NEO Coordination Centre


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Last update: 2020-09-24 14:51:00 UTC


NEOCC Close Approach Fact Sheet: 2020 SW

22 September 2020






NEOCC Newsletter: September 2020

04 September 2020

The ESA S2P-NEO Coordination Centre has released the September newsletter summarising the most relevant data and events on asteroids and comets approaching the orbit of the Earth. Please, feel free to forward it to potentially interested people.

We are releasing our fourth PDO riddle with this newsletter and with a deadline on 25 September. Find the release information here: http://neo.ssa.esa.int/neocc-riddles.





2020 QG, the closest close approach

18 August 2020

On the late morning (European time) of 16 August 2020 the Zwicky Transient Facility, a multi-purpose astronomical survey using the 1.22 m Schmidt telescope at Mt. Palomar, discovered a new moving object (ZTF's search for NEOs is funded through the NEO Observations program of NASA). Six astrometric observations, covering a timespan of a bit less than an hour, already showed that the object was likely small but very close to us.

As often happens with these very close objects, obtaining follow-up observations may not be easy, since the rapidly increasing ephemeris uncertainty makes them hard to locate even just a few hours after discovery.

Fortunately, as soon as the sun set over Europe, two facilities supported by ESA's Planetary Defence Office were ready to observe, and actually targeted this asteroid. The Tautenburg observatory in Germany got it first, using their 1.34 m Schmidt telescope, the largest instrument of this type in the world. Less than an hour later the object became observable from Tenerife, where our team observed it with ESA's own OGS telescope.

With these observations it became immediately evident that the object was indeed a very close approacher: it had passed by the Earth earlier that morning, missing our planet by less than 3000 km. It was the closest asteroid ever observed to pass by our planet without hitting it, and the fifth closest overall, if we include the four small asteroids that actually impacted.

Thanks to the observations from Tautenburg and Tenerife, the asteroid became easy to observe by other observatories, both in Europe and in the US. The following day it received its official designation by the Minor Planet Center: 2020 QG.

We now know it was a very small object, with a size of only a few meters, comparable with the other four impactors discovered so far. Had it hit the Earth, it would not have caused any significant damage on the ground.


Left image: it shows the 1.3x1.3 square degree field with 2020 QG in the zoomed cutout. The circle marks the position uncertainty. Credit: TLS Tautenburg. Right image: close approach visualisation for asteroid 2020 QG. In white the Moon and its orbit. Behind it, the orbit of the asteroid and its direction. In yellow, the position vector of the Sun relative to the centre of the Earth: Credit: ESA / NEOCC.



An even closer unexpected approach

06 May 2020

Animation of the Earth close approach trajectory of asteroid 2020 JJ as seen from the Ecliptic North Pole. Each new animation frame represents a time variation of one hour in the real trajectory.  Credit: ESA / NEOCC

Less than a week after the discovery of 2020 HS7 by University of Hawaii’s Pan-STARRS survey, on 4 May 2020 another telescope funded by NASA’s Planetary Defense Program, University of Arizona’s Catalina Sky Survey, discovered a new object that was already very close to Earth, and possibly in an impacting trajectory.

The events that unfolded over just a few hours showed how quickly the NEO community can react to a possible impactor, and gather the observations needed to accurately determine the trajectory of an incoming object.

The new asteroid, temporarily designated C2QQFV2 by the Catalina team, was detected in a set of four observations exposed by the Mt. Lemmon telescope between 05:53 and 06:16 UTC. Once the object was detected by their pipeline, and confirmed real by their observers, it was quickly reported to the MPC, which published the discovery observations at 06:38 UTC.

Within a few minutes, the various services monitoring the MPC's NEO Confirmation Page detected the new object, and run an analysis from which it became evident that the object was already very close, and had a ~5% chance of being on a collision course, for an impact happening less than 6 hours later.

These automatic alerts triggered various observers, including Catalina itself and the University of Hawaii’s ATLAS survey, to gather additional follow-up observations of the new object. At 07:12 UTC, less than an hour after the original discovery was achieved, the first follow-up observations started coming in, and within two hours, three other telescopes had collected additional observations from other locations.

With this new dataset, it immediately became evident that we had another near miss: the object would fly-by at about 12:03 UTC, at just 13 400 km from the Earth's centre.

The object, calculated to be between 3 and 6 metres in diameter, is now designated 2020 JJ, and it is already quickly receding from Earth. Had it been in a collision course, it would not have caused a significant threat, given its small size.

What is even more impressive is that the final dataset, collected over just two hours, is sufficient to determine the fly-by circumstances to a precision of about 10 seconds in time, and 5 kilometres in distance. Had the object been in a collision course, we would have been able to predict the point of entrance into the Earth's atmosphere with a comparable precision, showing how effective immediate optical follow-up can be at localising a possible imminent impact threat.