Orwell Astronomical Society (Ipswich)
Kuiper Belt Objects, 23 May 2009 - 28 March 2022
A trans-Neptunian object (TNO) is a minor planet that orbits the Sun at a greater average distance than Neptune, 30 astronomical units (AU) . A Kuiper belt object (KBO) is a TNO orbiting the Sun at an average distance of between 30 and 55 AU. Most KBOs have orbits that are close to circular, with a low inclination to the ecliptic.
Among the brighter KBOs are the bodies Haumea and Makemake, discovered in 2004 and 2005 respectively. In fact, both bodies could have been discovered much earlier if astronomers had known where to look! Many amateurs had equipment capable of imaging the bodies at least 10 years before their discovery by professional astronomers.
Key facts about the bodies are as follows:
|Discovered||28 December 2004||31 March 2005|
|Minor planet number||136,108||136,472|
|Distance from Sun (AU)||35-51||36-53|
|Orbital period (years)||284||309|
|Mean diameter (km)||1630||1440|
OASI members Nigel Evans and Mike Harlow have imaged Haumea, Makemake and other KBOs as described below.
March and April are good months in which to observe dwarf planets Makemake in Coma Berenices and Haumea in Boötes. Both are visible at magnitude 17, at a distance of 50+ AU, and moving very slowly against the background stars, at a rate of approximately 2.5 arcseconds per hour, 1 arcminute per day.
Three consecutive clear nights, 25-27 March 2022, provided the opportunity to record Makemake and Haumea and their motion against the background stars. The images below track the objects so the stars appear trailed in longer exposures.
In late March 2020, Makemake appeared in Coma Berenices. At approximately magnitude 16.7, it was difficult to identify using a planetarium program or an image from the Palomar Deep Sky Survey (DSS), as there are lots of other faint stars and remote galaxies in the vicinity. By far the most effective method is to take photographs over several days to track the movement of the dwarf planet against the background objects.
An opportunity arose in late March 2020. The Palomar DSS image shows objects considerably fainter than Makemake. However, plotting the motion of the dwarf planet in four images taken during the five nights from 21-22 to 25-26 March made it easy to identify. Celestron EdgeHD 200 mm Schmidt-Cassegrain telescope with SBIG 8300 camera.
Sunny weather by day in mid-February 2018 meant clear skies at night. Although the nights were cloud-free they were hazy, so much so that I wondered whether I could capture good images. I was pleasantly surprised! The following image shows Makemake, magnitude 17.1, during the period 12-16 February 2018. Celestron EdgeHD 200 mm Schmidt-Cassegrain telescope with SBIG 8300 camera.
The following images show Haumea, imaged during the period 18-20 April 2018. At the time, the object was visible all night but was rather faint at magnitude 17.3. With a motion of around 2.5 arcsec per hour, its motion was visible against the background stars. The LH image is processed to freeze the motion of the stars, resulting in Haumea exhibiting a trail; the RH image shows the results of processing the same images to freeze the motion of Haumea, resulting in the stars appearing trailed. Celestron EdgeHD 200 mm Schmidt-Cassegrain telescope with SBIG 8300 camera.
The following image shows the motion of Makemake during the period late-March to mid-April 2012. Celestron EdgeHD 200 mm Schmidt-Cassegrain telescope with SBIG 8300 camera.
During 2009, I captured images of four KBOs. Initially, just to see what my new Schmidt camera was capable of, I pointed it about 0.5° north of γ Comae Berenices on the nights of 23 and 24 May 2009 and took a long series of exposures. The two resulting images are below; they show the motion of Makemake (2005FY9) over a period of 24 hours, confirming its identity: in the time between the images it moved 33 arcsec.
Two days later, on 26 May, skies were clear and I couldn’t resist taking a couple more images of dwarf planets before the summer break. This time, I used my 30 cm reflector to give higher resolution than the Schmidt camera. I imaged Makemake again and also Haumea (2003EL61). The field of view of the image of Makemake is similar to that of the two earlier images and shows the body continuing its south-westerly motion at about 33 arcsec per day. Haumea, at magnitude 17.4, is slightly fainter than Makemake. I took only one image of Haumea, but confirmed the identity of body by comparing my image with on-line images from the Palomar Sky Survey which show nothing in the sky where the object appears in my image.
In 26 September 2009, after the summer nights of twilight, I attempted to image a much fainter object. The BAA Handbook for 2009 contains a list of the 20 brightest KBOs, and I consulted this to find that the best placed was 2002TX300 in Andromeda. (The object, discovered on 15 October 2002, is also catalogued as minor planet 55,636). Some other KBOs were slightly brighter, but were much too low in the sky to image.
The image below shows 2002TX300. At magnitude 19.6, it is the faintest object that I’ve imaged so far. Note that the star images are round whereas 2002TX300 appears slightly elongated as it moved just over 3 arcsec during the hour or so it took to accumulate the images. 2002TX300 is estimated to be just 600 km in diameter (slightly larger than Saturn’s moon Enceladus and much darker). It is currently 40.6 AU distant from Earth. It orbits the Sun once every 286 years.
2002TX300 is pushing the limits of what I can image with my telescope. Going fainter will require significant improvements to its tracking accuracy to enable me to stack many images each of several minutes exposure duration.
The BAA Handbook lists the brightest KBOs.
Orbital information: https://ssd.jpl.nasa.gov/sb/orbits.html
Pluto was the first TNO to be discovered. On its discovery in 1930, it was classified as a planet. In 2006, the International Astronomical Union (IAU) redefined objects in the Solar System resulting in Pluto being reclassified as a dwarf planet.
Nigel Evans, Mike Harlow