Comets at Queen’s University Belfast

Since the 1990's we have been interested in deriving physical parameters of cometary nuclei using ground-based observations. We mostly use imaging to obtain nuclear radii (assuming a standard albedo), and hereby derive a size distribution for cometary nuclei. Because we need to minimise the shielding effect of the outgassing, this generally involves imaging when the comet is at distances > 3 AU from the Sun.

People involved in this work are Prof. Alan Fitzsimmons, Dr. Stephen Lowry (JPL) and Dr. Colin Snodgrass (ESO). Dr. Martin Cartwright and Dr. Simon Collander-Brown also previously worked on this programme.

Size Distribution Programme

The 4.2-m William Herschel Telescope on La Palma. Photo Courtesy of the Isaac Newton Group of Telescopes,

Physical Properties Programme

An outcome of our size-distribution work is the identification of comets that are essentially inactive at large distances and are suitable for more detailed study. So in 2003 we started an observational programme deriving physical properties such as rotation periods and surface colours/spectra.

People involved in this work are Prof. Alan Fitzsimmons, Dr. Colin Snodgrass (ESO) and Dr. Stephen Lowry (JPL)

The 8.0-m Gemini-North Telescope. Photo Courtesy of Gemini.

Low-Activity Comets

Every year many asteroids are discovered whose orbits look like those belonging to short-period or even long-period comets. So are they really asteroids or comets? One way to find out to constrain this through measuring the composition of these objects. Another approach is to directly search for weak outgassing around objects described as asteroidal...we’ve got a few so far.

Comet C/2005 EL173 (LONEOS)

Discovered by LONEOS on 8th March 2005 and initially classed as asteroidal, it has an orbit similar to long-period comets. Therefore this object was imaged on May 10.0 UT 2005 while observing with the ESO 3.5-m NTT on La Silla. Individual 110-second exposures clearly showed a non-stellar appearence. This combined exposure of 1650 seconds shows the coma extending some 3.5 arcsec from the comet.

Comet P/2003 SQ215 (NEAT-LONEOS)

Discovered by NEAT and LONEOS on 18th September 2003 and initially classed as asteroidal, it's orbit is conspicuously comet-like. Gareth Williams (MPC) asked if we could take a look at this object, which we did on 18th/19th January 2004 while observing with the ESO 3.5-m NTT on La Silla. Individual 30-second exposures clearly showed a non-stellar appearence. This combination of 15 x 30-sec r'-band exposures shows the coma extending some 1.7 arcsec from the comet.

Comet P/2003KV2 (LINEAR)

This object was classified as a PHA after being discovered by LINEAR on 23rd May 2003. Left is an image of 2003KV2 on 29th May 2003. Analysis showed the image to be "fuzzier" than that of surrounding stars, and a faint tail is just visible to the South-East, showing it to be a comet. Combination of 30 x 20sec R-band exposures giving a total of 600 sec exposure time, obtained using the 1-m Jacobus Kapteyn Telescope.

Comet C/2005 E1 (Tubbiolo)

Imaged on the 4th March 2005 using the 2.0-m Faulkes Telescope North. This was an object originally placed on the NEOCP at the MPC, after being discovered the day before by A.F. Tubbiolo with the 0.9m Spacewatch telescope. A tail extending more than 15 arcsec to the upper right can be seen. This is a negative image, with stars and the comet appearing black and the sky white, to enhance the visibility of the tail.

Comet P/2002 EX12 (NEAT)

Imaged on the 29th July 2005 using the 2.0-m Faulkes Telescope North. This NEO was originally classified as asteroidal for 3 years, and indeed appeared so when we imaged it on May 13th 2005 using the 3.5-m NTT at La Silla when it was at 2.0 AU from the Sun. However Brian Warner at Palomar Divide Observatory saw a tail on the 28th and 29th July when it was much closer to us and the Sun, as did we (extending downwards and to the left). This is a negative image, with stars and the comet appearing black and the sky white, to enhance the visibility of the tail.

Comet P/2005 JQ5 (Catalina)

Imaged on the 17th May 2005 using the 2.0-m Faulkes Telescope North. This NEO was originally classified as asteroidal until we imaged it and found it was a comet via a visible coma extending several arcseconds from the object.

Comet C/2005 O1 (NEAT)

Imaged on the 31st July 2005 using the 2.0-m Faulkes Telescope North. This was an object originally placed on the NEOCP at the MPC, after being discovered on the 27th July with NEAT. We looked at it at the suggestion of Tim Spahr (MPC). This image shows a diffuse coma of diameter 7.2 arcsec, showing that this is in fact a comet. This is a negative image, with stars and the comet appearing black and the sky white, to enhance the visibility of the coma.

Comet C/2006 HW51 (Siding Spring)

This object looked cometary due to its comet-like orbit (parabolic!), and indeed when we observed it on June 4th and 5th 2006 we could see a compact dust coma extending 3 arcsec from the nucleus (as shown in this garish false colour image). A total R-band exposure of 350 seconds on June 5.3 UT in 1.6 arcsec seeing shows a coma extending 3 arcsec from the central object. Magnitudes within a 3 arcsec radius aperture were V=17.77, (V-R)=0.46.

P/2006 HR30 (Siding Spring)

This object was obviously a comet in 10-second exposures on the ESO 3.5-m NTT obtained on July 29.3 UT 2006. Co-addition of three exposures shows a coma extending to 5.5 " in pa 31 degrees.