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Planets galore like Earth await discovery ROYAL ASTRONOMICAL SOCIETY NEWS RELEASE Posted: April 5, 2005 How many planets like the Earth are there among the 130 or so known planetary systems beyond our own? How many of these "Earths" could be habitable?
Unfortunately, existing telescopes are not powerful enough to see these relatively small, distant "Earths". Orbiting close to a much brighter star, these very faint worlds resemble glow-worms hidden in the glare of a searchlight. All of the planets that have been detected so far are giants the mass of Neptune or larger. Even so, they cannot be directly seen with ground-based instruments. Almost all of the known exoplanets have been found through the "wobbling" motion they induce in their star as they orbit it, like a twirling dumb-bell in which the mass at one end (the star) is much greater than the mass at the other end (the giant planet). Speaking today at the RAS National Astronomy Meeting in Birmingham, Professor Jones explained how his team used computer models to see if "Earths" could be present in any of the currently known exoplanetary systems, and whether the gravitational buffeting from one or more giant planets in those systems would have torn them out of their orbits. "We were particularly interested in the possible survival of "Earths" in the habitable zone," said Professor Jones. "This is often called the 'Goldilocks zone,' where the temperature of an 'Earth' is just right for water to be liquid at its surface. If liquid water can exist, so could life as we know it." The Open University team created a mathematical model of a known exoplanetary system, with its star and giant planet(s), then launched an Earth-sized planet at some distance from the star to see if it survived. By detailed study of a few representative exoplanetary systems, they found that each giant planet is accompanied by two "disaster zones" - one exterior to the giant, and one interior. Within these zones, the giant's gravity will cause a catastrophic change in the Earth-like planet's orbit. The dramatic outcome is a collision with either the giant planet or the star, or ejection into the cold outer reaches of the system. The team found that the locations of these disaster zones depend not only on the mass of the giant planet (a well known result) but also on the eccentricity of its orbit. They thus established rules for determining the extent of the disaster zone. Having found the rules, they applied them to all of the known exoplanetary systems - a much quicker method than studying each system in detail. The range of distances from the star covered by its habitable zone was compared to the locations of the disaster zones to see if there was a full or partial safe haven for an Earth-like planet. They discovered that about half of the known exoplanetary systems offer a safe haven for a period extending from the present into the past that is at least long enough for life to have developed on any such planets. This assumes that "Earths" could have formed in the first place, which seems quite likely. However, the situation is complicated by the fact that the habitable zone migrates outwards as the star ages, and in some cases this changes the potential for life to evolve. Thus, in some cases a safe haven might have been available only in the past, while in other cases it might exist only in the future. These scenarios of past extinction and future birth increase to about two-thirds the proportion of the known exoplanetary systems that are potentially habitable at some time during the main-sequence lifetime of their central star. A paper by Barrie W. Jones, David R. Underwood, and P. Nick Sleep, entitled "Prospects for habitable 'Earths'," is scheduled to appear in the 1 April 2005 issue of the Astrophysical Journal. The 2005 RAS National Astronomy Meeting is hosted by the University of Birmingham, and sponsored by the Royal Astronomical and the UK Particle Physics and Astronomy Research Council (PPARC). |
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Take a behind-the-scenes look at the seven astronauts who will fly aboard the space shuttle return-to-flight mission in this movie that profiles the lives of the STS-114 crew. (10min 04sec file)
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Walk alongside space shuttle Discovery as the motorized transporter hauls the ship a quarter-mile from the Orbiter Processing Facility to the Vehicle Assembly Building. (3min 21sec QuickTime file)
This time-lapse movie captured from an overhead camera shows space shuttle Discovery's middle-of-the-night departure from its processing hangar at Kennedy Space Center to the roll to the Vehicle Assembly Building. (4min 30sec file)
Discovery arrives in the Vehicle Assembly Building as viewed in this time-lapse movie. The shuttle will be mated to the redesigned external fuel tank and twin solid rocket boosters in the VAB before rolling to the launch pad for the first post-Columbia mission. (5min 00sec file)
A foot-long Russian nanosatellite is flung overboard by the spacewalking International Space Station Expedition 10 crew. Station cameras watched the hand-launched deployment and the nanosat as it floated away. (4min 52sec file)
Highlights of the second spacewalk of the International Space Station's Expedition 10 crew is compiled into this movie. The crew completed external outfitting of gear that will guide European cargo ships to the outpost during dockings starting in 2006. (5min 00sec file)
Mission managers preview the next spacewalk by the Expedition 10 crew aboard the International Space Station, which will install external equipment on the Russian segment and hand-launch a tiny nanosatellite. (37min 00sec file)
This video retrospective remembers the first flight of space shuttle Endeavour. The maiden voyage set sail in May 1992 to rescue the Intelsat 603 communications spacecraft, which had been stranded in a useless orbit. Spacewalkers attached a rocket booster to the satellite for the critical boost to the correct altitude.
This video retrospective remembers the 2002 mission of Columbia that made a long distance service call to the Hubble Space Telescope, giving the observatory a new power system and extending its scientific reach into the Universe. Astronauts performed five highly successful spacewalks during the mission.
This retrospective remembers the third voyage of space shuttle Columbia. The March 1982 mission served as another developmental test flight for the reusable spacecraft, examining performance of its systems while also conducting a limited science agenda. STS-3 is distinguished by making the first landing at Northrup Strip in White Sands, New Mexico.