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Last update: 2020-01-20 14:32:00 UTC


The ZTF Survey scores the asteroid with the smallest aphelion distance

09 January 2020

The year has just started, and we already have a very interesting discovery of a new and so far unique asteroid.

The Zwicky Transient Facility (ZTF), a survey program currently operating the Samuel Oschin Telescope at the Palomar Observatory, has been dedicating some time to survey observations at very low solar elongations. These observations are capable of finding objects with orbits located entirely within the orbit of the Earth, the so-called Atira objects, or IEOs (Interior-Earth Objects). ZTF had already found quite a few of them last year, including 2019 LF6, the asteroid with the shortest known orbital period. So far, only about 20 are known, showing how difficult it is to discover them.

On 4 January 2020 they were observing an area at less than 40° of elongation from the Sun, when they discovered a new object that looked like a promising Atira candidate. Subsequent observations showed that the object was even more interesting: with an aphelion at just 0.654 au, the object's orbit is entirely contained within the orbit of planet Venus, making it the first known representative of the so-called "Vatira" class, the Venusian equivalent of Earth's Atiras.

The object is now designated 2020 AV2. It has an orbital period of 151 days, almost identical to 2019 LF6, but its lower eccentricity of just 0.178 makes it the natural object with the smallest known aphelion in our Solar System (except for planet Mercury).


2020 AV2 observed from the Abastumani observatory in Georgia on 6 January 2020, in the context of our collaboration with the ISON network. At the time of the observation, the asteroid was located just 20° over the local horizon, at an elongation of 39° from the Sun.

Credit: ISON Abastumani (Kharadze Abastumani Astrophysical Observatory, Ilya State University)



NEOCC Newsletter: January 2020

07 January 2020

The ESA SSA-NEO Coordination Centre has released the January 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.

You can download the newsletter by clicking on the button below; to subscribe to the service, please fill in the form on page




The power of precoveries

15 October 2019

Asteroid 2017 US imaged by the Catalina Sky Survey on 13 October 2017, three days before their own discovery of the object. The detections are extremely faint, too faint to be detected automatically by the pipeline, but visible to the trained human eye.

Credit: Catalina Sky Survey / University of Arizona / NASA

If you check our current risk list, you will notice that a significant number of objects in the top positions are extremely “old”, discovered in the first decade of the century.

Some of them actually only have observations taken around the time of discovery, and have not been seen ever since. The orbits of these objects are now very uncertain, and it is therefore difficult to obtain new observations and revise the impact threat assessment, unless they are re-observed by chance.

There is however a way to get some additional data. It is called "precovery search", and it consists of a systematic search of existing image archives in order to locate additional detections of the object, not recognised at the time the images were obtained.

In the past, we successfully found precovery observations of a significant number of objects in our risk list. Some of them were actually sufficient to fully exclude the threat posed by the object.

In order to continue this systematic effort, we started a very promising collaboration with the Catalina Sky Survey, a project of NASA’s Planetary Defense Program, to search for precovery detections in their extremely large and complete image archive, collected over two decades of survey work. Last week we reported the first results of this search to the Minor Planet Center: precovery detections of three objects in the top-20 positions of our risk list (2008 JL3, 2008 UB7 and 2017 US).

An example of one such detection is presented in this image: the object, 2017 US, is extremely faint, but it is visible to the human eye on the CCD images, and its position is measurable with accurate astrometric tools. The corresponding measurements resulted in a revised assessment of the impact threat, which was slightly lowered. The threat for the two other objects was also revised as a result of the precovery detections: one remained basically unchanged, the other was slightly increased. Overall, our knowledge of the orbits for all three objects was improved, in some cases quite significantly.

This search shows the power of historical image archives for threat assessment, and in particular the value of the extensive archives generated by Catalina and by the other asteroid surveys.