Armagh Observatory

In January this year, 2 students from Victoria College, Belfast, worked with astronomers at the Armagh Observatory, and found a very exciting object! Read their report of their observations here…

“The asteroid 2007 UR2 hadn’t been observed in over 2 years, which means that predicting its orbit would be particularly uncertain, making this asteroid quite difficult to find. 2007 UR2 is an asteroid which has an extremely unusual horseshoe orbit associated with the planet Mars; this coupled with the lack of observations of this asteroid makes our observations even more valuable.

In order to find this asteroid we had to work out a line of prediction, rather than just taking one prediction. We found where this asteroid was predicted to be on the Minor Planet Center; however, we knew that this prediction was likely to be uncertain. We therefore decided to calculate positions 2 arc minutes and 6 arc minutes on either side of the predicted position to point the telescope, with the field of view being 4.7 arc minutes. In fact it turned out that the prediction was so uncertain that we found the asteroid in the furthest position, 7 arc minutes away from the predicted position.

Line of variation search (+ marks predicted position, O marks actual position) – Images obtained using the Faulkes Telescope North, operated by Las Cumbres Observatory

We did all this planning the day before we used the telescope, and at 10.30 am on Thursday 21st January we took control of the Faulkes Telescope North in Hawaii. Once we had finished our observing session, which was a little stressful seeing as we had never used a telescope before and had only half an hour to take 8 photographs. With the help of David and Tolis, timing that it took us exactly 3 minutes to take each photograph, we managed to take 9 photographs, taking three exposures of the last position, which incidentally turned out to be where our asteroid was.

In order to distinguish between a star and our asteroid, we had to take two images of the same position and then compare the two images to see if any of the apparent stars moved. The only way to tell the difference between the asteroid and a star is that the asteroid will move, and in order to tell if it is the asteroid we want we need to check if the asteroid was moving in the right direction from the predictions. When we looked at our images, after a quick tea break and a calm down after using the telescope, we realised that we had found two asteroids from our observations. We thought, for a short period of time, that we might have actually found a new asteroid. However, David quickly stole our thunder, by working out that it was actually a known main belt asteroid (94020). Nonetheless, our observations were still very successful, as we worked out that the other asteroid was indeed 2007 UR2, the asteroid that we were looking for.

In order to report our sightings to the Minor Planet Center, to improve predictions of the asteroid’s orbit, we had to observe the asteroid again. So we spent the rest of the afternoon working out the exact location of the asteroid in our images, and then comparing it to the prediction. We then knew by how much the predicition was out and therefore could work out exactly were the asteroid would be. So, on Friday 22nd January at 10.00 am, we took control of Faulkes Telescope North, and pointed the telescope where we had newly predicted our asteroid to be, and sure enough there it was. We now had enough information to send our observations to the Minor Planet Center.

When using the telescope on the second day we also had a chance to view some other interesting objects. We observed 2010AH30, a near Earth asteroid, and 2009 YS6, a damocloid. These observations were also sent to the Minor Planet Center.

We had such an amazing time taking control of the telescope, and we honestly cannot believe that we actually recovered an asteroid, in 3 days of work experience at the Armagh Observatory. We would like to say a huge thank you to everyone at the Observatory, especially David Asher and Apostolos Christou, without whom we would have been completely lost, and confused.”

Catherine O’Prey and Christina Larkin (Victoria College, Belfast)