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Asteroids Asteroids that are on a collision course with Earth are called meteoroids. Because of the perturbing influence of the major planets, the asteroid orbits tend to "wander", and the calculation of whether (or when) a particular object might impact the Earth may require extremely accurate knowledge of the orbit, such as can be provided by radar observations. Asteroids which in this manner draw close to the Earth's orbit are referred to as near Earth objects (NEO), and are considered to pose the danger of potential impact with Earth. www.crystalinks.com /asteroids.html   (864 words)

Minor planet - Wikipedia, the free encyclopedia Eos asteroids have a semi-major axis between 2.99 AU and 3.03 AU, an eccentricity between 0.01 and 0.13, and an inclination between 8° and 12°. Nysa asteroids have a semi-major axis between 2.41 AU and 2.5 AU, an eccentricity between 0.12 and 0.21, and an inclination between 1.5° and 4.3°. Hilda asteroids have a mean orbital radius between 3.7 AU and 4.2 AU, an eccentricity greater than 0.07, and an inclination less than 20°. en.wikipedia.org /wiki/Minor_planet   (2450 words)

Hilda asteroid - Encyclopedia.WorldSearch   (Site not responding. Last check: 2007-10-22) Hilda asteroids are asteroids with a semi-major axis between 3.7 AU and 4.2 AU, an eccentricity greater than 0.07, and an inclination less than 20°. Hildas move in their orbits so that their aphelia put them opposite Jupiter, or 60 degrees ahead of or behind Jupiter at the L On the motion of the asteroid Hilda (153) encyclopedia.worldsearch.com /hilda_asteroid.htm   (123 words)

Encyclopedia: Minor planet The Themis Asteroid Family The Themis Asteroid Family is a Hirayama family of asteroids found in the outer portion of the main asteroid belt, between the orbits of Mars and Jupiter. Hilda asteroids are asteroids with a semi-major axis between 3. Damocloids are asteroids such as 5335 Damocles and 1996 PW that have long-period highly eccentric orbits typical of periodic comets such as 1P/Halley, but without showing a cometary coma or tail. www.nationmaster.com /encyclopedia/Minor-planet   (5181 words)

153 Hilda - Wikipedia, the free encyclopedia Hilda gives its name to an asteroid group called Hilda asteroids (or shorter Hildas). It is not an asteroid family since the members are not physically related. Hilda was observed to occult a star on the last day of 2002 from Japan. en.wikipedia.org /wiki/153_Hilda   (135 words)

Minor planet - Wikipedia, the free encyclopedia Veritas asteroids or Undina asteroids, named after 490 Veritas or 92 Undina, ~29 members. Apoheles are asteroids whose aphelion is less than 1 AU, meaning they orbit entirely within Earth's orbit. Some asteroids have unusual horseshoe orbits that are co-orbital with the Earth or some other planet. en.wikipedia.org /wiki/minor_planet   (2450 words)

ipedia.com: Minor planet Article   (Site not responding. Last check: 2007-10-22) Nysa asteroids have a mean orbital radius between 2.41 AU and 2.5 AU, an eccentricity between 0.12 and 0.21, and an inclination between 1.5° and 4.3°. Maria asteroids have a mean orbital radius between 2.5 AU and 2.706 AU and an inclination between 12° and 17°. Eos asteroids have a mean orbital radius between 2.99 AU and 3.03 AU, an eccentricity between 0.01 and 0.13, and an inclination between 8° and 12°. www.ipedia.com /minor_planet.html   (2040 words)

Hilda family -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-22) Rather, this is a dynamical family, made up of asteroids which are in a 2:3 (additional info and facts about orbital resonance) orbital resonance with ((Roman mythology) supreme god of Romans; counterpart of Greek Zeus) Jupiter. Hildas move in their orbits so that their (additional info and facts about aphelia) aphelia put them opposite Jupiter, or 60 degrees ahead of or behind Jupiter at the L The namesake is (additional info and facts about 153 Hilda) 153 Hilda, discovered by (additional info and facts about Johann Palisa) Johann Palisa in 1875. www.absoluteastronomy.com /encyclopedia/h/hi/hilda_family.htm   (145 words)

