Ancestors

Written by Mark McCaughrean on 2025-01-19 at 09:45

Earlier this week, Comet C/2024 G3 (ATLAS) made its closest approach to the Sun.

While doing so, it made a dramatic appearance sweeping through the wide-field LASCO C3 coronagraph of the ESA/NASA SOHO mission over a few days.

Here’s my take, a triplet of Deep Red, Orange, & Blue filter images taken over an hour around 09:00UTC on 14 January, as an RGB composite.

[#]C2024G3 💫

[#]CometATLAS ☄️

[#]Perihelion 🌞

[#]Photography 📷

[#]SpaceScience 🛰️

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Written by Mark McCaughrean on 2025-01-19 at 09:52

I make no claim that this is a scientifically accurate representation of the comet.

It was changing shape as it moved rapidly around the Sun during its perihelion passage & the three filter images were taken separated by roughly 30 mins each.

Thus after downloading the images as FITS files from the SOHO archive & processing them to maximise the dynamic range, I simply shifted & rotated them to align. No image scale or distortion terms were used.

So it’s close, but certainly not perfect 🤷‍♂️

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Written by Mark McCaughrean on 2025-01-19 at 09:57

The short horizontal spikes either side of the head of the comet are artefacts due to saturation of the detector. The comet was very bright & even in these short 4 second filtered exposures, slightly over-exposed.

The 17 sec clear / white light images also taken show the tail better but are heavily wiped out in the head region.

The green diagonal spike from the head is real though & must indicate a specific ionised gas emitting brightly in the LASCO Orange filter (shown as green in the RGB).

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Written by Simeon Schmauß on 2025-01-19 at 14:11

@markmccaughrean This comet is so cool! I'm currently learning a new python library (sunpy) so I can hopefully geometrically align these color filters and make a color processing too! The variation in the tail through the different filters is baffling.

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Written by Mark McCaughrean on 2025-01-19 at 17:08

@stim3on It’ll be interesting to see what you come up. My worry is that the comet is moving & changing so quickly as it passes perihelion, the ~30 minutes between the different colour filters will make it difficult to get something perfect. But if anyone can, it’ll be you 🙂👍

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Written by Simeon Schmauß on 2025-01-19 at 17:14

@markmccaughrean Cheers! I'm determined to make it work! Possibly I will need to stabilize the comet in its orbital plane using some fancy combination of SPICE and astropy...

Oh, and I'll need to take care of the stars, they need to be subtracted before I stabilize the comet, and then put back at their original place... (I think I'm already overcomplicating things again but well, that's what I do best :D )

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Written by Mark McCaughrean on 2025-01-19 at 17:17

@stim3on Perhaps 🙂 But if the comet physically changes shape between sequential images, there’s no amount of chicanery that can adjust for that, at least not scientifically. Remember: at perihelion, the angle between the direction of travel & the sunlight pushing the tail is changing rapidly.

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Toot

Written by Simeon Schmauß on 2025-01-19 at 17:19

@markmccaughrean Indeed. It will never be perfect.

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Descendants