Celestia Forums

As there is an Asteroids for Celestia topic, I thought it would be a good idea to create one for (real, not fictional) comets too ...

So, feel free to post your addons about comets, fragments, moons of them (or links to other threads that contain comets) below ...

Add-on by me: All comets of 2023: https://celestiaproject.space/forum/viewtopic.php?f=23&t=24376

Here are the list of comet addons with customized models, textures, and/or trajectories for Celestia:

• 1P/Halley
• 9P/Tempel
• 19P/Borrelly
• 26P/Grigg-Skjellerup
• 67P/Churyumov-Gerasimenko
• 73P/Schwassmann-Wachmann
• 81P/Wild
• 96P/Machholz
• 103P/Hartley
• C/2012 S1 (ISON)
• C/2013 A1 (Siding Spring)
• C/2022 E3 (ZTF)
• C/2023 A3 (Tsuchinshan-ATLAS)
• C/2023 P1 (Nishimura)
• D/1993 F2 (Shoemaker-Levy)
  

This addon adds 4 comets called "Gehrels" (270P/Gehrels, 90P/Gehrels 1, 78P/Gehrels 2 and 82P/Gehrels 3) to Celestia. Three of them (not 90P) had/have many flybys at the gas planets, and 78P was in a 2:1 resonance with Ceres (Ceres finishes 2 orbits while the comet finishes only 1) 4 times (many orbits each), separated by Jupiter flybys (they didn't ruin the 2:1 resonance with Ceres). 90P has a (much) stable orbit around the sun which doesn't change that much because it didn't/doesn't fly by Jupiter or Saturn closely.
All four comets have .xyzv trajectories for high precision which start at 1600 Jan 01 and end at 2500 Jan 01.

Note: The P designations (e.g. 1P, 2P, etc.) are in a different order than the comet numbers (Gehrels (1/2/3)) for some reason which caused little confusions but everything is fine now.

Flyby data (also available in flybys.txt inside the .zip):

This addon adds a full xyzv trajectory (1600-2500) for comet 81P/Wild (2)
Originally this comet orbited the Sun between the orbits of Jupiter and Neptune, until a close encounter with Jupiter in September 1974 brought it into the inner Solar System. On January 2, 2004, NASA's Stardust spacecraft collected samples from Wild 2's coma, which were returned to Earth in January 2006. The comet will remain in its current orbit until 2058, when it will pass close to Jupiter again.

xyzv trajectory made by me with data extracted from JPL HORIZONS. The comet's model, texture and physical/rotational parameters are from Celestia Origin.

A small correction in the Wild 2 ssc file, the "BlendTexture true" parameter was added, so that the specified color of the comet is filed with the texture. If you already have the addon installed, simply replace the ssc file with fixed. Remember to delete the old ssc so you don't create duplicates.

This addon adds a full xyzv trajectory (1600-2500) for comet 67P/Churyumov-Gerasimenko

For many centuries, 67P remained on a orbit whose perihelion was beyond the orbit of Mars, until an encounter with Jupiter in 1959 defined its perihelion between the orbits of Earth and Mars. Has made a series of close approaches to Jupiter over the centuries and will continue to do so.
67P/Churyumov-Gerasimenko was the target of ESA's Rosetta mission, which orbited the comet between August 2014 and September 2016. And on November 12, 2014, Philae became the first lander to land on a cometary nucleus.

xyzv trajectory made with data extracted from JPL HORIZONS. The comet's model, texture and physical/rotational parameters are from Celestia Origin.

This addon adds a full xyzv trajectory (1600-2500) for comet 19P/Borrelly

There is nothing particularly incredible about Borrelly's orbit, as most distant encounters with Jupiter only slightly change its orbital inclination, with few perihelion/aphelion changes.
In September 2001, the Deep Space 1 mission made a flyby of this comet, being the second cometary nucleus being photographed by a spacecraft, after Giotto's flyby of Halley in 1986.

xyzv trajectory made with data extracted from JPL HORIZONS. The comet's model, texture and physical/rotational parameters are from Celestia Origin.