Asteroids History - Asteroids Information Dozens of asteroids range from 200 to 300 kilometers (124 to 186 miles) in diameter, thousands are the size of a small city, and hundreds of billions are house-sized. Asteroids are small and distant, so even in telescopes they are only faint points of light gradually moving against the backdrop of the stars. Asteroid brightnesses change every few hours as they spin, first brightening when they are broadside to us and fading when end-on. www.bookrags.com /sciences/astronomy/asteroids-spsc-02.html   (1339 words)

Hilda Asteroids, Part 2 Typical Hilda asteroids are captured in the 3/2 resonance of mean motion with respect to Jupiter and show libration of an angular argument about 0 deg. Section 4 describes a resonance relation that corresponds to a near commensurability between the periods of the great inequalities of Jupiter and Saturn and an asteroidal period that depends on the period of libration and on the period of the revolution of a transformed longitude of perihelion. Considering the possibility that a resonance acts on asteroids with Ampl near 60 deg, I have isolated by digital filtering the frequencies that rule the variations of the semi-major axis of (1578) in the simplified model of the restricted three-body problem. www.rzuser.uni-heidelberg.de /~s24/hilda2.htm   (3405 words)

Hilda Asteroids Typical Hilda asteroids are captured in the 3/2 resonance of mean motion with respect to that of Jupiter. The low-eccentricity Hildas (1256) Normannia and (4196) Shuya have appeared as special cases that are separated from the Hildas with eccentric orbits by a wide gap in the distribution of the values of Epm (Schubart, 1991). In the Hilda group there are subgroups of orbits that nearly agree in the values of all the 3 characteristic parameters mentioned above (Schubart, 1991), in analogy to the well-known families of asteroids. www.rzuser.uni-heidelberg.de /~s24/hilda.htm   (2542 words)

abs-2   (Site not responding. Last check: 2007-10-22) Collision velocities and collision frequencies of Hilda asteroids. The collision probabilities of individual Hilda asteroids have a strong correlation with the eccentricity of their orbits, resulting in a wide range (about a factor of six) of collision probabilities among the Hilda objects. The mean collision velocity of the Hilda asteroids is 4.6 km/s, which is 0.5 km/s lower than the average for main-belt objects. earn.dlr.de /abstract/aa42.htm   (180 words)

Bibliographie des DLR (LIDO)   (Site not responding. Last check: 2007-10-22) A probable taxonomy was assigned to four Hilda asteroids (one P-type and three D-types) which previously were unclassified. The Hilda Asteroid 3694 Sharon was observed at low solar phase angles, and the obtained lightcurves indicate a reduced to nonexisting opposition effect for this asteroid. One Hilda asteroid, 2067 Aksnes, may be in a state of precession as no satisfactory two-maxima and two-minima lightcurve could be fitted to the data. www.dlr.de /lido/NE-PE/2000/1716762000.html   (329 words)

Asteroid (and Comet) groups Asteroids positions are computed for Apr. 7, 2004 and their orbital elements are taken from the MPCOrb database. Hilda asteroids are in a 3:2 resonance of mean motion with Jupiter (that means the orbital period of asteroids and that of Jupiter have ratio of 2:3). Asteroid taxonomic classes and albedos are taken from NASA PDS. sajri.astronomy.cz /asteroidgroups/groups.htm   (1433 words)

3 Hildas, Trojans, and SPCs   (Site not responding. Last check: 2007-10-22) This sample of 232 objects is about 6 times more numerous than that adopted by Dahlgren (1998) who used 40 Hilda asteroids in his numerical model, those larger than 50 km in diameter. On the other hand, the errors associated to the average impact velocity in Table 1 are fully comparable to those of Dahlgren, since they are in both cases standard deviations derived from the impact velocity distributions. This proves that the orbits of Hilda asteroids are well sampled in the phase space and that the group of 40 orbits was already representative of the collisional behaviour of this asteroidal population. aanda.u-strasbg.fr:2002 /papers/aa/full/2001/06/aa9972/node3.html   (702 words)

chapter 8 The Hilda asteroids, named after the biggest member of the group, are in 2/3 resonance with Jupiter. Approximating Jupiter's motion as circular, and neglecting the inclinations between the orbits, the motion of a typical Hilda asteroid is shown in fig. If the number of asteroids is plotted as a function of orbital period, or equivalently as a function of semimajor axis, there are a number of pronounced empty zones, the so-called Kirkwood gaps, in the neighborhood of periods commensurable with Jupiter's. history.nasa.gov /SP-345/ch8.htm   (4832 words)

abs-2   (Site not responding. Last check: 2007-10-22) A study of Hilda asteroids V. Lightcurves of 47 Hilda asteroids A probable taxonomy was assigned to four Hilda asteroids (1 P­type and 3 D­types) which previously were unclassified. One Hilda asteroid, 2067 Aksnes, may be in a state of precession as no satisfactory two­maxima and two­minima lightcurve could be fitted to the data. earn.dlr.de /abstract/aa38.htm   (350 words)

