Varuna.20081207 Occultation Dec 07, 2008

(last updated 2008 11 26)

The shaded area represents where the sun is more than 12 degrees below the horizon. Across the globe pictured above, the three lines correspond to the northern limit, centerline, and southern limit of Varuna's shadow. The northern and southern limits correspond to a radius of approximately 480 km.

 

 
Varuna
Geocentric Mid-time (yyyy month dd hh:mm:ss)
2008 December 7 02:10:16± 00:00:54 UT
Minimum Geocentric Separation
0.134± 0.019 arcsec
Position Angle (Object relative to star; measured N. through E.)
–164.54 degrees
Geocentric Velocity
20.8 km/sec
Prediction Version

Varuna.20081207-AST-1.0

 

Reference star position:
(UCAC2, at epoch of event)
RA (h:m:s; J2000) Dec (d:m:s; J2000) UCAC Mag1
Varuna.20081207 Catalog 07 29 48.1712 +25 40 07.715 14.84
Varuna.20081207 Measured 07 29 48.1722 +25 40 07.749  

1The UCAC bandpass (579-642nm) is between V and R.

Offsets from Reference Position/Ephemeris3
Body RA (arcsec) Dec (arcsec) Notes

Varuna.20081207

+0.0148± 0.0012 +0.034± 0.001 From 3 frames
Varuna4

–0.0798± 0.0373

–0.129± 0.017 See note 5

3All "offsets" are defined in the ("corrected" – "reference") or ("observed" – "calculated") sense. The offsets should be added to reference positions to get the measured positions, which we use to calculate the prediction.

4The reference positions for Varuna are those given by JPL Horizon's ephemeris (Pluto source file: JPL#13; Earth center source file: DE405).

5101 frames were used to develop a model to fit the residuals obtained from our measured positions compared to that of the object's JPL ephemeris.. The model includes the first-order effects of errors in the orbital elements of Pluto: (i) constant offsets in RA and Dec, (ii) linear (in time) offsets in RA and Dec, and (iii) sinusoidal terms with the Earth's orbital period.

6Varuna has a V magnitude of approximately 20.0.

Discussion

 

Observing Report


Predictions

Bruno Sicardy's Prediction

Iota's Prediction Updates Page

Dave Herald's Globe

Steve Preston's Prediction

Site Information

Site
East Longitude
Latitude

Altitude7

(km)

Varuna Distance8

(km)

Varuna Velocity

(km/s)

Central Florida
–81 19 11
28 25 48
0.100
4995 N.
20.84
Williams
–73 12 06
42 42 42
0.215
6160 N.
20.87
Wallace
–71 29 06
42 36 36
0.107
6103 N.
20.88
Geocentric
----------
---------
center of Earth
4113 N.
20.91

7Altitude of each observatory is measured in kilometers above sea level.

8"Distance" refers to the closest approach distance of the "Site" to the center of the object's shadow in the shadow plane. The errors on all closest approach distances are ±580 km (one standard deviation). "S." means the site is South of the center of the object's shadow. "N." means the site is North of the center of the object's shadow.

Varuna.20081207 Occultation Predictions for Individual Sites

Site
Varuna Immersion (UT)9
Varuna Mid-Time (UT)9

VarunaEmersion (UT)9

Central Florida
-----------
02:15:08 (18°)
-----------
Williams
-----------
02:14:32 (27°)
-----------
Wallace
-----------
02:14:30 (29°)
-----------
Geocentric
-----------
02:10:16
-----------

9The errors on all times are ±0:54 (54 seconds; one standard deviation). In parenthesis is the elevation of the body above the celestial horizon in degrees.


Last updated by Carlos A Zuluaga (czuluaga@mit.edu) 2008-11-26 02:00

Please direct all inquiries to Planetary Astronomy Lab (planetary-astronomy@mit.edu)