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Editor's Corner...

Here's a little background to the June 8 transit of Venus across the face of the Sun.

A Venus transit is a relatively rare event. It happens only when Venus is at inferior conjunction coincident with crossing the Earth's orbital plane (the Ecliptic). The last transit was in 1882. There will be another in June 2012, then none until December 2117. Unfortunately, this year's event takes place during darkness hours in western North America. In the northeastern states, the 6-hour transit will already be underway at sunrise. The whole event, from 1st contact through 4th contact, will be seen in Europe, Asia and most of Africa. We'll get our chance in June, 2012.

Some of you may recall that, before joining the SAS, Jeff Baldwin had twice traveled to distant parts to observe a solar eclipse...and was clouded out both times. Bummer! But even Jeff would have to sympathize with the eighteenth century French astronomer Guillaume le Gentil.

Here's the story, from a web site by David Sellers of Leeds, England.

In 1677, Edmund Halley (1656-1742) observed a transit of Mercury. He realized that careful timing of a transit of Venus from various latitudes would enable a more accurate determination of the Earth's radius and of its distance from the Sun. In 1716, he wrote a paper to the Royal Society admonishing future astronomers to make accurate observations of the transits of Venus predicted for 1761 and 1769.

"In 1761, Charles Mason and Jeremiah Dixon observed from South Africa, William Wales from Canada, Jean-Baptise Chappe d'Auteroche from Siberia and Alexandre-Gui Pingré from Madagascar. The French astronomer, Guillaume le Gentil set out to observe the transit from India, but unfortunately arrived too late.

"Having got there eventually, he decided to stay 8 years to make sure of seeing the 1769 transit. Tragically, he missed this one too, because in an otherwise cloud-free month a cloudy morning managed to totally obscure the transit. To add insult to injury, when he returned to France, he discovered that his relatives had given him up for dead and had divided up his estate!"

So when you are feeling a little left out by all the media accounts around June 8, spare a thought for poor Guillaume. It could be worse! And you'll get your chance eight years from now.

...Trevor Atkinson

There are numerous web sites devoted to the June 8 event.
Just do a Google search for "Venus transit".
To get the full background story from David Sellers, go to:
http://www.dsellers.demon.co.uk/venus/ven_ch_frames.htm
For a live webcast, go to:
www.exploratorium.edu/webcasts


Comet Season Continues

Comets NEAT and LINEAR have not provided the spectacle of Hyakutake in 1996 and Hale-Bopp in '97. However, for amateur astronomers who get a kick out of actually being able to see anything happening out of the ordinary, these comets of 2004 add interest to the night sky.

Best prospect for evening viewing is Comet NEAT. Clearly visible as a fuzzy blob in binoculars, Comet NEAT has steadily climbed the western evening sky during May. According to Sky and Telescope:

"It will remain ideally placed for viewing high in the northwest after dark through June and July as it dwindles away into the distance, eventually becoming visible only in telescopes."

Discovered by the the Lincoln Near Earth Asteroid Research (LINEAR) project in October of 2002, Comet LINEAR was closest to the Sun on April 23 and closest to Earth on May 19. In late May and June it may be visible "... above the west-southwest horizon at dusk, fading all the while."

http://skyandtelescope.com/observing/objects/comets/article_1229_1.asp

The Heavens Above web site has a daily finder chart for both comets:
www.heavens-above.com

Happy hunting!


The Science Directorate at NASA's Marshall Space Flight Center sponsors the Science@NASA web sites. The mission of Science@NASA is to help the public understand how exciting NASA research is and to help NASA scientists fulfill their outreach responsibilities.

Why So Dry?

by Patrick L. Barry, Dr. Tony Phillips

The western U.S. is facing yet another summer of severe drought. Science provides some answers - and some baffling questions.

May 21, 2004:  People often greet the first warm days of summer with eager anticipation for the sunny weather to come. But for many people in the western U.S., the arrival of warm weather this year is an harbinger of hard times ahead.

Lake Mead, an important water source in the West created in the 1930s by the construction of Hoover Dam, is approaching record low levels--hence the "bathtub ring" around the lake, shown here. Image courtesy US National Park Service.