39382 Opportunity - Information   (Site not responding. Last check: 2007-10-22) Asteroid 39382 Opportunity was discovered on September 24, 1960 by Ingrid van Houten-Groeneveld, Cornelis Johannes van Houten and Tom Gehrels. The asteroid was spotted by examining photographic plates of images taken by telescopes at the Palomar Observatory. The asteroid's orbit does not cross the path of any of the planets and therefore will not be pulled out of orbit by Jupiter's gravitational field. www.logicjungle.com /wiki/39382_Opportunity   (255 words)

The Austin Review A scientific team from the Harvard-Smithsonian Center for Astrophysics proposes that a group of 700 or so unusual asteroids are excellent evidence for their hypothesis that the planet Jupiter’s orbit moved some 50 million miles closer to the sun as our planetary system was forming. These asteroids, called the Hilda asteroids, orbit the sun in very elongated elliptical orbits three times each two Jupiterian years. Their computer simulations demonstrate that, if Jupiter had migrated that distance toward the sun in the course of 100,000 years, all Hilda objects that had circular orbits would have been propelled out of the solar system—leaving only those with elliptical orbits and the periodicity observed. www.austinreview.com /archives/2004/09/spin_doctrine_1.html   (143 words)

Asteroids   (Site not responding. Last check: 2007-10-22) This representation of the physical properties of interesting asteroids includes most of the asteroids larger than about 200 km in diameter. They are portrayed in their correct relative sizes and shapes (the limb of Mars is shown for comparison); colors and albedos are also indicated. Asteroids located near the top or bottom of the diagram occupy relatively eccentric or inclined orbits (or both), while those shown near the ecliptic plane move in relatively circular, noninclined orbits. alumnus.caltech.edu /~marcsulf/asteroid/asteroid.html   (445 words)

Astron. Astrophys. 336, 1056-1064 (1998)   (Site not responding. Last check: 2007-10-22) The collision probabilities and collision velocities have been determined from a data base of close encounters, obtained by numerical integrations of the orbits of 909 asteroids for 55 000 years. The mean collision probability is lower for Hilda asteroids than for main-belt, Cybele and Trojan asteroids. Out of ten collisions involving a Hilda object, about seven are with main-belt objects, and the other three collisions are evenly distributed among the three outer-belt groups. aa.springer.de /bibs/8336003/2301056/small.htm   (177 words)

Asteroids Astronomy Solar System Asteroids- Astronomy Solar System   (Site not responding. Last check: 2007-10-22) Histograms and scatter plots of asteroid orbital elements. Theoretical studies of impacts of one asteroid into another, and tsunami effects of an asteroid impact on Earth. A list of asteroids whose names are known to have a Canadian connection, usually because they are named after a Canadian. astronomy.designerz.com /astronomy-solar-system-asteroids.php   (501 words)

Earth Change News on Earth Changes TV on the Web The consistent increase in the discovery rate of new asteroids and Trans Neptunian Objects (TNOs) in these last years has urged an update of the values of intrinsic probability of collision and impact Velocity for some minor body populations. 1998) and for the clustering of the perihelion longitude of Main Belt asteroids and Hildas, caused by the presence of a forced component in the eccentricity. It is known, from observational data recorded from airbursts, that small asteroids breakup at dynamical pressures lower than their mechanical strength. www.earthchangestv.com /breaking/March_Part2_2001/PrinterFriendly/0322impact.htm   (457 words)

Astronomy: The Solar System: Other Objects   (Site not responding. Last check: 2007-10-22) Hilda asteroids in 2:3 resonance with Jupiter (∼ 7.8 yr period) This image, drawn by the Voyager II Planetarium Software, shows the major Hilda Asteroids and their orbits relative to the orbits of Jupiter (yellow), Mars (red), Earth (green), Venus (purple) and Mercury (orange). This image, drawn by the Voyager II Planetarium Software, shows the orbits of two Centaur Asteroids (outer Chiron and 1991DA) in relation to the orbits of Jupiter (yellow), earth (green), and Mars (red). www.physics.carleton.ca /~watson/LinR_course/solar_system/otherobjects.html   (401 words)

