Mercury’s socium tail

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  • #616940
    Dawson
    Participant

    Chris Hooker gave a brilliant talk at the Winchester Weekend on Mercury’s sodium tail. I now for the life of me can’t remember when were the best times to try and capture this.

    #616965
    Mike Harlow
    Participant

    Nice piece on Spaceweather.com about this: https://www.spaceweather.com/archive.php?view=1&day=15&month=04&year=2023
    So +/- 16 days from perihelion is the best time to image it.
    Mike.

    • This reply was modified 1 year, 1 month ago by Mike Harlow.
    #616985
    Chris Hooker
    Participant

    Thanks for your comment, James, and I’m glad you enjoyed the talk.
    The recent window for viewing the tail has now ended. Unfortunately the April weather continued to be unfavourable so I didn’t obtain any more images.
    The next window is the morning elongation in January 2024. It’s not as good as the last one, with Mercury reaching 4 degrees altitude while the Sun is still below 10 degrees from the 4th to the 10th of January. After that there is another opportunity in the evening from the 22nd to the 30th March, during which Mercury will be significantly higher.
    Ii’s been suggested that I should write a short article for the Journal based on my talk at Winchester, and I shall probably do that and include information about times when the tail can be detected. For now I’m attaching the slide from my talk that showed the observing windows for the next few years.

    Chris

    • This reply was modified 1 year, 1 month ago by Chris Hooker. Reason: Spelling
    #616999
    Dawson
    Participant

    Thanks Chris. I think an article or the like about this would be very good.

    #617020
    Chris Hooker
    Participant

    Thanks for the link, Mike.
    Strictly speaking the +/-16 days from perihelion are the times when Mercury’s radial velocity is greatest, and therefore the excitation of the tail is also greatest. The best time to image it may differ significantly from that depending on where Mercury is with respect to elongation. In the recent observing window I was able to image in the evenings 2, 3, 6 and 7 days after perihelion, and by 6 days the tail was already relatively bright and extended. If I had been able to image on the previous evening I’m fairly sure I would have captured something then. On the 17th the radial velocity was at its maximum, but Mercury was very faint and sinking rapidly lower in the twilight, so that was far from the optimal time to capture the tail. The best times are when Mercury is 16 +/-10 days from perihelion and simultaneously within about 10 days of greatest elongation (eastern in spring, western in autumn). Those two conditions do not necessarily coincide!

    Chris

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