and Gott's version of the giant impact theory."

The search will continue for many months to come. Lagrange points are not infinitesimal points in space; they are broad regions 50 million kilometers wide. The STEREO probes are only in the outskirts now. Closest approach to the bottoms of the gravitational wells comes in Sept-Oct. 2009. "We have a lot of observing ahead of us," notes Kaiser.

Readers, you may be able to help. The STEREO team is inviting the public to participate in the search by scrutinizing photos as they come in from the spacecraft. If you see a dot of light moving with respect to the stars, you may have found a Theiasteroid. Links to the data and further instructions may be found at sungrazer.nrl.navy.mil.

Let the hunt begin!

Author: Dr. Tony Phillips | Credit: Science@NASA

Yahoo! 'STEREO Hunters' discussion group -- a nice resource for people who would like to help find asteroids and comets in STEREO images

STEREO Sees the Dark Side of the Sun -- (Science@NASA)

NASA's Future: US Space Exploration Policy

3DEEP MINIMUM: "When the sun is in the pits of the deepest solar minimum in nearly 100 years, solar photographers have to get creative," says Greg Piepol of Rockville, Maryland. "Yesterday, I photographed the sun using a Lunt Solar Systems LS100 and rendered it as a 3D anaglyph." Put on your red-blue glasses and behold the composition Piepol calls 3Deep Minimum

"We had a very beautiful moonrise tonight," says Chasiotis. "The Moon was dimmed by thin clouds, so I set my Canon EOS 450D at ISO 400 and it worked perfectly."

more images: from Dennis Put of Brielle, Zuid-Holland, The Netherlands; from Doug Zubenel of Lenexa, Kansas; from Abraham Tamas of Zsámbék, Hungary

COMET Yi-SWAN: It's up all night long. Northern circumpolar Comet Yi-SWAN is gliding through the constellation Cassiopeia where it can be seen at almost any hour of the night through amateur telescopes. Working at his backyard observatory in Ellisville, Missouri, Gregg Ruppel took this picture on April 9th:

At the moment, the green, fuzzy comet is about as bright as an 8th-magnitude star--too dim for the naked eye. If predictions are correct, it will remain a telescopic comet, brightening only a little as it approaches the sun for a 190 million kilometer not-so-close encounter on May 8th. Astronomers will get a better look at the comet in the evenings ahead as the bright light of the full Moon fades.

Comet Yi-SWAN was co-discovered by amateur astronomers Dae-am Yi in Korea and Rob Matson in the USA. Yi photographed the comet himself using a Canon 5D and a 90 mm lens. Matson noticed it in images taken by the Solar and Heliospheric Observatory's SWAN sensor. Because of naming traditions (which should probably be modified) the comet bears SWAN's name, not Matson's.

This appears to be Comet Yi-SWAN's first visit to the inner solar system. A fresh comet exposed to intense sunlight for the first time can behave in unexpected ways. Will it grow a tail, fragment, brighten ... ? Stay tuned for updates.

related links: 3D orbit, ephemeris

UPDATED: April 2009 Aurora Gallery
[previous Aprils: 2008, 2007, 2006, 2005, 2004, 2003, 2002]

A solar wind stream flowing from
the indicated coronal hole should
reach Earth on April 9th or 10th.
Credit: SOHO Extreme UV Telescope

This polar crown prominence, a towering wall of plasma about 50,000 km high, was photographed yesterday by Jerome Grenier using a backyard solar telescope in Paris, France. Grenier's half-hour movie shows a phenomenon sometimes called "plasma falls." Narrow streams of plasma at the top of the prominence are constantly falling back to the bottom. Mysteriously, the streams plummet faster than ambient magnetic forces seem to allow. Nuclear engineers would like to figure out how this happens, because it also happens on a smaller scale in fusion reactors on Earth, frustrating their efforts to sustain an energy-producing reaction. Maybe prominences hold the key to the problem.