[No title]   (Site not responding. Last check: 2007-10-22) ======================================================================== The file "hilda-spectra-1.ps" contains the article "A Study of Hilda Asteroids I. CCD Spectroscopy of Hilda Asteroids" by M. Dahlgren and C.--I. Lagerkvist. Collision velocities and collision frequencies of Hilda Asteroids< " by M. Dahlgren. The file "hilda-lightcurve.ps" contains the article "A Study of Hilda Asteroids V. Lightcurves of 47 Hilda Asteroids" by M. Dahlgren J.F. Lahulla C.-I. Lagerkvist, J. Lagerros, S. Mottola, A. Erikson, M. Gonano-Beurer and M. Di Martino. www.astro.uu.se /ftp/articles/planet/P96/Readme   (140 words)

Asteroids with Canadian Connections   (Site not responding. Last check: 2007-10-22) His work has contributed to the understanding of cometary nongravitational forces, the use of radar data in asteroidal and cometary orbits, orbital error analyses, earth close approaches and impact probabilities. This Hilda group member is named in honour of the well-known Canadian geologist Alan R. Hildebrand (b. His linking of a "smoking gun" to a major extinction event in geologic history provided evidence of fundamental importance to the resolution of a centuries-old debate on the demise of the dinosaurs and the occurrence of catastrophes in the earth's history. www.rasc.ca /faq/asteroids/home.htm   (11161 words)

shatters.net :: View topic - I Suggest a revised definition of "planet"... Well, why a cut off line for appyling 'planetoid' to large KBO's when it fact it's a general term for those objects in the solar system that are planet-like (shine by reflected light) but are not planets (and that definition avoids defining planet). Asteroids and KBO's are all planetoids, but we distinguish between two separate belts of planetoids with those names: Asteroid Belt and Edgeworth-Kuiper Belt. The press and popular culture are oblivious to the discovery of planetoids and planetesimals, asteroids and little moons. www.shatters.net /forum/viewtopic.php?p=57381&sid=70d6371150f0f094110a...   (2779 words)

Gas Giants While Neptune may have moved out as much as 30 percent, however, Jupiter lost orbital energy because it absorbed or ejected the incoming planetesimals in its reach and so its orbit may have shrank by about two percent from this cause alone (Curtis Rist, Discover, September 2000; and Hahn and Malhotra, 2000). Supporting evidence of this in-migration comes from an unusual group of 700 or so rocky bodies known as the Hilda asteroids, which orbit the Sun three times for every two made by Jupiter, and of which vast majority have slightly elongated elliptical orbits, whereas many other asteroids have near-circular orbits. Computer simulations (led by Fred Franklin's team at the Harvard-Smithsonian Center for Astrophysics) indicate that Jupiter's early in-migration would have ejected any proto-Hilda asteroids with circular orbits from the Solar System and would have further elongated the orbits of those that remained (Franklin et al, 2004). www.solstation.com /stars/jovians.htm   (756 words)

190 Ismene Being a P-type asteroid, it has a very dark surface and may contain water. Ismene orbits near the outer edge of the asteroid belt. It is one of the Hilda asteroids, which are locked in 3:2 resonance with the planet Jupiter. www.omniknow.com /common/wiki.php?in=en&term=190_Ismene   (389 words)

[meteorite-list] Jupiter Drifted Towards Sun In Its Youth   (Site not responding. Last check: 2007-10-22) Jupiter and the Hilda asteroids The evidence comes from a curious group of 700 or so rocky chunks called the Hilda asteroids, which orbit the Sun three times for every two Jovian years. According to Fred Franklin's team at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, a migrating Jupiter could explain why so few Hilda asteroids have circular orbits. Their simulations show that if a young Jupiter had orbited about 10% farther from the Sun than it is now, and then spiralled in by about 70 million kilometres over a period of 100,000 years or more, its gravity would have ejected any proto-Hilda asteroids with circular orbits from the solar system. six.pairlist.net /pipermail/meteorite-list/2004-September/164477.html   (475 words)

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