Flight simulation "burn out" earlier this year has forced me to look elsewhere for my PC entertainment.....

I am now simulating the historical evolution of short period comet orbits with a very impressive piece of software called Halley - an electronic ephemeris of comets. It may not look like much to someone who is not interested in orbital mechanics, but I have always been fascinated with the orbits of short (and indeed, long) period comets. Frequent gravitational perturbations by the planets result in changes to their orbits, and this is fascinating to watch. I have input extremely accurate orbital elements (from the JPL Horizons database) for each of the numbered short period comets that are of interest (generally those that come close to, or cross Earth's orbit), and I am simulating them backwards in time, and recording the dates of perihelion passage (closest approach to the Sun), and also any approaches to Earth within 1AU (astronomical unit - the distance between Earth and Sun).

My target is to try and identify possible past apparitions of known short period comets. You would think that this would already have been done, but it is surprising how long it has taken for some known comets to be linked with ones seen several centuries ago. Whatever happens, it is really interesting to discover possible reasons why some comets were not seen prior to their discovery. This can be because Jupiter has recently perturbed them from a much larger orbit that came nowhere near Earth (or a gradual reduction of perihelion distance caused by multiple gravitational perturbations by Jupiter), but it can also be because those same subtle perturbations by Jupiter (or Saturn) have resulted in the comet not making any close approaches to Earth over extended periods of time (sometimes a century or more, and this is for comets with orbital periods as low as 5 or 6 years). Of course, more recently discovered comets could also be intrinsically faint (since we have better telescopes and cameras to detect them these days). However, there is always the chance that any comet can suffer what is known as an "outburst" at any time (a period of increased activity when relatively close to the Sun) that can make it appear much brighter than normal.

It should be a fascinating journey

http://iaaras.ru/en/dept/lsbss/halley/

Edited August 27, 20214 yr by Christopher Low

According to Shakespeare, Julius Caesar was killed right around the time the comets were showing wonders. Brutus and Cassius walk along watching the sky and grumbling about Caesar.

"The fault, dear Brutus, is not in our stars. But in ourselves, that we are underlings."

Julius Caesar I,ii, 140-141).

C/-43 K1

That is the official designation of the comet that was seen close to the time that knives were raining down on Julius Caesar. It is considered to be one of the most impressive comets to have been observed in the ancient world, and apparently could be seen in broad daylight during August 44BC.

Edited August 31, 20214 yr by Christopher Low

Your post "hearted" deeply.... 😁

In 1997 I sold my 8 inch Baush&Lomb Criterium 8000 Schmidt Cassegrain telescope, with it's huge 8 inch equatorial drive (220v 50Hz, tricky to use in the field...) to buy my first desktop PC for flight simulation, the main motivation being Flight Unlimited 1, Seamus Blackley creation ...

I loved Astronomy... Thanks for the info and links which I will surely follow.

Edited August 31, 20214 yr by jcomm

I am running a backwards integration as I type these words For the record, the comet in question is 212P/NEAT (Near Earth Asteroid Tracking; named after the automated telescope system located at the summit of the extinct Haleakala volcanic crater on Maui that discovered it), and the integration timespan is from the epoch of the orbital elements that are being used (2009 February 10.0) back to 1400 January 1.

Edited August 31, 20214 yr by Christopher Low

The two simulations that I will run tonight are:-

• 107P/Wilson-Harrington - discovered in 1949 as a comet, subsequently lost, and then recovered in 1979 as an asteroid (1979 VA). This simulation is probably not going to reveal any undiscovered past apparitions, but there will probably be a lot of close Earth approaches (since the perihelion distance is very close to Earth's orbit, and gravitational perturbations from Jupiter are minimal).
• 210P/Christensen - I do not know much about this object, so we will see what the simulation reveals....