With the continued growth of meteor detection networks across Europe and increased coverage of the sky many more bright fireballs or even “bolides” are being recorded.
Whilst “bolide” is a term not officially recognised by the International Astronomical Union many astronomers tend to use it to refer to an exceptionally bright fireball, and generally one that meets or exceeds the brightness of a full Moon. Here we are talking about the real heavyweight class of fireballs which are large and thankfully (depending on which way you look at it) quite rare. We will use the term bolide for this article regardless. Holding data for more than 2.6 million meteors, the EDMOND network database is a culmination of a 10 year collaboration between 21 countries worldwide ranging from Ukraine to the United Kingdom, from Brazil to Oceania. The UKMON project has, from the outset, worked closely with the EDMOND team (and indeed with other networks from countries all over the world) and has contributed more than 40,000 observations.
Processing meteors is straightforward - in most cases. Fireballs and bolides however are completely different animals; they need lot more attention and require different style of analysis. When a camera records a bolide which is brighter than Moon, the light reaching the CCD pixels is so intense that they reach saturation. The normal method of processing meteors will fail under these circumstances (the processing of saturated images will be the subject of a later article). Let’s have a look at the most interesting meteors of EDMOND network in more detail.
Bramon’s first bolide was recorded by two stations. At Sao Sebastiao (Eduardo P. Santiago) and Mogi das Cruzes (Marco Mastria) located in federal state Sao Paulo at 05:50:29 UT. This bolide was just 33rd meteor captured by newly established and very young BRAMON network. At that time both stations were using Samsung SCB 2000 cameras at frequency 29.97 frames per second.
This meteor was very slow when compared with typical observations, with measured 3.07 degrees per second from one station and 3.67 degrees per second. Two stations also showed slightly different length of the event with 5.14 second and 5.74 respectively. Geocentric velocity was just 6.9 km/s and because of the entry angle it was considered as possibly space junk re-entry but without any matching orbit it was ruled out. Orbital elements are then a=0,755 AU, q=0,513 AU, e=0,320, i=7,911°, peri=12,128°, node=323,322°. Also of interest is that the beginning and end altitudes of the of the event: Initial altitudes of unified orbit was determined to be HB at 75.5 km and terminal height HE at 24.4 km, while the total track length was 66.6 km. The meteor type was declared as Sporadic (i.e. not identified with any known meteor shower) with radiant at RA=248,1°, DEC=-0,6° and brightness was between -3 and -4 magnitude. 2D projection of the ground map and orbit are below.
At the time of writing this is the brightest bolide captured in 2014. Keep in mind that as some data is still to be processed it is too early to declare formally that this as a winner in the brightness stakes. This bolide was captured on 18 February 2014 by the Ukrainian network MeteorsUA stations Prilyki, Kyiv and Pilipovich at 20:45:56 UT.
Unfortunately video data from the two stations was corrupted and it was necessary to perform astrometry and photometry from modified pictures only.
Absolute magnitude was finally calculated at -11.7 mag and geocentric velocity at : a relatively slow 21.8 km. Orbital elements are then a=0,995 AU, q=0,338 AU, e=0,660, i=6,755°, peri=130,913°, node=149,878°. Again the start and terminal altitudes are of interest: the initial altitude was 78.9 km and its terminal altitude just mere 19.9 km. Total track length was 140.3 km and the meteor was classified again as Sporadic with observed radiant RA=166,9°, DEC=0,8°.
More interesting heavyweight fireballs called “bolides” will be covered in EDMOND fireballs Part 2. What’s interesting is that most of the largest fireballs happen during spring time and the so called “Big Spring Hole” a period of usually quiet meteor activity.
SOURCE: Jakub Koukal, Richard Kacerek, Peter Campbell-Burns