Sunday, November 18, 2007

WEEKLY UPDATE

Astronomer Questions Significance of COBE Images

Most astronomers say the Cosmic Background Explorer (COBE) satellite images show structures of the early universe. But 70-year-old radio astronomer and author Gerrit Verschuur of the University of Memphis, claims to have evidence that the images actually depict nearby hydrogen gas clouds in our own galaxy, calling into question one of the most important theories in the past 15 years. Verschuur's research will be published December 10 in the Astrophysical Journal.

NASA scientists announced in 1992 that their COBE satellite had imaged the ultimate baby pictures of the universe, revealing the seeds that grew into galaxies like our own Milky Way. And in 2003, higher-resolution images of the seeds were taken by another satellite, the Wilkinson Microwave Anisotropy Probe (WMAP).

According to Verschuur's research, the imaged seeds are located not on the edge of the universe, but nearby. Instead, they're just previously unmapped clouds of "neutral hydrogen" gas located inside the Milky Way. Verschuur sites at least 200 instances where the so-called cosmic seeds lie suspiciously close to known hydrogen clouds inside our galaxy.

Scientists who have reviewed his work suggest Verschuur’s correlations between the WMAP seeds and galactic hydrogen filaments are just coincidences. But as history has shown with previous debates over statistical interpretations, it is likely that Verschuur’s claim will not be settled anytime soon.

To learn more about the Cosmic Background Explorer (COBE) mission, visit the NASA website:
http://lambda.gsfc.nasa.gov/product/cobe/

Wilkinson Microwave Anisotropy Probe (WMAP) mission, visit the NASA website:
http://map.gsfc.nasa.gov/


Hubble Images Do Not Explain Comet 17P/Holmes Outburst

Astronomers are still uncertain what caused the brightening of normally-dim Comet 17P/Holmes, which erupted October 24 and is still shining brightly like a new star in the constellation Perseus.

In a November 15 announcement, three new comet images taken by the Hubble Space Telescope (HST) showed the core of Holmes as a field of particles extending some 15,000 miles across. The images also show that the particles appear to be coming from around the comet's hidden nucleus. This information, combined with another image taken by a ground-based telescope at the Calgary Science Centre (CSC) in Alberta, Canada, supplements the idea of some scientists that something must have broken off from around the nucleus and then disintegrated to become the dust cloud.

According to astronomers, the most likely explanation for the outburst is that a coating of relatively stable water ice, less than 10 miles thick around the comet's nucleus, was suddenly blown away by other, far more volatile chemical ices beneath the frozen water. As those ices heated and expanded violently, they blew the outer ice apart.

The new HST images show no large fragments in the cloud of particles that might suggest they were fragments of the nucleus itself or debris from a collision with a boulder-size asteroid orbiting between Mars and Jupiter - although some astronomers already have proposed that idea.

Seven years ago, HST imaged Comet Holmes, then nearly 150 million miles away. Astronomers inferred from the comet's brightness that its nucleus of rock and ice was barely more than 2 miles wide and that no dust obscured it. But the three new HST images have identified the 15,000-mile core of particles closest to the nucleus.

In addition, the new CSC image shows that at its brightest, the comet's particles extend for at least 2 million miles, with a thinner scattering of particles on its lower right side that may be the beginning of a comet tail.

When British amateur astronomer Edwin Holmes discovered the comet in November of 1892, he detected it because it had suddenly burst into a huge ball of light in his telescope. It then dimmed and, 73 days later, flared up briefly again.

At the time, U.S. astronomer Fred Whipple suggested that the flare-ups occurred because the comet had a double nucleus. Whipple proposed that one nucleus hit the other in a "grazing collision" that triggered the comet's first brilliant cloud of gas and dust, and then a full head-on crash 73 days later created the spectacular second outburst. In recalling Holmes' discovery, some will be watching in mid-January, hoping for a second display.

Still others suggest this year's flare-up might have resulted from a fragile nucleus spinning so fast that it just flew apart.

Astronomers at the Space Telescope Science Institute are studying the feasibility of a 2015 NASA mission to Comet Holmes or some other comet that has a history of flare-ups, and to orbit it long enough to learn the cause and maybe return a sample of the particles.


To learn more, visit Hubble Site, home of NASA's Hubble Space Telescope: http://hubblesite.org/

To learn more about the Calgary Science Centre in Alberta, Canada, visit their website: http://www.calgaryscience.ca/


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MARS IS COMING, PART 3

As the December 24 opposition approaches, please enjoy this third installment on the Red Planet Mars.