Drought has gripped some parts of the West for as many as seven consecutive years, causing one of the worst dry spells in decades. Soils are dry; reservoirs are low. Farmers and golf course managers are vying for irrigation water, residents face water rationing measures, and the politics of water "seniority" rights is heating up between cities and between states.

Hope for a reprieve fades with the departing winter, because little precipitation typically falls in the West during summer months. These regions depend on winter storms to stock the mountains with snow, which melts in summer and replenishes water supplies. The snowpack in April 2004, though, was only 40% to 75% of normal. The ongoing drought, which has affected 20% to 50% of the land area of the contiguous United States, isn't as bad as, say, the Dust Bowl drought of the 1930s. Then 70% of the U.S. was dry. In the Great Plains, precious topsoil blew away, agriculture collapsed, farmers literally lost their land. "The dispossessed were drawn west," wrote John Steinbeck in The Grapes of Wrath. "Families, tribes, dusted out, tractored out. Car-loads, caravans, homeless and hungry. They streamed over the mountains-restless as ants, scurrying to find work to do - to lift, to push, to pull, to cut - anything, any burden to bear, for food."

Most of the western U.S. is suffering from some degree of drought. The darkest color on this map represents the most extreme category of drought in NOAA's classification scheme. Image courtesy National Drought Mitigation Center.

What causes such severe droughts? Are they predictable? Scientists aren't sure, but they're learning by studying the current dry spell. Earth-orbiting satellites, which didn't exist during the Dust Bowl years, now provide crucial data about winds, rain, soil moisture,and the state of the oceans. Somewhere among those numbers lies the answer.

A key factor is the temperature of water in the Pacific Ocean, says Bob Oglesby, a climate dynamicist at NASA's Marshall Space Flight Center. Sea surface temperatures (SSTs) in the Pacific alter the course of the jet stream as it flows eastward over North America. This high-altitude "river" of fast-moving air is like a conveyor belt for storms, so the path it takes across the continent has a strong effect on where rain and snow will fall. By steering the jet stream, the Pacific Ocean acts like a baton-wielding orchestra conductor directing the symphony of weather patterns across North America.

For example, a strong "El Niño" pattern of warm Pacific surface waters near the equator will drive storms into California, while the opposite "La Niña" pattern steers moisture-bearing storms further north to Washington state and Canada. One causes drought, the other alleviates it. But there must be more to the story: While a mild La Niña lurked in the Pacific during the onset of the current drought - as would be expected - a shift to a weak El Niño in 2003 did not reverse the drought.

"It's a really active area of research right now as people are trying to decipher exactly what's causing what," Oglesby says. He and his colleagues at the Global Hydrology and Climate Center are among those working to understand what's going on. In particular, Oglesby is investigating how the land and atmosphere interact with each other during a drought, focusing on the roles that snow cover and soil moisture play.

Part of the difficultly in understanding drought lies in the fact that weather involves many feedback loops that complicate its behavior and defeat simple cause-and-effect explanations. Soil moisture creates such a feedback loop during dry weather. Oglesby explains "Once you get into a dry pattern and you start to dry the ground out, that reduction in soil moisture can help to intensify and perpetuate the drought." Normally, the evaporation of soil moisture consumes much of the energy contained in the summer sunshine; without this moisture, that energy heats the ground instead and raises temperatures even further. Warmer temperatures create a high pressure system which, in turn, blocks storms from coming into the area. Drought begets drought.

NASA climate dynamicist Bob Oglesby.

Drought is a natural part of cyclical weather patterns in North America, notes Oglesby. Physical clues about ancient weather, such as tree rings and lake sediment cores, show that dry spells such as the Dust Bowl and a similar drought in the 1950s typically occur a few times per century. The historical record also reveals a "mega-drought," longer and more severe than any recent episodes, 500 or so years ago.

In modern times "there's more to drought than simple lack of precipitation," adds Roger Pielke Sr., a state climatologist for Colorado and a professor of atmospheric sciences at Colorado State University. "You have to consider human factors like the amount of water being drained from rivers for crop irrigation and drinking water. In absolute terms, the ongoing dry spell is not yet as severe as the Dust Bowl of the 1930s, but the impacts have been relatively severe because the demands that people place on the water supply are so much greater now than they were back then."

