David_Aldrich's Blog

October 9, 2008: A team of internationally renowned astronomers and opticians may have found a way to make "unbelievably large" telescopes on the Moon.

"It's so simple," says Ermanno F. Borra, physics professor at the Optics Laboratory of Laval University in Quebec, Canada. "Isaac Newton knew that any liquid, if put into a shallow container and set spinning, naturally assumes a parabolic shape—the same shape needed by a telescope mirror to bring starlight to a focus. This could be the key to making a giant lunar observatory."

Borra, who has been studying liquid-mirror telescopes since 1992, and Simon P. "Pete" Worden, now director of NASA Ames Research Center, are members of a team taking the idea for a spin.

Right: An artist's concept of a spinning liquid mirror telescope on the Moon. Credit: Univ. of British Columbia.

On Earth, a liquid mirror can be made quite smooth and perfect if it its container is kept exactly horizontal and rests on a low-vibration low-friction air bearing that is spun by a synchronous motor having one stable speed. "It doesn't need to spin very fast," says Borra. "The rim of a 4-meter–diameter mirror—the largest I've made in my lab—travels only 3 miles per hour, about the speed of a brisk walk. In the low gravity of the Moon, it would spin even slower."

Most liquid-mirror telescopes on Earth have used mercury. Mercury remains molten at room temperature, and it reflects about 75 percent of incoming light, almost as good as silver. The biggest liquid-mirror telescope on Earth, the Large Zenith Telescope operated by the University of British Columbia in Canada, is 6 meters across—a diameter 20 percent larger than the famous 200-inch mirror of the Hale telescope at Palomar Observatory in California. Yet when completed in 2005, the Canadian Palomar-class liquid-mirror telescope cost less than $1 million to build—only a few percent the cost of a solid-mirror telescope of the same diameter--and, for that matter, only a sixth of Palomar's original cost in 1948.

Those economics are making astronomers sit up and begin noodling out plans for a lunar observatory.

"Our study [with Borra] started when I was still an astronomy professor at the University of Arizona before I came to NASA in 2006," Worden recalls. "The real appeal of this approach is that we could get an unbelievably large telescope on the Moon."

Mercury is unworkable on the Moon: it's very dense and thus heavy to launch, it's very expensive, and it would evaporate quickly when exposed to the lunar vacuum. In recent years, however, Borra and his colleagues have been experimenting with a class of organic compounds known as ionic liquids. "Ionic liquids are basically molten salts," Borra explains. "Their evaporation rate is almost zero, so they would not vaporize in the lunar vacuum. They can also remain liquid at very low temperatures." He and his colleagues are now seeking to synthesize ionic liquids that remain molten even at liquid-nitrogen temperatures.

Below: The University of British Columbia's 6-meter Large Zenith Telescope uses a liquid mirror to scan the heavens. [more]

Much less dense than mercury, ionic liquids are only slightly denser than water. Although not highly reflective themselves, a spinning mirror of an ionic liquid can be coated with an ultrathin layer of silver just as if it were a solid mirror. Weirdest of all, the silver layer is so thin—only 50 to 100 nanometers—that it actually solidifies. In the vacuum of space, a liquid mirror coated with a thin solid layer of silver would neither evaporate nor tarnish.

A liquid mirror can't be tilted away from the horizontal because the fluid would pour out, destroying the mirror. But that does not mean a liquid mirror telescope cannot be pointed. Optical designers are now experimenting with ways of electromechanically warping secondary mirrors suspended above a liquid mirror—or even slightly warping the liquid mirror itself—to aim at angles away from the vertical. Similar techniques are used to point the great Arecibo radio telescope in Puerto Rico.

Furthermore, says Borra, "if the telescope is located anywhere other than exactly at the poles, with each rotation of Earth or Moon it would scan a circular strip of sky. And the rotational axis of the Moon wobbles with a period of 18.6 years; so over a period of 18.6 years, the telescope would actually look at a good-sized region of the sky."

Right: The 1000-ft Arecibo radio telescope in Puerto Rico cannot be moved, but it can still scan a wide swath of sky using movable secondary mirrors. A lunar liquid mirror telescope might employ similar techniques. [more]

Locating a major liquid-mirror telescope near the lunar poles is appealing. The telescope itself could reside near the bottom of a permanently shadowed crater where it would stay at cryogenic temperatures, desirable for the best infrared astronomy. Yet solar panels could be erected on nearby permanently illuminated mountain peaks to generate power to keep the mirror spinning.

