ASTRONOMY NEWS AND EVENTS
Planet Saturn 2008 Opposition
February 24 marks this year’s opposition of Saturn, the point in Earth’s orbit when Saturn is opposite our sun in the sky. This is time of year when Saturn is closest and offers the best observing, though the good observing this year can be had from January to May. Saturn is currently shining at about 0.2 magnitude and can be found in the constellation Leo. Because the planet it at opposition (opposite the sun in our sky), it will rise when the sun sets and will set when the sun rises. Because of Saturn's brightness, a large telescope isn’t required, but can provide a brighter image. A good telescope for observing Saturn is one where the telescope and eyepiece combination is capable of offering a 100- to 200-power magnification without overtaxing the abilities of instrument or creating eye strain for the observer. For example, an 8-inch aperture Schmidt-Cassegrain telescope combined with a 10mm focal length eyepiece will provide a bright 100-power image. Using color filters will highlight features for better study. For example, both magenta and green filters (used separately) will highlight the rings of Saturn. Earth's oppositions of Saturn are just a little over a year apart. The next opposition will occur March 9, 2009.
In honor of this opposition, here is a quick overview of the Saturn system, provided by NASA's Solar System Exploration Web site: http://solarsystem.nasa.gov/
The Planet Saturn
Saturn was the most distant of the five planets known to the ancients. In 1610, Italian astronomer Galileo Galilei was the first to gaze at Saturn through a telescope. To his surprise, he saw a pair of objects on either side of the planet. He sketched them as separate spheres and wrote that Saturn appeared to be triple-bodied. Continuing his observations over the next few years, Galileo drew the lateral bodies as arms or handles attached to Saturn. In 1659, Dutch astronomer Christiaan Huygens, using a more powerful telescope than Galileo's, proposed that Saturn was surrounded by a thin, flat ring. In 1675, Italian-born astronomer Jean-Dominique Cassini discovered a 'division' between what are now called the A and B rings. It is now known that the gravitational influence of Saturn's moon Mimas is responsible for the Cassini Division, which is 4,800 kilometers (3,000 miles) wide.
Like Jupiter, Saturn is made mostly of hydrogen and helium. Its volume is 755 times greater than that of Earth. Winds in the upper atmosphere reach 500 meters (1,600 feet) per second in the equatorial region. (In contrast, the strongest hurricane-force winds on Earth top out at about 110 meters, or 360 feet, per second.) These super-fast winds, combined with heat rising from within the planet's interior, cause the yellow and gold bands visible in the atmosphere.
Saturn's ring system is the most extensive and complex in the so-lar system, extending hundreds of thousands of kilometers from the planet. In the early 1980s, NASA's two Voyager spacecraft revealed that Saturn's rings are made mostly of water ice, and they found 'braided' rings, ringlets, and 'spokes' - dark features in the rings that circle the planet at different rates from that of the surrounding ring material. Material in the rings ranges in size from a few micrometers to several tens of meters. Two of Saturn's small moons orbit within gaps in the main rings.
Saturn has 52 known natural satellites (moons) and there are probably many more waiting to be discovered. Saturn's largest satellite, Titan, is a bit bigger than the planet Mercury. (Titan is the second-largest moon in the solar system; only Jupiter's moon Ganymede is bigger.) Titan is shrouded in a thick, nitrogen-rich atmosphere that might be similar to what Earth's was like long ago. Further study of this moon promises to reveal much about planetary formation and, perhaps, about the early days of Earth. Saturn also has many smaller 'icy' satellites. From Enceladus, which shows evidence of recent (and ongoing) surface changes, to Iapetus, with one hemisphere darker than asphalt and the other as bright as snow, each of Saturn's satellites is unique.
Though Saturn's magnetic field is not as huge as Jupiter's, it is still 578 times as powerful as Earth's. Saturn, the rings, and many of the satellites lie totally within Saturn's enormous magnetosphere, the region of space in which the behavior of electrically charged particles is influenced more by Saturn's magnetic field than by the solar wind. Hubble Space Telescope images show that Saturn's polar regions have aurorae similar to Earth's. Aurorae occur when charged particles spiral into a planet's atmosphere along magnetic field lines.
