Space: Discovery of new Saturnian moon - full text
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It was revealed on July 19, 2007, that scientists had discovered a new moon, measuring about 2 km wide, orbiting at a distance of around 197,700 km from Saturn. The new Saturnian moon was detected whilst scientists were analysing photographic images captured on May 30 by the Cassini orbiter, part of the Cassini Huygens spacecraft. The moon was initially named S/2007 S 4, pending the designation of a permanent name by the International Astronomy Association, and was thought to be composed mostly of ice and rock.
Immediate Context
The detection of S/2007 S 4 was the latest in a series of discoveries about Saturn since the launch in October 1997 of the Cassini Huygens mission, a collaborative space research project involving scientists from the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), and the Italian Space Agency (ASI). In January radar observations of the northern hemisphere of Titan (Saturn's largest moon) provided “definitive” evidence of the existence on the moon's surface of some 75 lakes, composed largely of liquid methane. It was reported in August 2005 that the Cassini Huygens had helped to discover a permanent atmosphere of water vapour and carbon dioxide on one of Saturn's smaller moons, Enceladus.
The spacecraft entered into orbit around Saturn in July 2004, after having passed Jupiter in January 2001 at a distance of 9.7 million km. It successfully landed on Titan in January 2005, which the journal Science, in December 2005, regarded as one of the top 10 scientific achievements of the year.
Observational astronomy, the branch of astronomy used to detect S/2007 S 4, had also led to other recent celestial discoveries. In April 2007 astronomers from the Geneva Observatory using the European Southern Observatory at La Silla, Chile, detected the most “Earth-like” planet ever discovered, orbiting a red dwarf star named Gliese 581 in the constellation of Libra, some 20.5 light years distant.
The discovery in 2005 of Eris, the largest known “dwarf planet” in the Solar System, led in August 2006 to the International Astronomical Union (IAU) demoting Pluto from its status as the ninth and most remote planet.
In March 2003 it was reported that astronomers from the University of Hawaii and the University of Cambridge, using telescopes on Mauna Kea in Hawaii, had discovered eight new small moons orbiting Jupiter.
Reaction and Outlook
In a press release published on July 19 by NASA’s Jet Propulsion Laboratory (JPL), Professor Carl Murray, a UK-based scientist working on the Cassini project, said that the 60th Saturnian moon had been detected using the spacecraft's “powerful wide-angle camera”.
According to a press release published on July 19 by the US-based Cassini Imaging Central Library Laboratory for Operations (CICLOPS), the discovery of S/2007 S 4 suggested that the new moon (and its neighbouring moons Methone and Pallene) formed part of a larger “family” of moons in the region. Professor Murray also said that scientists at the JPL would “use Cassini's cameras to search for additional family members”, the BBC online news service reported on July 20.
Historical Context
Cassini Huygens was the fourth spacecraft launched to explore Saturn, the sixth most distant planet from the Sun and the second largest planet in the Solar System.
The first mission to explore Saturn involved the Pioneer 11 spacecraft, which was launched in 1973. Pioneer 11 orbited Saturn in August 1979, after completing a journey of over 17,000 million km and which took the craft past Jupiter in 1974. In September 1979 Pioneer 11 safely flew through Saturn’s distinctive ring system before flying on to study Titan.
Scientists received the first high-resolution images of Saturn during the Voyager I mission in August 1980. The Voyager 1 mission, launched in 1977, also prompted theories suggesting that Saturn’s rings numbered more than 100 and led scientists to discover that the planet was encircled by a cloud of hydrogen that was detectable only by ultra-violet light.
The Voyager 2 mission in June 1981 led to the discovery that Titan had a surface atmosphere of around 1,500 millibars (a unit of atmospheric pressure equal to one thousandth of a bar). At the time of the Voyager 2 mission scientists suspected that Saturn was orbited by no more than 23 moons.
In June 1990 NASA released a photograph taken on board Voyager 1 from the edge of the Solar System. Shot from a distance of more than 6,000 million km, the photograph showed Neptune, Uranus, Saturn, Jupiter, the Earth, and Venus in a single frame.
