Instructions for Ongoing Observations of the Dust Trail from the 2007 Outburst of Comet 17P/Holmes

These instructions provide guidance for the continuous observation of the dust trail resulting from the 2007 outburst of Comet 17P/Holmes.

1. Software and Access

To facilitate data collection and analysis the software is open-access.

2. Coordinate Data

The attached coordinate lists contain calculated coordinates for the dust trail of Comet 17P/Holmes. These coordinates are based on predictions for the behavior of the dust trail near the comet's 2007 outburst point (referred to as the northern node) and also at the southern node. The calculations were conducted according to the methodology detailed in Gritsevich et al. 2022.

3. Coordinate List Columns

The coordinate list includes the following columns:

•     Observatory name
•     Particle position in the narrowest part of the trail
•     JPL date-time
•     Julian Date (JD)
•     Right Ascension (RA) and Declination (DEC) in decimal notation
•     RA and DEC in normal notation
•     Altitude from the horizon
•     Azimuth
•     Distance to the trail from Earth in Astronomical Units (AU)

These coordinates are initially calculated for observatories in Kouvola, Utah, and Siding Spring, but they are adaptable for use with telescopes at any location on Earth.

4. Observation Period

The dust trail is expected to be observable using ground-based telescopes from September 2023 to March 2025, both at the northern and southern nodes.

5. Python Code

An attached Python code provides 3D positions of the dust trail. This code can be utilized with both ground-based and space-based telescopes. The Python program employs the Skyfield library and takes into account the topographical location of Earth, correcting for light time and atmospheric refraction.

6. Dust Particle Positions

The coordinates are calculated for five dust particles located closest to the narrowest point of the trail. These particles are named as follows: FarLeft, Left, Middle, Right, and FarRight particles. It is recommended to align your telescope with the Middle particle's position, as this provides the most accurate trail orientation. The other particles offer guidance on the trail's orientation within your telescopic field of view.

7. Trail Positions

Trail positions are based on the findings of Gritsevich et al. 2022 and are provided for various months, including September 2023, November 2023, January 2024, July 2024, and October 2024. All scripts included in the package are designed to calculate position data for the entire period from September 2023 to March 2025. To achieve the highest accuracy, select the script that corresponds to the nearest trail position relative to your specific observing date and time.

8. Image Subtraction

For image subtraction, it is recommended to use CCD images taken over two consecutive nights. Employ an unfiltered luminance filter for this purpose.

9. Brightness and Visibility

The most recent observations of the dust trail, to the best of our knowledge, were conducted by Jorma Ryske in February 2023. These observations confirmed the positioning of the dust trail as predicted. It is expected that the dust trail will maintain for some time a nearly consistent brightness level starting from September 2023. Further research is needed to assess the brightness of the dust trail at the southern node.

10. Particle Sizes

Particle sizes vary at the northern node, with larger particles present starting in September 2023 and finer dust particles predominant by October 2024. At the southern node, fine dust particles are found at the narrowest point of the trail. Additionally, there is a second, extremely dim trail view that is not expected to be observable. By October 2024, the head mass of the trail, consisting mainly of larger particles with an abundance of middle-sized particles, approaches the vicinity of the southern node.

11. Dust Trail Width and Comet's Orbital Plane

Our previous findings highlighted the hourglass shape of the dust trail, indicating that the trail's width varies along its path. Trail width at the northern node is estimated to be in September 2023 approximately 40 arc seconds. The trail is wider at the southern node than at the northern node. In our trail positions, the southern trail measures approximately 2 arc minutes in width at its narrowest point when Earth is not in the comet's orbital plane. This width naturally fluctuates depending on Earth's alignment with the comet's orbital plane. A narrower width of the trail results in a higher particle density, which in turn increases the trail's surface brightness. For ground-based observations, the most favorable geometry occurs when Earth crosses the comet's orbital plane. Earth intersects Holmes' orbital plane twice a year, in February and August.

12. Collaboration Opportunities

For additional in-depth information and references, please refer to the provided resources. We would be delighted to receive updates from your observing campaigns. We eagerly anticipate the possibility of collaborating on joint publications and the dissemination of research findings. In Gritsevich et al. 2022, we have identified open research questions that could be addressed with the help of additional observations. Your contributions are invaluable for advancing the current understanding of cometary outbursts and the subsequent evolution of dust trails. Together, we can explore new horizons in planetary science and share our discoveries with the scientific community and beyond!