Voyagers 1 and 2 flew by and photographed Saturn in 1981. The next chapter in our knowledge of Saturn is underway, as the Cassini- Huygens spacecraft continues its exploration of the Saturn system. The Huygens probe descended through Titan's atmosphere in January 2005, collecting data on the atmosphere and surface. Cassini will orbit Saturn more than 70 times during a four-year study of the planet and its moons, rings, and magnetosphere. Cassini-Huygens is sponsored by NASA, the European Space Agency, and the Italian Space Agency.
Saturn is home to a vast array of intriguing and unique worlds. From the cloud-shrouded surface of Titan to crater-riddled Phoebe, each of Saturn's moons tells another piece of the story surrounding the Saturn system.
Christiaan Huygens discovered the first known moon of Saturn. The year was 1655 and the moon is Titan. Jean-Dominique Cassini made the next four discoveries: Iapetus (1671), Rhea (1672), Dione (1684), and Tethys (1684). Mimas and Enceladus were both discovered by William Herschel in 1789. The next two discoveries came at intervals of 50 or more years - Hyperion (1848) and Phoebe (1898).
As telescopic resolving power increased through the 19th century, Saturn's family of known moons grew. In 1966 Epimetheus and Janus were discovered. By the time Cassini-Huygens was launched in 1997, Saturn's moon count had reached 18. The number of known moons soon increased with high-resolution imaging techniques used on ground-based telescopes. Cassini discovered four more moons after its arrival at Saturn and may find even more during its mission.
We've discovered a total of 52 natural satellites orbiting Saturn. Each of Saturn's moons bears a unique story. Two of the moons orbit within gaps in the main rings. Some, such as Prometheus and Pandora, interact with ring material, shepherding the ring in its orbit. Some small moons are trapped in the same orbits as Tethys or Dione. Janus and Epimetheus occasionally pass close to each other, causing them to periodically exchange orbits. Here's a sampling of some of the unique aspects of the moons:
- Titan is so large that it affects the orbits of other near-by moons. At 5,150 kilometers (3,200 miles) across, it is the second largest moon in the solar system. Titan hides its surface with a thick nitrogen-rich atmosphere. Titan's atmosphere is similar to Earth's atmosphere of long ago, before biology took hold on our home planet. Titan's atmosphere is approximately 95% nitrogen with traces of methane. While Earth's atmosphere extends about 60 kilometers (37 miles) into space, Titan's extends nearly 600 kilometers (ten times that of Earth's atmosphere) into space.
- Iapetus has one side as bright as snow and one side as dark as black velvet, with a huge ridge running around most of its dark-side equator.
- Phoebe orbits the planet in a direction opposite that of Saturn's larger moons, as do several of the recently discovered moons.
- Mimas has an enormous crater on one side, the result of an impact that nearly split the moon apart.
- Enceladus displays evidence of active ice volcanism: Cassini observed warm fractures where evaporating ice evidently escapes and forms a huge cloud of water vapor over the south pole.
- Hyperion has an odd flattened shape and rotates chaotically, probably due to a recent collision.
- Pan orbits within the main rings and helps sweep materials out of a narrow space known as the Encke Gap.
- Tethys has a huge rift zone called Ithaca Chasma that runs nearly three-quarters of the way around the moon.
- Four moons orbit in stable places around Saturn called Lagrangian points. These places lie 60 degrees ahead of or behind a larger moon and in the same orbit. Telesto and Calypso occupy the two Lagrangian points of Tethys in its orbit; Helene and Polydeuces occupy the corresponding Lagrangian points of Dione.
- Sixteen of Saturn's moons keep the same face toward the planet as they orbit. Called 'tidal locking,' this is the same phenomenon that keeps our Moon always facing toward Earth. The Cassini spacecraft will fly past Titan 45 times during its four-year primary mission. In addition, Cassini will gather data about many of the other satellites in an effort to fully understand the nature, formation, and dynamics of Saturn's moons.
Saturn's Ring System
The rings of Saturn have puzzled astronomers since Galileo Galilei discovered them with his telescope in 1610. Detailed study by the Voyager 1 and Voyager 2 spacecraft in the 1980s only increased the mystery.
There are thousands of rings made of up billions of particles of ice and rock. The particles range in size from a grain of sugar to the size of a house. The rings are believe to be pieces of comets, asteroids or shattered moons that broke up before they reached the planet. Each ring orbits at a different speed around the planet. Information from NASA's Cassini mission will help reveal how they formed, how they maintain their orbit and, above all, why they are there in the first place.
While the other three gas planets in the solar system - Jupiter, Uranus and Neptune - have rings orbiting around them, Saturn's are by far the largest and most spectacular. With a thickness of about 1 kilometer (3,200 feet) or less, they span up to 282,000 km (175,000 miles), about three quarters of the distance between the Earth and its moon.
Named alphabetically in the order they were discovered, the rings are relatively close to each other, with the exception of the Cassini Division, a gap measuring 4,700 kilometers (2,920 miles). The main rings are, working outward from the planet, known as C, B, and A. The Cassini Division is the largest gap in the rings and separates Rings B and A. In addition a number of fainter rings have been discovered more recently. The D Ring is exceedingly faint and closest to the planet. The F Ring is a narrow feature just outside the A Ring. Beyond that are two far fainter rings named G and E. The rings show a tremendous amount of structure on all scales; some of this structure is related to gravitational perturbations by Saturn's many moons, but much of it remains unexplained.
To enter Saturn's orbit, Cassini flew through the gap between the F and the G rings, farther from the planet than the Cassini Division. As a safe measure, during the crossing of the ring plane, instruments and cameras onboard the spacecraft were shut off temporarily. However, the spectacular crossing into Saturn's orbit brought incredible information, images and footage, while the instruments onboard are still collecting unique data that may answer many questions about the rings' composition.
To learn more about the Saturn system and the ongoing discoveries, visit the home page of the Cassini-Huygens mission to Saturn and Titan: http://saturn.jpl.nasa.gov/
To learn more about our solar system, visit NASA's Solar System Exploration home page: http://solarsystem.nasa.gov/
THE SKY THIS WEEK
Feb 24 - The planet Saturn is at opposition, the point when a planet farther from the sun than Earth appears opposite the Sun in the sky.
Feb 27 - The moon is at apogee, the point in the moon's orbit when it is farthest from Earth.
Feb 28, 9:18 P.M. EST (Feb 29, 02:18 UTC) - Last Quarter Moon
THIS WEEK IN HISTORY
Feb 24, 1968 - 40th anniversary of the discovery of pulsars by Irish radio astronomer Jocelyn Bell, now Jocelyn Bell Burnell (b. 1943), while a graduate student working with her thesis adviser Antony Hewish at the University of Cambridge.
Feb 24, 1969 - Launch of NASA's Mariner 6 spacecraft (U.S. Mars flyby mission)
Feb 27, 1897 - Birthday of French astronomer Bernard Ferdinand Lyot (1897-1952)
Mar ??, 2002 - Discovery of the meteorite NWA 1195 (A Mars meteorite)
Mar 1, 1966 - Venus impact of Soviet probe Venera 3
Mar 1, 1982 - Venus landing and flyby of Soviet combination probe Venera 13. The lander survived on the surface for 127 minutes.
Mar 1, 1980 - Discovery of Saturn moon Helene by Pierre Laques and Jean Lecacheux through ground based observations.
The Rainy Day
by Henry Wadsworth Longfellow (1807–1882), 1841
The day is cold, and dark, and dreary;
It rains, and the wind is never weary;
The vine still clings to the mouldering wall,
But at every gust more dead leaves fall.
And the day is dark and dreary.
My life is cold and dark and dreary.
It rains and the wind is never weary.
My thoughts still cling to the mouldering past.
And youth's fond hopes fall thick in the blast.
And my life is dark and dreary.
Be still, sad heart and cease repining
Behind the clouds is the sun still shining
Thy fate is the common fate of all
Into each life some rain must fall
Some days must be dark and dreary.
Henry Wadsworth Longfellow may be the best known of America's poets. During his life, Longfellow wrote twenty books and more than 150 poems. Following is death, Longfellow was the first American poet to have a memorial bust placed in the Poet’s Corner in Westminster Abbey. Even today his work was highly regarded and quoted often. And yet his life was not without tragedy and loss. Longfellow lost two wives in terrible and differing circumstances. And he himself was badly scarred and nearly died from burns suffered while attempting to save his second wife.
Even in the midst of this and other events, Longfellow was still able to keep some perspective on the peaks and valleys of his life. We can see this in a poem that he wrote in 1841 around the age of 34. It was some time after the death of his first wife of three years. Longfellow was a professor at Harvard and had not as of yet fully committed to writing exclusively. He was staying at the Wadsworth-Longfellow family home in Portland, Main. It happened to be a particularly rainy day and Longfellow's room overlooked the family garden, where he could clearly see the effects of the wind and rain. While reflecting on the oppressive and dreary nature of the day, Longfellow could still observe that, regardless of the individual, "Into each life some rain must fall."
