Occultation by Hektor (2019-08-28)

Warning: this prediction has been discarded after an update.

Occultation map

prediction map

Download map

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 Wed. 28 Aug. 2019 03:21:16
Star position (ICRF) 23 19 11.2117 -02 40 30.695
C/A 1.152 arcsec
P/A 350.98 °
velocity -17.01 km/s
Geocentric distance Δ 4.4012 au
G mag* 9.6
RP mag* 9.0
H mag* 7.7
Magnitude drop 5.0
Uncertainty in time 3.9 sec
Uncertainty in C/A 13.2 mas
Uncertainty in projected distance 42.1 km
Probability of occultation on centrality 99.2%
Maximum duration 13.2 sec
Moon distance to the object 132.2°
Fraction of illuminated Moon 7.9 %
Solar elongation 165.0°

Star & Object data

Occulted star

Star source ID 2637737195423457408
Stellar catalogue GAIADR2
Star astrometric position in catalogue (ICRF) 23 19 11.2024 -02 40 30.770
Star astrometric position with proper motion (ICRF) 23 19 11.2117 -02 40 30.695
Star apparent position (date) 23 20 12.0973 -02 34 01.144
Proper motion μRA* = (33.8 ± 0.1)mas/yr; μDEC = (17.9 ± 0.1) mas/yr
Source of proper motion GAIADR2
Uncertainty in the star position RA* = 0.5 mas; DEC= 0.3 mas
G magnitude 9.8
RP magnitude (source: GAIADR2) 9.2
BP magnitude (source: GAIADR2) 10.3
J magnitude (source: 2MASS) 8.4
H magnitude (source: 2MASS) 7.9
K magnitude (source: 2MASS) 7.8


Object (624) Hektor
Diameter 225.0 km
Apparent diameter 70.5 mas
Object astrometric position (ICRF) 23 19 11.1997 -02 40 29.557
Object apparent position (date) 23 20 12.0853 -02 34 00.006
Uncertainty in position RA* = 18.6mas DEC = 16.1mas
Apparent magnitude 14.8
Ephemeris NIMAv3
Dynamic class(1) trojan
Semi major axis 5.3 au
Eccentricity 0.023 au
Inclination 18.2°
Perihelion 5.1 au
Aphelion 5.4 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.