Comet Ashbrook–Jackson was discovered by two astronomers namely Joseph Ashbrook from Arizona, United States and Cyril Jackson from Yale–Columbia Station, Johannesburg, South Africa. While visiting the Lowell Observatory, Arizona in US to study minor planets, Joseph Ashbrook discovered a diffused comet with a short tail. On the other hand, Cyril Jackson was experimenting with a 50 cm focus camera, which could take pictures of the fast moving minor planets and a comet appeared. It is the 47th comet discovered twice within 12 hours on 26th August, 1948. Hence, it was named as 47P/Ashbrook–Jackson.
Observations about this comet upon its discovery and subsequent apparitions include:
- This comet was observed to be made up of gas and dust. Data suggests that it is very gassy with a higher ratio of gas as compared to that of dust.
- An important observation also suggests that it has a perihelion asymmetry. In other words, a great activity was noted when it was closest to the sun on its orbital path.
- Its nucleus measures about 5.6 km and its orbit is inclined at 13°.
- After its 7th apparition in 2001, it was observed that this comet has a rapid rate of brightening and fading.
On its discovery in 1948, comet Ashbrook–Jackson had a magnitude of about 11.5 and it appeared bright. However, its last observation revealed a magnitude of about 18. Though very bright, it appears faded due to its large perihelion distance.
The perihelion distance of the comet 47P/ Ashbrook–Jackson or its orbital point closest to the Sun is noted at about 2.815558 AU. When discovered, its perihelion distance was noted at 2.3 AU. The perihelion and aphelion distances of the comet are affected due to the gravitational pull and push of the giant planet Jupiter.
The orbital period of comet 47P/ Ashbrook–Jackson is noted at around 8.38 years. At the time of its discovery, the orbital period was noted at 7.49 years. Comet 47P/ Ashbrook–Jackson has the most eccentric orbit as its perihelion and aphelion distances keep changing.
Comet 47P/ Ashbrook–Jackson was recovered by Michael Mattiazzo on 4th July, 2000. Comet Ashbrook–Jackson’s apparition depends on its orbital period around the sun.
Comet 47P/ Ashbrook–Jackson had a close encounter with Jupiter in 1945, which reduced its perihelion distance of 3.8 AU to 2.3 AU and led to its discovery in 1948.
It is expected to reappear around 6th October, 2017. Its last apparition was on 31st January, 2009