Archive for January 24th, 2011

P/2006 U1 – evolution of the orbit of a pinpoint comet

R. Ligustri, F. Romanello / CARA

I want to return again to the recently recovered comet P/2006 U1 (LINEAR). There are several reasons. First, this comet comes close to the Earth and merits a detailed analysis of the future evolution of its orbit. Second, this is a very unusual long-period comet. Looking at the picture at the left, you will understand what I have in mind.

A little history: the comet was discovered as an “asteroid” October 19, 2006 by the American sky survey Lincoln Near Earth Asteroid Research (LINEAR). After being placed on the NEOCP confirmation page, several observers commented on the presence of a long tail for this new object. The coma was very compact. The external appearance of the new comet was similar to 133P/Elst-Pizarro.

Let us return to the evolution of the comet’s orbit. After its recovery, the observation arc was now 4.24 years. Calculations were made with the help of the programming complex EPOS (V.N. Lvov, S.D. Tsekmeister) and numerical ephemerides DE406. Below is shown a graph of the osculating elements – semimajor axis (a), eccentricity (e), orbital inclination (i), perihelion distance (q), for a period of 2000-3000 years.

So what can we conclude from this graph? First – from the beginning of this century the orbital elements of the comet have begun to seriously change. The orbital inclination, after falling to a minimum value of 7.22° in the 70s of this century at the moment of closest approach of the comet to the Earth, April 26, 2076 (?=0.0505 a.u. noted on the graph), will grow over the course of the next seven centuries, achieving a magnitude of 37.7° by the middle 70s of the 28th century.

Along with the increase in inclination, the perihelion distance will also increase (the comet will pass farther from the Sun), although perihelion will not pass the limit of the Earth’s orbit (qmax = 0.81 a.u.). Along with that, the size of the eccentricity will begin to decrease to e=0.71, so the comet’s orbit will still remain eccentric. However, the most important outcome: after the 2076 apparition, the comet will begin to pass farther from the Earth. After 200 years, the distance of passage will increase by a factor of 10. Comet P/2006 U1 will not be hazardous to the Earth for the forseeable future.

In the current passage of 2011, there have already been several observations. All were made at our observatory. In the near future we will return to this comet to observe chages in its cometary activity. Will it delight us this time with its unusual tail? We will soon see!

January 2011
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