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JPL Small-Body Database Browser
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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 2458600.5 (2019-Apr-27.0) TDB
Reference: JPL 36 (heliocentric ecliptic J2000)
 Element Value Uncertainty (1-sigma)   Units 
e .1924869425288242 3.9114e-08  
a 3.004002706718768 1.4648e-08 au
q 2.42577141035416 1.1634e-07 au
i 10.69987702125215 4.4741e-06 deg
node 321.1670201885605 2.3096e-05 deg
peri 249.4546243573874 2.5726e-05 deg
M 282.598097764885 1.3625e-05 deg
tp 2459009.382044615575
(2020-Jun-08.88204462)
7.3203e-05 TDB
period 1901.730213483406
5.21
1.3909e-05
3.808e-08
d
yr
n .1893012991262239 1.3846e-09 deg/d
Q 3.582234003083376 1.7467e-08 au
  Orbit Determination Parameters
   # obs. used (total)      2434  
   data-arc span      33330 days (91.25 yr)  
   first obs. used      1928-09-05  
   last obs. used      2019-12-07  
   planetary ephem.      DE431  
   SB-pert. ephem.      SB431-N16  
   condition code      0  
   norm. resid. RMS      .43498  
   source      ORB  
   producer      Otto Matic  
   solution date      2019-Dec-13 20:51:03  

Additional Information
 Earth MOID = 1.44689 au 
 Jupiter MOID = 1.58087 au 
 T_jup = 3.197 
[ hide covariance matrix ]
Orbital Elements at Epoch 2455902.5 (2011-Dec-07.0) TDB
Reference: JPL 36 (heliocentric ecliptic J2000)
 Element Value Uncertainty (1-sigma)   Units 
e .1977068680805035 3.9268e-08  
q 2.40508336469581 1.1733e-07 au
tp 2455205.265264885164
(2010-Jan-08.76526489)
6.3708e-05 TDB
node 321.548744063558 2.3193e-05 deg
peri 248.737873960414 2.5615e-05 deg
i 10.68771863730973 4.4703e-06 deg
  Orbit Determination Parameters
   # obs. used (total)      2434  
   data-arc span      33330 days (91.25 yr)  
   first obs. used      1928-09-05  
   last obs. used      2019-12-07  
   planetary ephem.      DE431  
   SB-pert. ephem.      SB431-N16  
   condition code      0  
   norm. resid. RMS      .43498  
   source      ORB  
   producer      Otto Matic  
   solution date      2019-Dec-13 20:51:03  

Additional Information
 Jupiter MOID = 1.58087 au 
 T_jup = 3.197 
Orbit Covariance (6×6)
  e q tp node peri i
e 1.541939519754161E-15 -4.585626067168842E-15 -2.859015504106065E-13 -7.204016704244917E-15 -2.469436229005462E-14 -5.752335051118201E-16
q -4.585626067168842E-15 1.376522973995178E-14 8.909992644034965E-13 2.531964544780133E-14 8.352028896403718E-14 2.908125398751288E-15
tp -2.859015504106065E-13 8.909992644034965E-13 4.058731907675744E-9 1.907982326670031E-12 7.173430200274545E-10 2.859687019415482E-12
node -7.204016704244917E-15 2.531964544780133E-14 1.907982326670031E-12 5.379111055399808E-10 -5.277282099470803E-10 7.808052803748066E-12
peri -2.469436229005462E-14 8.352028896403718E-14 7.173430200274545E-10 -5.277282099470803E-10 6.561476583221818E-10 -7.465766715522078E-12
i -5.752335051118201E-16 2.908125398751288E-15 2.859687019415482E-12 7.808052803748066E-12 -7.465766715522078E-12 1.998390033653041E-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-January); 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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