Occultation by 2002MS4 (2019-07-06)

Warning: this prediction has been discarded after an update.

Occultation map

prediction map

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Information about the map:

  • The straight and continue lines are the shadow limits considering the estimated radius; when the shadow crosses the Earth's surface, the path is projected on the Earth;
  • Each blue dot is spaced by one minute and the big blue dot corresponds to the nominal occultation time (which is the geocentric closest approach);
  • The arrow shows the direction of the shadow motion;
  • The 1-σ precision along the path is represented by the red dotted line;
  • The star G* and RP* are the G (from Gaia) and RP (red photometer from GaiaDR2) magnitudes, normalized to a body moving at 20km/s in order to enhance very slow events;
  • The body offset is at the upper right corner, if JPL ephemeris is used;
  • Areas in dark grey correspond to full night (Sun elevation below -18 degrees) and areas in light grey correspond to twilight (Sun elevation between -18 and 0 degrees) while daytime is in white;
  • Be careful, the dates are from the moment of the event in Universal Time, the night of the event may begin at the date before.

Occultation circumstances

Date Sat. 6 Jul. 2019 01:09:20
Star position (ICRF) 18 45 33.0296 -06 23 56.609
C/A 0.022 arcsec
P/A 355.82 °
velocity -25.22 km/s
Geocentric distance Δ 45.6142 au
G mag* 15.5
RP mag* 14.7
H mag* 11.4
Magnitude drop 5.1
Uncertainty in time 118.1 sec
Uncertainty in C/A 70.7 mas
Uncertainty in projected distance 2339.9 km
Probability of occultation on centrality 15.8%
Maximum duration 37.0 sec
Moon distance to the object 130.4°
Fraction of illuminated Moon 14.3 %
Solar elongation 163.4°

Star & Object data

Occulted star

Star source ID 4253195715398244608
Stellar catalogue GAIADR2
Star astrometric position in catalogue (ICRF) 18 45 33.0290 -06 23 56.568
Star astrometric position with proper motion (ICRF) 18 45 33.0296 -06 23 56.609
Star apparent position (date) 18 46 36.2146 -06 22 34.797
Proper motion μRA* = (2.1 ± 0.1)mas/yr; μDEC = (-10.4 ± 0.1) mas/yr
Source of proper motion GAIADR2
Uncertainty in the star position RA* = 0.3 mas; DEC= 0.3 mas
G magnitude 15.3
RP magnitude (source: GAIADR2) 14.5
BP magnitude (source: GAIADR2) 15.9
J magnitude (source: 2MASS) 13.3
H magnitude (source: 2MASS) 11.1
K magnitude (source: 2MASS) 10.7


Object (307261) 2002MS4
Diameter 934.0 km
Apparent diameter 28.2 mas
Object astrometric position (ICRF) 18 45 33.0295 -06 23 56.587
Object apparent position (date) 18 46 36.2145 -06 22 34.775
Uncertainty in position RA* = 89.4mas DEC = 71.6mas
Apparent magnitude 20.3
Ephemeris NIMAv4
Dynamic class(1) cubewano
Semi major axis 41.9 au
Eccentricity 0.144 au
Inclination 17.7°
Perihelion 35.9 au
Aphelion 47.9 au
(1) Data from the johnston archive list.

Sky map (Aladin)

link to sky-map
For declination above -25 °, Pan-STARRS survey is displayed by default whereas below -25 °, DSS is displayed.

Interactive Map

The large blue line represents the centrality of the nominal prediction. The thin blue lines represent the body's limits of the nominal prediction. Red dotted lines show the 1-σ uncertainty on the body's limits. The white area represents the daylight part on Earth and the blue area represents the region on Earth where the object is not visible. The shadow at nominal time is displayed. The Sun symbol indicates the place where the Sun is at the zenith at the nominal time. The star symbol indicates the place where the occulted star is at the zenith at the nominal time. Grey zone represents the night area.
By clicking on one place, you will have an infobox with :
  • Coordinates: longitude and latitude;
  • ρ and Δd: Impact parameter (i.e. projected distance to the central line) and σ distance; Δd is (ρ-r)/σd where r is the object radius and σd is the uncertainty in distance;
  • mid time: mid time of the occultation at the selected place;
  • expected duration: expected duration of the occultation at the selected place;
  • Probability: Probability to observe the occultation on the specified place. This depends on the distance to the centrality, the size of the object and the uncertainty in the geocentric closest approach;
  • Object elevation: Object's elevation above the horizon at the selected place at the mid time.
  • Sun elevation: Sun's elevation above the horizon at the selected place at the mid time.
Once the place selected, the shadow at mid-time of the occultation for the location is displayed. The chord for your location appears in as a green dotted line. Sun and star symbols as well as the night area and area where the star is not visible are ajusted at the mid-time of your location.