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Ross 54
2010-Oct-08, 02:22 PM
Newly discovered Near Earth Asteroid 2010 BS5, which will pass within ~5.5 times lunar distance on Jan. 11, 2011, may have a 2:1 orbital period resonance with Earth. This is only a preliminary observation, based on the limited accuracy of the graphical orbit display at: http://neo.jpl.nasa.gov/ca/, but seems to hold for the period 2003--2017, the extent to which I checked it. Every alternate January, Earth and the asteroid have a fairly close encounter. It would be interesting to learn if this holds up under a more accurate determination of the orbit, and over longer periods of time.

Ross 54
2010-Oct-09, 01:43 PM
Sorry for the mix-up. The correct designation of the asteroid is 2009 BS5. It has been bumped off the bottom of the list of upcoming close encounters by the addition of other objects, but the orbit diagram can be found by going to that section of the above website, and inserting the designation into the object search function.

Ross 54
2010-Oct-09, 10:34 PM
Earth makes two orbits for every one of 2009 BS5. I have not yet found a another instance of an asteroid with 2:1 orbital resonance with Earth.

frankuitaalst
2010-Oct-10, 08:53 AM
2009BS5 indeed behaves as a temporary 2:1 resonator to Earth if the current ephemeris are correct for some years . In the near future it will loose this status .
Maybe there are other asteroids which show this behaviour.
Here is a list from the NEA site sorted for orbital period which are also candidates for a 2:1 resonance . ( I havent checked this out )

136773*(1996*TR6) 158.495.266 0.18037242 220.989.935 1.176.240.094 1.963.464.342 254.410.070 12.991 1.87 2 18.71 0.380272
*******(2009*BS5) 158.601.023 0.386490157 16.228.374 1.512.761.331 3.066.214.338 2.802.250.542 0.973 2.2 2 27.4 0.00627
*******(2010*KK37) 158.618.106 0.443555257 90.462.025 3.058.921.206 2.392.701.724 516.882.041 0.8826 2.29 2 25.7 0.000245
*******(2008*FH) 158.625.060 0.505271622 34.651.770 2.641.024.363 52.025.466 3.312.678.907 0.7848 2.39 2 24.39 0.0154
*******(2008*BS2) 158.692.921 0.471111681 141.400.272 3.509.630.080 3.111.584.412 2.575.546.152 0.8393 2.33 2 18.16 0.156109
162038*(1996*DH) 158.702.251 0.276599235 172.308.651 3.514.586.577 3.093.460.355 2.983.277.528 11.481 2.03 2 16.42 0.135013
*******(2008*GG2) 158.725.647 0.277936705 130.173.604 0.1666995 1.987.750.346 519.957.305 11.461 2.03 2 22.67 0.145046
*******(2006*UP) 158.734.790 0.302060679 22.832.464 3.347.271.814 480.444.638 3.199.312.853 11.079 2.07 2 23.1 0.113003
*******(2009*TM8) 158.737.905 0.416424378 21.536.165 2.187.360.421 2.058.318.923 1.213.835.897 0.9264 2.25 2 28.57 0.001002
*******(2010*RV11) 158.780.971 0.338734679 43.389.589 12.311.413 3.372.400.805 3.399.196.314 10.500 2.13 2 26.99 0.040677
*******(2008*YL2) 158.809.380 0.539306189 229.282.092 1.032.267.705 2.679.587.693 248.031.967 0.7316 2.44 2 24.47 0.0119
*******(2004*FG11) 158.845.380 0.724050073 31.119.947 2.275.552.925 846.353.868 275.661.044 0.4383 2.74 2 20.93 0.021372
*******(2004*DD) 158.930.496 0.459365823 115.885.566 84.576.473 37.498.188 1.695.571.446 0.8592 2.32 2 19.02 0.130507
Object a e i w Node M q Q P* H MOID
(AU) (deg) (deg) (deg) (deg) (AU) (AU) (yr) (mag) (AU)

frankuitaalst
2010-Oct-10, 08:35 PM
I believe at least 6 NEA's may be intitled to behave in a 2:1 mean motion resonance to Earth :
http://www.orbitsimulator.com/cgi-bin/yabb/YaBB.pl?num=1286741368/2#2

Ross 54
2010-Oct-10, 10:24 PM
Thank you, Frankuitaalst, for all your work in clarifying the issue of 2:1 resonance of asteroids. I scrutinize the orbits of near Earth asteroids for other reasons, and merely happened upon the instance of 2009 BS5. I thought it might be unique, but as you show, there are other, and better examples of this resonance. Ross