The fact that a liquid-mirror telescope always looks straight up vastly simplifies its construction and reduces mass by eliminating heavy mounts, gearing, and pointing-control systems needed for a steerable telescope. "All you'd need is the liquid-mirror container, which might be an umbrella-like device that self-deploys, plus a nearly frictionless superconducting bearing and its drive motor," Borra says. Worden estimates that all the materials for an entire lunar telescope 20 meters across would be "only a few tons, which could be boosted to the Moon in a single Ares 5 mission in the 2020s." Future telescopes might have mirrors as large as 100 meters in diameter—larger than a football field.

"A mirror that large could peer back in time to when the universe was very young, only half a billion years old, when the first generation of stars and galaxies were forming," Borra exclaimed. "Potentially more exciting is pure serendipity: new things we might discover that we just don't expect."

Says Worden: "Putting a giant telescope on the Moon has always been an idea of science fiction, but it soon could become fact."

Author: Trudy E. Bell | Editor: Dr. Tony Phillips | Credit: Science@NASA

Mercury as Never Seen Before

Oct. 7, 2008: Yesterday, NASA's MESSENGER spacecraft flew past Mercury and photographed a broad swath of never-before-seen terrain. The first of more than 1,200 high-resolution images are arriving back at Earth now.

"The MESSENGER team is extremely pleased by the superb performance of the spacecraft and the payload," says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "We are now on the correct trajectory for eventual insertion into orbit around Mercury, and all of our instruments returned data as planned."

This spectacular image – one of the first to be returned – was snapped by the spacecraft's Wide Angle Camera (WAC) about 90 minutes after MESSENGER's closest approach to Mercury, when the spacecraft was at a distance of about 27,000 kilometers (about 17,000 miles):

Above: New photographs of Mercury's unseen side reveal a dramatic system of globe-straddling rays. [full caption]

The most striking characteristic of this newly imaged area is the large pattern of rays streaking downward from the planet's northern regions. The ray system appears to emanate from a relatively young crater previously seen in Earth-based radar images but photographed by a spacecraft for the very first time just yesterday. This view of the planet is distinctly unique from what MESSENGER saw during its first flyby in Jan. 2008.

In the mid-1970s when Mariner 10 flew past Mercury three times, the probe imaged less than half the planet. MESSENGER's first flyby in January of this year covered another 20 percent of the planet's surface. Yesterday, Oct. 6th, MESSENGER successfully completed its second flyby of Mercury, unveiling another 30 percent of Mercury's surface that had never before been seen by spacecraft.

"When these data have been digested and compared, we will have a global perspective of Mercury for the first time," notes Solomon.

Data from the flyby continue to stream down to Earth, including higher resolution close-up images of this previously unseen terrain.

Visit the MESSENGER photo gallery for updates.

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

Pretty amazing stuff.  I think Galileo would have been impressed.

----- David

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How Round is the Sun?

Oct. 2, 2008: Scientists using NASA's RHESSI spacecraft have measured the roundness of the sun with unprecedented precision, and they find that it is not a perfect sphere. During years of high solar activity the sun develops a thin "cantaloupe skin" that significantly increases its apparent oblateness. Their results appear the Oct. 2nd edition of Science Express.

"The sun is the biggest and smoothest natural object in the solar system, perfect at the 0.001% level because of its extremely strong gravity," says study co-author Hugh Hudson of UC Berkeley. "Measuring its exact shape is no easy task."

The team did it by analyzing data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager, RHESSI for short, an x-ray/gamma-ray space telescope launched in 2002 on a mission to study solar flares. Although RHESSI was never intended to measure the roundness of the sun, it has turned out ideal for the purpose. RHESSI observes the solar disk through a narrow slit and spins at 15 rpm. The spacecraft's rapid rotation and high data sampling rate (necessary to catch fast solar flares) make it possible for investigators to trace the shape of the sun with systematic errors much less than any previous study. Their technique is particularly sensitive to small differences in polar vs. equatorial diameter or "oblateness."

Above: "Cantaloupe ridges" on the sun. The glowing white magnetic network is what gives the sun its extra oblateness during times of high solar activity. Los Angeles astronomer Gary Palmer took the picture in July 29, 2005, using a violet calcium-K solar filter. [larger image]

"We have found that the surface of the sun has rough structure: bright ridges arranged in a network pattern, as on the surface of a cantaloupe but much more subtle," describes Hudson. During active phases of the solar cycle, these ridges emerge around the sun's equator, brightening and fattening the "stellar waist." At the time of RHESSI's measurements in 2004, ridges increased the sun's apparent equatorial radius by an angle of 10.77 +- 0.44 milli-arcseconds, or about the same as the width of a human hair viewed one mile away.

