Occultation by (950) Ahrensa, 2024-06-23

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Occultation map

prediction map

Occultation circumstances

Occultation event id 10548
Date Sun. 23 Jun. 2024 02:14:57
Star position (ICRF) 20 38 41.9504 +13 28 59.410
C/A 1.686 arcsec
P/A 22.41 °
velocity -6.81 km/s
Geocentric distance Δ 1.8009 au
Star G magnitude 13.1
Magnitude drop 2.5
Max occultation duration (main body) 2.1 sec
Moon distance to the object 46.5°
Fraction of illuminated Moon 98.5 %
Solar elongation 127.8°
Prediction source JPL60

Star & Object data

Occulted star

Star source ID 1756086405051721344
Stellar catalogue GaiaDR3
Star astrometric position in catalogue (ICRF) 20 38 41.9456 +13 28 59.521
Star astrometric position with proper motion (ICRF) 20 38 41.9504 +13 28 59.410
Star apparent position (date) 20 39 51.9920 +13 34 03.695
Proper motion μRA* = (8.2 ± 0.0)mas/yr; μDEC = (-13.1 ± 0.0) mas/yr
Source of proper motion GaiaDR3
Uncertainty in the star position RA* = 0.1 mas; DEC= 0.1 mas
G mag* 12.0
J mag* 11.5
H mag* 10.6
RP magnitude (source: GaiaDR3) 12.7
BP magnitude (source: GaiaDR3) 13.5
J magnitude (source: 2MASS) 12.1
H magnitude (source: 2MASS) 11.8
K magnitude (source: 2MASS) 11.7
RUWE (source: Gaia) 1.02

Main Object

(ID) Object Ahrensa
Diameter 14.4 km
Uncertainty in diameter 0.11 km
Apparent diameter 11.0 mas
Semi-major Axis 2.37 au
Object astrometric position (ICRF) 20 38 41.9946 +13 29 00.967
Object apparent position (date) 20 39 52.0361 +13 34 05.254
Apparent magnitude 15.5

Binary system characteristics (satellite)

Measure(1) #1
Estimated separation 1 41.50 km
Uncertainty in separation 1 5.88 km
Estimated separation 2 -
Uncertainty in separation 2 -
Diameter (sol° 1) 2.76 km
Uncertainty in diameter (sol° 1) 0.02 km
Max occultation duration (sol° 1) 0.41 s
Diameter (sol° 2) 12.63 km
Uncertainty in diameter (sol° 2) 0.17 km
Max occultation duration (sol° 2) 1.86 s
p-value 0.00 %
Quality factor 1.00
SNR flag 1
(1) Some asteroids may have differents measures concerning their binary characteristics, they are summed up here.

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

Observation advice
To be able to observe the asteroid satellite, we recommend that you start recording your observations at t = min{(separation+3*sigma_separation) / velocity,15 minutes} beforehand.
The large blue line represents the centrality of the nominal prediction. The thin dotted blue lines represent the body's limits of the nominal prediction. Red lines show the MINIMUM region where the satellite can be. 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 (main body): Expected duration of the occultation of the main body at the selected place;
  • Max expected duration (satellite): Expected maximum duration of the occultation of the satellite at the selected place, the two values corresponds to the two possibles solutions for the satellite diameter;
  • Object elevation: Object's elevation above the horizon at the selected place at the mid time;
  • Sun and Moon elevation: Sun's and Moon'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.