The number of known near-Earth asteroids (NEAs) reached the round total of 20 000 this week. This family of asteroids whose orbit brings them close to Earth is steadily growing at a pace of roughly 160 new discoveries each month, thanks to the work done by the main asteroid surveys.

A few months ago a long thin tail was noticed on main belt asteroid (6478) Gault. An international collaboration led by scientists of the Institute for Astronomy of the University of Hawaii published a paper today explaining the mechanism that led to this sudden onset of activity.

Every few hours observing the Moon, ESA’s ‘NELIOTA’ project discovers a brilliant flash of light across its surface – the result of an object hurtling through space and striking our unprotected rocky neighbour at vast speed. Based at the Kryoneri telescope of the National Observatory of Athens, this important project is now being extended to January 2021.

Andrea Milani, professor of mathematics at Pisa University, passed away unexpectedly last Wednesday while cycling near Pisa. With his deep knowledge and understanding on the Solar System dynamics, Andrea was a pioneer in a discipline started by him and a few others at the end of the past century: asteroid impact monitoring.

Registration is open for the ESA NEO and Debris Detection Conference - Exploiting Synergies, which will be held at ESA/ESOC, Darmstadt, Germany, 22 - 24 January 2019. The deadline for the submission of abstracts is 1 October 2018.

'Oumuamua, an object from another star system that made a brief appearance in our skies turns out to be a tiny interstellar comet. Read more: https://www.esa.int/Our_Activities/Space_Science

For the third time in recent history of asteroid detection a NEO was detected a few hours before it entered the Earth atmosphere (the two previous cases were 2008 TC3 and 2014 AA). Asteroid 2018 LA was discovered by the Catalina Sky Survey in the early morning (European time) of this Saturday, 2 June. In a matter of hours additional observations were made and it became very probable that it would collide with the Earth.

One of our collaborators, E. Schwab, has been featured in a recent story by the Calar Alto observatory (CAHA) in Spain.

At approximately 09:30 UT on 14 April 2018 the Catalina Sky Survey, in Arizona, discovered a bright magnitude 15 object moving at a sky speed of 10" per minute, in the constellation Libra. Follow-up observations obtained over the next few hours, by Catalina's own facilities and by other observers in the US Southwest, quickly showed that this was an unknown asteroid, which was about to have a close fly-by with our planet less than a day later. The asteroid was subsequently designated 2018 GE3.

During the first month of 2018 two objects reached a Torino Scale level of 1, and attracted the attention of observers with the goal of collecting additional observations necessary to remove the possible risk. One of them 2017 YZ1, was removed from the risk list within a few days thanks to new observations of various observers, including David Tholen from Hawaii, and our team working in collaboration with the OASI telescope in Brazil.

A few weeks ago the Pan-STARRS survey discovered a new NEO, temporarily identified as P10G8tt and then formally designated 2018 AM12. Follow-up observations over the next few days allowed the determination of its distance, and consequently its absolute magnitude, which turned out to be roughly 21.4. This brightness should correspond to a diameter between about 150 m and 300 m, depending on the unknown albedo of the object's surface.

On 19 October the Pan-STARRS telescope, one of the NASA-funded surveys dedicated to discovering new NEOs, found an object that proved to be extremely unique: for the first time, an asteroid originated around another star had been spotted when transiting inside our Solar System. The object, first labelled P10Ee5V by the discovery team, was quickly followed up by a few observatories, including by our team using the ESA Optical Ground Station in Tenerife.

A bright fireball occurred over The Netherlands on 21 September 2017 at 19:00 UTC (21:00 CEST). In addition to many individual sightings, it was also recorded by an all-sky camera dedicated to recording exactly such events.

As part of an international observing campaign, the OSIRIS-REx spacecraft has been imaged during our normal monthly observing run on 16 September with the OGS telescope in Tenerife. In the attached image one can observe the OSIRIS-REx spacecraft as the tiny point at the centre of the image moving from left to right. The larger spot moving in the same direction, but located more to the left, is main belt asteroid (50587) 2000 ET45.

An international campaign has revealed that an asteroid will come within 44 000 km of our planet in October, providing a rare opportunity for intensive studies. Astronomers recently spotted asteroid 2012 TC4 under a collaboration between ESA and the European Southern Observatory (ESO) to locate faint objects that might strike Earth. This is the first observation since 2012, when the asteroid was discovered by the Pan-STARRS observatory in Hawaii. It was found this time by ESO's Very Large Telescope in Chile.

On the morning of 30 May 2017 our team, in collaboration with ESO and using the Very Large Telescope (VLT) in Chile, obtained recovery observations of 1991 VG, a famous near-Earth object with an interesting historical background.

Using a system developed under an ESA contract, the Greek NELIOTA project has begun to detect flashes of light caused by small pieces of rock striking the Moon's surface. NELIOTA is the first system that can determine the temperature of these impact flashes.

The word "precovery" has entered the astronomical jargon rather recently but it quickly grew in popularity among asteroid hunters. It refers to the finding of an archival observation of an object which was not recognized as such because the corresponding image originally served other purposes. Hence the name "precovery", which explains why we may have direct measurements of an asteroid position at a time well ahead its discovery date.

The number of known near-Earth asteroids (NEAs) has just surpassed the threshold of 15000. That is a 50% increase over the number known in 2013, when we posted a similar news item on our portal for the crossing of the 10000 threshold.

Asteroid 2016 RB1 has hit the news because of a peculiar close passage on 7 September 2016 at 19:20 CEST. About the size of a cottage, the asteroid flew past our planet at an altitude of 34000 km, roughly the same as the so-called "geostationary ring" where most telecommunication satellites reside. Yet it posed no hazard neither to our planet nor to the satellite operators.