  "That may sound like a very small angle, but it is in fact significant," says Alexei Pevtsov, RHESSI Program Scientist at NASA Headquarters. Tiny departures from perfect roundness can, for example, affect the sun's gravitational pull on Mercury and skew tests of Einstein's theory of relativity that depend on careful measurements of the inner planet's orbit. Small bulges are also telltale signs of hidden motions inside the sun. For instance, if the sun had a rapidly rotating core left over from early stages of star formation, and if that core were tilted with respect to its outer layers, the result would be surface bulging. "RHESSI's precision measurements place severe constraints on any such models."

The "cantaloupe ridges" are magnetic in nature. They outline giant, bubbling convection cells on the surface of the sun called "supergranules." Supergranules are like bubbles in a pot of boiling water amplified to the scale of a star; on the sun they measure some 30,000 km across (twice as wide as Earth) and are made of seething hot magnetized plasma. Magnetic fields at the center of these bubbles are swept out to the edge where they form ridges of magnetism. The ridges are most prominent during years around Solar Max when the sun's inner dynamo "revs up" to produce the strongest magnetic fields. Solar physicists have known about supergranules and the magnetic network they produce for many years, but only now has RHESSI revealed their unexpected connection to the sun's oblateness.

Right: In this diagram, the sun's oblateness has been magnified 10,000 times for easy visibility. The blue curve traces the sun's shape averaged over a three month period. The black asterisked curve traces a shorter 10-day average. The wiggles in the 10-day curve are real, caused by strong magnetic ridges in the vicinity of sunspots. [larger image]

"When we subtract the effect of the magnetic network, we get a 'true' measure of the sun's shape resulting from gravitational forces and motions alone," says Hudson. "The corrected oblateness of the non-magnetic sun is 8.01 +- 0.14 milli-arcseconds, near the value expected from simple rotation."

"These results have far ranging implications for solar physics and theories of gravity," comments solar physicist David Hathaway of the NASA Marshall Space Flight Center. "They indicate that the core of the sun cannot be rotating much more rapidly than the surface, and that the sun's oblateness is too small to change the orbit of Mercury outside the bounds of Einstein's General Theory of Relativity."

Further analysis of RHESSI oblateness data could also help researchers detect a long-sought type of seismic wave echoing through the interior of the sun: gravitational oscillations or "g-modes." The ability to monitor g-modes would open a new frontier in solar physics—the study of the sun's internal core.

"All of this," marvels Hathaway, "comes from clever use of data from a satellite designed for something entirely different. Congratulations to the RHESSI team!"

The paper reporting these results, "A large excess in apparent solar oblateness due to surface magnetism," was authored by Martin Fivian, Hugh Hudson, Robert Lin and Jabran Zahid, and appears in the Oct. 2nd issue of Science Express.

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

"Global warming has paused."

The Sun has gone to sleep. 

It is spotless, according to NASA. 

Translation ?  Prepare for cold.

And 5 agencies have acknowledged the switch.

1.  Hadley Climate Research Center (UK)

2.  Japan Meteorological Agency

3.  National Oceanic and Atmospheric Administration (NOAA)

4.  University of East Anglia (UK)

5.  University of Alabama - Huntsville

But somehow the message is lost.

Perhaps, you can explain to me why.

CLICK HERE

and

CLICK HERE

No spots ?  Prepare for cold. 

---- David

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Spotless Sun: Blankest Year of the Space Age

Sept. 30, 2008: Astronomers who count sunspots have announced that 2008 is now the "blankest year" of the Space Age.

As of Sept. 27, 2008, the sun had been blank, i.e., had no visible sunspots, on 200 days of the year. To find a year with more blank suns, you have to go back to 1954, three years before the launch of Sputnik, when the sun was blank 241 times.

"Sunspot counts are at a 50-year low," says solar physicist David Hathaway of the NASA Marshall Space Flight Center. "We're experiencing a deep minimum of the solar cycle."