The Atmosphere (Part 1)

In 1947, Dutch-American astronomer Gerard P. Kuiper (1905-1973) determined from telescopic observations that the Martian atmosphere is composed mainly of carbon dioxide. The atmosphere is very thin, pushing at less than 1 percent of Earth's atmospheric pressure at the surface. The altitude varies greatly over the Martian surface, causing surface pressures to range over a factor of 15. Today's atmosphere has only small amounts of water. If it all was extracted and frozen, it would form a layer of ice crystals only 10 micrometers (0.0004 inch) thick, which could be gathered into a solid block of ice not much larger than one of Earth's medium-size icebergs. Geologic evidence suggests that in the distant past the atmosphere was much denser and water was much more abundant at the surface.

The average temperature in the lower atmosphere is about 200 kelvins (K; -100 °F, -70 °C), which is generally colder than the average daytime surface temperature of 250 K (-10 °F, -20 °C). These values are in the same range as those on Earth in Antarctica during winter. In summer above a very dark surface, daytime temperatures at the height of a human can peak at about 290 K (62 °F, 17 °C). Above the turbulent layer close to the surface, temperature decreases with elevation at a rate of about 1.5 K (2.7 °F, 1.5 °C) per km (about 2.4 K [4.3 °F, 2.4 °C] per mile) of altitude.

Unlike that of Earth, the atmosphere of Mars has large seasonal variations in pressure. During each hemisphere’s winter, the main component, carbon dioxide, “snows out” over the winter pole. And during each hemisphere’s spring, the carbon dioxide returns directly to a gas (sublimes). Because the southern winter cap is larger than the northern, atmospheric pressure reaches a minimum during southern winter when the southern cap is at its largest. From Viking lander measurements of the pressure, which was found to vary by 26 percent annually over the mean, scientists calculated that some 7.9 trillion metric tons of carbon dioxide leave and reenter the atmosphere seasonally. This is equivalent to a thickness of at least 23 cm (9 inches) of solid carbon dioxide (dry ice) or several meters of carbon dioxide snow averaged over the vast area of the seasonal polar caps.

Direct chemical analysis at the surface by the Viking landers and spectral observations from orbiting spacecraft allowed scientists to precisely determine the composition of the atmosphere. Where the atmosphere is well mixed by turbulence—below an altitude of 125 km (about 80 miles)—95.3 percent of the atmosphere by weight is carbon dioxide (see the table). This is a comparatively large amount—nine times the quantity now in Earth's much more massive atmosphere. Much of Earth's carbon dioxide, however, is chemically locked in sedimentary rocks; the amount in the Martian atmosphere is less than a thousandth of the terrestrial total. The balance of the Martian atmosphere consists of molecular nitrogen, water vapor, and noble gases (argon, neon, krypton, and xenon). There are also trace amounts of gases that have been produced from the primary constituents by photochemical reactions, generally high in the atmosphere; these include molecular oxygen, carbon monoxide, nitric oxide, and small amounts of ozone.

The lower atmosphere supplies gas to the planet's ionosphere, where densities are low, temperatures are high, and components separate by diffusion according to their masses. Various constituents in the top of the atmosphere are lost to space, which affects the isotopic composition of the remaining gases. For example, because hydrogen is lost preferentially over its heavier isotope deuterium, Mars's atmosphere contains five times more deuterium than Earth's.

Although water is only a minor constituent of the Martian atmosphere (a few molecules per 10,000 at most), primarily because of low atmospheric and surface temperatures, it plays an important role in atmospheric chemistry and meteorology. The Martian atmosphere is effectively saturated with water vapor, yet there is no liquid water present on the surface. The temperature and pressure of the planet are so low that water molecules can exist only as ice or as vapor. Little water is exchanged daily with the surface despite the very cold nighttime surface temperatures.

Most of the information about atmospheric water on Mars has come from the Viking orbiters, which observed seasonal patterns of water content in the atmosphere over a full Martian year. Water vapor is mixed uniformly up to altitudes of 10–15 km (6–9 miles) and shows strong latitudinal gradients that depend on the season. The largest changes occur in the northern hemisphere. During summer in the north, the complete disappearance of the carbon dioxide cap leaves behind a water-ice cap. Sublimation of water from the residual cap results in a strong north-to-south concentration gradient of water vapor in the atmosphere. In the south, where a small carbon dioxide cap remains in summer and only a small amount of water ice has been detected, a strong water vapor gradient does not normally develop in the atmosphere.

The atmospheric water vapor is thought to be in contact with a much larger reservoir in the Martian soil. Subsurface layers of ice are thought to be ubiquitous on Mars at latitudes between 40° and the poles; the very low subsurface temperatures would prevent the ice from subliming. The 2001 Mars Odyssey spacecraft, which began orbital observations of the planet in late 2001, confirmed that ice is present within a meter of the surface at these latitudes, but it is not known how deep the ice layer extends. In contrast, at low latitudes, ice is unstable, and any ice present in the ground would tend to sublime into the atmosphere.

The Viking landers' analytical instruments also measured the isotopic composition of the major and minor atmospheric gases. The similarity of the ratios of isotopes of carbon and oxygen to their terrestrial values implies that large reservoirs of carbon dioxide and water ice exist on Mars and that gases from the reservoirs exchange with those in the atmosphere. The results of other isotopic measurements from Viking suggest that larger amounts of carbon dioxide, nitrogen, and argon were present in the atmosphere in the past and that Mars may have lost much of its inventory of volatile substances early in its history, either to space or to the ground (i.e., locked up chemically in rocks). Some scientists have conjectured that Mars may once have had a much thicker atmosphere but that it was lost to the surface through chemical reactions, which formed carbonates, and to space through large asteroid impacts, which blew off atmospheric gases.

Next Time: “The Atmosphere, Part 2”


Bibliography

Mars. (2007). In Encyclopædia Britannica. Retrieved October 26, 2007 , from Encyclopædia Britannica Online: http://www.britannica.com/eb/article-9110149

Mars (2007). In The Columbia Encyclopedia, Sixth Edition 2007. Copyright 2007 Columbia University Press. Retrieved October 26, 2007 from Encyclopedia.com
http://www.encyclopedia.com/doc/1E1-Mars-ast.html

Planets: Mars. In NASA Solar System Exploration, Last updated October 23, 2007. Retrieved October 26, 2007, from the NASA Solar System Exploration website, maintained by NASA's Jet Propulsion Laboratory:
http://solarsystem.jpl.nasa.gov/planets/profile.cfm?Object=Mars


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THE SKY THIS WEEK


Nov 17, 5:33 PM EST - First Quarter Moon

Nov 17 - Neptune is 1.0° north of Moon, occultation. An occultation occurs when one object passes in front of a smaller one, temporarily obscuring all or part of the background object from view.

Nov 17 - Leonid meteors

Nov 19 - Uranus is 2° south of Moon

Nov 23 - Moon is at perigee, the point in the Moon's orbit when it is closest from Earth.

Nov 24, 9:30 AM EST - Full Moon. Called the “Beaver Moon” or “Snow Moon,” this was the time to set beaver traps before the swamps froze, in order to ensure a supply of winter furs. Others suggest the name refers to the fact that beavers were actively preparing for winter. This full moon is also sometimes called the “Frosty Moon.”

Nov 24 - Uranus is stationary. The body appears motionless in the sky due to the turning point between its direct and retrograde motion.


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THIS WEEK IN HISTORY

Nov 18, 1989 – Launch of The Cosmic Background Exporer satellite (COBE)

Nov 20, 1889 – Birthday of Edwin Hubble

Nov 20, 2004 - Mars Rover “Spirit” landing on Mars


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MUSICAL DIVERSION

The Dutch folk song "Wilder dan wilt" (Wilder than wild) has been traced back at least to the late 1500s. The song began "Wilder dan wilt, wie sal mij temmen," or "Wilder than wild, who will tame me?" Here are the verses.


Wilder Dan Wilt

Wilder dan wildt, wie sal my temmen,
plach ick te singhen vroech ende laet;
ick heb geluystert na Christi stemmen,
die heeft my getrocken tot anderen staet.

Ick was soo wilt, 't mocht aen my blijcken,
als eenen voghel vliecht in de locht;
Heer Jesus heeft my met sijn practijcken
soo soetkens al in sijn net ghebrocht.

Vry, liber, en los, en onghebonden,
mijn willeken volchde ick over al;
dat heeft my doen vallen in soo veel sonden,
het welck ick met recht beklaghen sal.

Heer Jesus leert my mijn willeken breken,
al vallet my somtijdts hert en swaer;
daer door kan ick veel quaedts versteken,
in alles gherust volgh' ick hem naer.

Ick plach te gaen proncken lancks de straten,
verciert als een goddinneken ient;
heer Jesus heeft my dit doen verlaten,
mijn kruysken opnemen, dat hy my sent.

Cupido begon my heel te minnen
en te bestralen met sijn venijn;
nu leer ick aen Jesum vast leggen mijn sinnen,
om gracy te vinden voor sijn aenschijn.

Voor 't slempen, en dempen, en triomferen,
oock danssen en springhen met herten bly,
moet'ick nu vasten en abstineren;
mijnen tijdt beschreyen, is mijn party.


O Prince, ick wacht mijn recompence,
als ghy sult oordeelen in den troon;
dat ick dan hooren mach die sentence:
‘komt hier mijn bruydt, ontfanght de kroon.’

-----

Some have suggested this was a bawdy song, but a quick scan of the Dutch lyrics and a rough translation here and there will show several references to "Lord Jesus" and "Christ" and "my sin." Such an observation will tell you this was more of a hymn than a tavern song. The tune may be even older than these words. Whatever the case, it seems apparent that the tune was well known because it was later set to other Dutch lyrics. On January 24, 1597 at the Battle of Turnhout, the Dutch Prince Maurice of Orange defeated Spanish occupiers of a region that is now part of the Netherlands. The Dutch Protestants, who had been forbidden to practice their faith under the Catholic King Philip II of Spain, rejoiced through new hymns that celebrated their victory. On such hymn was written by a poet and writer of songs named Adriaen Valéry, who wrote under Latinized name Adrianus Valerius (1575-1625). He actually wrote this new hymn during the year of the Dutch Protestant victory, but it was not widely published until the year after Valéry's death. We can thank his son François for publishing his collecton, entitled "Nederlandtsche Gedenckclanck." The hymn was entitled “Wilt Heden Nu Treden.”


Wilt Heden Nu Treden

Wilt heden nu treden voor God, den Heere,
Hem boven al loven van harte zeer,
En maken groot zijns lieven namens eere,
Die daar nu onzen vijand slaat terneer.

Ter eeren ons Heeren wilt al uw dagen
Dit wonder bijzonder gedenken toch.
Maakt u, o mensch, voor God steeds wel te dragen,
Doet ieder recht en wacht u voor bedrog!

Bidt, waket en maket, dat g'in bekoring
En 't kwade met schade toch niet en valt.
Uw vroomheid brengt den vijand tot verstoring,
Al waar' zijn rijk nog eens zoo sterk bewald!

-----

In 1877, the German chorus master Eduard Kremser (1838-1914) published a translation of the lyrics from Dutch to Latin along with an arrangement of the tune for chorus and orchestra. From that point, the tune became known to many simply as “Kremser.” A few years later, in 1894, the text was loosely translated to English by U.S.-born musical scholar Theodore Baker (1851-1934). Some of the militant flavor of the original was lost, but essence of the text remained. He called the hymn “We Gather Together.”


We Gather Together

We gather together to ask the Lord’s blessing;
He chastens and hastens His will to make known.
The wicked oppressing now cease from distressing.
Sing praises to His Name; He forgets not His own.

Beside us to guide us, our God with us joining,
Ordaining, maintaining His kingdom divine;
So from the beginning the fight we were winning;
Thou, Lord, were at our side, all glory be Thine!

We all do extol Thee, Thou Leader triumphant,
And pray that Thou still our Defender will be.
Let Thy congregation escape tribulation;
Thy Name be ever praised! O Lord, make us free!

-----

This hymn has become for many an important part of their annual Thanksgiving Day celebrations. And then in 1902, J. Archer Gibson, the organist of the Brick Presbyterian Church in New York City, approached active church member Mrs. Julia B. Cory (1882-1963) with a request for a new setting to the tune. For her inspiration, Cory returned to Valéry’s original hymn text. The new hymn was premiered on the very next Thanksgiving Day, and it was first published in “Hymns of the Living Church” in 1910. Cory called her hymn “We Praise Thee, O God, Our Redeemer, Creator.”


We Praise Thee, O God, Our Redeemer, Creator

We praise Thee, O God, our Redeemer, Creator,
In grateful devotion our tribute we bring;
We lay it before Thee, we kneel and adore Thee,
We bless Thy holy Name, glad praises we sing.

We worship Thee, God of our fathers, we bless Thee;
Through life’s storm and tempest our guide have Thou been;
When perils overtake us, escape Thou will make us,
And with Thy help, O Lord, our battles we win.

With voices united our praises we offer,
To Thee, great Jehovah, glad anthems we raise.
Thy strong arm will guide us, our God is beside us,
To Thee, our great Redeemer, forever be praise.

(Cory later added this Christmas stanza)

Thy love Thou didst show us, Thine only Son sending,
Who came as a Babe and Whose bed was a stall,
His blest life He gave us and then died to save us;
We praise Thee, O Lord, for Thy gift to us all.

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To view the lyrics of “Wilder Dan Wilt” visit this link - http://www.dbnl.org/tekst/duys001oude03_01/duys001oude03_01_0169.htm

To see and hear more on the hymn, “Wilt Heden Nu Treden” visit this page of "The Cyber Hymnal" - http://www.cyberhymnal.org/non/nl/wilthede.htm

To see and hear more on the hymn, “We Gather Together” visit this page of "The Cyber Hymnal" - http://www.cyberhymnal.org/htm/w/e/wegattog.htm

To see and hear more on the hymn, “We Praise Thee, O God, Our Redeemer, Creator” visit this page of "The Cyber Hymnal" - http://www.cyberhymnal.org/htm/w/p/wptogorc.htm

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