Or maybe they're just fun to watch. Readers, if you have a solar telescope, point it at the limb of the sun and enjoy the show.

more images: from James Kevin Ty of Manila, the Philippines; from N. Ferrin, J. Harmon and John Stetson of South Portland, Maine; from Eric Roel of Orion Observatory, Rancho La Compañía, México; from Greg Piepol of Rockville, Maryland; from Steve Rismiller of Milford, Ohio; from Stefano Sello of Pisa -Italy;

Thank goodness for prominences!" says Piepol who took the picture on April 3rd from his backyard observatory in Rockville, Maryland. "They are one form of solar activity that seems to continue even during a Deep Solar Minimum."

It's true, clouds of hydrogen dance along the solar limb throughout the 11-year solar cycle. Yesterday, Piepol counted three, and today there are four. The "prominence number" is much larger than the sunspot number, giving solar astronomers reason to keep looking at the sun.

"To photograph the prominences, I used a brand new type of H-alpha scope, the LS100THa from Lunt Solar Systems," adds Piepol. "These images are the very first light through the scope."

more images: from Eric Roel of Orion Observatory, Rancho La Compañía, México; from Steve Rismiller of Milford, Ohio; from Guenter Kleinschuster of Feldbach, Styria, Austria

Plume of Sulfur Dioxide floating above the ocean

SULFUR DIOXIDE LOOP: A loop of sulfur dioxide gas approximately 600 miles in diameter is swirling off the coast of California. It came from Alaska where Mt. Redoubt unleashed its biggest eruption yet on April 4th. Click on the link to launch a 4-day animation of the volcano's SO₂ emissions

http://www.spaceweather.com/swpod2009/07apr09/gome2_so2_anim_big.gif?PHPSESSID=a8k7lo726sen3ingl9da1kth57

Sulfur dioxide and associated aerosols have been known to produce sunsets of exceptional beauty. Examples from the 2008 eruption of Kasatochi may be found here and here. Readers in the path of Redoubt's clouds should be alert for rare colors and rays in the evening sky.

Solar wind
speed: 266.6 km/sec
density: 0.2 protons/cm³
explanation | more data
Updated: Today at 2343 UT

4-2-09  - No sunspots today

April 1, 2009: The sunspot cycle is behaving a little like the stock market. Just when you think it has hit bottom, it goes even lower.

2008 was a bear. There were no sunspots observed on 266 of the year's 366 days (73%). To find a year with more blank suns, you have to go all the way back to 1913, which had 311 spotless days: plot. Prompted by these numbers, some observers suggested that the solar cycle had hit bottom in 2008.

Maybe not. Sunspot counts for 2009 have dropped even lower. As of March 31st, there were no sunspots on 78 of the year's 90 days (87%).

It adds up to one inescapable conclusion: "We're experiencing a very deep solar minimum," says solar physicist Dean Pesnell of the Goddard Space Flight Center.

"This is the quietest sun we've seen in almost a century," agrees sunspot expert David Hathaway of the Marshall Space Flight Center.

Above: The sunspot cycle from 1995 to the present. The jagged curve traces actual sunspot counts. Smooth curves are fits to the data and one forecaster's predictions of future activity. Credit: David Hathaway, NASA/MSFC. [more]

Quiet suns come along every 11 years or so. It's a natural part of the sunspot cycle, discovered by German astronomer Heinrich Schwabe in the mid-1800s. Sunspots are planet-sized islands of magnetism on the surface of the sun; they are sources of solar flares, coronal mass ejections and intense UV radiation. Plotting sunspot counts, Schwabe saw that peaks of solar activity were always followed by valleys of relative calm—a clockwork pattern that has held true for more than 200 years: plot.

The current solar minimum is part of that pattern. In fact, it's right on time. "We're due for a bit of quiet—and here it is," says Pesnell.

A 50-year low in solar wind pressure: Measurements by the Ulysses spacecraft reveal a 20% drop in solar wind pressure since the mid-1990s—the lowest point since such measurements began in the 1960s. The solar wind helps keep galactic cosmic rays out of the inner solar system. With the solar wind flagging, more cosmic rays are permitted to enter, resulting in increased health hazards for astronauts. Weaker solar wind also means fewer geomagnetic storms and auroras on Earth.