A spotless day looks like this:

The image, taken by the Solar and Heliospheric Observatory (SOHO) on Sept. 27, 2008, shows a solar disk completely unmarked by sunspots. For comparison, a SOHO image taken seven years earlier on Sept. 27, 2001, is peppered with colossal sunspots, all crackling with solar flares: image. The difference is the phase of the 11-year solar cycle. 2001 was a year of solar maximum, with lots of sunspots, solar flares and geomagnetic storms. 2008 is at the cycle's opposite extreme, solar minimum, a quiet time on the sun.

And it is a very quiet time. If solar activity continues as low as it has been, 2008 could rack up a whopping 290 spotless days by the end of December, making it a century-level year in terms of spotlessness.

Hathaway cautions that this development may sound more exciting than it actually is: "While the solar minimum of 2008 is shaping up to be the deepest of the Space Age, it is still unremarkable compared to the long and deep solar minima of the late 19th and early 20th centuries." Those earlier minima routinely racked up 200 to 300 spotless days per year.

Above: A histogram showing the blankest years of the last half-century. The vertical axis is a count of spotless days in each year. The bar for 2008, which was updated on Sept. 27th, is still growing. [Larger images: 50 years, 100 years]

Some solar physicists are welcoming the lull.

"This gives us a chance to study the sun without the complications of sunspots," says Dean Pesnell of the Goddard Space Flight Center. "Right now we have the best instrumentation in history looking at the sun. There is a whole fleet of spacecraft devoted to solar physics--SOHO, Hinode, ACE, STEREO and others. We're bound to learn new things during this long solar minimum."

  As an example he offers helioseismology: "By monitoring the sun's vibrating surface, helioseismologists can probe the stellar interior in much the same way geologists use earthquakes to probe inside Earth. With sunspots out of the way, we gain a better view of the sun's subsurface winds and inner magnetic dynamo."

"There is also the matter of solar irradiance," adds Pesnell. "Researchers are now seeing the dimmest sun in their records. The change is small, just a fraction of a percent, but significant. Questions about effects on climate are natural if the sun continues to dim."

Pesnell is NASA's project scientist for the Solar Dynamics Observatory (SDO), a new spacecraft equipped to study both solar irradiance and helioseismic waves. Construction of SDO is complete, he says, and it has passed pre-launch vibration and thermal testing. "We are ready to launch! Solar minimum is a great time to go."

Coinciding with the string of blank suns is a 50-year record low in solar wind pressure, a recent discovery of the Ulysses spacecraft. (See the Science@NASA story Solar Wind Loses Pressure.) The pressure drop began years before the current minimum, so it is unclear how the two phenomena are connected, if at all. This is another mystery for SDO and the others.

Who knew the blank sun could be so interesting? More to come...

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

CLICK HERE

In a word...Ugh.

I think this article speaks for itself. 

CLICK HERE

A fascinating article and possible implications with Solar Cycle 24.  Check it out.  It hints at a very cold future (last paragraph). 

 ---- David

They say, if you throw enough mud on the wall, something will stick.

It is kinda like this forecast. 

We are going to get the rain, but does something get the name ?

It is the tale of two Lows.  The most impressive one will be the one off the Carolina coast.  The secondary one appears to be much slower near Hispaniola.

Check out this image for a look at the storm's streamlines:

CLICK HERE

Remember, summer may be over, but hurricane season is not.

Since late last week, I have been tracking what appears to be our next Tropical storm into the Philadelphia area.  "Kyle" and "Laura" are the next two names on the Atlantic storm list.  Given the drop-off in shower activity between Jamaica and Panama, it appears the storms around Puerto Rico are now the only game in town, so to speak.

If this area of low pressure forms into a tropical storm, it will be assigned the name "Kyle."

The timing of this coastal storm (let's assume it's "Kyle") still seems favorable for Friday and Saturday, September 26th and September 27th for the Philadelphia area.

For the latest discussion on this developing storm...

CLICK HERE

Compare this new system with Hanna's track.  They are very similar.

Storms that originate from this location make New Jersey, Delaware and Southeastern Pennsylvania vulnerable.

CLICK HERE

Below is a copy of my detailed prediction, dated last Friday morning.

_________________________________________________>

something Tropical ?

Sep 19, 2008 | 6:20 AM
Category: Weather

It's just after 6 AM on Friday morning.

There is a distrurbing trend on the models that I wanted to share with you regarding next weekend, specifically Friday and Saturday, September 26th and 27th.

Whether it's the GEM, GFS or ECMWF, many of the models are not sure what to do with the area of low pressure that is currently sitting offshore.  (This weekend, a few showers may "dog" the beaches in North Carolina, but obviously no big deal here.)