This makes a complicated situation even more complicated. Land-use and water-use by humans; large-scale atmospheric circulation changes caused by ocean temperatures; feedbacks between the land and atmosphere: they all play a role. Climatologists can't yet put these factors together to predict what will happen many years in advance. Next winter is mystery enough. Will it bring much snow ... and relief? No one knows.

One thing seems sure, though: With levels of moisture in the soil and snow on the mountains both below average, people in the western U.S. are facing at least one more long, dry summer.




Far-out Ideas

by Patrick L. Barry

Ever had a great idea for a new spacecraft propulsion system, or for a new kind of Mars rover? Have you ever wondered how such "dinner napkin sketches" evolve into real hardware flying real missions out in the cold blackness of space?

The road to reality for each idea is a unique story, but NASA has defined some common steps and stages that all fledgling space technologies must go through as they're nursed from infancy to ignition and liftoff.

Suppose, for example, that you've thought of a new way to shield astronauts from harmful radiation during long space missions. In the first stage, you would simply "flesh out" the idea: Write it down, check the physics, and do some quick experiments to test your assumptions.

If the idea still looks good, the next step is to build a "proof of concept." This is the "science fair project" stage, where you put together a nifty demonstration on a low budget-just to show that the idea can work.

For your radiation-shielding idea, for example, you might show how a Geiger counter inside a miniature mock-up doesn't start clicking when some radioactive cobalt-60 is held nearby. The shielding really works!

Once that hurdle is cleared, development shifts into a higher gear. In this stage, explains Dr. Christopher Stevens of JPL, the challenge isn't just making it work, but making it work in space.

"Some conditions of space flight cannot be adequately simulated here on Earth," Stevens says. Cobalt-60 doesn't truly mimic the diverse mixture of radiation in space, for example, and the true microgravity of orbit is needed to test some technologies, such as the delicate unfolding of a vast, gossamer solar sail. Other technologies, such as artificial intelligence control systems, must be flight tested just because they're so radically new that mission commanders won't trust them based solely on lab tests.

Stevens is the manager of NASA's New Millennium Program (NMP), which does this sort of testing: Sending things to space and seeing if they work. In recent years the NMP has tested ion engines and autonomous navigation on the Deep Space 1 spacecraft, a new "hyperspectral" imager on the Earth Observing 1 satellite, and dozens of other "high risk" technologies.

Thanks to the NMP, lots of dinner napkin sketches have become real, and they're heading for space. You can learn more at the NMP website, nmp.nasa.gov/.

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.


Jane Houston Jones was, until recently, president of the Astronomical Association of Northern Califonia, and one of the most active amateur astronomers in the Bay Area. She is now Senior Communications Specialist for the Cassini Mission, at JPL in Pasadena. She and Mojo have clearly wasted no time getting involved in amateur astronomy activities in Southern California. She still sends occasional articles to newsletter editors of AANC member clubs. Here is her most recent contribution.

Dome Sweet Dome

by Jane Houston Jones

The 12 day old waxing Moon brings sunrise to western Oceanus Procellarum, the ocean of storms. That means Aristarchus and Vallis Schroteri are near their visible best on this night, a night that Mojo and I set up our two sidewalk telescopes on a Monrovia corner sidewalk.

We were soon joined by Mark and Lisa Rooney, fellow members of the Los Angeles Astronomical Society (LAAS) and the Sidewalk Astronomers who we met just the week before at a Griffith Park star party. Mark set up his Meade LX200 next to our two scopes. Soon we were joined by LAAS members Dave Nakamoto and Tim Thompson, who provided telescope nudging relief and astronomical interpretation to the nearly 200 visitors to our eyepieces over the next 2 hours. Mojo aimed at Jupiter. Mark aimed at Saturn, and I got dibs on the Moon.

If you are a Lunatic like me, the Vallis Schroteri region is an area of never ending awe. This part of Oceanus Procellarum is rich in volcanic structures. Selected as a landing site for the Apollo missions, it lost out to Hadley Rille as Apollo 15th's landing site. Among the many interesting features in this area is the bright young crater, Aristarchus. You've all seen a bright white crater north west of Copernicus. That's Aristarchus! It almost looks like someone put a dab of whiteout on a crater. Aristarchus is even visible on the night side of the moon during Earthshine!

