| アブストラクト |
About 550,000 asteroids were discovered to date and ~8,000 of them are NEOs (Near-Earth Objects) and ~1,100 are PHOs (Potentially Hazardous Objects=潜在的地球衝突可能性天体), a subset of NEOs, closely approach Earth’s orbit to within 0.05 AU (~20 Moon distances). PHO collisions to Earth occur infrequently, but the threat is large enough when averaged over time. On the other the connection between NEOs and Earth impactors such as meteorites or meteors are still under debate due to observational biases, large uncertainties of orbital elements and chaotic orbital evolutions due to perturbations by planet gravity and thermal effect called Yarkovsky effect. The Pan-STARRS PS1 (the Panoramic Survey Telescope And Rapid Response System, prototype single-mirror telescope) started a dedicated sky survey to detect NEOs efficiently since autumn in 2010. PS1 can provide more opportunities to investigate the NEO families which shares nearly identical orbit and their connection to meteorites. This talk will provide a discussion on the origin and evolution of PHOs. |
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