There is a possibility of something TROPICAL or even subtropical forming offshore of New Jersey by Friday and Saturday, September 26th and 27th.

The next few names on the Atlantic Storm List include:  Kyle and Laura.

If Kyle forms from the disturbance near the Lesser Antilles, our system may be given the name Laura.

It's WAY TOO EARLY to commit, but in a worst case scenario, we could be dealing with another "Hanna" type storm here in the Tri-State by Friday and Saturday, September 26th and 27th.  This would mean HEAVY RAIN, WIND and even isolated tornadoes (remember East Allentown ?)

CLICK HERE

Pretty cool site to see pictures from space.

CLICK HERE

Did you know that Arctic ice has only been observed since 1979 ?

That is not a very long time frame.  Just food for thought.

Hurricane Ike is a tragedy in the making.  Keep Texas in your thoughts and prayers.  They'll need it.

-----  David

CLICK HERE    for Ike updates and video.

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Spooky Hurricane Science

Sept. 12, 2008: There's a special room at the Marshall Space Flight Center. Researchers call it the "Anechoic Chamber" and they love to test their high-tech instruments there. Normal people think it's just plain spooky.

"In here, no one can hear you scream," says engineer Mark James as he opens the door on the surreal:

Above: The electromagnetically quiet Anechoic Chamber at the Marshall Space Flight Center in Huntsville, Alabama. [larger image]

The door creaks shut behind James and suddenly it's like someone hit the mute button. Dead silence. Pyramids on the wall seem to be closing in. The urge to scream ... hard to resist.

James just gets on with the job. He's lead engineer on a research team using this cavernous facility to test a prototype hurricane sensor called HIRAD. Short for Hurricane Imaging Radiometer, HIRAD is designed to scan large areas of ocean for microwave signals that portend storm strength and dynamics. By collecting and transmitting these data to forecasters, HIRAD could reduce property damage and even save lives.

  The Anechoic Chamber is the perfect place to check HIRAD's antenna.

Weird shapes lining the chamber's walls are made of a radio-frequency damping material arranged in a pattern akin to soundproof rooms. The shapes minimize microwave reflections and eliminate electromagnetic interference.

"The electromagnetic quiet allows us to test and fully characterize the HIRAD antenna," explains James. "Lack of sound is just a weird bonus."

A microwave source at one end of the chamber sends signals to the HIRAD antenna at the other end. In this way, engineers can explore the antenna's beam pattern to check that it meets the requirements of the mission ahead.

Using microwaves, "HIRAD will be able to map out wind speeds on the ocean's surface--in particular the hurricane strength within the eye wall and elsewhere," says Tim Miller, HIRAD principal investigator at the National Space Science and Technology Center in Huntsville, Alabama. "We can also determine how heavy the rain is and the temperature of the ocean surface, more indicators of hurricane characteristics."

(Note: To learn more about how HIRAD works, read the Science@NASA story "In the Blink of a Hurricane's Eye.")

Because of its design, HIRAD can make observations over a wider swath of area than instruments currently used by NOAA. And by using electronic rather than mechanical means to scan and create a two-dimensional image of the storm's dynamics, HIRAD can operate on less power than current wind measuring instruments. It's also smaller, lighter, and relatively inexpensive to build.

Right: Engineer David Simmons adjusts the HIRAD antenna in the MSFC Anechoic Chamber. [larger image]

"HIRAD's observations will not only give weather officials more and better real-time information on storm strength, but it will also help them determine how the storm will develop and where it will go," says Miller. "All of this adds up to more advanced warnings to the public."

How is HIRAD doing so far in the "bat cave" testing?

"We're still reviewing our test data, but so far HIRAD is passing with flying colors," says Robbie Hood of the MSFC, former principal investigator for the project and still intimately involved in its development.

The next step, she says, "is to build the real thing. This is just a test unit – a laboratory prototype. Ultimately, HIRAD will be more compact and lighter weight than the unit we're testing now."

The team hopes to have HIRAD ready to fly checkout tests onboard an aircraft by fall 2009, and ready for its first hurricane experiment in 2010. HIRAD will have to compete with other candidate instruments for the hurricane experiment.

The whole team feels confident that their instrument is going to succeed. "We've got top-notch personnel working long hours to make it happen," says Miller. "We all know that HIRAD is a valuable instrument, and we want to place it in the hands of weather officials so it can do its work -- saving lives."

The trick, says James with a smile, "is not getting locked in the bat cave."

What?

Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA