Discovery of an extraordinary outburst of an unidentified moving object at Crni Vrh Observatory

On images taken by J. Vales in the course of the Crni Vrh Asteroid and Comet Search program PIKA, on April 16, 2010 an unusually bright unknown object (mag. 12.5) was automatically detected. The object was near opposition, in an area searched by Catalina Sky Survey (CSS) just a day before.

Periodic Comet P/2010 H2
Unfiltered false color image of comet P/2010 H2, obtained on 2010 Apr. 16.854UT with 60-cm, f/3.3 Deltagraph telescope and CCD. Exposure time was 60 seconds. Image scale is 0.93 arc sec/pixel. Copyright © 2010 by H. Mikuz, Crni Vrh Observatory.

As it is not usual to encounter unknown objects of this magnitude in the area recently scanned by sky surveys, a question of its nature naturally appeared. The object was placed on the Near Earth Object Confirmation Page and with the help of observations from other observatories it became apparent very soon that it is about 2 AU away. In case that this was an asteroid (as we would infer from the stellar appearance on the discovery images) this would mean a diameter in the order of 100 km, which is extremely unlikely. The remaining explanation within common knowledge of the Solar system is that it is a cometary outburst of a large magnitude. Recently a similar outburst was experienced by comet 17/P Holmes. This object has triggered massive activity of 40 observatories around the world which contributed altogether 226 observations to the Minor Planet Center (MPC). The observers from the CSS confirmed that the object is not visible on their images taken only 15 hours before the discovery. There was a lively debate about the nature of this object on the Minor Planet Mailing List with most plausible explanation that it is a previously unknown comet in outburst. Further observations by several observers showed that the object has a wider profile than nearby stars and Alain Maury detected faint coma on long exposures made from Chile. At 19:25 UT on April 17 the MPC issued an electronic circular MPEC 2010-H12 where the object is designated as a comet P/2010 H2 (Vales). The orbit is still not very well determined, but most likely it has a semimajor axis of 3.9 AU and eccentricity of 0.2. This is similar to the orbital elements of the asteroids of the Hilda family. This object will undoubtedly be investigated further in the days to come.

 

Periodic Comet P/2010 H2

Periodic Comet P/2010 H2 (Vales)
Animation image was made from four 50 second unfiltered discovery frames, taken between 2010 Apr. 16.0038 - 16.0401UT with a 0.60-m f/3.3 Cichocki Sky Survey Telescope at Črni Vrh Observatory. Image scale is 1.86 arc sec/pixel. Copyright © 2010 by J. Vales, and H. Mikuz, Črni Vrh Observatory.