Discovery @ Raheny

Written By Dave Grennan

Raheny Observatory is the discovery site of a number of astronomical objects. To-date three supernovae and two minor planets (asteroids) have been discovered.

So what constitutes a discovery?

A discovery is typically the first observation of a previously unknown astronomical object. These days large scale well funded professional observatories make most of the new discoveries but Raheny observatory has proven that there is still a place for the amateur astronomer to make a permanent legacy by being the very first person to see a new object. New discoveries are judged by the International Astronomical Union and only when significant proof of this discovery has been established will the discoverer be given the appropriate credit as the objects discoverer.

So what has been discovered at Raheny then?

Let’s begin with the asteroids!

(215016) Catherinegriffin

Minor Planet 2008 US3 discovery image sequence. (C) D. Grennan – Click for full size

October 21st 2008 was a very special day at Raheny. In the course of my normal asteroid survey, I stumbled upon a whole new asteroid. After reporting this to the IAU minor planet center it was initially given the designation ‘2008 US3’. Infact the only information received from the IAU was a one line email.

DG00001 K08U03S

This simple email meant that the object I had reported as DG00001 has now been designated K08U03S or in longhand 2008 US3 the lack of a leading ‘(‘ before the K meant this object is previously unknown and the observation which I have submitted is currently considered the discovery observation. I was elated. In fact elation is an understatement Just a couple of weeks previous to that Dave McDonald at Celbridge observatory had become the first person in Ireland to discover an asteroid from Ireland in 148years and barely two weeks later we had a second discovery from irish soil. What followed in the months and years after this discovery was a long process to continually improve the known orbit of this asteroid. Observations from observatories all over the world were added to the records and finally enough data was available for the minor planet center to confirm the discovery and give a proper designation. 2008 US3 became (215016)2008 US3.

Minor Planet 2008 US3 discovery image.  In this image the minor planet is held static and as such the background stars appear to trail. (C) D. Grennan

As the discoverer of a minor planet is afforded the opportunity to name the object I quickly set about choosing a name. My mum passed away in 2004. She and my dad always supported my astronomy studies, so I felt it was fitting to give her a permanent memorial in space. A 3km wide minor planet orbiting between Mars and Jupiter!!

I submitted the following citation;

(215016) Catherinegriffin = 2008 US3
Catherine Grennan (née Griffin, 1939-2004) was the mother of the discoverer. She encouraged his interest in amateur astronomy, and this led to the discovery of this minor planet.

This minor planet is now forever called (215016) Catherinegriffin. I had originally proposed that the asteroid be called (215016) Catherinegrennan. I was advised by the late Brian Marsden who was chair of the naming committee that that was unlikely to be approved as ‘No part of the discoverers name may appear in such a proposal’. He suggested that I use my mums maiden name instead and so this was used instead.


Catherine (Kay) Grennan (Née Griffin) 1939 – 2004

2009 FV19

2009 FV19 discovery image

2009 FV19 discovery image (C) D. Grennan

March 2009 saw my second and most recent asteroid discovery. 2009 FV19 is a main belt asteroid again orbiting between Mars and Jupiter. It’s approximately 2km in diameter. As yet it’s un-named. (Note: A name for this minor planet has been chosen so suggestions cannot be considered). The discovery process was very similar to 215016 and enough data has been collected to formally designate this as (312546) 2009 FV19.

So why was this the last asteroid discovery from Raheny? Well that’s a good question and the answer is down to a change of rule by the minor planet center. Over the years large professional surveys collect images of the sky in a fully automated manner. Asteroids are noted but not identified and positional information is reported by a robotic process to the IAU. Note that no human is likely to have had a hand or made any concious decision that any of these asteroids exist or made any attempt to identify them. Nevertheless these anonymous positions lay dormant on computer servers for possibly many years. Now comes along somebody who actually notes an object and can find no previous discovery information on record. That person reports his/her ‘discovery’ and usually a new designation is given. As weeks and months pass computers at the minor planet center crunch orbital information and a link may be established between the new ‘discovery’ and a previous unmanned robotic observation sitting in the archives as possibly a ‘one night stand’. The latest ‘discovery’ observation is then considered as a secondary observation and discovery credit switches to the survey which submitted the original positional information.

Given that these professional observatories have been operating for many years and have now probably unkowingly reported positional information on the vast majority of main belt asteroids, it is now highly likely that any new ‘discovery’ credit will revert to the professional survey and thus the days of amateur discoveries of main belt asteroids are probably over.

There is stiall a chance for an amateur to stumble upon a NEO (Near Earth Object) as many of these are discovered by professional observatories on a daily basis however the odds are not in the favour of the amateur.

I now concentrate my minor planet research on providing confirmation positional astromentry for these NEO objects. It is vital that a reasonably accurate orbit is determined as quickly as possible for all objects which come in close proximity to our planet I now consider this research far more important than searching for main belt asteroids which pose no threat to our planet.

Coming soon – The supernovae discovery years.