Jesus made a similar observation during his sermon on the mount as recorded in the Gospel of Matthew chapter 5. Jesus reminded us that the triumphs and tragedies of our earthly existence are no different from those of our enemy, and that as children of God our purpose, come rain or shine, is to love our enemy in His name.
"Ye have heard that it hath been said, Thou shalt love thy neighbour, and hate thine enemy. But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you; That ye may be the children of your Father which is in heaven: for he maketh his sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust." (Matthew 5:43-45, KJV)
Joseph Brackett was born in Cumberland, Maine on May 6, 1797. Sometime later, the Brackett family moved to Gorham, Maine, where the family and their farm became part of a new community of the Society of Friends, a Christian organization commonly known as the Shakers. In 1819, Joseph moved with the rest of the Gorham community to Poland Hill, Maine.
Eventually, Joseph served as first minister of the Maine Shaker societies, as well as Church Elder at the New Gloucester, Maine community, which is now known as Sabbathday Lake, the last remaining Shaker community. Elder Joseph Brackett died on July 4, 1882.
In 1848 while at the Shaker community in Alfred, Maine, Elder Joseph Brackett wrote a new song for the worship services. While some Shaker songs can be quite lengthy, Brackett's song had only one verse. Its length and its construction seemed to encapsulate the very essence of what it means to be a Shaker. The words expressed many of their basic philosophies, including their worship practices of dance and movement, the simplicity of their societal structure and of their faith, and their emphasis on servanthood. Brackett called the song "Simple Gifts."
'Tis the gift to be simple, 'tis the gift to be free,
'Tis the gift to come down where we ought to be,
And when we find ourselves in the place just right,
'Twill be in the valley of love and delight.
When true simplicity is gain'd,
To bow and to bend we shan't be asham'd,
To turn, turn will be our delight,
Till by turning, turning we come round right.
Composer Aaron Copland used the melody in his score for Martha Graham's ballet, Appalachian Spring, which was first performed in 1944. Copland used the melody again in 1950 as part of his first set of Old American Songs for voice and piano, which was later orchestrated.
The melody has been adapted or arranged many times by folksingers and composers. Probably the best known example was first published in 1963 and written by Sydney Bertram Carter (1915-13 - 2004), British poet, songwriter, folk musician and Quaker. Carter was inspired partly by Jesus, and partly by Nataraja, the dancing embodiment of the Hindu god Shiva. In the song, Christ dances the shape and pattern of creation and our lives and then, as the piper, calls us to the dance. Carter entitled the song "Lord of the Dance." He adapted the "Simple Gifts" melody as a tribute to the Shakers and because it seemed so appropriate for the song.
"Lord of the Dance" is copyrighted internationally by Stainer & Bell Ltd. The copyright in the United States and Canada is held by Hope Publishing Company. Because of copyrights, the text could not be listed here without first obtaining the proper permissions. Instead, the link to Stainer & Bell's song page is provided below for your enjoyment.
Lord of the Dance. Words & Music by Sydney Carter. Copyright Stainer & Bell Ltd.
Lord of the Dance. Words & Music by Sydney Carter. Stainer & Bell Ltd. Retrieved February 18, 2008 from http://www.stainer.co.uk/lotd.html
Lord of the Dance. Words: Sydney B. Carter, 1963. Music: 19th Century Shaker tune, adapted by Sydney Carter, 1963. LORD OF THE DANCE © 1963 Stainer & Bell Ltd. Administered by Hope Publishing Company. The Cyber Hymnal. Last updated 21:33, December 5, 2007. Retrieved 07:30, February 18, 2008, from www.cyberhymnal.org/htm/l/o/r/lordoftd.htm
Simple Gifts. (2008, February 16). In Wikipedia, The Free Encyclopedia. Retrieved 12:46, February 18, 2008, from http://en.wikipedia.org/w/index.php?title=Simple_Gifts&oldid=191929815
Sydney Carter. (2007, December 10). In Wikipedia, The Free Encyclopedia. Retrieved 21:40, February 18, 2008, from http://en.wikipedia.org/w/index.php?title=Sydney_Carter&oldid=177008464
Post a Comment