Occultation of a star by KBO 2003 AZ84

KBOs (Kuiper Belt Objects) are large bodies located at the outer reaches of the solar system, also known as TNOs (Trans-Neptunian Objects). Due to their large distance from the Sun and their relatively low albedo, their intrinsic brightness is such that not much information about these objects can be obtained telescopically. Finding the size of these remote objects is therefore extremely difficult.

One of the methods employed for obtaining this purpose is an occultation. During an occultation, a solar system object ‘hides’ the light of a faraway star for a certain duration, usually in the order of seconds of time. From this duration, while knowing the object’s precise distance from the Sun during the occultation, one can measure the occulting object’s unknown size.

A Kuiper Belt Object (KBO)’s occultation is a rare event and the prediction of the occultation path often shifts quite significantly several days before the event itself. The night of the occultation, February 3rd 2012, was almost lost due to bad weather, which cleared just in time for preparing the observatory for this demanding observation.

As it turns out, from the 17 observatories which participated in the campaign to observe KBO 2003 AZ84’s occultation, only two were able to contributed data – one in India, which had scant information and the WIS MKO, which saw the full duration of the occultation. From this data is was deduced that the size of the KBO is between 575 km (lower limit) and 1125 km (upper limit). A lightcurve of the data analysis of the occultation can be seen here: