2025 March 16
Recent close pass of Apollo asteroid 2025 EF4 spied
An object measuring some 30-70 m across was discovered on an Earth-approaching course on 2025 March 11 by Santel Observatory, El Leoncito with nearest pass some 1.2 lunar-distances away on March 15. Interestingly, the same body made a very similar rendezvous with Earth’s orbit on 1965 March 15. Both events happened when the asteroid was close to perihelion at a heliocentric distance of 0.996 au. Its aphelion is 1.546 au when it can also approach the planet Mars. Peter Birtwhistle sent out an alert via The Astronomer Electronic Circular No 3870 on March 13 and the details were passed on to the ARPS groups.io with favourable observing circumstances available during the following two nights as seen from the UK.
Here are some preliminary lightcurves reported to the Section. First from Jean-François Gout commenting:
The recently discovered NEO 2025 EF4 is currently doing its closest approach. With a magnitude around 14V and a “reasonable” sky motion (~150″ per minute), it is a great target for photometry. I’ve acquired 600 8-seconds frames with my 11-inch SCT last night, covering a bit more than 2 hours.I measured a rotation period of 15.7 minutes with a large amplitude (~1.5 mag, although this seemed to change and was difficult to estimate because the asteroid was near my detection limit at its dimmest).
This from Wayne Hawley:
And finally a really high signal-to-noise lightcurve from Peter Birtwhistle:
Peter has analysed his longer observing series and has confirmed the tumbling nature of this body for which he was able to deconvolve his data to show the composite lightcurves of the two component periodicities of close to 10 minutes and 16 minutes:
Here’s a brief animation provided by Wayne:
And a link to a nice example as to how it looked tracking at the speed of the asteroid courtesy of section member, Mohammed Shawkat Odeh taken from Al-Khatim Astronomical Observatory (M44).
Animation from Al-Khatim Astronomical Observatory (M44)
Richard Miles
2025 March 16
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