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Intro/FAQ Videos Analysis Campaigns Publications Contact Observatory Home

Analysis of Observations

Below are the results of the observations made on May 19th 2021 by Dave Gault and Peter Nosworthy. These were the first known detections of the suspected satellite of (4337) Arecibo.

Light Curves

Peter Nosworthy's light curve

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Dave Gault's's light curve

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Both Curves on The Same Time Scale

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Chord Plot - May 19 2021

The chords from the initial observations on May 19 indicate a main body diameter of 24.5km (assuming a circular fit). The diameter of the moon is not clear because both chords appear to be very close to the edge of the object.

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Excluding the 'Double Star' Hypothesis (Limiting Magnitude Analysis)

If the observations were the result of one body occulting two components of a double star, it would require that one component of the double be brighter than G-band mag. 14.4. This possibility can be excluded by confirming that the target star dropped below mag. 14.4 during both occultation events.

We used dim comparison stars in the field of view to measure the limiting magnitudes of the recordings.

The limiting magnitudes were 15.4 (Gault) and 15.5 (Nosworthy). This confirms that the target star dropped below G-band mag. 14.7 during all four recorded events.

The asteroid was mag. 17.0, well below the limiting magnitude of both recordings.

From this we conclude that a single body occulting a double star could not account for the observations. This makes the case for a 'moon' much more likely.

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Discovery Confirmation

On June 9, 2021 two observers in California, Kirk Bender and Richard Nolthenius, observed this event in which (4337) Arecibo occulted a mag. 12 star in Ophiuchus.

Both observers detected double occultation events consistent with a satellite of Arecibo.

See also Richard's Page describing this event.

Kirk Bender's Light Curve

Richard Nolthenius's Light Curve

These observations confirm the existence of the moon beyond reasonable doubt.


Chord Plot - June 9 2021

The chords from the June 9 observations were plotted with assumed circular fits for both objects. This indicates diameters of 24.4km and 13.5km for the two objects.

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