Discovery of the hazardous asteroid 2015 BK515 in collaboration with ESA

2015 February – The potentially hazardous asteroid 2015 BK515 was found by amateur astronomer Erwin Schwab from Germany, working with ESA’s Space Situational Awareness programme. He conducted his asteroid hunt in January 2015 during a regular observation slot at European Space Agency’s Optical Ground Station (ESA OGS)  in Tenerife, Spain.

Detlef Koschny, head of ESA’s Near Earth Objects Segment in the Space Situational Awareness (SSA) programme, determined Erwin Schwab to plan and analyze rediscoveries of hazardous asteroids. The scheduled target was the Near Earth Object (NEO) 2013 GD34, which Schwab could find 0.4° away (about the apparent size of the Moon) from its predicted position. After the successful rediscovery by releasing a Minor Planet Electronic Circular announcing the new observations, he checked the picture for unknown objects. Very close to the edge of the field he found an unidentifiable fast moving object and submitted the position measurements to the US-based Minor Planet Center, which collect all asteroid measurements from observers worldwide.

When the discovered asteroid belongs with high probability to the class of Near Earth Objects, follow-up observations must be done extremely fast to ensure it is not subsequently lost. Therefore the Minor Planet Center had listed this discovery immediately onto the Near Earth Objects Confirmation webpage to inform other Observatories as quickly as possible. But the high star density in the area of the new object made follow-up observations very difficult.

Animation of Discovery images from 19.1.2015
credit: ESA / E. Schwab

Detail of 5×5 arc minutes, unedited original field has 47×47 arc minutes
Animation of Confirmation images from 27.1.2015
credit: DLR / S. Hellmich & S. Mottola

Fortunately a week after discovery the confirmation succeed by Stephan Hellmich and Stefano Mottola at the Calar Alto Observatory in Spain. On 2015 February 7. the discovery was published in the Minor Planet Electronic Circular and the result of orbit determination showed that 2015 BK515 is a hazardous Asteroid, which can approach the Earth closer than about 7 million km.

Ephemeris uncertainty after 24-day-arc elements, generated with service of  NEODyS:

Table of the next close approaches, brighter 22. magnitude, calculated with FINDORB after 24-day-arc elements:

Date distance to Earth magnitudes
2015 June 0,261 AU 20,6 mag
2022 April 0,090 AU 19,4 mag
2029 February 0,204 AU 19,9 mag
2036 August 0,820 AU 21,9 mag
2052 July 0,430 AU 21,7 mag
2059 June 0,115 AU 18,6 mag
2066 March 0,058 AU 17,0 mag

Ephemeris uncertainty after 94-day-arc elements, generated with service of  NEODyS:

Ephemeris uncertainty after 145-day-arc elements, generated with service of  NEODyS:

external links for PHA 2015 BK515
released MPEC
Neodys database
JPL database
MPC database