“Anuradhapura”, another far off Asteroid
Anuradhapura, the name of Sri Lanka’s ancient city has been assigned to Asteroid #311231 which was discovered on January 16, 2005 by Spacewatch at Kitt Peak and been known as 2005 BC23. It was found to be the same as 2000 WT178 observed previously by Dr. Nalin Samarasinha.
The name was suggested by Dr. Samarasinha with the citation ‘Anuradhapura is a UNESCO World Heritage site, situated in north-central Sri Lanka and was the capital city of the island for over a millennium.’ This is the second Asteroid to be named by him for a Sri Lanka World Heritage site, after Sigiriya named three years ago.
Naming of celestial objects is a formal procedure governed by the International Astronomical Union(IAU) which now has around 11,000 professional astronomers as members.
Since most stars and all galaxies are very far away, their apparent motion in the sky is small. They are identified by celestial coordinates, except for those named before the IAU formed in 1918. This simplifies their observations without ambiguity. However relatively nearby objects associated with our solar system move and are therefore assigned names in age-old tradition. Planets and dwarf planets are identified by Gods of ancient mythology. Comets are named after the discoverer. Asteroids can be named by the discoverer based on strict IAU guidelines. For example among the three page guidelines issued in 2013 August. See http://www.iau.org/static/public/naming/planets_and_satellites.pdf state that:
The process cannot request nor make reference to any revenues, for whatever purpose.
Names of individuals, places or events principally known for political, military, or religious activities are unsuitable.
In the recent past the search for Near Earth Objects (NEOs) has discovered large numbers of Asteroids, now totaling over 600,000. Of these just about 18,000 (3%) have been named. Attempts to sell naming rights to fund the search for more NEOs has been strongly declined by IAU. See http://www.iau.org/public_press/news/detail/iau1301/
The LINEAR NEO Survey by the Massachusetts Institute of Technology (MIT) promotes science education through the Ceres Connection program. This program names minor planets in honour of students in fifth through twelfth grades who win awards at the Intel International Science and Engineering Fair (ISEF). Two students in the USA of Lankan origin as well as two students from Sri Lanka have won these awards so far.
While Sir Arthur Clarke was the first Lankan resident to have an Asteroid named, and Prof Ganesh Chanmugam is the first of Lankan origin to do so, Dr.Nalin Samarasinha is the first Sri Lankan citizen. Ganindu Nanayakkara from Ananda College, Colombo was the first Sri Lankan citizen who is a resident of Sri Lanka as he was awarded first place in the 2010 ISEF for his computer-science project.
More recently 19-year-old Dinesh Kapuge, from Mihintale Central College, was placed first in the engineering, electrical and mechanical category in the 2013 ISEF. An asteroid has not been assigned as yet in his name, a process that can take more than a year.
There are now nine asteroids associated with Sri Lanka and one pending.
Perihelion distance is the nearest distance of orbit from Sun measured in Astronomical Units (AU) which is the mean distance of the Earth from the Sun. Diameter ranges from a one to 10 km with Serendip the largest at 10 km. The diameter estimated statistically, is based on the observed brightness and distance from Earth at times of observation, averages over non-spherical objects.
The only other unknown in the equation is the reflectivity of asteroid. Known as Albedo it is unity for perfect reflection and near zero for a dark asteroid which absorbs most of the visible light. The estimated optical albedo ranges from 0.04 for Nanayakkara to 0.37 for Samarasinha. It is assumed to be 0.15 if unknown, and then the estimated diameter is very uncertain.
These are all Main Belt Asteroids that orbit between Mars and Jupiter with periods of 3-6 years. None come closer than 250 million km from earth and there is no danger from any of them to life on Earth. We surely don’t want another incident like cyclone Mahasen of 2013 May.