Telescopes of all sizes can pick out Vallis Schroteri, the largest sinuous valley on the moon. At the beginning of the snakelike valley is the cobra head feature, a 10 km widening just north of a tiny crater.

The valley meanders in a "U" shape for 160 kilometers from the crater Herodotus to the south. At some points the valley narrows to only 500 meters wide. It terminates at a 1,000 meter high precipace on the edge of an uplifted tetragonal shaped continent called the Aristarchus Plateau. David Nakamoto commented that the plateau really did appear elevated with respect to the surrounding lunarscape when he took a look.

That's the beauty of frequent lunar observing. You really see amazing details when the sun angle is just right, and hour by hour, the angle shows old favorite features in a new light, literally.

Another unusual landscape that was starkly lit by sunrise was the Marius Hills. This area, like all the features I mention in this write up look best at sunrise, 4 days after first quarter or at sunset, 4 days after last quarter. This is an area of 300 small steep-sided hills and domes.

Domes in a section of Marius Hills - (from Lunar Orbiter image IV-157H2.)

The best way for me to describe it in words is that it looked like shadows over a piece of pebbly laminate, like the ebony star or Wilsonart pebble sand laminate on the sides of my telescope. If I pretend a piece of laminate is the surface of moon near the terminator, and I shine a flashlight across it at a low angle, mimicking a rising sun over the laminate, the raised "bumps" look like the Marius Hills with shadows pointing away from the flashlight or away from the sunrise.

That's what the Marius Hills looked like to me. Like hundreds of small bumps, each with a shadow facing the terminator. It was quite an amazing sight!

There are many interesting studies of lunar domes. C. Weitz and J. Head of JPL studied the volcanic features of the Marius Hills complex using multispectral data from the Clementine UV- visible camera, and compared them to other lunar domes and cones. An abstract of their work is provided below, as are some images and observing notes. I hope this article encourages you to observe familiar areas of the moon and look for some of the amazing lunar domes.

References:
Spectral Properties of the Marius Hills
http://www.agu.org/pubs/abs/je/1998JE000630/1998JE000630.html

The Hitchhiker Guide to the Moon
http://www.shallowsky.com/moon/hitchhiker.html - click on the numbered sections for observing notes of the areas. These sections correspond to the Rukl Atlas of the Moon maps. Aristarchus Map 18, Marius Hills Map 29.

Lunar Photo of the Day images of the Procellarum Volcanic Group
http://www.lpod.org/LPOD-2004-04-12.htm

More on lunar domes
http://www.uai.it/sez_lun/domes.htm

Lunar links galore
http://www.shallowsky.com/moon/moonlinks.html

Prospective Apollo landing sites, including the Marius Hills
http://www.lpi.usra.edu/expmoon/orbiter/orbiter-sites.html


Upcoming Events

Shingletown Star Party 2004
June 16 through June 20, 2004

(Star party closes June 21, 2004)

This is the SSP's third year. It offers some of California's darkest skies and convenient easy-highway access. The star party is held on the runway of a closed airport, so there's no dirt or tumbleweeds on the setup field.

This years SSP is adding a shower truck and ice truck to its list of amenities. Just a few miles away is the resort community of Shingletown which provides full services. Beautiful Mount Lassen National Volcanic Park is 17 miles up the mountain.

Registration Now Open -- (Registration this year is limited to 300 attendees)

Find information about SSP 2004 at www.shingletownstarparty.org


Attend a Conjunction!
AstroCon 2004
is coming to the San Francisco Bay Area
July 20-24, 2004

Here's a conjunction you can actually attend-not just observe: a truly once-in-a-lifetime conjunction of the Astronomical League, the American Association of Variable Star Observers, the Association of Lunar and Planetary Observers, and the Astronomical Society of the Pacific.

Highlights:

www.astrocon2004.org
Visit the website for complete details,
including secure on-line registration and payment

Co-hosted by the Astronomical Association of Northern California,
the Eastbay Astronomical Society,
and the San Jose Astronomical Association



Copyright © 2004 by Stockton Astronomical Society
Last Updated: 6/8/2004
http://www.stocktonastro.org/Newsletter/VS0406.html