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949 Hel (A921 EM)
Classification: Main-belt Asteroid          SPK-ID: 2000949
Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances | Close-Approach Data ]

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Orbital Elements at Epoch 2459000.5 (2020-May-31.0) TDB
Reference: JPL 42 (heliocentric ecliptic J2000)
 Element Value Uncertainty (1-sigma)   Units 
e .1922948809866955 3.8794e-08  
a 3.002913051643463 1.1634e-08 au
q 2.425468243764289 1.1576e-07 au
i 10.70138760620475 4.0221e-06 deg
node 321.1674265255299 2.1848e-05 deg
peri 249.5416512626959 2.3871e-05 deg
M 358.2562027325603 9.3877e-06 deg
tp 2459009.706743739666
(2020-Jun-09.20674374)
4.9563e-05 TDB
period 1900.695572912484
5.20
1.1046e-05
3.024e-08
d
yr
n .1894043449832225 1.1007e-09 deg/d
Q 3.580357859522638 1.3871e-08 au
  Orbit Determination Parameters
   # obs. used (total)      2930  
   data-arc span      33630 days (92.07 yr)  
   first obs. used      1928-09-05  
   last obs. used      2020-10-02  
   planetary ephem.      DE431  
   SB-pert. ephem.      SB431-N16  
   condition code      0  
   norm. resid. RMS      .40347  
   source      ORB  
   producer      Otto Matic  
   solution date      2020-Nov-13 04:24:03  

Additional Information
 Earth MOID = 1.44636 au 
 Jupiter MOID = 1.58163 au 
 T_jup = 3.198 
[ show covariance matrix ]

Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances | Close-Approach Data ]

Physical Parameter Table
Parameter Symbol Value Units Sigma Reference Notes
absolute magnitude H 9.8   n/a MPO347521  
diameter diameter 63.494 km 0.743 urn:nasa:pds:neowise_diameters_albedos::2.0[mainbelt] (http://adsabs.harvard.edu/abs/2014ApJ...791..121M)  
rotation period rot_per 8.215 h n/a LCDB (Rev. 2019-August); Warner et al., 2009 Result based on less than full coverage, so that the period may be wrong by 30 percent or so.
Published Reference List:
[Brines, P.; Lozano, J.; Rodrigo, O.; Fornas, A.; et al. (2017) Minor Planet Bull. 44, 145-149.]
geometric albedo albedo 0.058   0.013 urn:nasa:pds:neowise_diameters_albedos::2.0[mainbelt] (http://adsabs.harvard.edu/abs/2014ApJ...791..121M)  

949 Hel (A921 EM)          Discovered 1921-Mar-11 by Wolf, M. at Heidelberg
Reference: DISCOVERY.DBLast Updated: 2003-08-29

[ show close-approach data ]
Alternate Designations
 A921 EM = 1952 DN = 1954 SN1 
Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances | Close-Approach Data ]
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