ADDITIONAL NOTE: Since Borrelly already exists in the default Celestia, the addon's ssc includes the "Replace" parameter.

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This addon adds a full xyzv trajectory (1600-2500) for comet 9P Tempel (1)
We already know that Jupiter family comets make many encounters with Jupiter itself, and Tempel 1 is no exception. On 2024-May-26, it will pass within 0.55 AU of Jupiter.
In 2011-Nov-10, it passed 6.03 million km from Ceres and in 2183-Oct-17 it will pass 2.86 million km from Mars.

Tempel 1 was the target of NASA's Deep Impact mission, which aimed to create a crater on the comet to study its interior composition. On 2005-Jul-4, the impactor collided with the comet and the flyby spacecraft photographed the plume, but was unable to see the crater.
After returning samples from Wild 2's coma, the Stardust spacecraft was redirected to Tempel 1 to photograph the crater left during the Deep Impact mission.

xyzv trajectory made with data extracted from JPL HORIZONS. The model and physical/rotational parameters are from Celestia Origin. The comet's texture is from Shadow-Dragon-777.

This addon adds a full xyzv trajectory (1600-2500) for comet 103P/Hartley (2). Is a Jupiter-family comet that measures about 1.6 km in diameter.

Interesting approximations:

- 1947-Aug-26, 0.184 AU from Jupiter;
- 1971-Apr-28, 0.085 AU from Jupiter;
- 2010-Oct-20, 0.12 AU from Earth.

Hartley 2 was the target of the EPOXI mission (Deep Impact extension), with a flyby on 2010-Nov-04 at a distance of around 700 km from the nucleus.

xyzv trajectory made with data extracted from JPL HORIZONS. The comet's model, texture and physical/rotational parameters are from Celestia Origin.

12P/Pons-Brooks is a periodic Halley-type comet, with an orbital period of approximately 71 years.
Pons-Brooks will reach perihelion in 2024-Apr-21, with closest approach to Earth (1.55 AU) in 2024-Jun-02. Given that the comet has already been observed by several amateur astronomers, I felt the need to release this early (previously it would have been released in a single addon containing the periodic comets 10P to 18D). If you want to try to find and observe 12P/Pons-Brooks, now try using Celestia as a night map!

xyzv trajectory made with data extracted from JPL HORIZONS. The model and texture (generic, obviously) are from Celestia Origin.

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C/2024 L5 (ATLAS) is a comet discovered on 2024-Jun-14 by the Asteroid Terrestrial-impact Last Alert System (ATLAS). What makes this comet stand out is a close encounter with Saturn on 2022-Jan-24, which placed it on a escape trajectory (hiperbolic) from Solar System. Before this encounter, its orbit around the Sun was retrograde and similar to that of a centaur.

Some details of the trajectory of C/2024 L5:
- Closest approach to Saturn on 2022-Jan-24 02:50:00 UTC), 340,340 km.
- Reaches perihelion in 2025-Mar-10, 3.4322 AU;
- Closest approach to Jupiter in 2026-Aug-18, 0.59517 AU;

C/2024 S1 (ATLAS) was a sungrazer and probable Kreutz comet discovered on 2024-Sep-27. It was predicted to reach perihelion in 2024-Oct-28, and if it survived the Sun's intense heat, it could potentially become visible to the naked eye during the day, with magnitude estimated to be between -5 and -7. However, just before reaching perihelion, the comet's nucleus completely disintegrated, as observed by SOHO LASCO.

NOTE: To see the comet, you need to set the time in Celestia to sometime before 2024-Oct-28 07:00 UTC

An update for C/2024 S1 was posted to the original post above. The comet disintegrated just before perihelion. Furthermore, he was not hyperbolic (until then, the data were preliminary and the observation arc very short).