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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 ]

[ show orbit diagram ]
Orbital Elements at Epoch 2459000.5 (2020-May-31.0) TDB
Reference: JPL 40 (heliocentric ecliptic J2000)
 Element Value Uncertainty (1-sigma)   Units 
e .1922948811592338 3.8844e-08  
a 3.002913051514011 1.1688e-08 au
q 2.425468243141612 1.1595e-07 au
i 10.70138786041629 4.0682e-06 deg
node 321.1674263620377 2.1853e-05 deg
peri 249.5416513219348 2.3899e-05 deg
M 358.2562028838677 9.5186e-06 deg
tp 2459009.706742940211
(2020-Jun-09.20674294)
5.0255e-05 TDB
period 1900.695572789579
5.20
1.1097e-05
3.038e-08
d
yr
n .1894043449954701 1.1058e-09 deg/d
Q 3.580357859886409 1.3936e-08 au
  Orbit Determination Parameters
   # obs. used (total)      2842  
   data-arc span      33522 days (91.78 yr)  
   first obs. used      1928-09-05  
   last obs. used      2020-06-16  
   planetary ephem.      DE431  
   SB-pert. ephem.      SB431-N16  
   condition code      0  
   norm. resid. RMS      .40544  
   source      ORB  
   producer      Otto Matic  
   solution date      2020-Jun-23 15:23:36  

Additional Information
 Earth MOID = 1.44636 au 
 Jupiter MOID = 1.58163 au 
 T_jup = 3.198 
[ hide covariance matrix ]
Orbital Elements at Epoch 2456334.5 (2013-Feb-11.0) TDB
Reference: JPL 40 (heliocentric ecliptic J2000)
 Element Value Uncertainty (1-sigma)   Units 
e .1955836064255129 3.8899e-08  
q 2.415798714425526 1.1691e-07 au
tp 2457103.634143311904
(2015-Mar-22.13414331)
5.0119e-05 TDB
node 321.4025940466991 2.1951e-05 deg
peri 248.8822726073394 2.3864e-05 deg
i 10.67756508033283 4.0613e-06 deg
  Orbit Determination Parameters
   # obs. used (total)      2842  
   data-arc span      33522 days (91.78 yr)  
   first obs. used      1928-09-05  
   last obs. used      2020-06-16  
   planetary ephem.      DE431  
   SB-pert. ephem.      SB431-N16  
   condition code      0  
   norm. resid. RMS      .40544  
   source      ORB  
   producer      Otto Matic  
   solution date      2020-Jun-23 15:23:36  

Additional Information
 Jupiter MOID = 1.58163 au 
 T_jup = 3.198 
Orbit Covariance (6×6)
  e q tp node peri i
e 1.51311073147209E-15 -4.533329172742503E-15 -4.409652885626238E-13 -1.108959118187837E-15 -5.944726001611252E-14 -1.849989490380352E-15
q -4.533329172742503E-15 1.366681325087709E-14 1.247701815951832E-12 6.188833352135396E-15 1.562539393261639E-13 4.932021988933324E-15
tp -4.409652885626238E-13 1.247701815951832E-12 2.511911848284513E-9 3.782418700667767E-12 4.85762681537566E-10 4.708904301225433E-12
node -1.108959118187837E-15 6.188833352135396E-15 3.782418700667767E-12 4.818398876955629E-10 -4.733393153314798E-10 1.944600860245685E-11
peri -5.944726001611252E-14 1.562539393261639E-13 4.85762681537566E-10 -4.733393153314798E-10 5.694954540461036E-10 -1.860998314395413E-11
i -1.849989490380352E-15 4.932021988933324E-15 4.708904301225433E-12 1.944600860245685E-11 -1.860998314395413E-11 1.649416359907565E-11

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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