FRIENDS OF THE PLANETARIUM NEWSLETTER – AUGUST 2008
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The big news this month is that our solar system has a new member. The International Astronomical Union has agreed to give to the transneptunian dwarf planet, or 'plutoid’, (136472) 2005 FY9 the name "Makemake". Makemake is around 2000 km in diameter. It orbits the sun in 307 years ranging in distance from 5700 million kms. from the Sun at closest, out to 7900 million kms. Makemake is the creator of humanity and the god of fertility in the mythology of the South Pacific island of Rapa Nui. His material symbol, a man with a bird's head, can be found carved in petroglyphs on the island.
In other solar system news, the Phoenix lander mentioned in our last newsletter has confirmed the existence of water (in the form of ice ) on Mars. Laboratory tests aboard NASA's Phoenix Mars Lander have identified water in a soil sample. The lander's robotic arm delivered the sample to an instrument that identifies vapours produced by the heating of samples. "We have water," said William Boynton of the University of Arizona, lead scientist for the Thermal and Evolved-Gas Analyzer, or TEGA. "We've seen evidence for this water ice before in observations by the Mars Odyssey orbiter and in disappearing chunks observed by Phoenix last month, but this is the first time Martian water has been touched and tasted." With enticing results so far and the spacecraft in good shape, NASA also announced operational funding for the mission will extend through Sept. 30. The original prime mission of three months ends in late August. The mission extension adds five weeks to the 90 days of the prime mission.
Mars is not the only place in our solar system where water appears. The Cassini mission has just completed a close flyby of Saturn’s moon Enceladus. In a feat of interplanetary sharpshooting, NASA's Cassini spacecraft has pinpointed precisely where the icy jets erupt from the surface of Saturn's geologically active moon Enceladus. New carefully targeted pictures reveal exquisite details in the prominent south polar "tiger stripe" fractures from which the jets emanate. The images show the fractures are about 300 metres deep, with V-shaped inner walls. The outer flanks of some of the fractures show extensive deposits of fine material. Finely fractured terrain littered with blocks of ice tens of metres in size and larger (the size of small houses) surround the fractures. One highly anticipated result of this flyby was finding the location within the fractures from which the jets blast icy particles, water vapour and trace organics into space. Scientists are now studying the nature and intensity of this process on Enceladus, and its effects on surrounding terrain. This information, coupled with observations by Cassini's other instruments, may answer the question of whether reservoirs of liquid water exist beneath the surface. The high-resolution images were acquired during an Aug. 11 flyby of Enceladus, as Cassini sped past the icy moon at 64,000 kilometers per hour. A special technique, dubbed "skeet shooting" by the imaging team, was developed to cancel out the high speed of the moon relative to Cassini and obtain the ultra-sharp views. One of the detailed images is shown here. The names of the features were taken from Tales of the Arabian Nights.
In other news, New Zealand will offer strong support for Australia's bid to host the world's largest radio telescope, the Square Kilometre Array (SKA), the Prime Minister Helen Clark announced on August 19. The Square Kilometre Array or SKA is a "next generation" radio telescope, and would be more than 50 times more sensitive than any radio telescope currently built. While a radio telescope usually consists of a single dish, the completed SKA will be a single radio telescope consisting of several thousand individual dishes, all linked together as a single instrument. This is possible by building several hundred clusters, each consisting of 50 to 100 individual dishes, spaced out over hundreds of kilometres. Each cluster will be linked together with cables enabling the high-speed sharing of data. The clusters of dishes will be arranged as a concentric spiral spreading outward. In the Australasian proposal the spiral begins in the NW of Western Australia with two arms of the spiral crossing all of Australia and ending in New Zealand. The completed SKA will have a collection area equivalent to one square kilometre.
In the night sky, watch carefully over the next month as our three neighbouring terrestrial planets perform a complex ballet in the constellation of Virgo. The early evening sky will be marked by the close grouping of 3 planets for much of the month. Venus, Mercury and Mars are within a 10-degree circle up to September 25. The three are less than 5 degrees apart from the 4th until the 19th and are therefore in a binocular field of view. Venus will be at its usual brilliance, Mars a relatively faint magnitude 1.7 while Mercury will dim from magnitude 0.0 on the 1st to 1.0 on the 25th and 2.2 five nights later. During the month the planets' relative positions change from night to night with a number of closest approaches. On September 2 the three planets will be joined by a thin crescent Moon only 6% lit. The Moon will be 8 degrees above Venus, with Mercury between and Mars to the right. On the 8th Mercury will be 2.6 degrees to the left of Mars, which itself will be just over 2 degrees above Venus. Four nights later, on the 12th, Mars will be just 19 minutes to the left of Venus, under two-thirds the diameter of the full Moon. The full Moon covers half a degree or thirty minutes of angular distance. Mercury will be about 3.5 degrees to their upper left. Also by then Spica, the brightest star in Virgo, will be less than 10 degrees above Venus. Spica at magnitude 1.1, will be brighter than Mars. On the 15th Venus, leaving Mars behind, passes Mercury which will be just over 3.5 degrees to the left of the brighter planet. Spica will be just over 5 degrees above Venus. Four nights later Venus will be at its closest to Spica about 2.5 degrees to the right and slightly lower than the star. Mercury will be a similar distance to the left of the star, but a little lower than Venus. Mars will be almost 5 degrees below the star. Spica and the three planets will form a broad cross in the western sky. By then Mercury will be at magnitude 0.5. After this Venus will start pulling away from the other three, which will stay in a close group as they sink into the evening twilight. Up to September 27, Mars and Mercury will be less than 5 degrees apart with Spica between them. Mars on the right will gradually move up past the star while Mercury on the left moves down. From night to night the three will get lower in the sky and more difficult to see in the twilight. Also Mercury will dim rapidly to magnitude 2.2 on September 30.
Jupiter, meanwhile, will be prominent, high in the sky, moving from the northeast to the northwest during the evening. It can be found in Sagittarius, about 3 degrees below the star Nunki, magnitude 2.1. Enjoy the show!