A 12-year low in solar "irradiance": Careful measurements by several NASA spacecraft show that the sun's brightness has dropped by 0.02% at visible wavelengths and 6% at extreme UV wavelengths since the solar minimum of 1996. The changes so far are not enough to reverse the course of global warming, but there are some other significant side-effects: Earth's upper atmosphere is heated less by the sun and it is therefore less "puffed up." Satellites in low Earth orbit experience less atmospheric drag, extending their operational lifetimes. Unfortunately, space junk also remains longer in Earth orbit, increasing hazards to spacecraft and satellites.

Above: Space-age measurements of the total solar irradiance (brightness summed across all wavelengths). This plot, which comes from researcher C. Fröhlich, was shown by Dean Pesnell at the Fall 2008 AGU meeting during a lecture entitled "What is Solar Minimum and Why Should We Care?"

A 55-year low in solar radio emissions: After World War II, astronomers began keeping records of the sun's brightness at radio wavelengths. Records of 10.7 cm flux extend back all the way to the early 1950s. Radio telescopes are now recording the dimmest "radio sun" since 1955: plot. Some researchers believe that the lessening of radio emissions is an indication of weakness in the sun's global magnetic field. No one is certain, however, because the source of these long-monitored radio emissions is not fully understood.

All these lows have sparked a debate about whether the ongoing minimum is "weird", "extreme" or just an overdue "market correction" following a string of unusually intense solar maxima.

"Since the Space Age began in the 1950s, solar activity has been generally high," notes Hathaway. "Five of the ten most intense solar cycles on record have occurred in the last 50 years. We're just not used to this kind of deep calm."

Deep calm was fairly common a hundred years ago. The solar minima of 1901 and 1913, for instance, were even longer than the one we're experiencing now. To match those minima in terms of depth and longevity, the current minimum will have to last at least another year.

In a way, the calm is exciting, says Pesnell. "For the first time in history, we're getting to see what a deep solar minimum is really like." A fleet of spacecraft including the Solar and Heliospheric Observatory (SOHO), the twin STEREO probes, the five THEMIS probes, Hinode, ACE, Wind, TRACE, AIM, TIMED, Geotail and others are studying the sun and its effects on Earth 24/7 using technology that didn't exist 100 years ago. Their measurements of solar wind, cosmic rays, irradiance and magnetic fields show that solar minimum is much more interesting and profound than anyone expected.

NASA's Solar Dynamics Observatory. Bristling with advanced sensors, "SDO" is slated to launch later this year--perfect timing to study the ongoing solar minimum. [more]

Modern technology cannot, however, predict what comes next. Competing models by dozens of top solar physicists disagree, sometimes sharply, on when this solar minimum will end and how big the next solar maximum will be. Pesnell has surveyed the scientific literature and prepared a "piano plot" showing the range of predictions. The great uncertainty stems from one simple fact: No one fully understands the underlying physics of the sunspot cycle.

Pesnell believes sunspot counts will pick up again soon, "possibly by the end of the year," to be followed by a solar maximum of below-average intensity in 2012 or 2013.

But like other forecasters, he knows he could be wrong. Bull or bear? Stay tuned for updates.

Solar wind
speed: 358.4 km/sec
density: 2.1 protons/cm³
explanation | more data
Updated: Today at 1915 UT

X-ray Solar Flares
6-hr max: A0 1915 UT Apr01
24-hr: A0 0610 UT Apr01
explanation | more data
Updated: Today at: 1915 UT

NO SUNSPOTS: As April begins, the sun has been spotless for 24 consecutive days. How long can the blank spell continue? The longest stretch of blank suns in the past 100 years was 92 days in April, May and June of 1913. To match that streak, today's sun must remain spotless until early June 2009. That's a lot of quiet; stay tuned